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National Management Measures
for the Control of Nonpoint
Pollution from Agriculture
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U.S. Environmental Protection Agency
Office of Water (4503T)
1200 Pennsylvania Avenue, NW
Washington, D.C. 20460
EPA-841-B-03-004
2003
Cover photos:
1-V. 'Urn McCtibc, Natural Resources Conservation Service
4: Lynn Belts, Natural Resources Conservation Service
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Disclaimer
This document provides guidance to States, Territories, authorized Tribes, and
the public regarding management measures that may be used to reduce nonpoint
source pollution from agricultural activities. This document refers to statutory
and regulatory provisions which contain legally binding requirements. This
document does not substitute for those provisions or regulations, nor is it a
regulation itself. Thus, it does not impose legally-binding requirements on EPA,
States, Territories, authorized Tribes, or the public and may not apply to a
particular situation based upon the circumstances. EPA, State, Territory, and
authorized Tribe decision makers retain the discretion to adopt approaches on a
case-by-case basis that differ from this guidance where appropriate. Interested
parties are free to raise questions and objections about the appropriateness of the
application of the guidance to a particular situation, and EPA will consider
whether or not the recommendations in this guidance are appropriate in that
situation. EPA may change this guidance in the future.
National Management Measures to Control Nonpoint Pollution from Agriculture
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Acknowledgments
Steven A. Dressing, formerly of the Nonpoint Source Control Branch, Office of Water, U.S. Environmental
Protection Agency, Washington, DC, was the primary author of this guidance document.
Many individuals assisted in this effort, including the following:
John Kosco, formerly of the Municipal Support Division, Office of Water, U.S. EPA, Washington, DC
Thomas Davenport, Region 5, U.S. EPA, Chicago, IL
David Rathke, Region 8, U.S. EPA, Denver, CO
Don Meals, consultant, Burlington, VT
Tommy C. Daniel, Department of Agronomy, University of Arkansas, Fayetteville, AR
Brent Hallock, Soil Science, Department, California Polytechnic State University, San Luis, Obispo, CA
Ray Knighton, USDA-CRES, Washington, D.C., formerly of the Soil Science Department, North Dakota
State University, Fargo, ND
Jerry Hatfield, USDA-ARS, Washington, DC
Robert Goo, Nonpoint Source Control Branch, Office of Water, U.S. EPA, Washington, DC
Roger Dean, Region 8, U.S. EPA, Denver, CO
Amy Sosin, Department of Justice, Washington, DC
Chris Laabs, Watershed Branch, Office of Water, U.S. EPA, Washington, DC
Joan Warren, Watershed Branch, Office of Water, U.S. EPA, Washington, DC
Kristen Martin Dors, formerly of Region 6, U.S. EPA, Dallas, TX
Steven W. Coffey, Division of Soil and Water Conservation, NC Department of Environment and Natural
Resources, Raleigh, NC
Judith A. Gale, Galeforce Consulting, Raleigh, NC
Richard E. Phillips, retired, Biological and Agricultural Engineering Department, North Carolina State
University, Raleigh, NC
Ron Marlow, USDA-NRCS, Washington, DC
Alan Dixon, Registration Support Branch, Office of Pesticide Programs, Washington, DC
Sharon Buck, formerly of the Nonpoint Source Control Branch, Office of Water, U.S. EPA, Washington, DC
Stuart Lehman, Nonpoint Source Control Branch, Office of Water, U.S. EPA, Washington, DC
Katie Flahive, Nonpoint Source Control Branch, Office of Water, U.S. EPA, Washington, DC
The following team from North Carolina State University, Raleigh, NC, contributed as subcontractors to
Tetra Tech, Inc., providing much of the writing and editing:
Laura Lombardo, Daniel E. Line, Garry L. Grabow, Jean Spooner, Terry W. Pollard, Janet M. Young and
Catherine Scache, of the NCSU Water Quality Group, Deanna L. Osmond and Rich McLaughlin of the Soil
Science Department, and Frank J. Humenik, Animal Waste Management Programs, College of Agriculture
and Life Sciences. In addition, George Townsend and Leslie Shoemaker from Tetra Tech, Inc. provided
valuable contributions.
Public comment was solicited in the Federal Register, October 17, 2000, on the draft version of the guidance.
Comments were received from approximately 50 individuals. These comments were valuable in making this
a better document and EPA appreciates the efforts of these individuals.
National Management Measures to Control Nonpoint Pollution from Agriculture
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Table of Contents
Chapter 1: Introduction 1
The Purpose and Scope of this Guidance 1
What is Nonpoint Source Pollution? 3
National Efforts to Control Nonpoint Source Pollution 4
Nonpoint Source Program — Section 319 Clean Water Act 4
National Estuary Program 5
Pesticides Program 5
Coastal Nonpoint Pollution Control Program 5
Source Water Protection Program 6
Rural Clean Water Program (RCWP) 6
Farm Bill Conservation Provisions 7
Chapter 2: Overview 9
Agricultural Nonpoint Source Pollution 9
Nutrients 9
Sediment 15
Animal Wastes 16
Salts 19
Pesticides 21
Habitat Impacts 24
Mechanisms to Control Agricultural Nonpoint Source Pollution 27
Management Measures 28
Management Practices 28
Resource Management Planning Concepts 29
Chapter 3: Management Practices 31
How Management Practices Work to Prevent Nonpoint Source Pollution 31
Water Quality Effects of USDA-NRCS Practices 32
Management Practice Systems 34
Types of Management Practice Systems 34
Site-Specific Design of Management Practice Systems 35
Practices Must Fit Together for Systems to Perform Effectively 36
Chapter 4: Management Measures 37
4A: Nutrient Management 37
Management Measure for Nutrients 37
Management Measure for Nutrients: Description 38
Sources of Nutrients 39
National Management Measures to Control Nonpoint Pollution from Agriculture iii
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Nutrient Movement into Surface and Ground Water 50
Nutrient Management Practices and Their Effectiveness 54
Factors in the Selection of Management Practices 64
Cost and Savings of Practices 65
4B: Pesticide Management 69
Management Measure for Pesticides 69
Management Measure for Pesticides: Description 69
Pesticides: An Overview 71
Pesticide Movement into Surface and Ground Water 73
Pesticide Management Practices and Their Effectiveness 77
Factors in the Selection of Management Practices 85
Relationship of Pesticide Management Measures to Other Programs 85
Cost and Savings of Practices 85
4C: Erosion and Sediment Control 89
Management Measure for Erosion and Sediment 89
Management Measure for Erosion and Sediment: Description 89
Sediment Movement into Surface and Ground Water 90
Erosion and Sediment Control Practices and Their Effectiveness 94
Factors in the Selection of Management Practices 103
Cost and Savings of Practices 105
4D: Animal Feeding Operations 107
Management Measure for Animal Feeding Operations 107
AFOs, CAFOs, and CZARA 110
Management Measure for Animal Feeding Operations: Description Ill
Contaminant Movement from Animal Feeding Operations into Surface
and Ground Water 115
Animal Feeding Operation Management Practices and Their Effectiveness 119
Factors in the Selection of Management Practices 125
Cost of Practices 126
4E: Grazing Management 129
Grazing Management Measure 129
Management Measure for Grazing: Description 130
Grazing and Pasture: An Overview 132
Potential Environmental Impacts of Grazing 140
Grazing Management Practices and Their Effectiveness 142
Factors in the Selection of Management Practices 151
Cost and Savings of Practices 152
4F: Irrigation Water Management 157
Management Measure for Irrigation Water 157
Management Measure for Irrigation Water: Description 158
Irrigation and Irrigation Systems: An Overview 158
iv National Management Measures to Control Nonpoint Pollution from Agriculture
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Irrigation Water Management Practices and Their Effectiveness 185
Factors in Selection of Management Practices 196
Cost and Savings of Practices 197
Chapter 5: Using Management Measures to
Prevent and Solve Nonpoint Source Problems in Watersheds 203
Watershed Approach 203
Implementing Management Measures in Watersheds 204
Technology-based Implementation 205
Water Quality-based Implementation 205
Chapter 6: Monitoring and Tracking Techniques 215
Water Quality Monitoring 215
Tracking Implementation of Management Measures 219
Determining Effectiveness of Implemented Management Measures 220
Quality Assurance and Quality Control 222
Chapter 7: Load Estimation Techniques 225
Estimating Pollutant Loads through Monitoring 227
Components of a Load 227
Measuring Water Discharge 228
Measuring Pollutant Concentration 228
Calculating Pollutant Loads 231
Estimating Pollutant Loads Through Modeling 232
Types of Models Available 233
Watershed Loading Models 233
Planning and Selection of Models 236
Model Calibration and Validation 238
Unit Loads 240
Addressing Uncertainty in Modeling Predictions 240
Model Applications Using GIS Technology 241
ChapterS: Glossary 243
Chapter 9: References 247
Appendix 281
Appendix A: Best Management Practices — Definitions and Descriptions 281
Appendix B: SCS Field Office Technical Guide 299
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List of Figures and Tables
Chapter 3: Management Practices 31
Table 3-1. NRCS Conservation practices, pollutants potentially controlled, and
sources of pollutants 33
Table 3-2. Animal waste management, BMP systems used in two agricultural
pollution control projects 36
Chapter 4: Management Measures 37
4A: Nutrient Management 37
Figure 4a-l. The nitrogen cycle 39
Figure 4a-2 .The phosphorus cycle 40
Table 4a-l. Common fertilizer minerals 41
Highlight- Precision Farming: A new era of production 42
Table 4a-2. Fertilizer recommendations for corn in New York state 44
Table 4a-3. N and P mass balances on several New York dairy farms 45
Table 4a-4. Representatives values for nutrients in manure, sludge, and whey, as applied 46
Table 4a-5. Nutrients available for crop use in the first year after spreading manure 47
Table 4a-6. Quantity of livestock or poultry manure needed to supply 100 kg of nitrogen 47
Table 4a-7. Representative values for first-year nitrogen credits for previous legume crops 48
Table 4a-8. Calculating N contributions from irrigation water 48
Table 4a-9. N loading in atmospheric deposition, NADP/NTN data 49
Table 4a-10. Crop nutrient removal 50
Figure 4a-3. P added in poultry litter compared with crop requirements 51
Table 4a-ll. Allowable P application rates for organic by-products (e.g. manure) 55
Figure 4a-4. Example of soil test report 56
Figure 4a-5. Example of Penn State's soil quicktest form 57
Table 4a-12. Required nutrient management plan elements for confirmed animal
operations in the Pequa-Mill Creek National Monitoring Program project 60
Table 4a-13. Missisquoi Crop Management Association 1997 nutrient recommendations 60
Table 4a-14. Plan summary from a sample plan 61
Table 4a-15. Reported changes in average annual nutrient application rates 63
Table 4a-16. Relative effectiveness of nutrient management 64
Highlight - USDA/NRCS Comprehensive Nutrient Management Planning Technical Guidance 67
4B: Pesticide Management 69
Figure 4b-l. Pesticide Fate: Major Pathways 70
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Figure 4b-2. Pesticide Fate: Losses to the Atmosphere 0-30% of Applied Pesticide 74
Figure 4b-3. Pesticide Fate: Plant Uptake 1-10% of Applied Pesticide 74
Figure 4b-4. Pesticide Fate: Soil 50-100% of Applied Pesticide 75
Table 4b-l. Typical pesticide leaching potential (PLP) index values calculated for six herbicides 81
Table 4b-2. Effect of BMPs on pesticide losses compared to conventional tillage
or no filter strips 81
Table 4b-3. Summary of buffer studies measuring trapping efficiencies for specific pesticides 82
Highlight - EPA's Office of Pesticide Programs promotes registration of lower risk pesticides 84
Table 4b-4. Estimated scouting costs by coastal region and crop in the coastal zone 87
Table 4b-5. Summary of results of farm-level economic evaluations of IPM programs 87
4C: Erosion and Sediment Control 89
Figure 4c-l. The different ways soil can move during wind erosion 93
Figure 4c-2. Diversion 96
Figure 4c-3. Stripcropping and rotations 98
Figure 4c-4. Gradient terraces with tile outlets 99
Figure 4c-5. Gradient terraces with waterway outlet 99
Table 4c-l. Relative gross effectiveness of sediment control measures ; 103
Table 4c-2. Representative costs of selected erosion control practices 106
Table 4c-3. Annualized cost estimates and life spans for selected management practices
from Chesapeake Bay installations 106
4D: Animal Feeding Operations 107
Highlight - USDA-EPA Unified national strategy for animal feeding operations 108
Table 4d-l. Large and small confirmed animal facilities under CZARA Ill
Highlight - Management of soil phosphorus levels to protect water quality 112
Figure 4d-l. Animal feeding operation 114
Figure 4d-2. Management measure for animal feeding operations 115
Table 4d-2. Waste characteristics from dairy farms 117
Table 4d-3. Annual waste production on a typical 100 cow dairy 117
Table 4d-4. Manure reduction methods and costs for milking centers 118
Table 4d-5. Phosphorus reduction methods and costs 118
Table 4d-6. Relative gross effectiveness (load reduction) of animal feeding operation
control measures 122
Table 4d-7. Concentration reductions in barnyard and feedlot runoff treated with
solids separation 122
Table 4d-8. Summary of average performance of wetlands treating wastewater from
confined animal feeding operations 123
National Management Measures to Control Nonpoint Pollution from Agriculture vii
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Table 4d-9. Nitrogen loading rates and mass removal efficiencies for the
constructed wetlands, Duplin Co., NC 123
Table 4d-10. Nitrogen volatilization losses during land application of manure 126
Table 4d-ll. Calibration methods 127
Table 4d-12. Costs for runoff control systems 128
4E: Grazing Management 129
Highlight- Recommendations for grazing management in riparian areas 131
Figure 4e-l. Relationship between forage digestibility, the amount of forage ruminants
can eat, and the amount of forage needed to meet nutrient requirements 134
Figure 4e-2. Relationship of forage allowance to forage intake and utilization 136
Table 4e-l. Some commonly used grazing systems 139
Figure 4e-3. Benefits that a riparian buffer can provide 141
Highlight - Five steps to a successful prescribed grazing management plan 143
Table 4e-2. Bacterial water quality responses to four grazing strategies 148
Table 4e-3. Nitrogen losses from medium-fertility, 12-month pasture program 148
Table 4e-4. Grazing management influences on two brook trout streams in Wyoming 149
Table 4e-5. Streambank characteristics for grazed versus rested riparian areas 150
Table 4e-6. The effects of supplemental feeding location on riparian area vegetation 151
Table 4e-7. Cost of forage improvement/reestablishment for grazing management 153
Table 4e-8. Cost of water development for grazing management 154
Table 4e-9. Cost of livestock exclusion for grazing management 155
4F: Irrigation Water Management 157
Figure 4f-l. Irrigated land in farms 158
Figure 4f-2. On-farm hydrologic cycle for irrigated lands 160
Table 4f-l. Soil-water-plant relationship terms 160
Figure 4f-3. Soil textural triangle for determining textural class 162
Figure 4f-4. Typical water release curves for sand, loam, and clay 163
Figure 4f-5. Ainsworth Unit in northern Nebraska 167
Figure 4f-6. Water infiltration characteristics for sprinkler, border,
and furrow irrigation systems 165
Figure 4f-7. Irrigation system options for irrigation by gravity 167
Figure 4f-8. Typical types of sprinkler irrigation systems 168
Figure 4f-9. Micro-irrigation system components 168
Figure 4f-10. Basin bubbler system 169
Figure 4f-ll. Typical irrigation system layouts 170
Table 4f-2. Types of irrigation systems 173
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Figure 4f-12. Fate of water and pollutants in an irrigated hydrologic system 174
Figure 4f-13. Typical water extraction pattern in uniform soil profile 176
Figure 4f-14. Soil moisture measurement devices 176
Table 4f-3. Devices and methods to measure soil moisture 177
Figure 4f-15. Graphical format for irrigation scheduling 178
Equation 4f-l. Soil-water depletion volume 178
Figure 4f-16. Crop water use for corn, wheat, soybean, and potato based on average
climatic conditions for North Dakota 179
Figure 4f-17. NRCS (SCS) Scheduler-seasonal crop ET 179
Table 4f-4. System capacity needed in gal/min-acre for different soil textures and
crops to supply sufficient water in 9 out of 10 years 181
Table 4f-5. Measures of irrigation efficiency 182
Figure 4f-18. Typical tailwater collection and reuse facility for quick-cycling
pump and reservoir 184
Figure 4f-19. Basic components of a trickle irrigation system 189
Figure 4f-20. Backflow prevention device using check valve with vacuum
relief and low pressure drain 192
Table 4f-6. Sediment removal efficiencies and comments on BMPs evaluated 194
Table 4f-7. Ranges of irrigation application efficiencies from various sources 194
Table 4f-8. Ranges of application efficiency and runoff, deep percolation, and
evaporation losses 194
Table 4f-9. Overall efficiencies obtainable by using tailwater recovery and reuse facility 195
Table 4f-10. Irrigation efficiencies of selected irrigation systems for cotton 195
Table 4f-ll. Cost of soil water measuring devices 197
Highlight - Polyacrylamide application for erosion and infiltration management 198
Table 4f-12. Design lifetime for selected salt load reduction measures 201
Chapter 5: Using Management Measures to Prevent
and Solve Nonpoint Source Problems in Watersheds 203
Highlight - Basins 2.0: A powerful tool for managing watersheds 210
Table 5-1. Sediment removal effectiveness of selected individual BMPs 213
Chapter 6: Monitoring and Tracking Techniques 215
Figure 6-1. Development of a monitoring project 216
Table 6-1. General characteristics of monitoring types 218
Figure 6-2. Land treatment and water quality monitoring program design 221
Table 6-2. Common QA and QC activities 223
Chapter?: Load Estimation Techniques 225
Figure 7-1. Flux and cumulative load over time 231
Figure 7-2. Effect of missing concentration data 232
Figure 7-3. Load estimation models 235
National Management Measures to Control Nonpoint Pollution from Agriculture ix
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Introduction
The nation's aquatic resources are among its most valuable assets. While
environmental protection programs in the United States have successfully
improved water quality during the past 25 years, many challenges still remain.
Although significant strides have been made in reducing the impacts of discrete
pollutant sources, aquatic ecosystems remain impaired, primarily due to com-
plex pollution problems caused by nonpoint source (NFS) pollution.
The most recent national water quality inventory shows that, as of 2000, 39% of
assessed stream miles, 45% of assessed lake acres, and 51% of assessed estuary
acres are impaired. The leading causes of impairment are nutrients, siltation,
metals, and pathogens. State inventories indicate that agriculture, including crop
production, animal operations, pastures, and rangeland, impacts 18% of the total
river and stream miles assessed, or 48% of the river and streams identified as
impaired (EPA, 2002).
The Purpose and Scope of this Guidance
This guidance document is intended to provide technical information to state
program managers and others on the best available, economically achievable
means of reducing NFS pollution of surface and ground water from agriculture.
The guidance provides background information about agricultural NFS pollu-
tion, where it comes from and how it enters the nation's waters, discusses the
broad concept of assessing and addressing water quality problems on a water-
shed level, and presents up-to-date technical information about how to reduce
agricultural NFS pollution. This document is not intended to be a "how to"
technical guide for natural resource assessment, planning, design, and imple-
mentation.
The causes of agricultural NFS pollution, specific pollutants of concern, and
general approaches to reducing the impact of such pollutants on aquatic re-
sources are discussed in the Overview (Chapter 2). A general discussion of best
management practices (BMPs) and the use of combinations of individual
practices (BMP systems) to protect surface and ground water is given in Chapter
3. Management measures for nutrient management; pesticide management;
erosion and sediment control; managing facility wastewater, manure and runoff
from animal feeding operations; grazing management; and irrigation water
management are described in Chapter 4. Also in Chapter 4 are discussions of
BMPs that can be used to achieve the management measures, including cost and
effectiveness information. Chapter 5 summarizes watershed planning principles,
and Chapters 6 and 7 give overviews of nonpoint source monitoring and pollut-
ant load estimation, respectively.
While the scope of this guidance is broad, covering diverse agricultural NFS
pollutants from a range of sources, there are a number of issues that are not
covered. Such issues include nutrient transfer over long distances (e.g., the
Agriculture is listed
as a source of
pollution for 48% of
the impaired river
miles reported in the
United States.
This guidance is
designed to provide
current information
to state program
managers on
controlling
agricultural nonpoint
source pollution.
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1-1
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Chapter 1: Introduction
This document does
not impose legally-
binding requirements
on EPA, the states,
or the public.
This guidance does
NOT replace the
1993 Guidance
Specifying
Management
Measures for
Sources of Nonpoint
Pollution in Coastal
Waters.
shipping of feed from one state to another in which the resulting animal waste is
then applied to fields), animal nutrition (e.g., changing the nutrient mix fed to
livestock as an approach to managing nutrients in animal waste), alternatives for
manure (such as composting or regional distribution of manure from farms that
do not need it to farms that can use it), odor control, and methane production.
Furthermore, because it is national in scope, this document cannot address all
practices or techniques specific to local or regional soils, climate, or agronomic
conditions. In addition, new BMPs are being developed as a result of ongoing
agricultural research. Readers should consult with state or local agencies includ-
ing the United States Department of Agriculture (USDA)-Natural Resources
Conservation Service (NRCS), Cooperative Extension, land grant universities,
conservation districts, and agricultural organizations for additional information
on agricultural nonpoint source pollution controls applicable to their local area.
This document provides guidance to states, territories, authorized tribes, and the
public regarding management measures that may be used to reduce nonpoint
source pollution from agricultural activities. This document refers to statutory
and regulatory provisions which contain legally binding requirements. This
document does not substitute for those provisions or regulations, nor is it a
regulation itself. Thus, it does not impose legally-binding requirements on EPA,
states, territories, authorized tribes, or the public and may not apply to a particu-
lar situation based upon the circumstances. EPA, state, territory, and authorized
tribe decision makers retain the discretion to adopt approaches on a case-by-case
basis that differ from this guidance where appropriate. EPA may change this
guidance in the future.
Readers should note that this guidance is entirely consistent with the Guidance
Specifying Management Measures for Sources of Nonpoint Pollution in Coastal
Waters (EPA, 1993a) published under Section 6217 of the Coastal Zone Act
Reauthorization Amendments of 1990 (CZARA). This guidance, however, does
not supplant or replace the 1993 coastal management measures guidance for the
purpose of implementing programs under Section 6217.
Under CZARA, states that participate in the Coastal Zone Management Program
under the Coastal Zone Management Act are required to develop coastal
nonpoint pollution control programs that ensure the implementation of EPA's
management measures in their coastal management area. The 1993 guidance
continues to apply to that program.
This document modifies and expands upon supplementary technical information
contained in the Coastal Management Measures Guidance both to reflect cir-
cumstances relevant to differing inland conditions and to provide current techni-
cal information. It does not set new or additional standards for either CZARA
Section 6217 Coastal Nonpoint Pollution Control Programs or Clean Water Act
Section 319 Nonpoint Source Management Programs. It does, however, provide
information that can be used by government agencies, private sector groups, and
individuals to understand and apply measures and practices to address agricul-
tural sources of nonpoint source pollution.
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Chapter 1: Introduction
What is Nonpoint Source Pollution?
Nonpoint source pollution generally results from precipitation, land runoff,
infiltration, drainage, seepage, hydrologic modification, or atmospheric deposi-
tion. As runoff from rainfall or snowmelt moves, it picks up and transports
natural pollutants and pollutants resulting from human activity, ultimately
depositing them into rivers, lakes, wetlands, coastal waters, and ground water.
Technically, the term nonpoint source is defined to mean any source of water
pollution that does not meet the legal definition of point source in Section
502(14) of the Clean Water Act of 1987:
The term point source means any discernible, confined
and discrete conveyance, including but not limited to any
pipe, ditch, channel, tunnel, conduit, well, discrete fissure,
container, rolling stock, concentrated animal feeding
operation, or vessel or other floating craft from which
pollutants are or may be discharged. This term does not
include agricultural stormwater discharges and return
flows from irrigated agriculture.
Although diffuse runoff is generally treated as nonpoint source pollution, runoff
that enters and is discharged from conveyances such as those described above is
treated as a point source discharge and hence is subject to the permit require-
ments of the Clean Water Act. In contrast, nonpoint sources are not subject to
federal permit requirements. Point sources generally enter receiving water
bodies at some identifiable site(s) and carry pollutants whose generation is
controlled by some internal process or activity, rather than weather. Point source
discharges such as municipal and industrial waste waters, runoff or leachate
from solid waste disposal sites and concentrated animal feeding operations, and
storm sewer outfalls from large urban centers are regulated and permitted under
the Clean Water Act.
While it is imperative that water program managers understand and manage in
accordance with legal definitions and requirements, the non-legal community
often characterizes nonpoint sources in the following ways:
G Nonpoint source discharges enter surface and/or ground waters in a
diffuse manner at intermittent intervals related mostly to meteorological
events.
G Pollutant generation arises over an extensive land area and moves
overland before it reaches surface waters or infiltrates into ground
waters.
G The extent of NFS pollution is related to uncontrollable climatic events
and to geographic and geologic conditions and varies greatly from place
to place and from year to year.
G The extent of NPS pollution is often more difficult or expensive to
monitor at the point(s) of origin, as compared to monitoring of point
sources.
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Chapter 1: Introduction
Section 319 requires
states to assess
NPS pollution and
implement
management
programs.
Section 319
authorizes EPA to
provide grants to
assist state NPS
pollution control
programs.
d Abatement of nonpoint sources is focused on land and runoff manage-
ment practices, rather than on effluent treatment.
O Nonpoint source pollutants may be transported and/or deposited as
airborne contaminants.
Nonpoint source pollutants that cause the greatest impacts are sediments,
nutrients, toxic compounds, organic matter, and pathogens. Hydrologic modifi-
cation can also cause adverse effects on the biological, physical, and chemical
integrity of surface and ground waters.
National Efforts to
Address Nonpoint Source Pollution
Nonpoint Source Program — Section 319 of the
Clean Water Act
During the first 15 years of the national program to abate and control water
pollution (1972-1987), EPA and the states focused most of their water pollution
control activities on traditional point sources. These point sources are regulated
by EPA and the states through the National Pollutant Discharge Elimination
System (NPDES) permit program established by Section 402 of the 1972
Federal Water Pollution Control Act (Clean Water Act). Discharges of dredged
and fill materials into wetlands have also been regulated by the U.S. Army Corps
of Engineers and EPA under Section 404 of the Clean Water Act.
As a result of the above activities, the nation has greatly reduced pollutant loads
from point source discharges and has made considerable progress in restoring
and maintaining water quality. However, the gains in controlling point sources
have not solved all of the nation's water quality problems. Recent studies and
surveys by EPA and by states, tribes, territories, and other entities, indicate that
the majority of the remaining water quality impairments in our nation's rivers,
streams, lakes, estuaries, coastal waters, and wetlands result from NPS pollution
and other nontraditional sources, such as urban storm water discharges and
combined sewer overflows.
In 1987, in view of the progress achieved in controlling point sources and the
growing national awareness of the increasingly dominant influence of NPS
pollution on water quality, Congress amended the Clean Water Act to provide a
national framework to address nonpoint source pollution. Under this amended
version, referred to as the 1987 Water Quality Act, Congress revised Section
101, "Declaration of Goals and Policy," to add the following fundamental
principle:
It is the national policy that programs for the control of
nonpoint sources of pollution be developed and
implemented in an expeditious manner so as to enable the
goals of this Act to be met through the control of both point
and nonpoint sources of pollution.
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 1: Introduction
More importantly, Congress enacted Section 319 of the 1987 Water Quality Act,
which established a national program to address nonpoint sources of water
pollution. Under Section 319, states address NFS pollution by assessing NFS
pollution problems and causes within the state and implementing management
programs to control the NFS pollution. Section 319 authorizes EPA to issue
grants to states to assist them in implementing management programs or portions
of management programs which have been approved by EPA. For additional
information and a list of state contacts, see www.epa.gov/owow/nps.
National Estuary Program
EPA also administers the National Estuary Program under Section 320 of the
Clean Water Act. This program focuses on point and NFS pollution in geo-
graphically targeted, high-priority estuarine waters. In this program, EPA assists
state, regional, and local governments in developing and implementing compre-
hensive conservation and management plans that recommend priority corrective
actions to restore estuarine water quality, fish populations, and other designated
uses of the waters.
Pesticides Program
Another program administered by EPA that controls some forms of NFS pollu-
tion is the pesticides program under the Federal Insecticide, Fungicide, and
Rodenticide Act (FIFRA). Among other provisions, this program authorizes EPA
to control pesticides that may threaten ground and surface water. FIFRA pro-
vides for the registration of pesticides and enforceable label requirements, which
may include maximum rates of application, restrictions on use practices, and
classification of pesticides as "restricted use" pesticides (which restricts use to
certified applicators trained to handle toxic chemicals).
Coastal Nonpoint Pollution Control Program
In November 1990, Congress enacted the Coastal Zone Act Reauthorization
Amendments (CZARA). These amendments were intended to address several
concerns, including the impact of NFS pollution on coastal waters.
To more specifically address the impacts of NFS pollution on coastal water
quality, Congress enacted Section 6217, Protecting Coastal Waters (codified as
16 U.S.C. Section 1455b). Section 6217 provides that each state with an ap-
proved Coastal Zone Management Program must develop and submit to EPA and
the National Oceanic and Atmospheric Administration (NOAA) for approval a
Coastal Nonpoint Pollution Control Program. The purpose of the program "shall
be to develop and implement management measures for nonpoint source pollu-
tion to restore and protect coastal waters, working in close conjunction with
other state and local authorities."
Coastal Nonpoint Pollution Control Programs are not intended to supplant
existing coastal zone management programs and NFS management programs.
Rather, they are intended to serve as an update and expansion of existing NFS
The Federal Coastal
Nonpoint Pollution
Control Program
(6217) is designed
to enhance state and
local efforts to
manage land use
activities that
degrade coastal
habitats and waters.
National Management Measures to Control Nonpoint Pollution from Agriculture
1-5
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Chapter 1: Introduction
In selected
watersheds, the
RCWP showed that
implementation of
agricultural BMPs
improved water
quality.
management programs and are to be coordinated closely with the coastal zone
management programs that states and territories are already implementing
pursuant to the Coastal Zone Management Act of 1972. The legislative history
indicates that the central purpose of Section 6217 is to strengthen the links
between federal and state Coastal Zone Management and Water Quality Pro-
grams and to enhance state and local efforts to manage land use activities that
degrade coastal waters and habitats.
Section 6217(g) of CZARA requires EPA to publish, in consultation with
NOAA, the U.S. Fish and Wildlife Service, and other federal agencies, "guid-
ance for specifying management measures for sources of nonpoint pollution in
coastal waters." Management measures are defined in Section 6217(g)(5) as:
economically achievable measures for the control of the
addition of pollutants from existing and new categories
and classes of nonpoint sources of pollution, which reflect
the greatest degree of pollutant reduction achievable
through the application of the best available nonpoint
source control practices, technologies, processes, siting
criteria, operating methods, or other alternatives.
EPA published Guidance Specifying Management Measures for Sources of
Nonpoint Source Pollution in Coastal Waters (EPA, 1993a). In EPA's (1993a)
document, management measures for urban areas; agricultural sources; forestry;
marinas and recreational boating; hydromodification (channelization and chan-
nel modification, dams, and streambank and shoreline erosion); and wetlands,
riparian areas, and vegetated treatment systems were defined and described. The
management measures for controlling agricultural NFS pollution discussed in
Chapter 4 of this document are based on those outlined by EPA (1993a).
Source Water Protection Program
The 1996 Amendments to the Safe Drinking Water Act provided for source
water assessment and protection programs to prevent drinking water contamina-
tion. States are required to develop comprehensive Source Water Assessment
Programs (SWAPs) that will: identify the areas that supply public tap water;
inventory contaminants and assess water system susceptibility to contamination
and inform the public of the results. EPA is responsible for the review and
approval of state SWAPs. Several programs specifically address ground water
protection.
Rural Clean Water Program (RCWP)
The Rural Clean Water Program (RCWP), an NFS pollution control program
implemented by USDA and EPA, was conducted from 1980 to 1990 as an
experimental effort to address agricultural NFS pollution in watersheds across
the country.
The objectives of the RCWP were to:
G Achieve improved water quality in the approved project area in the most
cost-effective manner possible while providing food, fiber, and a quality
environment;
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 1; Introduction
G Assist agricultural landowners and farm operators in reducing agricul-
tural NFS water pollutants and improving water quality in rural areas to
meet water quality standards or goals; and
O Develop and test programs, policies, and procedures for the control of
agricultural NFS pollution.
Twenty-one experimental projects were funded across the United States. Each
project included implementation of BMPs to reduce NFS pollution and water
quality monitoring to evaluate the effects of BMPs. The BMPs were targeted to
critical areas in each project — sources of NFS pollutants identified as having
significant impacts on the impaired water resource. Landowner participation was
voluntary, with cost-sharing and technical assistance offered as incentives for
implementing BMPs.
The linkage of water quality monitoring to land treatment efforts in the RCWP
helped improve targeting of BMPs to sources most in need of treatment. Water
quality findings from the RCWP projects were also used to adjust and refine
agricultural NFS programs and BMPs. Additional details are available in the
project evaluation report (EPA, 1993c).
2002 Farm Bill Conservation Provisions
Technical and financial assistance for landowners seeking to conserve, improve,
and sustain our soil and other natural resources is authorized by the federal
government under provisions of the Food Security and Rural Investment Act
(Farm Bill). The following sections summarize provisions in the 2002 Act
relating directly to installation and maintenance of BMPs. For additional infor-
mation, see the U.S. Department of Agriculture's website at www.usda.gov.
Environmental Quality Incentives Program (EQIP) — The EQIP was
established by the 1996 Farm Bill to provide a voluntary conservation program
for farmers and ranchers who face serious threats to soil, water, and related
natural resources. Funding increases are authorized from $200 million to
$1.1 billion between 2002 and 2007. EQIP offers financial, technical, and
educational help to install or implement structural, vegetative, and management
practices designed to conserve soil and other natural resources. The law dictates
that 60% of the available monies be directed to livestock-related concerns. Cost-
sharing generally pays up to 75% of the costs for certain conservation practices.
Incentive payments may be made to encourage producers to perform land
management practices such as nutrient management, manure management,
integrated pest management, irrigation water management, and wildlife habitat
management. Cost-share for construction of animal waste management facilities
is now allowed for livestock operations over 1,000 animal units.
Conservation Reserve Program (CRP) — First authorized by the Food
Security Act of 1985 (Farm Bill), this is a voluntary program that offers annual
rental payments, incentive payments, and cost-share assistance for establishing
long-term, resource-conserving cover crops on highly credible land. Conserva-
tion Reserve Program contracts are issued for a duration of 10 to 15 years for up
to 39.2 million acres of cropland and marginal pasture. Land can be accepted
into the CRP through a competitive bidding process where all offers are ranked
using an environmental benefits index, or through continuous sign-up for
Many Farm Bill
programs provide
funds for land
treatment. Please
contact your state or
local USDA office for
details.
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 1: Introduction
eligible lands where certain special conservation practices (e.g. filter strips and
riparian buffers) will be implemented.
Conservation Security Program — This 2002 Farm Bill program provides
incentive payments to producers who adopt or maintain existing conservation
practices. Producers may receive up to 20,000, 35,000, or 45,000 dollars per
year for practice falling into 3 tiers. The higher payments go to the more com-
prehensive sets of practices. The program contracts are for 5 to 10 years.
The Conservation Reserve Enhancement Program (CREP) is a 1996 initiative
continued in the 2002 Farm Bill. CREP is a joint, state-federal program designed
to meet specific conservation objectives. CREP targets state and federal funds to
achieve shared environmental goals of national and state significance. The
program uses financial incentives to encourage farmers and ranchers to voluntar-
ily protect soil, water, and wildlife resources.
Wetlands Reserve Program (WRP) — The WRP is a voluntary program to
restore and protect wetlands and associated lands. Participants may sell a
permanent or 30-year conservation easement or enter into a 10-year cost-share
agreement with USDA to restore and protect wetlands. The landowner voluntarily
limits future use of the land, yet retains private ownership. The NRCS provides
technical assistance in developing a plan for restoration and maintenance of the
land. The landowner retains the right to control access to the land and may lease
the land for hunting, fishing, and other undeveloped recreational activities. The
acreage is expanded by 1.2 million acres to 2.275 million acres in 2002.
Wildlife Habitat Incentives Program (WHIP) — This program is designed for
people who want to develop and improve wildlife habitat on private lands. Plans
are developed in consultation with the NRCS and local Conservation District.
USDA will provide technical assistance and cost-share up to 75% of the cost of
installing the wildlife practices. Participants may get bonus payments for agree-
ments over 15 years.
Forest Land Enhancement Program (FLEP) — Authorized in the 2002 Farm
Bill, the FLEP creates a new title for Forestry. It replaces and expands the
Stewardship Incentive program and Forestry program. The new Forest Land
Enhancement program will provide up to $100 million over six years to private,
non-industrial Forest owners. The new title also provides $210 million to help
fight fire on private land and address prevention.
Grazing Reserve Program (GRP) — This 2002 provision will use 30 year
easements and rental agreements to improve management of up to 2 million
acres of private grazing land. 500,000 acres are to be reserved for protected
tracts of 40 acres or less as native grasslands. Restoration costs may go as high
as 75%.
Funding Sources
For information on sources of funding to address nonpoint source pollution, see
EPA's Nonpoint Source website at www.epa.gov/owow/nps/funding.html.
1-8 National Management Measures to Control Nonpoint Pollution from Agriculture
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Overview
Agricultural Nonpoint Source Pollution
State water quality assessments continue to show that nonpoint source pollution
is the leading cause of impairments in surface waters of the U.S. According to
these assessments, agriculture is the most wide-spread source of pollution for
assessed rivers and lakes. Agriculture impacts 18% of assessed river miles and 14%
of assessed lake acres. The state reports also indicate that agriculture impacts
48% of impaired river miles and 41% of impaired lake acres (EPA, 2002).
The primary agricultural NFS pollutants are nutrients, sediment, animal wastes,
salts, and pesticides. Agricultural activities also have the potential to directly
impact the habitat of aquatic species through physical disturbances caused by
livestock or equipment. Although agricultural NFS pollution is a serious prob-
lem nationally, a great deal has been accomplished over the past several decades
in terms of sediment and nutrient reduction from privately-owned agricultural
lands. Much has been learned in the recent past about more effective ways to
prevent and reduce NFS pollution from agricultural activities.
The purpose of this chapter is to describe the general causes of agricultural NFS
pollution, the specific pollutants and problems of concern, and the general
approaches that have been found most effective in reducing the impact of such
pollutants and problems on aquatic resources.
Nutrients
Nitrogen (N) and phosphorus (P) are the two major nutrients from agricultural
land that degrade water quality. Nutrients are applied to agricultural land in
several different forms and come from various sources, including:
G Commercial fertilizer in a dry or fluid form, containing nitrogen,
phosphorus, potassium (K), secondary nutrients, and micronutrients;
G Manure from animal production facilities including bedding and other
wastes added to the manure, containing N, P, K, secondary nutrients,
micronutrients, salts, some metals, and organics;
G Municipal and industrial treatment plant sludge, containing N, P, K,
secondary nutrients, micronutrients, salts, metals, and organic solids;
G Municipal and industrial treatment plant effluent, containing N, P, K,
secondary nutrients, micronutrients, salts, metals, and organics;
G Legumes and crop residues containing N, P, K, secondary nutrients, and
micronutrients;
G Irrigation water;
D Wildlife; and
G Atmospheric deposition of nutrients such as nitrogen, phosphorus, and
sulphur.
Commercial
fertilizers and
manure are the
primary sources of
crop nutrients for
agriculture.
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2-9
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Chapter 2: Overview
Overloading with
nitrogen and
phosphorus causes
eutrophication which
reduces the
suitability of
waterways for
beneficial uses.
In addition, decomposition of organic matter and crop residue may be a source
of mobile forms of nitrogen, phosphorus, and other essential crop nutrients.
Surface water runoff from agricultural lands may transport the following pollutants:
d Particulate-bound nutrients, chemicals, and metals, such as phosphorus,
organic nitrogen, and metals applied with some organic wastes;
d Soluble nutrients and chemicals, such as nitrogen, phosphorus, metals,
and many other major and minor nutrients;
D Particulate organic solids, oxygen-demanding material, and bacteria,
viruses, and other microorganisms applied with some organic waste; and
a Salts.
Ground water infiltration from agricultural lands to which nutrients have been
applied may transport the following pollutants:
n Soluble nutrients and chemicals, such as nitrogen, phosphorus, metals;
Gl Other major and minor nutrients;
D Salts; and
n Bacteria and other pathogens applied with some organic waste.
All plants require nutrients for growth. Nitrogen and phosphorus generally are
present in aquatic environments at background or natural levels below 0.3 and
0.01 mg/L, respectively. When these nutrients are introduced into a stream, lake,
or estuary at higher rates, aquatic plant productivity may increase dramatically.
This process, referred to as cultural eutrophication, may adversely affect the
suitability of the water for other uses.
Excessive aquatic plant productivity results in the addition to the system of more
organic material, which eventually dies and decays. Bacteria decomposing this
organic matter produce unpleasant odors and deplete the oxygen supply avail-
able to other aquatic organisms. Depleted oxygen levels, especially in colder
bottom waters where dead organic matter tends to accumulate, can reduce the
quality of fish habitat and encourage the propagation of fish that are adapted to
less oxygen or to warmer surface waters. Anaerobic conditions can also cause
the release of additional nutrients from bottom sediments.
Highly enriched waters will stimulate algae production, consequently increasing
turbidity and color. In addition, certain algae can produce severe taste and odor
problems that impair the quality of drinking water sources (EPA, 1999a). For
example, the City of Tulsa, OK spends an additional $100,000 a year to correct
taste and odor problems, resulting from extreme algae growth in the city's drink-
ing water source (Lassek, 1997). Excess algae growth may also interfere with
recreational activities such as swimming and boating. Algae growth is also believed
to be harmful to coral reefs (e.g., Florida coast). Furthermore, the increased
turbidity results in less sunlight penetration and availability to submerged
aquatic vegetation (SAV). Since SAV provides habitat for small or juvenile fish,
the loss of SAV has severe consequences for the food chain. Tampa Bay is an
example in which nutrients are believed to have contributed to SAV loss.
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 2: Overview
Nitrogen
All forms of transported nitrogen are potential contributors to eutrophication in
lakes, estuaries, and some coastal waters. In general, though not in all cases,
nitrogen availability is the limiting factor for plant growth in marine ecosystems.
Thus, the addition of nitrogen can have a significant effect on the natural func-
tioning of marine ecosystems.
Eutrophication in coastal waters has been linked to increased nutrient loads from
rivers, as evidenced by increasing incidence of noxious algal blooms and hy-
poxia in bottom waters (Justic et al., 1995.) The Gulf of Mexico has experienced
midsummer hypoxia (low dissolved oxygen) since the early 1970s. From 1993
through 1999, the extent of bottom-water hypoxia ranged from about 6,200 to 7,700
square miles (16,000 to 20,000 km2), greater than twice the surface area of the
Chesapeake Bay (Rabalais et al., 1999). The hypoxia is thought to be due to
eutrophication resulting from high nutrient loading to the Gulf. Recent analysis has
shown that about 89 percent of the annual total nitrogen flux to the Gulf (1.57
million metric tons) was from nonpoint sources, and the remaining 11 percent was
from municipal and industrial point sources (Goolsby and Battaglin, 2000).
The toxic dinoflagellate Pfiesteria piscicida, implicated in causing about 50% of
the major fish kills in North Carolina's estuaries and coastal waters from 1991 to
1993, has been linked to conditions of over-enrichment of nutrients such as
nitrogen and phosphorus (Burkholder, 1996). More research is needed to deter-
mine the specific physical, chemical, and biological factors that promote out-
breaks of Pfiesteria piscicida. Pfiesteria-like species have also been tracked to
eutrophic sudden-death fish kill sites in estuaries, coastal waters, and aquacul-
ture facilities from the mid-Atlantic through the Gulf Coast (Burkholder et al.,
1995).
Excessive ammonia
In addition to eutrophication, excessive nitrogen causes other water quality can be toxic to fish.
problems. Dissolved ammonia at concentrations above 0,2 mg/L may be toxic to —^^——•—
fish, especially trout. Also, nitrates in drinking water are potentially dangerous
to newborn infants. Nitrate is converted to nitrite in the digestive tract, which
reduces the oxygen-carrying capacity of the blood (methemoglobinemia),
resulting in brain damage or even death. The U.S. Environmental Protection
Agency has set a limit of 10 mg/L nitrate-nitrogen in water used for human
consumption (EPA, 1989a).
Nitrogen is naturally present in soils but must be added to meet crop production
needs. Nitrogen is added to the soil primarily by applying commercial fertilizers
and manure, but also by growing legumes (biological nitrogen fixation) and
incorporating crop residues. Not all nitrogen that is present in or on the soil is
available for plant use at any one time. Applied nitrogen may be stored in the
soil as organic material, soil organic matter (humus), or adsorbed to soil par-
ticles. For example, in the eastern Corn Belt, it is normally assumed that about
50% of applied nitrogen is assimilated by crops during the year of application
(Nelson, 1985). Organic nitrogen normally constitutes the majority of the soil
nitrogen. It is slowly converted (2 to 3% per year) to the more readily plant-
available inorganic ammonium or nitrate. Nitrogen conversions are governed by
carbon to nitrogen rations of crop residue and environmental conditions (e.g.,
temperature, moisture).
National Management Measures to Control Nonpoint Pollution from Agriculture 2-11
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Chapter 2: Overview
Nitrate-nitrogen can
readily leach below
the root zone into
shallow ground water
and can threaten
water supplies if it
exceeds water
quality standards.
The chemical form of nitrogen affects its impact on water quality. The most
biologically important inorganic forms of nitrogen are ammonium (NH4-N),
nitrate (NO3-N), and nitrite (NO2-N). Organic nitrogen occurs as paniculate
matter, in living organisms, and as detritus. It occurs in dissolved form in
compounds such as amino acids, amines, purines, and urea.
Nitrate-nitrogen is highly mobile and can move readily below the crop root zone,
especially in sandy soils. It can also be transported in surface runoff. Ammo-
nium, on the other hand, becomes adsorbed to the soil and is lost primarily with
eroding sediment. Even if nitrogen is not in a readily available form as it leaves
the field, it can be converted to an available form either during transport or after
delivery to water bodies.
Data collected in the U.S. Geological Survey NAWQA program sites showed
that nitrate concentrations in ground water were highest in samples from wells in
agricultural areas, with concentrations exceeding the drinking water standard of
10 mg/L in about 12% of domestic wells (Mueller and Helsel, 1996). Over the
period 1986 - 1992, annual flow-weighted mean nitrate concentrations in ground
water in the highly agricultural Big Spring basin of Iowa ranged from 5.7 mg/L
in the very dry water year 1989 to 12.5 mg/L in the very wet water year 1991
(Rowdenetal.,1995).
Across the U.S., nitrate levels in ground water are associated with source
availability (i.e., population density, nitrogen inputs in fertilizer, manure, and
atmospheric sources) and regional environmental factors (i.e., soil drainage
characteristics, precipitation, cropland acres) (Spalding and Exner, 1993; Nolan
et al., 1997). In Iowa's Big Spring basin, for example, the proportion of land in
corn directly affected nitrogen concentrations and loads to surface and ground
water because the greatest nitrogen inputs were fertilizers applied to corn
(Rowden et al.,1995). In general, areas with high nitrogen input, well-drained
soils, and high cropland areas have the highest potential for ground water
contamination by nitrate (Nolan et al., 1997). Large areas of ground water where
nitrate concentrations exceed the 10 mg/L limit occur in regions of irrigated
cropland on well-drained soils; most of these areas are west of the Mississippi
River where irrigation is necessary (Spalding and Exner, 1993). In the eastern
U.S., localized nitrate-nitrogen contamination occurs beneath cropped, well-
drained soils that receive excessive applications of fertilizer and manure, notably
in the middle Atlantic states and the Delmarva Peninsula.
Soil drainage has reduced ground water nitrate problems in the Corn Belt states,
because extensive tiling and ditching intercept soil water and carry it to surface
water. High nitrogen inputs in such areas are more likely to affect surface water
than ground water (Nolan et al., 1997). Studies in Walnut Creek, Iowa, showed
that nitrate levels in the stream ranged from 10 to 20 mg/L (Hatfield et al.,
1995). Walnut Creek, like many Midwestern streams, is fed by subsurface
drainage, and high nitrate levels originated from the bottom of the root zone (1 -
1.2 m) in corn-soybean cropland in the watershed.
Phosphorus
Phosphorus can also contribute to the eutrophication of both freshwater and
estuarine systems. Studies on the Cannonsville Reservoir, New York, showed
that eutrophication was accelerated by phosphorus loading (Brown et al., 1986).
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 2; Overview
The low dissolved oxygen levels associated with eutrophication impacted fish
populations, and use of the lake for recreational fishing was much less than at
nearby Pepacton Reservoir. Moreover, the accelerated phosphorus loadings also
contributed to the impairment of the drinking water supply for New York City
because both reservoirs serve as major drinking water sources for the New York
City water supply system. Also, nutrients are the major cause of use impairment
in Lake Champlain, Vermont, with phosphorus the main culprit (Vermont
Agency of Natural Resources, 1996). It is estimated that 55 - 66% of the NFS
phosphorus load to Lake Champlain is derived from agricultural activities
(Meals and Budd, 1998; Hegman et al., 1999).
While phosphorus typically plays the controlling role in freshwater systems, in
some estuarine systems both nitrogen and phosphorus can limit plant growth.
Algae consume dissolved inorganic phosphorus and convert it to the organic
form. Phosphorus is rarely found in concentrations high enough to be toxic to
higher-level organisms.
Phosphorus can be found in the soil in dissolved, colloidal, or particulate forms.
Although the phosphorus content of most soils in their natural condition is low
(between 0.01 and 0.2% by weight), soil test data indicate that decades of P
application to agricultural land in excess of crop removal have resulted in
widespread increases in soil P levels in the U.S. and elsewhere (Sims, 1993;
Sharpley et al., 1993; Sims et al., 2000). Long-term trends in soil test values
show that soil P in many areas of the world is excessive, relative to crop require-
ments; the greatest concern occurs with animal-based agriculture, where farm
and watershed-scale P surpluses and over-application of P to soils are common
(Sims et al., 2000). Manures are normally applied at rates needed to meet crop
nitrogen needs, yet the ratio of nitrogen to phosphorus in most manures results
in over-application of phosphorus (Sharpley et al., 1996).
Most often,
phosphorus is
sediment-attached.
Phosphorus may
also be dissolved.
Either form can
contribute to
eutrophication.
The main forces controlling P movement from land to water are transport
(runoff, infiltration, and erosion) and source factors (surface soil P and manage-
ment of fertilizer/manure applications) (Sharpley et al., 1993; Daniel et al.,
1998). Erosion processes control particulate P movement, while runoff processes
drive dissolved P movement. Particulate P movement is a complex function of
rainfall, irrigation, runoff, and soil management factors affecting erosion.
Movement of dissolved P is a function of sorption/desorption, dissolution, and
extraction of P from soil and plant material by water. Whereas surface runoff is
typically the dominant pathway of P loss from agricultural land, there is increas-
ing evidence that leaching of P from some soil types, especially on tile-drained
fields, can present a threat to water quality (Beauchemin et al. 1998; Schoumans
and Groenendijk, 2000; Simard et al., 2000).
Farm practices, such as manure or fertilizer applications and tillage, largely
determine the quantity of P available in the soil to be moved by transport factors.
Accumulation of P near the soil surface (0-2 inches) has been widely observed
to influence the concentration and loss of P in runoff. Significant linear relation-
ships have been demonstrated on a variety of soils and cropping systems be-
tween the amount of soil test P in surface soil and dissolved P concentrations in
surface runoff (Sharpley et al., 1993; Sharpley, 1995b; Pote et al., 1996; Pote et
al., 1999; Sims et al., 2000; Sharpley et al., 2000; Sims, 2000). Soil P saturation
status, rather than simply soil test P value, is thought to be a better predictor of
runoff P loss, especially as the theoretical basis to establish environmental soil
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 2: Overview
test P limits, because it integrates the effect of soil type (Sharpley, 1995b; Sims
etal.,2000).
While there is little doubt that increased P concentrations at the soil surface
contribute to higher P concentrations in runoff, the value of using soil test P as
the sole predictor of transportable P is questionable (Coale, 2000). Consideration
of hydrology is critical to understanding P export from a watershed. (Daniel et
al., 1998). Chemical soil tests quantify concentration of soluble, biologically
available, and potentially desorbable P in soils, but they provide no information
on transport processes and management practices that influence movement of P
from soil to water. They also do not characterize direct release of P from fertiliz-
ers, animal manure, and biosolids applied to soils (Sims et al., 2000).
Although soil P content is clearly important in determining the concentration of
P in agricultural runoff, surface runoff and erosion potential, as well as misman-
agement of fresh P inputs will often override soil P levels in determining P
export. Use of a single threshold value for soil test P is too limited in its predic-
tion of surface runoff P to be the only criterion to guide P management
(Sharpley, 2000). Data from soil P testing must be integrated with understanding
of transport processes and information on P management to predict P loss to
water.
Lemunyon and Gilbert (1993) described an index for identifying soils, land-
forms, and management practices that could cause phosphorus problems in water
bodies. The index uses soil erosion rates, runoff, soil test values of available
phosphorus, and fertilizer and organic phosphorus application rates to assess the
potential for phosphorus movement from the site. Sharpley (1995a) applied the
Lemunyon and Gilbert phosphorus index to 30 watersheds in the Southern
Plains, and concluded that the index is a valuable tool for identifying sources
where phosphorus management is most needed. Several recommendations were
made for improving the accuracy and utility of the index.
Gburek et al. (2000a and 2000b) have stressed that management of watershed
phosphorus export should focus not just on areas of high soil P or P saturation
but on critical source areas (CSA) that represent the intersection of surface
runoff source areas (i.e., areas of actual or potential transport mechanisms) with
areas of high soil P and high fertilizer/manure application. It is suggested that
management of phosphorus loss from agricultural watersheds must focus on
identifying, targeting, and remediating these spatially variable areas.
Runoff and erosion can carry some phosphorus to nearby water bodies. Dis-
solved inorganic phosphorus (orthophosphate phosphorus) is probably the only
form directly available to algae, but eutrophication can be stimulated by the
bioavailable phosphorus derived from the upper 5 cm of agricultural soils
(Sharpley, 1985). Bioavailable phosphorus consists of dissolved phosphorus and
a portion of paniculate phosphorus that varies from site to site. Sharpley (1993)
developed a method using iron-oxide impregnated paper to estimate the amount
of phosphorus in soil that is available for algal growth. This method covers both
dissolved and adsorbed phosphorus. Particulate and organic phosphorus deliv-
ered to water bodies may later be released as dissolved phosphorus and made
available to algae when the bottom sediment of a stream becomes anaerobic,
causing water quality problems.
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Chapter 2: Overview
Sediment
Sediment is the result of erosion. It is the solid material, both mineral and
organic, that is in suspension, is being transported, or has been moved from its
site of origin by wind, water, gravity, or ice. The types of erosion associated with
agriculture that produce sediment are (1) sheet and rill erosion, (2) ephemeral
and classic gully erosion, (3) wind erosion, and (4) streambank erosion. Soil
erosion can be characterized as the transport of particles that are detached by
rainfall, flowing water, or wind. Eroded soil is either redeposited on the same
field or transported from the field in runoff or by wind.
Soil loss reduces nutrients and deteriorates soil structure, causing a decrease in
the productive capacity of the land from which it is eroded. Wind erosion may
cause abrasion of crops and structures by flying soil particles, air pollution by
particles in suspension, transport of sediment-attached nutrients and pesticides,
and burial of structures and crops by drifting soil.
Sediment affects the use of water in many ways. Suspended solids reduce the
amount of sunlight available to aquatic plants, cover fish spawning areas and
food supplies, smother coral reefs, clog the filtering capacity of filter feeders,
and clog and harm the gills of fish. Turbidity interferes with the feeding habits
of certain species of fish. These effects combine to reduce fish, shellfish, coral,
and plant populations and decrease the overall productivity of lakes, streams,
estuaries, and coastal waters. Recreation is limited because of the decreased fish
population and the water's unappealing, turbid appearance. Turbidity also
reduces visibility, making swimming less safe.
Deposited sediment reduces the transport capacity of roadside ditches, streams,
rivers, and navigation channels. Decreases in capacity can result in more fre-
quent flooding. Sediment can also reduce the storage capabilities of reservoirs
and lakes and necessitate more frequent dredging.
The use of Highland Silver Lake, Illinois, as a public water supply was impaired
by high turbidity levels and sedimentation (EPA, 1990b). Similarly, sediment
surveys revealed that Lake Pittsfield, also in Illinois, was losing storage capacity
at a rate of 1.08%, which would cause the lake to fill in with sediment in 92
years if no efforts had been made to control erosion (Davenport and Clarke,
1984). Due to erosion control efforts the rate of storage capacity loss has been
reduced from 15% over 13 years to 10% over the subsequent 18 years (EPA,
1996). In addition, a water supply intake on Long Creek, North Carolina, was
clogged due to erosion from surrounding lands, necessitating annual dredging of
the water supply intake pool (EPA, 1996).
At current rates of sedimentation, Morro Bay, California, could be lost as an
open water estuary within 300 years unless erosion control efforts are stepped up
(EPA, 1996). Sedimentation has been associated with the lack of ocean-run trout
in tributary streams, as well as significant economic losses to the oyster industry
in the bay. Also, a trout fishery in Long Pine Creek, Nebraska, was impaired by
high sediment loadings from streambank erosion and irrigation discharge
(Hernismeyer, 1991). Irrigation return flows with high sediment loads and
streambank erosion caused negative impacts to salmonid spawning and recre-
ational uses of Rock Creek, Idaho (Yankey et al., 1991).
Sediment threatens
water supplies and
recreation, and
causes harm to plant
and fish
communities.
National Management Measures to Control Nonpoint Pollution from Agriculture
2-15
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Chapter 2: Overview
Sediment from
topsoil, often
containing higher
levels of nutrients
and pesticides, can
be a greater threat to
water quality
compared to subsoil
sediment.
Runoff containing
animal waste that
reaches surface
water can result in
oxygen depletion
and fish kills.
Chemicals such as some pesticides, phosphorus, and ammonium are transported
with sediment in an adsorbed state. Changes in the aquatic environment, such as
decreased oxygen concentrations in the overlying waters or the development of
anaerobic conditions in the bottom sediments, can cause these chemicals to be
released from the sediment. Adsorbed phosphorus transported by the sediment
may not be immediately available for aquatic plant growth but does serve as a
long-term contributor to eutrophication.
Sediments from different sources vary in the kinds and amounts of pollutants
that are adsorbed to the particles. For example, sheet, rill, ephemeral gully, and
wind erosion mainly move soil particles from the surface or plow layer of the
soil. Sediment that originates from surface soil has a higher pollution potential
than that from subsurface soils. The topsoil of a field is usually richer in nutri-
ents and other chemicals because of past fertilizer and pesticide applications, as
well as nutrient cycling and biological activity. Topsoil is also more likely to
have a greater percentage of organic matter. Sediment from gullies and
streambanks usually carries less adsorbed pollutants than sediment from surface
soils.
Soil eroded and delivered from cropland as sediment usually contains a higher
percentage of finer and less dense particles than the parent soil on the cropland.
This change in composition of eroded soil is due to the selective nature of the
erosion process. For example, larger particles are more readily detached from
the soil surface because they are less cohesive, but they also settle out of suspen-
sion more quickly because of their size. Organic matter is not easily detached
because of its cohesive properties, but once detached it is easily transported
because of its low density. Clay particles and organic residues will remain
suspended for longer periods and at slower flow velocities than will larger or
more dense particles. This selective erosion can increase overall pollutant
delivery per ton of sediment delivered because small particles have a much
greater adsorption capacity than larger particles. As a result, eroding sediments
generally contain higher concentrations of phosphorus, nitrogen, and pesticides
than the parent soil (i.e., they are enriched).
Animal Wastes
Animal waste (manure) includes the fecal and urinary wastes of livestock and
poultry; process water (such as from a milking parlor); and the feed, bedding,
litter, and soil with which they become intermixed. The following pollutants
may be contained in manure and associated bedding materials and could be
transported by runoff water and process wastewater from confined animal
facilities:
d Oxygen-demanding substances;
O Nitrogen, phosphorus, and many other major and minor nutrients;
D Organic solids;
O Salts;
CD Bacteria, viruses, and other microorganisms;
d Metals; and
O Sediments.
2-16
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 2: Overview
When such runoff, process wastewater or manure enters surface waters, excess
nutrients and organic materials are added. Increased nutrient levels can cause
excessive growth of aquatic plants and algae. The decomposition of aquatic
plants depletes the oxygen supply in the water, creating anoxic or anaerobic
conditions which can lead to fish kills. Amines and sulfides are produced in
anaerobic waters, causing the water to acquire an unpleasant odor, taste, and
appearance. Methane, a greenhouse gas, can also be produced in anaerobic
waters. Such waters can be unsuitable for drinking, fishing, and other recre-
ational uses. Investigations in Illinois have demonstrated the impacts of animal
waste on water quality, including fish kills associated with a hog facility, a cattle
feeding operation, and surface application of liquid waste on frozen or snow-
covered ground (Ackerman and Taylor, 1995). In addition, North Carolina
experienced six spills from animal waste lagoons in the summer of 1995,
totaling almost 30 million gallons. This total included a spill of 22 million
gallons of swine waste into the New River, which killed fish along a 19-mile
downstream area (EPA Office of Inspector General, 1997).
A study of Herrings Marsh Run in the coastal plain of North Carolina showed
that nitrate levels in stream and ground water were highest in areas with the
greatest concentration of swine and poultry production (Hunt et al., 1995).
Orthophosphate levels were affected only slightly by animal waste applications
since most of the phosphorus was bound by the soil. In addition, runoff from
feedlots has long been associated with severe stream pollution. Feedlots, which
are devoid of vegetation and subjected to severe hoof action, generate runoff
containing large amounts of bacteria, which may cause violations of water
quality standards (Baxter-Potter and Gilliland, 1988).
Diseases can be transmitted to humans through contact with animal or human
feces. Runoff from fields receiving manure will contain extremely high numbers
of microorganisms if the manure has not been incorporated or the microorgan-
isms have not been subject to stress. Shellfishing and beach closures can result
from high fecal coliform counts. Although not the only source of pathogens,
animal waste has been responsible for shellfish contamination in some coastal
waters.
The pathogen Cryptosporidium, a protozoan parasite, is common in surface
waters, especially those containing high amounts of sewage contamination or
animal waste. Without advanced filtration technology, Cryptosporidium may
pass through water treatment filtration and disinfection processes in sufficient
numbers to cause health problems, such as the gastrointestinal disease
cryptosporidiosis. The most serious consequences of cryptosporidiosis tend to be
focused on people with severely weakened immune systems. In 1993, Milwau-
kee, Wisconsin, which draws its water from Lake Michigan, experienced an
outbreak of cryptosporidiosis, affecting 400,000 people, with more than 4,000
hospitalized and over 50 deaths attributed to the disease (EPA, 1997c). While the
source of contamination is uncertain, the problem was linked to suboptimal
performance of the water treatment plant, together with unusually heavy rainfall
and runoff. The watersheds of two rivers which discharge into Lake Michigan
contain slaughterhouses, human sewage discharges, and cattle grazing ranges
(Lisle and Rose, 1995).
Giardia is another commonly identified pathogen in surface waters. Giardia is
the intestinal parasite that causes the disease giardiasis. Giardiasis is sometimes
National Management Measures to Control Nonpoint Pollution from Agriculture 2-17
-------
Chapter 2: Overview
referred to as "backpacker's disease" since the disease frequently occurs in
hikers and nature lovers who unwittingly drink water from contaminated springs
or streams. However, several community-wide outbreaks of giardiasis have been
linked to contaminated municipal drinking water (CDC, n.d.). The commonly
associated symptoms of giardiasis are persistent diarrhea, weight loss, abdomi-
nal cramps, nausea, and dehydration. With proper treatment and a healthy
immune system, giardiasis is not deadly, but it can be life threatening to AIDS
patients, small children, the elderly, or someone recovering from major surgery.
The best strategy to protect a drinking water supply from Giardia contamination
is the physical removal of the organism. This can be accomplished by control-
ling land use within a watershed to prevent degradation of the source water and
by utilizing a properly designed and operated water filtration plant.
Viruses in animal waste also pose a potential health threat to humans. Enteric
viruses are the most significant virus group affecting water quality and human
health (EPA, 2001). There are over 100 different types of enteric viruses, all
considered pathogenic to man (EPA, 1984). When ingested, enteric viruses may
attack the gastrointestinal track or the respiratory system, sometimes, fatally.
More typically, infection causes sore throat, diarrhea, fever and nausea. Enteric
viruses may be found in livestock excrement from barnyards, pastures, range-
lands, feedlots, and uncontrolled manure storage areas; and areas of land appli-
cation of manure and sewage sludge (NCSU, 2001). When animal waste is
applied to agricultural land for irrigation or fertilization purposes, enteric viruses
can survive in soil for periods of weeks or even months (EPA, 1984). Enteric
viruses in land applied manure or sewage sludge can leach into ground water
and/or eventually be transported by overland flow into surface water bodies,
thus creating a potential for the contamination of water resources. Management
measures should be instituted in all situations in which sludge is used for
irrigation or fertilization, to prevent the contamination of vegetables and drink-
ing water sources by enteric viruses (EPA, 1984).
Since pathogenic organisms present in polluted waters are generally difficult to
identify and isolate, scientists typically choose to monitor indicator organisms.
Indicator organisms are usually nonpathogenic bacteria assumed to be associated
with pathogens transmitted by fecal contamination but are more easily sampled
and measured. Fecal indicators are used to develop water quality criteria to
support designated uses, such as primary contact recreation and drinking water
supply. For example, studies conducted by USEPA have demonstrated that the
risk to swimmers of contracting gastrointestinal illness seems to be predicted
better by enterococci than by fecal coliform bacteria since the die off rate of
fecal coliform bacteria is much greater than the enterococci die off rate (EPA,
2001). Moreover, a comparison of various fecal indicators of potential pathogens
with disease incidence revealed that elevated levels of enterococci bacteria were
most strongly correlated with gastroenteritis in both fresh and marine recre-
ational waters (EPA, 1986). The USEPA believes that enterococci is best suited
as an indicator organism for predicting the presence of gastrointestinal illness-
causing pathogens in fresh water and marine waters and recommends that people
do not swim in fresh waters that contain 33 or more enterococci per 100 millili-
ters (mL) or marine waters with 35 or more enterococci per 100 mL (EPA,
2000b).
2-18 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 2: Overview
Pesticide losses are generally greatest when rainfall is intense and occurs shortly
after pesticide application, a condition for which water runoff and erosion losses
are also greatest.
A study of herbicides and nutrients in storm runoff from nine stream basins in
the Midwestern states from 1990-1992 showed sharp increases in triazine
herbicides (e.g., atrazine) in the post-planting period (Scribner et al., 1994).
Atrazine levels increased from 1.0 ug/L to peaks of 10-75 ug/L. EPA's maximum
contaminant level (MCL) for atrazine in public water supplies is 3.0 ug/L. In this
and many other studies, EPA MCLs are utilized as reference points for assessing
water quality. It should be noted that an exceedance of the MCL in these surface
or ground water quality monitoring studies does not necessarily indicate viola-
tion of a water quality standard.
In the Scribner et. al study (1994), it was concluded that transport of herbicides
to streams was seasonal, with peaks from early May to early July. In a related
study of 76 Midwestern reservoirs from April 1992 through September 1993,
atrazine was the most frequently detected and persistent herbicide, followed by
alachlor ethane sulfonic acid, deethylatrazine, deisopropylatrazine, metolachlor,
cyanazine amide, and cyanazine (Scribner et al., 1996). Eight reservoirs had
concentrations of one or more herbicides exceeding EPA's maximum contami-
nant levels or health advisory levels for drinking water during late April through
mid-May, 1992, while 16 reservoirs had these high contaminant levels in late
June through July, 1992. The annual average concentrations on which the MCLs
are based are usually not exceeded, however, because residues drop to low or
undetectable levels at other times of the year.
Research at the 5,600-ha Walnut Creek watershed in Iowa also showed that
atrazine levels in runoff increased to above the MCL with heavy rains after
chemical application. The total loss of atrazine and metolachlor in stream flow
was about 1% of the amount applied each year. Herbicide concentrations in tile
drains were often near the detection limit of 0.2 ug/L, while only atrazine and
metolachlor exceeded 3.0 ug/L once in more than 1,700 ground water samples.
Water balance studies indicated that the predominant flow path in the prairie-
pothole watershed is from the bottom of the root zone into the stream through
tile drains (Hatfield et al., 1995).
Concentrations of atrazine, alachlor, cyanazine, and metolachlor in Midwestern
streams and reservoirs increased suddenly during rainstorms following herbicide
applications (Goolsby et al., 1995). Atrazine levels less than 0.2 ug/L also persist
year-round in Midwestern streams, partly due to the discharge of contaminated
waters from surface and ground water reservoirs.
Elevated monthly average pesticide concentrations in Lake Erie tributaries
usually occur in May to August, and smaller tributaries had higher maximum
concentrations, more frequent concentrations below the detection limit, and
fewer intermediate concentrations than larger tributaries (Richards and Baker,
1993).
From calculations combining estimated pesticide use data with measured load
data, it was estimated that less than 2% of applied pesticides reached surface
waters in the Mississippi River basin (Larson et al., 1995). Since the relative
percentages of specific pesticides reaching the rivers were often not in agree-
ment with projected runoff potentials, it was concluded that soil characteristics,
National Management Measures to Control Nonpoint Pollution from Agriculture 2-23
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Chapter 2: Overview
weather, and agricultural management practices are more important than chemi-
cal properties in the delivery of pesticides to surface waters. Richards and Baker
(1993) concluded that average pesticide concentrations in Lake Erie tributaries
are correlated with amount applied, but are also affected by chemical properties
and modes of application of the pesticides.
The rate of pesticide movement through the soil profile to ground water is
inversely proportional to the pesticide adsorption partition coefficient or Kd (a
measure of the degree to which a pesticide is adsorbed by the soil versus dis-
solved in the water). The larger the Kd, the slower the movement and the greater
the quantity of water required to leach the pesticide to a given depth. Other factors
affecting pesticide movement include pesticide solubility as well as soil pH and
temperature.
Pesticides can be transported to receiving waters either in dissolved form or
attached to sediment. Dissolved pesticides may be leached to ground water
supplies. Both the degradation and adsorption characteristics of pesticides are
highly variable.
Pesticides have been widely detected in ground water, with concentrations
usually much lower than in surface water but with greater longevity (Barbash
and Resek, 1996). The most common detected are corn and soybean herbicides,
which were reported to occur in up to 30% of samples in a national water quality
assessment (Barbash et al., 2001). Of those with detections, 98% were below 1.0 ug/
L and only exceeded the MCL in 2 of 2,227 sites. In another study, herbicides,
including atrazine, prometron, metolachlor, and alachlor were detected in 24 percent
of shallow aquifers in the Midwest sampled by USGS (Burkhart and Kolpin, 1993).
Reported concentrations for all compounds were less than 0.5 ug/1. In Walnut
Creek, Iowa, herbicides were not generally found in concentrations above 0.2
ug/1 in shallow ground water (Hatfield et al. 1993). In the Mid-Atlantic region,
pesticide compounds, including atrazine and its metabolites, metolachlor,
prometron, and simazine, have been detected in about half of ground water samples
analyzed, but rarely at concentrations exceeding established MCLs (Ator and
Ferrari, 1997). The occurrence of pesticides in ground water of the Mid-Atlantic
region was related to land cover and rock type: agricultural and urban land use
practices are likely sources of pesticides, and rock type affects the movement of
these compounds into and through the ground water system. Recently, Kolpin et
al. (2000) found that one or more pesticides were detected at nearly half of 2500
USGS NAWQA ground water sites sampled across the United States. Observed
pesticide concentrations were generally low. Pesticides were commonly detected
beneath both agricultural and urban areas.
Habitat Impacts
The functioning condition of riparian-wetland areas is a result of interaction
among geology, soil, water, and vegetation. Riparian-wetland areas are function-
ing properly when adequate vegetation is present to
D Dissipate stream energy associated with high water flows, thereby
reducing erosion and improving water quality;
O Filter sediment and aid floodplain development;
2-24 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 2: Overview
Management practices can be structural (e.g., waste treatment lagoons, terraces,
or sediment basins) or managerial (e.g., rotational grazing, nutrient management,
pesticide management, or conservation tillage). Management practices generally
do not stand alone in solving water quality problems, but are used in combina-
tions to build management practice systems. For example, soil testing is a good
practice for nutrient management, but without estimates of realistic yield; good
water management; appropriate planting techniques and timing; and proper
nutrient selection, rates, and placement; the performance expectations for
nutrient management cannot be achieved.
Each practice, in turn, must be selected, designed, implemented, and maintained
in accordance with site-specific considerations to ensure that the practices
function together to achieve the overall management goals. For example, a
grassed waterway must be designed to handle all of the water that will be
conveyed to it from upland areas, including all water re-routed with diversions
and drainage pipes. Design standards and specifications must be compatible for
practices to work together as effective systems.
A summary of agricultural management practices and how they function in
systems is given in Chapter 3. Management practices that can be used to achieve
each of the six agricultural management measures are described in Chapter 4,
Resource Management Planning Concepts
Resource management planning, also known as conservation planning, for
agricultural operations is a natural resource problem solving and management
process. The process integrates economic, social (including cultural resources),
and ecological considerations to meet goals and objectives. It involves setting of
personal, environmental, economic, and production goals for the farm or ranch.
The challenge in resource management planning is to balance the short-term
demands for production of food, fiber, wood, and other agricultural products,
with long-term sustainability of a quality environment.
Resource management systems are combinations of conservation practices and
resource management, identified by land or water uses, for the treatment of all
natural resource concerns for soil, water, air, plants, and animals that meets or
exceeds the quality criteria for resource sustainability. The quality criteria are
described in the USDA Natural Resources Conservation Service (NRCS) Field
Office Technical Guide (FOTG). See Appendix B for additional information on
the FOTG.
Resource management planning is preferred by land managers who have a
negative reaction to "single purpose plans" that address individual economic or
natural resource issues. Essential goals for a farm or ranch resource management
plan include:
O Improving or ensuring profitability by finding solutions that save money,
increase sales, improve product quality, or simplify/reduce the work;
O Reducing water pollution through application of appropriate systems of
management practices;
A resource
management plan
for the farm serves
to maintain quality of
life while achieving
goals for profitability
and water quality.
National Management Measures to Control Nonpoint Pollution from Agriculture
2-29
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Chapter 2: Overview
d Coordinating regulatory input so that implementation of the resource
management plan will assure compliance with all applicable regulations
impacting the agricultural operation; and
D Incorporating the farm or ranch family's personal goals for quality of
life.
NRCS and its cooperating conservation partners use a three-phase, nine-step
planning process. This process is very dynamic, frequently requiring planners to
cycle back to previous steps in order to fully achieve the goals set for the plan.
Many states are developing their own resource management planning protocols.
An example of one of these efforts is the Idaho One Plan. The Idaho program
was developed to reduce diverse agency requirements and to produce a user-
friendly product that allows farmers and ranchers to develop resource manage-
ment plans unique to their operations.
Individuals interested in resource management planning should contact their
local NRCS office, soil and water conservation district, cooperative extension
service, land grant university, state department of agriculture, or other appropri-
ate agency to learn more about locally available information.
2-30 National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Management Practices
Management practices are implemented on agricultural lands for a variety of
purposes, including protecting water resources, protecting terrestrial or aquatic
wildlife habitat, and protecting the land resource from degradation by wind, salt,
and toxic levels of metals. The primary focus of this guidance is on agricultural
management practices that control the generation and delivery of pollutants into
water resources or remediate or intercept pollutants before they enter water
resources.
NRCS maintains a National Handbook of Conservation Practices (USDA-NRCS,
1977), updated continuously, which details nationally accepted management
practices. These practices can be viewed at the USDA-NRCS web site at
www.ncg.nrcs,usda.gov/practice_stds.html. In addition to the NRCS standards,
many States use locally determined management practices that are not reflected in
the NRCS handbook. Readers interested in obtaining information on management
practices used in their area should contact their local Soil and Water Conservation
District or local USDA office. Two very helpful handbooks for farmers in the Midwest
are 60 Ways Farmers Can Protect Surface Water (Hirschi et al., 1997), and 50 Ways
Farmers Can Protect their Ground Water (Hirschi et al., 1993).
How Management Practices Work to Prevent
Nonpoint Source Pollution
Management practices control the delivery of nonpoint source (NFS) pollutants to
receiving water resources by
n minimizing pollutants available (source reduction);
n retarding the transport and/or delivery of pollutants, either by reducing
water transported, and thus the amount of the pollutant transported, or
through deposition of the pollutant; or
G remediating or intercepting the pollutant before or after it is delivered to
the water resource through chemical or biological transformation.
Management practices are generally designed to control a particular pollutant
type from specific land uses. For example, conservation tillage is used to control
erosion from irrigated or non-irrigated cropland. Management practices may also
provide secondary benefits by controlling other pollutants, depending on how the
pollutants are generated or transported. For example, practices which reduce
erosion and sediment delivery often reduce phosphorus losses since phosphorus is
strongly adsorbed to silt and clay particles. Thus, conservation tillage not only
reduces erosion, but also reduces transport of paniculate phosphorus.
In some cases, a management practice may provide environmental benefits
beyond those linked to water quality. For example, riparian buffers, which reduce
Management
practices can
minimize the delivery
and transport of
agriculturally derived
pollutants to surface
and ground waters.
Although a wide
variety of BMPs are
available, all require
regular inspection
and maintenance.
National Management Measures to Control Nonpoint Pollution from Agriculture
3-31
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Chapter 3: Management Practices
Control of surface
transport may
increase leaching of
pollutants.
phosphorus and sediment delivery to water bodies, also serve as habitat for many
species of birds and plants.
Sometimes, however, management practices used to control one pollutant may
inadvertently increase the generation, transport, or delivery of another pollutant.
Conservation tillage, because it creates increased soil porosity (i.e., large pore
spaces), may increase nitrate leaching through the soil, particularly when the
amount and timing of nitrogen application is not part of the management plan.
Tile drains, used to reduce runoff and increase soil drainage, can also have the
undesirable effect of concentrating and delivering nitrogen directly to streams
(Hirschi et al., 1997). In order to reduce the nitrogen pollution caused by tile
drains, other management practices, such as nutrient management for source
reduction and biofilters that are attached to the outflow of the tile drains for
interception, may be needed. On the other hand, practices which reduce runoff
may contribute to reduced in-stream flows, which have the potential to adversely
impact habitat. Therefore, management practices should only be chosen after a
thorough evaluation of their potential impacts and side-effects.
Water Quality Effects of USDA-NRCS Practices
USDA-NRCS conservation practices can be structural (e.g., Waste Treatment
Lagoons; Terraces; Sediment Basins; or Fences) or agronomic (e.g., Prescribed
Grazing; Nutrient Management; Pest Management; Residue Management; or
Conservation Cover.) Not all USDA-NRCS conservation practices are applicable
in all areas of the United States. When and where applicable, their effects on
water quality may vary based on many factors. Some of these factors include
climate, soils, topography, geology, existing cultural and management activities,
as well as modifications made to the practice standards that govern how the
practices are to be applied in local settings.
Guidance identifying expected effects of USDA-NRCS conservation practices has
been prepared and is being kept up to date by discipline and resource specialist in
each state. Technical guidance for water quality effects is found in the Conserva-
tion Practice Physical Effects (CPPE) documents in Section V of the NRCS Field
Office Technical Guide (FOTG). Table 3-1 is a simplified table developed from
the CPPE in the Oregon FOTG Section V. This table shows the kind of informa-
tion available at the local level that can be used to help evaluate the effects of
specific conservation practices. For example, in the area for which this guidance
was prepared it has been determined that Contour Buffer Strips (NRCS Practice
Code 332) can be expected to have beneficial effects on surface water quality, but
because the practice increases infiltration it can be expected to have detrimental
effects on ground water quality.
3-32
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 3: Management Practices
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National Management Measures to Control Nonpoint Pollution from Agriculture
3-33
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Chapter 3: Management Practices
Management Practice Systems
If multiple sources of
a pollutant exist,
more than one
management practice
system
will be needed to
provide effective
control.
Water quality problems cannot usually be solved with one management practice
because single practices do not typically provide the full range and extent of
control needed at a site. Multiple practices are combined to build management
practice systems that address treatment needs associated with pollutant generation
from one or more sources, transport, and remediation. Management practice
systems are generally more effective in controlling the pollutant since they can be
used at two or more points in the pollutant delivery process. For example, the
objective of many agricultural NFS pollution projects is to reduce the delivery of
soil from cropland to water bodies. A system of management practices can be
designed to reduce soil detachment, erosion potential, and off-site transport of
eroded soil. Such a system could include conservation tillage to reduce soil
detachment and cropland erosion. Grassed waterways could be included to carry
concentrated flows from the fields in a non-erosive manner, while filter strips
might be used to filter sediment from water leaving the field in shallow, uniform
flow (Hirschi et al., 1997). Sediment retention basins could be added to trap
sediment and runoff from the farm if other practices failed to provide the level of
control needed.
Similarly, if nitrogen is the pollutant of concern, nutrient management can be used
to minimize the availability of nitrogen for transport from cropland. This can be
achieved by matching the application rate with crop needs, based upon soil
testing, analysis of nutrient sources, and realistic yield expectations. Proper
timing of nutrient application will also reduce nitrogen availability since the time
frame over which the applied nitrogen is available but not used by the crop is
minimized. Conservation tillage can help reduce overland transport of nitrogen by
reducing erosion and runoff, and nutrient management will minimize subsurface
losses due to the resulting increased infiltration. Filter strips can be used to
decrease nitrogen transport by increasing infiltration, and through uptake of
available nitrogen by the field border crop. Nitrogen not controlled by nutrient
management, conservation tillage, and filter strips can be intercepted and
remediated through denitrification in riparian buffers.
A set of practices does not constitute an effective management practice system
unless the practices are selected and designed to function together to achieve
water quality goals reliably and efficiently. In the Oregon RCWP project (see
Chapter 1 for a discussion of RCWP), dairy farmers installed animal waste
management systems to reduce fecal coliform runoff into an important shellfish-
producing estuary. Although 12 practices (waste storage, guttering, dike, drains,
etc.) initially comprised the animal waste management systems, these systems
were not as effective as needed because the practices addressed manure storage
but not land application of the manure. Utilization of manure was added as a
practice which enabled implementation of complete management practice systems
that successfully addressed the need for managing land application to achieve
water quality goals (Gale et al., 1993).
Types of Management Practice Systems
Management practice systems can be separated into three categories:
D repetitive treatment,
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 3: Management Practices
O necessary diversification, or
n a combination of the first two.
Systems that combine individual management practices to treat a pollutant at
different points in the pollutant delivery process achieve management objectives
through repetitive treatment. The above examples for sediment and nitrogen
control both employ repetitive treatment. Conservation tillage, grassed water-
ways, field borders, and sediment retention basins control soil particles and runoff
at various stages in the pollutant delivery process. Nutrient management, conser-
vation tillage, field borders, and riparian buffers provide similar repetitive treat-
ment to control nitrogen losses in the second example.
In some cases a management practice cannot be used without an accompanying
practice. For example, if it is necessary to install fence to keep cows from a
stream, watering devices may be needed to provide drinking water for the cows.
This is an example of necessary diversification.
Some management practice systems include both treatment redundancy and
necessary diversification. An example of such a system is an animal waste
management system in which some components are included to help others
function. For example, diversions and subsurface drains may be necessary to
convey runoff and wastes to a waste treatment lagoon for treatment. While the
diversions and subsurface drains may not provide any measurable pollution
control of their own, they are essential to the overall performance of the animal
waste management system. Other components, such as lagoons and waste utiliza-
tion plans, are added to provide repetitive treatment.
Site-Specific Design of Management Practice Systems
There is no single, ideal management practice system for controlling a particular
pollutant in all situations. Rather, the system should be designed based on the
type of pollutant; the source of the pollutant; the cause of the pollution at the
source; the agricultural, climatic, and environmental conditions; the pollution
reduction goals; the economic situation of the farm operator; the experience of the
system designers; and the willingness and ability of the producer to implement and
maintain the practices. The relative importance of these and other factors will vary
depending upon other considerations such as whether the implementation is voluntary
(e.g., State cost-sharing program) or mandatory (e.g., discharge permits).
An example of site-specific design of management practice systems can be found
in the Rural Clean Water Program (RCWP) which was discussed in Chapter 1. A
similar water quality problem existed in RCWP projects conducted in Utah and
Florida (Gale et al., 1993). In both projects, eutrophication was caused partly by
excess phosphorus contained in dairy runoff. Animal waste management systems
were installed in both projects. In the Florida project, seven individual manage-
ment practices (referred to as "BMPs" in the RCWP) were needed to control the
animal manure in barnyard areas, whereas only five BMPs were needed in Utah
(Table 3-2). Some BMPs were used in both projects, while other BMPs were used
in one but not both projects. Differences existed because the regions in which the
two projects were located have significantly different climatic, ecological, and soil
characteristics, requiring different approaches to mitigate animal waste problems.
In Florida, annual rainfall is approximately 50 inches per year, whereas annual
National Management Measures to Control Nonpoint Pollution from Agriculture 3-35
-------
Chapter 3: Management Practices
Table 3-2. Animal waste management BMP systems used in two agricultural pollution
control projects (Utah and Florida).
NRCS Code
312
313
356
362
425
428
430
633
Individual Animal Waste Management BMPs
Waste Management System
Waste Storage Structure
Dike
Diversion
Waste Stirage Pond
Concrete Lining
Pipeline
Waste Utilization
UT FL
** **
** **
**
** **
** **
**
**
**
NRCS = Natural Resources Conservation Service, U.S. Department of Agriculture
Source for NRCS codes: USDA—NRCS, 1977
precipitation in Utah is approximately 16 inches per year. Surface water is largely
derived from snowmelt in Utah. Dikes were used in the Florida project to prevent
runoff and phosphorus from entering the drainage ditches. These dikes were not
needed in Utah due to the lower rainfall producing less runoff.
Practices Must Fit Together for Systems to Perform
Effectively
Each practice in a management practice system must be selected, designed,
implemented, and maintained in accordance with site-specific considerations to
ensure that the practices function together to achieve the overall management
goals. If, for example, nutrient management, conservation tillage, filter strips, and
riparian buffers are used to address a nitrogen problem, then planting and nutrient
applications need to be conducted in a manner consistent with conservation tillage
goals and practices (e.g., injecting rather than broadcasting and incorporating
fertilizer). In addition, runoff from the fields must be conveyed evenly to the filter
strips which, in turn, must be capable of delivering the runoff to the riparian
buffers in accordance with design standards and specifications.
3-36
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
level of dissolved P in the soil solution is controlled by the chemical environ-
ment of the soil (e.g. pH, oxidation-reduction, iron concentration) and by the P
content of the soil.
Commercial Fertilizers
Fertilizers represent the largest single source of N, P, and K applied to most
cropland in the U.S. Major commercial fertilizer N sources include anhydrous
ammonia, urea, ammonium nitrate, and ammonium sulfate. Major P fertilizer
sources include monoammonium phosphate, diammonium phosphate, triple
superphosphate, ammonium phosphate sulfate, and liquids. The predominant
source of potassium (K) fertilizer is potassium chloride. Descriptions of com-
mon fertilizer materials are given in Table 4a-l. The use of any particular
material or blend is governed by the characteristics of the formulation (such as
volatilization potential and availability rate), suitability for the particular crop,
crop needs, existing soil test levels, economics, application timing and equip-
ment, and handling preferences of the producer. An example of general fertilizer
Table 4a-1. Common fertilizer minerals.
^^^^^^^^•I^^^^^^^^^^MH^^^^^^^^^^^V
Common Name
Nitrogen materials
Ammonium nitrate
Ammonium sulfate
Ammonium nitrate-urea
Anhydrous ammonia
Aqua ammonia
Urea
Phosphate materials
Superphosphate
Ammoniated
superphosphate
Monoammonium
phosphate
Diammonium
phosphate
Urea-ammonium
phosphate
Potassium materials
Muriate of potash
Monopotassium phosphate
Potassium hydroxide
Potassium nitrate
Potassium sulfate
Chemical Formula
NH4NO3
(NH4)2S04
NH4NO3+(NH2)2CO
NH3
NH4OH
(NH2)2CO
Ca{H2PO4)2
Ca(NH4HaPO4)2
NH4H2P04
(NH4)2HP04
(NH2}2CO+(NH4)SHP04
KCI
KH2PO4
KOH
KN03
K2SO4
Source: Pennsylvania State University. 1997. The Penn State Agronomy Guide,
Cooperative Extension, 1997.
University, Ithaca, NY.
N
34
21
32
82
20
46
0
5
13
18
28
0
0
0
13
0
Analysis
P O
I2W5
0
0
0
0
0
0
20-46
40
52
46
28
0
50
0
0
0
1997-1998, University
1997 Cornell Recommendations for Integrated Field Crop
Management
(%)
K20
0
0
0
0
0
0
0
0
0
0
0
60
40
70
45
50
Park, PA. Cornell
Resource Center, Cornell
National Management Measures to Control Nonpoint Pollution from Agriculture
4-41
-------
Chapter 4: Management Measures
Precision Farming
A New I'j'a oj Production
, also lenown as site-specific management, is a fairly new practice thai has been attract-"
' ipjj' Increasing attenti5n b6$h within and outside the agricultural industry over -the past few yea/s. If is a
pfaette& Concerned with making mdrireducated.and well-informed agricultural decisions'. Precision
farming provides tooKfor tailoring .production inputs to specific plot^ Corrections) within a field. The •
s.ize of the plots typically range ten one to- three .acres, depending 'better matching inputs' to specific crop naeds, father than.applying fertilizer or pesticides to an entire ( .
' field at a single rate of application, .toners First-test the soil andxrop yields df specific plots, and then
apply the apprppriate'amount of ferfil&er, water, 'andfor chemicals needed to ajfeviate-the problems in ",
thoise s6ction^ of die field, Precision, farming requires certain technology, which Is 3h added cost, as, welt, '
: as increased management demands* •'•'-.• ' ''"•'' • - * ' • - "'"-
farming irchanging_the way farmers think about their land, They are- increasingly concerned-
not wiih the average needs of the'entire jield, but with the actual needs' of specific plots, , wMch-can
fluctuate fiA)m one squ^e "meter to the nexC The practice of precision farming acknowledges tike fa6t that -
. • conditions for agricultural production vary across gpace and over finiej With this in, mind, ^rdcision^
fatmejrs are1 now malcing mana^ment decisions more specific to jiihe and place father than regularly - - -
scheduled and uniform applications. ,° ° \ ' . . ' ..',"*-.• - . " ,
/-The approach trf precision fprmtrig involves using -a wide iahge' of com|)uter:relaie4 -information techholo- '
gies, many just redehtly intodduced to j^oduction ^gi^culture, to precisely match ^crops and cultivation to
'. 4e various growing conditions. The key to successfully nsing the' new technologies available to the '
'precision fermer to maximize possiWe benefits associated with this abroach & information. Data coUec^
tioh efforts begin before crop production and continue until after the harvest Mormationrgatbering '
technologies needed prior ta crop-producUott include grj4 soil sampling^ past $eld.tfeomtoririg,nremote- •;
spnsing, and crop geouting, Tfiese (teta collectidn efforts are even ftiriher enhaneed by -obtaining pfecise ' -
location coordinates of plot boundaries, roads, wetlands* etc., .using a global positioning system (GPS). ,
Other data collection takes p&ce during prbfjuetton -through. Mloaal" sen^ng instruments mounted directly
, oafarm machinery. Variable rate technology (VRT) uses cMnpyterized controllbrs to change rates of [
inputs such* as seed, pesticides^ aai| nutrtes 'thr^u^h planters, ^pr&yeis, or irrigation 'equipment. For , -'
^exam^leVsoil probes mouHted oh the^fi^nt of fertilizer §pi»adefs can continuously monitor electrical
. 'conductivity* soil moisture; -and other variables to predict soil nutrient concentrations arid accordingly
adjust- lertilizer application "on-the-fly*' at th& rear of the spreader. Other, direct sensors ^v^lable include
yield monitors^ ^-ain.quality sensors,^alinky raster fields.,' wether monitors, and s^etroscopy devices'. ; "
Optical scanners can be used to detect soil organic matter," to reco^rn^ weeds, and to instantaneously '
alter itfee Amount o/ application of herbicides allied ' '"•_*' •"«.' • (" ' .
rThe precision fanner can feen take theplinldnnat^
'compiiter. The personal computer on] hel^ today's" farmer organize and manage the information collected
tfaore effectively, 'Compuie^programs', including spreadsheets,, databases-, 'geographic information systems
tOlS), and oth6r>. types of apjdica'tion software; are readily available. By tying specific location ooofdi-* '
nates obtained from the GPS in with the' other ild data obtained, the farmer can use the GIS, capability, to l
4-42
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
aitefeji ami other.Variables of j
inf
systems; to simulate anything •from cjdp ;
of nutti^atsiaiid pesticides through
s, Information systems-based oil inj
to sr^y £of sjecificests, ^4iettito;tfli;iKj s£ fotth.
'• -for the fanner's field based on past, currenj, and e^peeted
-------
Chapter 4: Management Measures
4-44
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
recommendations for corn is shown in Table 4a-2. Commercial fertilizers offer
the advantage of allowing exact formulation and delivery of nutrient quantities
specifically tailored to the site, crop, and time of application in concentrated,
readily available forms.
Organic Nutrient Sources
Organic nutrient sources, such as manure, sludge, and compost, can supply all or
part of the N, P, and K needs for crop production. Organic nutrient sources offer
additional advantages because they also contain secondary nutrients and micro-
nutrients (e.g. iron, boron), add organic matter to the soil, provide nutrients to
crops for several years after application, and provide a practical outlet to recycle
manure and other farm organic materials. The use of manure is particularly
important on livestock and poultry farms because nutrients can build up in the
soil, be lost to the atmosphere, leach into ground water, or runoff to surface
waters as more nutrients are brought onto the farm than leave in products sold.
Table 4a-3 shows examples of estimated N and P mass balances for several New
York dairy farms.
Table 4a-3. N and P mass balances on several New York dairy farms.
INPUT
Nitrogen
Size (# of cows)
45 85 120
—tons of N/yr —
purchased fertilizer 1.0 2.2 4.6
purchased feed
legume N fixation
Total:
OUTPUT
milk
meat
crops sold
Total:
REMAINDER
3.8 9.7 21.4
U2 1.1 &2
6.1 13.0 29.2
2.0 3.8 6.3
0.1 0.4 0.6
0.1 0.5 —
2.2 4.7 6.9
3.9 8.3 22.3
remaining on farm 64% 64% 76%
Source: Klausner, S.
95CUWFP1, Cornell
1995. Nutrient Management: Crop
University, Ithaca, NY.
Phosphorus
Size (# of cows)
45 85 120
—tons of P/yr —
1.2 0.9 1.3
1.0 1,7 5.4
— — —
2.2 2.6 6.7
0.4 0.7 1.1
<0.1 0.1 0.2
<0.1 <0.1 —
0.4 0.8 1.3
1.8 1.8 5.4
81% 69% 81%
Production and Water Quality.
The nutrient content of manure and other organic materials can vary greatly
according to the type of animal, type of feed, storage and handling procedures,
climate, and management. In order to use them efficiently, these materials must
be analyzed for their nutrient content. Examples of average values for nutrient
content of organic materials are shown in Table 4a-4; however, it is important to
note that the nutrient content of manure even on neighboring farm operations
may vary widely from the average.
A difficulty in using organic nutrient sources is that their nutrient content is
rarely balanced for the specific soil and crop needs. For example, the ratio of
N:P in applied manure is usually around 3 or less, while the ratio at which crops
National Management Measures to Control Nonpoint Pollution from Agriculture
4-45
-------
Chapter 4: Management Measures
Table 4a-4. Representative values for nutrients in manure, sludge, and whey, as applied.
SOLID MANURE
Species
Dairy cattle
Beef cattle
Swine
Poultry
Sheep
Horse
LIQUID MANURE
Species
Dairy cattle
Beef cattle
Veal calf
Swine
Poultry
DIGESTED SLUDGE
WHEY
% dry matter
18-22
15-50
18
22-76
28
46
% dry matter
1-8
1-11
3
1-4
13
Total N
6-17
11-21
8-10
20-68
14-18
14
4-32
4-40
24
4-36
69-80
20
12
-lb/1000 gal-
4-18
9-27
25
2-27
36-69
lb/1000 gal-
12
lb/1000 gal-
9
ICO1
5-30
5-34
51
4-22
33-96
18
1 Convert values for P2O5 and K2O to P and K by multiplying by 0.43 and 0.83, respectively.
Sources; Midwest Plan Service. 1985. Livestock Waste Facilities Handbook. Iowa State University, 1991 a.
Ames, IA. Klausner, S. 1995. Nutrient Management: Crop Production and Water Quality. 95CUWFP1, Cornell
University, Ithaca, NY. University of Wisconsin-Extension and Wisconsin Dept. of Agriculture, Trade, and
Consumer Protection. 1989. Nutrient and Pesticide Best Management Practices for Wisconsin Farms. WDATCP
Technical Bulletin ARM-1, Madison, Wl. University of Vermont. 1996. Agricultural Testing Laboratory - Manure
Analysis Averages, 1992-1996, Dept. of Plant & Soil Science, University of Vermont, Burlington, VT.
Credits for previous
year manure
applications and
nitrogen-fixing crops
should be
considered in the
plan for nitrogen
management.
use nutrients typically ranges from 5 to 7. Therefore, when manure is applied at
rates based solely on N analysis and crop need for N, excess amounts of P are
added. Because the amounts of P added in manure exceed the amounts removed
by crops, continuous manure usage can result in accumulations of excess P in
the soil, increasing the potential for P to be transported in runoff and erosion
(Daniel et al., 1997).
Another difficulty in efficient use of manure nutrients involves nutrient avail-
ability. Not all nutrients in manure are immediately available for crop uptake.
The organic N in manure, for example, must be mineralized before it can be used
by plants, a process that may take 3 or more years to complete. Examples of
average amounts of nutrients available for crop growth in the first year of
application in Wisconsin are shown in Table 4a-5. Actual quantities of available
nutrients at a specific site will depend on initial nutrient content of the manure,
soil type, temperature, and soil moisture. Failure to account for this slow avail-
ability can result in under-supply of nutrients in a given year of manure applica-
tion. Perhaps more critically, it must be recognized that when manure is applied
to the same field over the years, each succeeding year requires the addition of
4-46
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
Table 4a-5. Nutrients available for crop use in the first year after spreading manure.
Animal
Dairy
Beef
Swine
Poultry
N
Incorp.
4
4
5
15
SOLID
N
not incorp.
3
4
4
13
P2C
3
5
3
14
Source: University of Wisconsin-Extension and Wisconsin
1989. Nutrient and Pesticide Best Management Practices
1, Madison, Wl.
>s N
incorp.
10
12
15
41
Dept. of Agriculture,
for Wisonsin Farms.
LIQUID
N
not incorp.
8
10
12
35
PA
8
14
6
38
Trade, and Consumer Protection.
WDATCP Technical Bulletin ARM-
Table 4a-6. Quantity of livestock or poultry manure needed to supply 100 kg of Nitrogen
over the cropping year with repeated applications of manure (Schepers and
Fox, 1989).
Number of
years applied
1
2
3
4
5
10
15
20
Quantity (metric tons) needed for manure with these percent N
0.25
154
79
54
41
33
17
12
9
1.0
22
16
13
11
10
7
6
5
2.0
7
6
5
5
4
3.7
3.3
3.0
4.0
1.4
1.4
1.4
1.3
1.3
1.3
1.2
1.2
less N to maintain an adequate supply of plant available N (Table 4a-6). Failure
to consider this N carryover could lead to excessive application of N.
Since organic nutrient sources contain valuable nutrients and have soil-condi-
tioning properties, application to land should never be considered disposal. In
cases where organic nutrient sources are disposed of as waste with no regard
given to their N and P content, excessive levels of available nutrients and losses
to surface or ground waters are likely to occur.
Because of their ability to "fix" atmospheric nitrogen, legumes grown in rotation
can represent a significant input of N into the soil of a crop field. Alfalfa has
been reported to fix from 60 to 530 Ib N/ac (pounds of nitrogen per acre);
soybeans may fix from 13 to 275 Ib N/ac. Some of this fixed N is removed in
harvest, but some remains in crop residue or in the soil and is available for
subsequent crops. Table 4a-7 shows representative values for residual N contri-
butions from legume crops. Failure to account for such added N could result in
excessive application of N from other sources.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-47
-------
Chapter 4: Management Measures
Table 4a-7. Representative values for first-year nitrogen credits for previous legume crops.
Crop
Nitrogen Credit (Ib N/ac)
Forages
Alfalfa-
>50%
25-50%
<25%
Red Clover and Trefoil8
>50%
25-50%
<25%
Soybeans
80-120
50-80
0-40
60-90
40-60
0-30
1 Ib N/ac for each bu/ac harvested
up to 40 Ib N/ac
Green Manure Crops (plowed down after growing season of seeding year)
Sweet clover 80-120
Alfalfa60-100
Red clover 50 - 80
Vegetable Crops (residue not removed)
Peas, snap beans,
lima beans
10-20
a The percentage of stand of the particular crop.
Sources: Pennsylvania State University. 1997. The Penn State Agronomy Guide, 1997-1998, University Park,
PA. University of Wisconsin-Extension and Wisconsin Dept. of Agriculture, Trade, and Consumer Protection.
1989. Nutrient and Pesticide Best Management Practices for Wisconsin Farms. WDATCP Technical Bulletin
ARM-1, Madison, Wl.
Irrigation Water
Irrigation water, if drawn from already nutrient-enriched sources, can supply
significant amounts of N. In the Central Platte River Valley in Nebraska, ground
water used to irrigate corn contributed an average of 41 Ib N/ac, nearly one-third
of the N fertilizer requirement (Schepers et al., 1986). Ground water used to
irrigate potatoes in Wisconsin contributed an average of 51 Ib N/ac, or 25% of
the N added as fertilizer (Saffigna and Keeney, 1977). Table 4a-8 shows guide-
lines for calculating the N contribution from irrigation water.
Table 4a-8. Calculating N contributions from irrigation water.
Water Application Rate (acre-feet)
N In water (mg/l)
2
4
6
8
10
Source: Kansas State University
0.5
3
5
8
11
13
Cooperative Extension
of Wheat Growers Foundation. 1994. Best Management
Foundation, Washington, D.C.
1.0
5
11
16
13
27
1.5
8
16
24
32
40
2.
11
22
32
43
54
System and The National Association
Practices for
Wheat.
NAWG
4-48
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
So/7 Nutrients
The release of N, P, K, and micronutrients from soil reserves provides an addi-
tional source of plant-available nutrients. The amount of nutrient release de-
pends on soil moisture, aeration, temperature, pH, and the amount of organic
matter in the soil. The magnitude of this source can be assessed accurately only
through soil testing.
Atmospheric Sources
Finally, atmospheric deposition can significantly contribute nutrients, especially
N, to the soil. Because of the atmospheric linkages of the N cycle and industrial
additions of N to the atmosphere, N loading from atmospheric deposition can be
significant. From 1983-1994, average annual inorganic N deposition over the
Chesapeake Basin ranged from 3.5 to 7.7 kg N/ha; average annual NO3+NH4
atmospheric deposition loading rates ranged from 6.7 to 7.8 kg N/ha (Wang et al.,
1997). McMahon and Woodside (1997) cite wet NO3 and NH4 deposition rates
of 9.8 kg N/ha/yr and 2.8 kg N/ha/yr, respectively, for the Albemarle-Pamlico
Drainage Basin in North Carolina and Virginia. Examples of atmospheric deposi-
tion rates for various forms of N across the U.S. are given in Table 4a-9.
Table 4a-9. N loading in atmospheric deposition, NADP/NTN data, 1996.
Location
Vermont
North Carolina
Florida
Wisconsin
Indiana
Arkansas
Nebraska
California
Alaska
Hawaii1
all data reported
1 1993
Station
Mt. Mansfield (VT99)
Mt. Mitchell (NC45)
Quincy (FL14)
Popple River (WI09)
Purdue Ag Res Ctr(IN41)
Fayetteville (AR27)
North Platte Ag Exp Sta (NE99)
Davis (CA88)
Poker Creek (AK01)
Mauna Loa (HIOO)
as N
NH4-N
1.78
2.39
1.06
1.93
3.29
2.55
2.54
2.18
0.05
0.05
Source: National Atmospheric Deposition Program (NRSP-3)/National Trends
NTN Coord. Office, Illinois State Water Survey, 2204 Griffith Dr., Champaign,
NO3-N
2.95
2.92
1.60
2.16
3.64
2.24
1.58
0.82
0.11
0.05
Network (June
IL 61820.
Inorganic N
4.73
5.31
2.66
4.10
6.94
4.80
4.12
3.00
0.16
0.10
24, 1998). NADP/
Atmospheric deposition of P is generally very small. Ahl (1988) cited atmo-
spheric deposition of 0.05-0.5 kg P/ha/yr in Canada. Annual P loading rates to
the Chesapeake Basin have been estimated at 0.16 to 0.47 kg/ha (Wang et al.,
1997). A similar P deposition rate of 0.16 kg/ha/yr has been measured in the
Lake Champlain basin (VTDEC and NYS DEC, 1997). An estimated annual
load of 0.66 kg P/ha by atmospheric deposition has been cited for the Albemarle-
Pamlico Basin (McMahon and Woodside, 1997).
National Management Measures to Control Nonpoint Pollution from Agriculture
4-49
-------
Chapter 4: Management Measures
Some general
principles govern
nutrient movement.
Site specific crop
history, climate,
soils, watershed, and
farming
characteristics result
in specific local
nutrient pathways
and transformations.
The most comprehensive collection of data on precipitation chemistry and
atmospheric deposition is available from the National Atmospheric Deposition
Program/National Trends Network (NADP/NTN) at: http://nadp.sws.uiuc.edu/.
Data are available for precipitation chemistry, annual and seasonal wet deposi-
tion totals, isopleth maps of precipitation chemistry and wet deposition, and
other variables for over 200 sites in the continental U.S., Alaska, Hawaii, Puerto
Rico, and the Virgin Islands. While deposition data from the NADP network
may not be exactly applicable to a specific site due to local factors such as
elevation, air movement, or industrial emissions, NADP data can help provide an
initial screening estimate of the possible significance of atmospheric nutrient
sources. If atmospheric inputs are estimated to be significant, specific local data
can be sought from university or agency research activities.
Nutrient Movement into Surface and Ground Water
Nutrients in harvested crops typically represent the largest single component of
nutrient output from agricultural land. Table 4a-10 gives representative values
for annual crop nutrient removal. However, crop uptake of added N and P is by
no means complete. Overapplication of nutrients relative to crop need results in
build-up of N and P surplus in agricultural soils. Nutrient surpluses have been
documented at both the farm scale (Klausner, 1995) and the watershed scale
(McMahon and Woodside, 1997; Cassell et al., 1998). Soil test values show that
soil P in many areas is excessive, relative to crop requirements; the greatest
concern occurs with animal-based agriculture, where farm and watershed-scale P
surpluses and over-application of P to soils are common. (Breeuwsma et al.,
1995; Lander et al., 1998; Sims et al., 2000). Accumulation of P in cropland
soils may be especially high if the N requirement of the crop is met with animal
waste, adding P in excess of crop P uptake (Figure 4a-3). The magnitude of
potential loss of nutrients to surface and ground waters is directly related to
accumulation of excessive nutrient levels in soils.
Table 4a-10. Crop nutrient removal.
Crop
Corn
Corn silage
Grain sorghum
Soybeans
Wheat/rye
Oats
Barley
Alfalfa
Orchardgrass
Tall fescue
Sugar beets
Sources: Pennsylvania State
University Park, PA; Midwest
State University, Ames, IA.
Yield
/nr*
/al*
125 bu
21 t
125 bu
40 bu
60 bu
80 bu
75 bu
5t
6t
3.5 t
30 t
N
95
190
65
130
90
90
105
250
300
135
275
University, 1997. The Penn State Agronomy Guide
Plan Service. 1985.
P
22
46
33
18
26
31
20
33
44
29
37
1997-1998,
Livestock Waste Facilities Handbook. Iowa
4-50
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
Figure 4a-3. P added in poultry litter compared with crop requirements
(Sharpleyetal., 1994).
CROP
Bermuda
grass
Corn
Sorghum
Wheat
YIELD 0
Mg ha'1
22
12
AMOUNT OF P (kgPha'V1)
20 40 60 80 100 120
45
60
B Litter P
I I Crop P
1—' requirement
60 Excess P
Amount of P added in poultry litter compared with crop P requirements,
if litter application rates are determined by crop N requirements.
N and P not removed in the harvested crop can become available for transport to
surface and ground waters. The movement of applied nutrients is primarily
driven by the movement of water and eroded soil, but the specific transport
pathways are largely determined by the characteristics of the nutrient source,
soil characteristics, and related environmental conditions (e.g., soil temperature).
As noted in the earlier discussion of nutrient cycles, readily soluble nitrate
moves easily in the liquid phase. Due to its strong affinity for soil particles,
phosphorus usually moves primarily with eroding soil particles. Nitrogen can
volatilize directly from fertilizers such as urea and ammonia and from surface-
applied manure; N lost to the atmosphere in this way may be washed from the
atmosphere by rain a great distance away. Nitrogen can also be lost to the
atmosphere as harmless nitrogen gas through denitrification. Other factors
influencing nutrient movement include topography, precipitation patterns, and,
of course, land use and management.
Movement to Surface Waters
Transport of nutrients to surface waters depends on the availability of nutrients
in the upper soil zone, how easily the nutrients and/or associated soil particles
are detached, whether the chemical is transported in the dissolved form or
attached to soil, and any deposition that may occur before delivery to a water-
way. Nutrients are most susceptible to runoff loss while they are in a thin (<3
cm) layer at the soil surface where overland flow, chemicals, and soil intermix
during runoff. Once nutrients are below this mixing zone, they are usually less
vulnerable to ordinary runoff losses. Nitrate is an exception, as it can be readily
leached through the soil.
Nitrogen can be delivered to surface waters through runoff, erosion, and subsur-
face flow. Some N in the form of ammonium can be lost by erosion along with
National Management Measures to Control Nonpoint Pollution from Agriculture
4-51
-------
Chapter 4: Management Measures
organic N attached to soil particles. Soluble N can be carried in surface runoff,
but most soluble nitrate is lost via leaching through the soil. Leached nitrate may
move into surface waters through shallow subsurface flow or be transported to
deeper ground water. Drainage tiles may provide an important short circuit for
delivery of N from shallow subsurface flow to surface waters. Concentrations of
nitrate in tile drain flow are normally higher than levels found in surface runoff.
The majority of phosphorus lost from agricultural land is transported via surface
runoff, mostly in particulate form attached to eroded soil particles. Because P is
so strongly adsorbed to soil particles, the P level in the soil is a critical factor in
determining loads of P delivered to surface waters (Daniel et al., 1997). In-
creased residual P levels in the surface soil can lead to increased P loadings to
surface water, both attached to soil particles and in dissolved form. Soluble P
losses from cropland can also be significant if runoff occurs very soon after
heavy addition of phosphate fertilizer.
Runoff of Dissolved P
Phosphorus can be exported from agricultural land in particulate and dissolved forms. In most
cases, the majority of P loss occurs in surface runoff in particulate form. However, dissolved P
carried in surface runoff or subsurface flow may be a critical consideration because dissolved P
tends to be immediately available to stimulate growth in receiving waters.
• Loss of dissolved P in runoff is often directly related to the P content of surface
soils — linear relationships have been observed between dissolved P concentration
in runoff and P content of surface soils in cropped and grassed watersheds (Daniel
et al., 1997; Pole et al., 1999; Schoumans and Groenendijk, 2000).
• P losses from grassland may be high, particularly because fertilizers and animal
waste are not usually incorporated into the soil. Significant phosphorus export has
been measured in surface runoff and interflow from grazed grassland, with losses
of over 0.5 kg P/ha during major storm events, especially when events closely
followed inorganic fertilizer application (Haygarth and Jarvis, 1997).
• Soluble P losses may be greater from pasturelands than from croplands due to the
presence of animal waste on the land surface, P release from plant decomposition,
and low amounts of suspended sediment to sorb dissolved P (Baker et al., 1978;
Sharpley and Menzel, 1987; Sharpley et al., 1992).
• In the Chesapeake Basin, dissolved P concentrations in storm runoff were higher
from pastureland than from either cropland or forest (Correll et al., 1995).
4-52 National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
Movement to Ground Water
The magnitude of nutrient loss to ground water, especially through leaching,
depends on the availability of the chemical in the soil profile, the ease with
which the nutrient form is detached from the soil, the rate and path of downward
transport or percolation of water and chemicals, and any possible removal or
deposition of the chemical before it reaches ground water. Nutrients may be
introduced to ground water by direct routes such as abandoned wells, irrigation
wells, sinkholes, or back-siphoning of nutrients when filling tanks. Such path-
ways are especially significant because transport through soil is bypassed,
eliminating any opportunity for adsorption or uptake. While it is important to
protect all ground water through the proper use of nutrients, in areas where
ground water quality problems are known to exist, special emphasis should be
placed on nutrient management planning and the careful use of nutrients.
Leaching of soluble nutrients to ground water can occur as chemicals are carried
with precipitation or irrigation water moving downward past the root zone to the
ground water table. Over-application of irrigation water can enhance leaching of
nutrients to ground water by carrying dissolved nutrients quickly below the root
zone. Ponded water in surface depressions due to large runoff events can be a
significant source of nutrient transport to ground water, as ground water mounds
underneath the depression (Zebarth and DeJong, 1989). Summer fallow may
have a higher ground water contamination risk than continuous cropping be-
cause of the increased water storage in soil profiles that may increase deep percola-
tion (Campbell et al., 1984; Bauder et al., 1993). Finally, idling of cropland either
due to normal rotations or to commodity or conservation programs can in some cases
initially increase nutrient leaching to ground water as nutrients are not taken up by
growing plants and are available for leaching loss (Webster and Goulding, 1995).
Nitrogen in the form of nitrate is normally the nutrient most susceptible to
leaching to groundwater. Nitrate not used by crops or denitrified by soil bacteria,
is subject to leaching. Leaching potential is a function of soil type, crop, climate,
tillage practices, fertilizer management, and irrigation and drainage manage-
ment. Coarse textured soils pose a greater potential problem than fine textured
soils, and crops with poor nitrogen use efficiencies present a greater hazard. In
some studies, no-till systems have been shown to reduce nitrate leaching over
conventional tillage, as well as proper crop rotation, especially those including a
nitrogen-fixing crop (Meek et. al, 1995). However, other studies have shown that
conservation tillage increases the infiltration rate of soils (Baker, 1993). Soil
macroporosity and the proportion of rainfall moving through preferential flow
paths often increase with the adoption of conservation tillage, potentially
increasing the transmission of nitrates and other chemicals available in the upper
soil to subsoils and shallow groundwater (Shipitalo et al., 2000). Over-irrigation,
particularly on sandy soils, is a primary cause of nitrate leaching to groundwater.
Leaching of phosphorus to ground water is generally not a significant problem.
However, organic soils and sandy soils, which lack the iron and aluminum oxides
important for P adsorption, are exceptions; P losses in leaching from intensive
cropping on such soils can be large. The degree of leaching will vary with soil
structure, geologic conditions, climate, and management practices. Recent reports
document phosphorus leaching in areas of intensive manure application to highly
enriched soils over shallow water tables (Breeuwsma et al., 1995), or in areas of
artificial drainage or preferential flow through soil macropores (Simard et al., 2000).
Increasing efficiency
and reducing
nutrient losses is
founded upon the
development of
sound soil and water
conservation
principles.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-53
-------
Chapter 4: Management Measures
Nutrient Management Practices and Their Effectiveness
Nutrient Management Principles
Soil and Water
Conservation
Districts, NRCS, or
Extension offices
can assist growers
with the selection of
nutrient
management
practices.
There are several fundamental principles that should be applied to managing
nutrients for both crop production and water quality protection. These principles
focus on improving the efficiency of nutrient use and thereby reducing the
potential for nutrient loss to surface or ground waters:
0 Determine realistic yield goals, preferably on a field-by-field basis
G Account for available nutrients from all sources before making
supplemental applications
O Synchronize nutrient applications with crop needs; N is needed most
during active crop growth and N applied at other times may be lost
G Reduce excessive soil-P levels by balancing P inputs and outputs
Because of the complex cycling and multiple sources of N in the soil-crop
system, careful accounting for all sources is often the most critical step in
improving N management. Since the level of P in the soil is a major factor
determining the amount of P lost from agricultural land, reducing soil P levels
will ultimately reduce P delivery to surface and ground waters.
Additional practices may be needed to reduce detachment and transport of N and
P and delivery to surface or ground waters. Erosion control practices are particu-
larly critical to reduce losses of P and sediment-bound forms of N. Efficient
water management can reduce leaching of soluble N from irrigated cropland,
and improved irrigation practices can reduce water, sediment, and nutrient
transport in tailwaters. Crop failure due to a lack of water leaves nutrients in the
soil, rendering them vulnerable to leaching or runoff loss.
Nutrient Management Practices
Numerous practices are available to address the above principles. Many of these
are specific to the cropping system, soils, climate, and management activities
associated with particular crops and regions of the country. Readers are encour-
aged to contact their State Land Grant universities, NRCS, cooperative extension
offices, State agriculture departments, or producer organizations for more site
specific practices.
Following are practices, components, and sources of information that should be
considered in the development of a nutrient management plan:
1. Use of soil surveys in determining soil productivity and identifying
environmentally sensitive sites. Aerial photographs or maps and a soil
map should be used. If the agricultural lands lie within a watershed that
has been designated as having impaired surface or ground water quality
associated with nutrients, then nutrient management plans should
include an assessment of the potential for N or P from the agricultural
lands to be contributing to the impairment.
2. Use of producer-documented yield history and other relevant
information to determine realistic crop yield expectations. Appropriate
methods include averaging the three highest yields in five consecutive
crop years for the planning site or other methods based on criteria used
4-54
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
4.
in developing the State Land Grant University's nutrient
recommendations. Increased yields due to improved management and/or
the use of new and improved varieties and hybrids should be considered
when yield goals are set for a specific site.
Application of N and P at recommended rates for realistic yield goals.
Through remote sensing and precision farming techniques, yield and
fertilization can be optimized. Accurately located (e.g. via Global
Positioning System, GPS) soil testing can help evaluate soil variability
between and within fields, and use of on-the-go yield monitors and GPS-
driven variable rate application can match inputs to soil and field
variations and place nutrients where increased yield potential exists.
Limit manure and sludge applications to phosphorus crop needs,
supplying any additional nitrogen needs with nitrogen fertilizers or
legumes.
It may be necessary in some cases to route excess phosphorus in
manures or sludge to fields that will be rotated into legumes, to other
fields that will not receive manure applications the following year, or to
sites with low runoff and low soil erosion potential.
USDA has developed P application guidelines for situations where
animal manure or other agricultural by-products are applied (see Table
4a-ll). Producers unable to meet the P-based application rate
requirement of the standard initially are encouraged to do so in a
reasonable period of time using progressive planning approaches.
Soil testing for pH, phosphorus (Figure 4a-4), potassium, and nitrogen
(Figure 4a-5). Preplant or midseason soil profile nitrate testing (e.g., a
pre-sidedress nitrate test) should be used when appropriate. Sub-soil
sampling for residual nitrate may be needed for irrigated croplands.
Surface layer sampling (0-2 inches) for elevated soil P and soil acidity
may be needed when there is permanent vegetation, non-inversion
Soil, tissue, and
manure testing
provide useful
information for
nutrient
management
planning.
Table 4a-11. Allowable P Application Rates for Organic By-products (e.g., manure)
A-NRCS, 1977, revised 1999).
The following guidelines are contained in USDA's Conservation Practice Standard 590 for Nutrient Management.
For phosphorus, one of the following options should be used to establish acceptable phosphorus application rates
when manure or other organic by-products are applied:
• Phosphorus Index (PI) Rating. Nitrogen based manure application on Low or Medium Risk sites,
phosphorus based or no manure application on High and Very High Risk Sites.**
• Soil Phosphorus Threshold Values. Nitrogen based manure application on sites on which the soil test
phosphorus levels are below the threshold values. Phosphorus based or no manure application on sites on
which soil phosphorus levels equal or exceed threshold values.**
• Soil Test. Nitrogen based manure application on sites on which there is a soil test recommendation to apply
phosphorus. Phosphorus based or no manure application on sites on which there is no soil test
recommendation to apply phosphorus.**
** Acceptable phosphorus based manure application rates shall be determined as a function of soil test recommendation or
estimated phosphorus removal in harvested plant biomass. Guidance for developing these acceptable rates is found in the
NRCS General Manual, Title 190, Part 402 (Ecological Sciences, Nutrient Management, Policy), and the National Agronomy
Manual, Section 503).
National Management Measures to Control Nonpoint Pollution from Agriculture
4-55
-------
Chapter 4: Management Measures
Figure 4a-4. Example of soil test report (Pennsylvania State University, 1992a).
I
07/31/84 0004
DATE LAI HO.
700234
SERIAL HO.
SOMERSET
COUXTY
25 KPBUU1 READZHOTOH
ACRES FIELD COZL
___ THE FEmSYLVAMZA STATE UXZVEKSITY s*-*^
/^5^\ COLLEGE OF AGRICULTURE /fTjTVV
(!&S5fifc) MEMtE LABORATORY - SOZL 6 FORAGE TESTIHC [(&£$«)
\JS& UKVERS1TY PARK, FA 16102 \Sm:^^^^^3
•
nw%^ .
ouvr erepi M« ST 2 eoMwt 1 1
C«lciu» C»rbon»tt tqulv»l«nt
PHOSPHATE (F,0.) POTASH (K,0) NAOnCZIM (MgO)
Wlb/A
Wlb/A ,,lb/A
• USE A STARTER FERTILIZER
• LIMESTONE NECOMMENOATION. IP ANV, IS TO MINO THE SOIL PH TO «.O • «.l.
MULTIPLY THE UCHANOAILE ACIDITY IV 1000 TO I IT I MATE THI LIME RIOUIMMENT FOR
PH «.t • 7.0.
• RICOMMENOEO LIMESTONE CONTAINING .3% MOO WILL MIIT THI MO REQUIREMENT.
• IF MANURE WILL IE APPLIED. SIE IT- 10 'USE 0' MANURE"
(•LABORATORY HISU, is
6.2 50
SOZL pH F lb/A
4.1 0.
ACIDITY
EXCHANGEAB
OTHER TESTS i oROAMIC KATTER -
*** we*
i.a
a, 4
• .7
t
19 0.6 7.8 12.6 l.i *'7 *1*8
1C Mg C« CEC K *9 i*
LE CATZOHS (M^/lOO Q» * SATURATZOJI
2.2 %
4-56
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
Figure 4a-5. Example of Penn State's soil quicktest form (Pennsylvania State University, 1992a).
PENNSTATE
PRE-SIDEDRESS SOIL NITROGEN TEST FOR CORN
QUICKTEST EVALUATION PROJECT
- SOIL TEST INFORMATION AND REPORT FORM -
SHfl*lfl (PUAii PRINT]
TNAMIT
T STREET CM R.O. MO, t
TC
-------
Chapter 4; Management Measures
tillage, or when animal manure or other organic by-products are
broadcast or surface-applied.
5. Plant tissue testing, e.g. chlorophyll testing in corn.
6. Manure, sludge, mortality compost, and effluent testing.
7. Quantification of nutrient impacts from irrigation water, atmospheric
deposition, and other important nutrient sources.
8. Use of proper timing, formulation, and application methods for nutrients
that maximize plant utilization of nutrients and minimize the loss to the
environment. This includes split applications and banding of the
nutrients, use of nitrification inhibitors and slow-release fertilizers, and
incorporation or injection of fertilizers, manures, and other organic
sources. In addition, fall application of N fertilizer on coarse-textured
soils should be avoided. Manure should be applied uniformly in
accordance with crop needs, but surface application to no-till cropland
should be avoided.
9. Coordination of irrigation water management with nutrient management.
For example, in-field measurement of crop and soil N status during the
growing season can be coupled with high-frequency irrigation to match
N applications with crop needs and reduce N losses (Onken et al., 1995).
Irrigation should also be managed to minimize leaching and runoff.
10. Use of small grain cover crops or deeply-rooted legumes to scavenge
nutrients remaining in the soil after harvest of the principal crop,
particularly on highly leachable soils. Consideration should be given to
establishing a cover crop on land receiving sludge or animal waste if
there is a high leaching potential. Sludge and animal waste should be
incorporated or subsurface injected.
11. Use of buffer areas or intensive nutrient management practices to
address concerns on fields where the risk of environmental
contamination is high, such as:
G Karst topographic areas containing sinkholes and shallow soils over
fractured bedrock,
G Subsurface drains (e.g., drain tile),
G Lands near surface water,
G High leaching index soils,
G Irrigated land in humid regions,
O Highly erodible soils,
O Lands prone to surface loss of nutrients, and
O Shallow aquifers and drinking water supplies.
For example, nitrification inhibitors may be needed when conditions
promote leaching, and banding or ridge application may render
applied N or P less susceptible to leaching. Manure should not be
applied to frozen or saturated soils, to shallow soils over fractured
bedrock, or to excessively drained soils.
12. Use of soil erosion control practices to minimize runoff and soil loss.
13. Calibrate nutrient application equipment regularly.
4-58 National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
14. A narrative accounting of the nutrient management plan that explains the
plan and its use.
The best means for implementing and coordinating many of the above activities
is through a comprehensive, site-specific nutrient management plan. Nutrient
management plans should be reviewed annually to determine if modifications
are needed for the next crop, and a thorough review of the plan should be done
at least once every 5 years or once per crop rotation period. Application equip-
ment should be calibrated and inspected for wear and damage periodically and
repaired when necessary. Records of nutrient use and sources should be main-
tained along with other management records for each field. This information
will be useful when it is necessary to update or modify the management plan.
A list of the required nutrient management plan elements for confined animal
operations in the Pequea-Mill Creek (PA) National Monitoring Program project
is shown Table 4a-12. Table 4a-13 shows a set of nutrient recommendations
from a Vermont Crop Management Association. Table 4a-14 shows two sum-
mary tables from a sample plan.
Practice Effectiveness
Following is a summary of information regarding pollution reductions that can
be expected from installation of nutrient management practices.
G The State of Maryland estimates that average reductions of 34 pounds of
nitrogen and 41 pounds of P2O5 applied per acre can be achieved
through the implementation of nutrient management plans (Maryland
Department of Agriculture, 1990), These average reductions may be
high because they apply mostly to farms that use animal wastes; average
reductions for farms that use only commercial fertilizer may be lower.
G As of July 1990, the Chesapeake Bay drainage basin states of
Pennsylvania, Maryland, and Virginia had reported that approximately
114,300 acres (1.4% of eligible cropland in the basin) had nutrient
management plans in place (EPA, 1991a). The average nutrient reductions
of TN and TP were 31.5 and 37.5 pounds per acre, respectively. The States
initially focused nutrient management efforts on animal waste utilization.
Because initial planning was focused on animal wastes (which have a
relatively high total nitrogen and phosphorus loading factor), estimates of
nutrient reductions attributed to nutrient management may decrease as
more cropland using only commercial fertilizer is enrolled in the program.
O In Iowa, average corn yields remained constant while nitrogen use
dropped from 145 pounds per acre in 1985 to less than 130 pounds per
acre in 1989 and 1990 as a result of improved nutrient management. In
addition, data supplied from nitrate soil tests indicated that at least 32%
of the soils sampled did not need additional nitrogen for optimal yields
(Iowa State University, 1991b).
O Data from the 66,640-acre Big Spring ground water basin in
northeastern Iowa indicate that reduced application of nitrogen fertilizer
associated with the 1983 payment-in-kind set-aside program resulted in
reduced nitrate levels in ground water two years later (Hallberg et al.,
1993). Based upon this analysis, it is postulated that water quality
improvements at the watershed level will be definable over time in
National Management Measures to Control Nonpoint Pollution from Agriculture 4-59
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Chapter 4: Management Measures
Table 4a-12. Required nutrient management plan elements for confined animal operations in the Pequea-Mill Creek
National Monitoring Program project, Pennsylvania.
A. Farm Identification
including location, receiving waters, size of operation, and farm maps of fields, soils, and slopes
B. Summary of Plan
Manure summary, including annual manure generation, use, and export
Nutrient application rates by field or crop
Summary of excess manure utilization procedures
Implementation schedule
Manure management and stormwater BMPs
C. Nutrient Application
Inventory of nutrient sources
Animal populations
Acreage and expected crop yields for each crop group
Nutrients necessary to meet expected crop yields
Nutrient content of manure
Nitrogen available from manure
Residual N from legumes and past manure applications
Planned manure application rate
Target spreading rates for manure application
Nitrogen balance calculation
Winter manure spreading procedures (if applicable)
D. Alternative Manure Use
Amount, destination, and use of manure exported to other landowners, brokers, markets, or used in other than
agricultural application
E. Barnyard Management
F. Storm Water Runoff Control
Source: Penn State Cooperative Extension. 1997. Pequea-Mill Creek Information Series. Smoketown, PA.
Table 4a-13. Missisquoi Crop Management Association 1997 nutrient recommendations.
Crop
Corn
Alfalfa
New
Seeding
Grass
1st Cut
Grass
2nd Cut
Field
Name
#7
#9A
#11
Spooner 3
#1
#3
#1
#3
Manure
Applied Recom.
Acres In Fall Manure
Rate
9.7 9742 0
or 373711
11.3 2000 5226
20.0 5625 8798
4.3 3333
orO
10.0 4135
or 0
10.8 7986 0
10.0 0
10.8 3755
Loads A
3375 gal Ib/A N ?2^5 K20 Mlcronutrients
0 150 10 20 20 with 1.33% Zinc
150 10 20 20 with 1.33% Zinc
17 150 10 20 20 with 1,33% Zinc
52 250 10 20 20 with 0.8% Zinc
NONE
300 5 10 30 with 0.6% Boron
12 NONE
200 23 0 30
NONE
200 23 0 30
12 NONE
Fter Manure& Fertilizer
—Remaining Need-
N P2(>5 «20
47
0
0
0
0
0
0
0
6
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
26
40
0
0
0
-Lime
Mg
0
0
0
0
0
0
0
0
0
0
0
Need
2.0
2.0
2.0
1.0
4-60
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4A: Nutrient Management
Table 4a-14.
Plan Summary from a Sample Plan (Pennsylvania State University Cooperative Extension, 1997).
Manure Summary Table
Generated
Manure Source on the Farm
liquid dairy 523,000 gal
uncollected solid dairy 263 tons
collected solid dairy 175 tons
solid poultry 1 ,860 tons
Nutrient Application Rates by Crop Group
Starter Fertilizer
Nutrients
Crop Group
Corn, grain
(liquid manure)
Corn, grain
(liquid manure)
Corn, silage
(liquid manure)
Corn, silage
(solid manure)
Alfalfa (new)
Alfalfa
-All numbers
Acres
32
18
12
9
21
53
(Ibs
N
10
10
20
20
10
0
per acre)
PA K.O
20 10
20 10
20 10
20 10
20 10
0 0
Used on the Farm
523,000 gal
263 tons
175 tons
0 tons
Planned
Manure
Application
Rate/ac.
9,000 gal
9,000 gal
6,000 gal
20 tons
0
0
When
Manure
Applied
Exported
from the Farm
Ogal
0 tons
0 tons
1 ,860 tons
Additional Chemical
Fertilizer Nutrients
(Incorp. time) N
spring
(2-4 days)
fall
(2-4 days)
fall
(2-4 days)
fall/spring
(2-4 days)
-
-
0
50
0
0
0
0
Applied
PA
0
0
0
0
40
120
K20
0
0
0
20
230
200
rounded off recognizing the built-in variation in figures used.
- Manure application Is
restricted
a) within 100 feet of the farm welt
(unless the
manure is
supplemental fertilizer
in the following
areas:
(field A-13) and the neighbor's wel
incorporated within 24 hours
needs may
b) within 100 feet of Little Fishing
of application, in
(field A-7), where
surface flow is towards the well
which case manure application rates and
need to be adjusted)
Creek when the ground is frozen, snow-covered, or saturated (fields A-2 and A-3)
c) within the grassed waterway when the ground is frozen, snow-covered, or saturated
(fields A-1 and
A-2)
responsive ground water systems if significant changes in nitrogen
application are accomplished across the watershed.
In a pilot program in Butler County, Iowa, 48 farms managing 25,000
acres reduced fertilizer nitrogen use by 240,000 pounds by setting
realistic yield goals based on soils, giving appropriate crop rotation and
manure credits, and some use of the pre-sidedress soil nitrate test
(Hallberg et al., 1991). Other data from Iowa showed that in some areas
fields had enough potassium and phosphorus to last for at least another
decade (Iowa State University, 1991b).
In Garvin Brook, Minnesota, fertilizer management on corn resulted in
nitrogen savings of 29 to 49 pounds per acre from 1985 to 1988 (Wall et
al., 1989). In this Rural Clean Water Program (RCWP) project, fertilizer
management consisted of split applications and rates based upon
previous yields, manure application, previous crops, and soil test results.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-61
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Chapter 4: Management Measures
G Baker (1993) concluded that the downward trends in total and soluble
phosphorus loads from Lake Erie tributaries for the period from the late
1970s to 1993 indicate that agricultural controls have been effective in
reducing soluble phosphorus export. Tributary nitrate concentrations
increased, however, possibly due to adoption of conservation tillage,
which enhances water percolation into the soil, and the extensive use of
tile drainage systems in the watersheds,
G Berry and Hargett (1984) showed a 40% reduction in statewide nitrogen
use over 8 years following introduction of improved fertilizer
recommendations in Pennsylvania. Findings from the RCWP project in
Pennsylvania indicated that, for 340 nutrient management plans, overall
recommended reductions (corn, hay, and other crops) were 27% for
nitrogen, 14% for phosphorus, and 12% for potash (USDA-ASCS,
1992a). Producers achieved 79% of the recommended nitrogen
reductions and 45% of the recommended phosphorus reductions. In the
same project area, Hall (1992) documented 8 to 32% decreases in
median nitrate concentrations in ground water samples following
decreases of 39-67% in N application rates under nutrient management.
G Base flow concentrations of dissolved nitrate-nitrite from a 909-acre
subwatershed under nutrient management decreased slightly relative to a
915-acre paired subwatershed in the Little Conestoga Creek watershed in
Pennsylvania, suggesting that nutrient management had a positive impact
on water quality (Koerkle et al., 1996). Nutrient applications in the 909-
acre treated subwatershed (study site) decreased in the period 1986-1989
by about 30% versus the period 1984-1986 (pre-implementation) as 85%
of the land was placed under nutrient management. Less than 10% of the
land was under nutrient management in the 915-acre untreated
subwatershed (control site). The study was extended for two years to
improve upon the findings, but implementation at the control site resulted
in nutrient management on 40% of agricultural land, while
implementation for the study site stood at 90% (Koerkle and Gustafson-
Minnich, 1997). Nitrogen applications for the period 1989-1991 were
about 7% less than for the period 1984-1986 at the study site, a much
smaller decrease than the 30% decrease reported for the period 1986-
1989. Nutrient application data were not available for the control site.
The lack of statistically significant reductions in dissolved nitrate-nitrite
for the period 1989-1991 versus 1984-1986 is interpreted as an indication
that a reduction in nitrogen input of 30% (as achieved in 1986-1989) is
needed to cause a 0.5 mg/L decrease in dissolved nitrate-nitrite.
A related study in the Conestoga River headwaters, Pennsylvania,
showed that nutrient management caused statistically significant
decreases in nitrate concentrations in ground water (Hall et al., 1997).
Changes in nitrogen applications to the contributing areas of five wells
were correlated with nitrate concentrations in the well water on a 55-acre
crop and livestock farm in carbonate terrain. Lietman et al. (1997) showed
that terracing decreased suspended-sediment yield as a function of runoff,
but also increased nitrate-nitrite yields in runoff, and increased nitrate
concentrations in ground water at 4 of the wells ona23.1-acre site.
G A 6-year study in the 403-acre Brush Run Creek watershed in
Pennsylvania showed that monthly and annual base flow loads of total
4-62 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4A: Nutrient Management
nitrogen, dissolved nitrite-nitrate, total ammonia plus organic nitrogen,
and total and dissolved phosphorus and orthophosphorus decreased
during the 3-year period when nutrient management was implemented
(Langland and Fishel, 1996), However, stormflow discharges of total
nitrogen and total phosphorus increased by 14 and 44%, respectively,
while nitrogen and phosphorus applications were reduced by 25 and
61%. Fewer storms were sampled during two of the three years under
nutrient management due to a significant decrease in precipitation
during the growing seasons. Maximum total nitrogen concentrations
were 21 mg/L above the tile drains before nutrient management, and
2,400 mg/L in the tile drains before nutrient management (Langland and
Fishel, 1996). Median concentrations of total nitrogen and dissolved
nitrite-nitrate were reduced from 3.3 and 1.2 mg/L, respectively, to 2.5
and 0.90 mg/L when nutrient management was applied above the tile
drains. Nutrient management in this tile-drained watershed resulted in a
14% decrease in nitrogen and 57% decrease in phosphorus applied as
commercial and manure fertilizer.
In Vermont, research suggested that a newly introduced, late spring soil
test resulted in about a 50% reduction in the nitrogen recommendation
compared to conventional technologies (Magdoff et al., 1984). Research
in New York and other areas of the nation documented fertilizer use
reductions of 30 to 50% for late spring versus preplant and fall
applications, with yields comparable to those of the preplant and fall
applications (Bouldin et al., 1971).
Improved nutrient management on a case-study group of 8 United States
Department of Agriculture (USDA) Demonstration Projects (DP) and 8
Hydrologic Unit Area (HUA) Projects resulted in reported nitrogen
application reductions ranging from 14 to 129 Ib/ac and phosphorus
Table 4a-15. Reported changes in average annual nutrient application rates on land with practice adoption in
19 USDA Demonstration and Hydrologic Unit Area Projects, 1991-1995.
Nitrogen Reductions Phosphorus Reductions
Project Purpose1
AL HUA N, P
IN HUA N, P
Ml HUA N, P
NY HUA N, P
UT HUA P
DE HUA N, P
ILHUA N, P
OR HUA N
MDDP N, P
NC DP N, P
Wl DP N, P
FLOP N, P
MN DP N, P
NEDP N
TX DP N, P
CA DP N, P
Mb/ac>
129
21
41
14
—
118
117
52
43
72
78
14
30
21
21
47
(Ib/ac)
106
30
18
21
0
96
36
—
42
n/a
18
3
21
— -
18
11
1 Nutrients to be controlled as project objective: N=nitrogen, P=phosphorus
— = data not applicable
n/a = data not available
Source: Meals, D.W., J.D. Button, and R.H.
Griggs. 1996. Assessment of Progress
of Selected Water Quality Projects of
USDA and State Cooperators. USDA-NRCS, Washington, D.C.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-63
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Chapter 4: Management Measures
application reductions of 0 to 106 Ib/ac (Table 4a-15). The case study
group included both animal and crop agriculture and both irrigated and
non-irrigated cropland.
Additional results from evaluations of practice effectiveness may exist for
specific practices in particular regions. Potential sources of such documentation
include the USDA MSEA/ADEQ (Management Systems Evaluation Areas/
Agricultural Systems for Environmental Quality) Programs (http://
www.nps.ars.usda.gov/) and the US EPA Section 319 National Monitoring
Program (http://h2osparc.wq.ncsu.cdu/319index.html).
A summary of the literature findings regarding the effectiveness of nutrient
management in controlling nitrogen and phosphorus is given in Table 4a-16.
Table 4a-16. Relative effectiveness1' of nutrient management (Pennsylvania State
University, 1992l>).
Practice
Nutrient Management0
Percent Change in Total
Phosphorus Loads
-35
Percent Change in Total
Nitrogen Loads
-15
a Most observations from reported computer modeling studies
b An agronomic practice related to source management; actual change in contaminant load
to surface and ground water Is highly variable.
Effective nutrient
management will not
transfer problems
from surface to
ground water, or vice
versa.
Factors in Selection of Management Practices
The movement of available nutrients to surface and/or ground waters
depends on the properties of the nutrients involved, climate, soil and geologic
characteristics, and land management practices such as crops grown, fertilizer
applications, erosion control, and irrigation water management. These factors
determine which specific strategies and practices should be selected to reduce
nutrient movement in a given situation. Land management practices such as
selection of fertilizer formulation or rate and method of application can be
controlled, while environmental factors such as climate cannot. Other factors,
such as crop selection and farming equipment, are governed to varying degrees
by economic considerations and may therefore limit nutrient management
options in some cases.
Care should be taken that practices to control surface runoff do not increase the
risk of ground water contamination, and vice versa. In general, practices that
increase the efficiency of nutrient use and thereby reduce availability of nutri-
ents for loss are the first line of defense in nutrient management. Control of
detachment and transport of nutrients in the particulate phase and of runoff and
leaching of soluble forms may be achieved with other practices or management
measures, including erosion and sediment control and irrigation water manage-
ment.
The characteristics of the agricultural operation are critical considerations in
selection of appropriate practices for nutrient management. Specific nutrient
management practices will differ markedly, for example, between a large grain
farm, where all nutrients are supplied by purchased fertilizer and can be applied
by precision farming methods, and a small dairy farm, where nutrients are
4-64
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4A: Nutrient Management
supplied by animal waste, legumes, and purchased fertilizer, and exact nutrient
balance is difficult to achieve. The equipment and facilities available to the
producer, such as manure or fertilizer application equipment and the type of
waste storage system influence both the form of the nutrients and the producer's
ability to efficiently manage the nutrients.
Climatic and other environmental conditions such as soils and geology are key
determinants in the selection of practices. For example, the need for irrigation to
grow crops in the Columbia Basin of Washington places a premium on careful
scheduling of fertigation to protect ground water below sandy soils (Annandale
and Mulla, 1995), whereas the yield variability in midwestern claypan soils
makes "on-the-go" changes in fertilizer application rates essential to maximizing
the efficiency of N uptake (Kitchen et al., 1995). In addition, local environmen-
tal factors, such as the presence of sensitive or protected waterbodies, may
require additional practices such as buffer strips or vegetative filter strips to
reduce delivery of nutrients lost from agricultural land.
Local and regional agricultural economies and land use mix can also be impor-
tant factors in selecting nutrient management practices. In livestock agriculture,
the available land base with respect to animal populations may limit the poten-
tial for full use of manure nutrients on farm land and require efforts to export
manure from an area in order to follow a nutrient management plan. Proximity
to residential and urban centers can offer opportunities for exporting manure
nutrients, but may also limit some forms of nutrient management due to odor
problems or other perceived nuisances.
Finally, a range of issues such as the availability of soil, manure, and plant
testing services; the availability of nutrient management consultants; the oppor-
tunity for producer training; the availability of rental equipment for specialized
operations; and State, Tribal, and local laws and regulations may all affect the
selection of best management practices for any given location.
Cost and Savings of Practices
Costs
In general, most of the costs documented for this management measure are
associated with technical assistance to landowners to develop nutrient manage-
ment plans. Some costs are also involved in ongoing nutrient management
activities such as soil, manure, and plant tissue testing. Technical assistance in
nutrient management is typically offered by universities, farm service dealers,
and independent crop consultants. Rates vary widely depending on the extent of
the service and type and value of the crop. Fees can range from about $5 per
acre for basic service up to $30 per acre for extensive consultation on high-value
crops (NAICC, 1998).
Typical nutrient management costs for Vermont dairy farms begin with a $150
fixed charge for a nutrient management plan. There is an additional $6 per acre
for corn land, which includes record-keeping for manure, fertilizer, and pesticide
applications, soil analysis for each field, manure test, and a PSNT; cost for
grassland is $4 per acre, which includes the same services as for corn fields
except the PSNT (Stanley, 1998).
National Management Measures to Control Nonpoint Pollution from Agriculture 4-65
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Chapter 4: Management Measures
In Pennsylvania, where state law requires extensive nutrient management
planning, charges for development of a plan range from $400 to $900. Specific
costs vary from around $3 to $4 per acre for a "generic" plan without soil
sampling or weed and insect control recommendations, up to $8 to $12 per acre
for a complete plan with full scouting (Craig, 1998).
In Maryland, again subject to a recent state law requiring all farms to have
nutrient management plans, average costs across the state are about $3 per acre,
which includes writing the plan, technical recommendations on fertilization and
waste management, maps, and record-keeping (Maryland Dept. of Agriculture,
1998). Soil and manure testing are additional costs, at $2 to $5 per analysis.
Charges listed by an Illinois crop consultant range from $5 to $15 per acre for
services including scaled maps, manure analysis, soil testing, and site specific
recommendations for fertilizer and manure applications (Cochran, 1998).
A Wisconsin agronomic service charges $5 to $8 per acre for nutrient manage-
ment services that include farm aerial maps; identification of fields with manure
spreading restrictions; soil test reports; animal inventory with manure analysis;
written plans for each field specifying crop to be grown, previous crop grown,
fertilizer recommendations, legume and manure credits, manure application
rates, and record-keeping sheets; and regular field scouting (Polenske, 1998).
In Nebraska, a crop consulting service charges $5 per acre for basic soil fertility
and pest and water management, another $4 per acre for precision-farming GPS
grid samples, plus a separate soil analysis charge (Michels, 1998).
Savings
In many instances landowners can actually save money by implementing nutri-
ent management plans. For example, Maryland estimated (based on the over 750
nutrient management plans that were completed prior to September 30, 1990)
that plan recommendations would save the landowners an average of $23 per
acre per year (Maryland Dept. of Agriculture, 1990). This average savings may
be high because most of the 750 plans were for farms using animal waste.
Savings for farms using commercial fertilizer may be less.
In the South Dakota RCWP project, the total cost (1982-1991) for implementing
fertilizer management on 46,571 acres was $50,109, or $1.08 per acre (USDA-
ASCS, 1991a). In the Minnesota RCWP project, the average cost for fertilizer
management for 1982-1988 was $20 per acre (Wall et al., 1989). Assuming a
cost of $0.15 per pound of nitrogen, the savings in fertilizer cost due to im-
proved nutrient management on Iowa corn was about $2.25 per acre as rates
dropped from 145 pounds per acre in 1985 to about 130 pounds per acre in 1989
and 1990 (Iowa State University, 199la).
4.66 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4A: Nutrient Management
USDA/NRCS Comprehensive Nutrient Management
Planning Technical Guidance, December 1, 2000.
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National Management Measures to Control Nonpoint Pollution from Agriculture
4-67
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Chapter 4: Management Measures
4-68 National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4B: Pesticide Management
4B: Pesticide Management
To reduce ccmtamjiiatioa
JnYeato
history/
& Use anti-backflow devices &$&& wausr
, mixing and lo&Olng practices smell as a ss
; " 'k^ttg; and various new te<%blegi0$ f
*
Six general
principles guide safe
pesticide
management.
Management Measure for Pesticides: Description
The goal of this management measure is to reduce contamination of ground and
surface water from pesticides. The basic concept of the pesticide management
measure is to foster effective and safe use of pesticides without causing degrada-
tion to the environment. The most effective approach to reducing pesticide
pollution of waters is, first, to release a lesser quantity of and/or less toxic
pesticides into the environment and, second, to use practices that minimize the
movement of pesticides to ground and surface water (Figure 4b-l). In addition,
pesticides should be applied only when an economic benefit to the producer will
be achieved. This usually results in some reduction in the amount of pesticides
being applied to the land, plants, or animals, thereby enhancing the protection of
water quality and possibly reducing production costs as well.
The pesticide management measure identifies a series of steps or thought
processes that producers should use in managing pesticides. First, the pest
problems, previous pest control measures, and cropping history should be
evaluated for pesticide use and water contamination potential. Second, the
physical characteristics of the soil and the site, including mixing, loading, and
storage areas, should be evaluated for leaching and/or runoff potential. Inte-
grated pest management (IPM) strategies should be used to minimize the amount
of pesticides applied. In rare cases, IPM practices may not be available for some
Pesticide
management
consistent with this
management
measure is based on
pesticide application
only when an
economic benefit is
anticipated.
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Chapter 4: Management Measures
Figure 4b-1. Pesticide Fate: Major Pathways
Pesticide labels must
be followed.
Calibrating
equipment saves
money and reduces
damage to the
environment.
commodities or in certain regions. An effective IPM strategy should call for
pesticide applications only when an economic benefit to the producer will be
achieved and not on a routine schedule. In addition, pesticides should be applied
efficiently and at times when runoff and leaching losses are unlikely.
When pesticide applications are necessary and a choice of materials exists,
producers are encouraged to choose the most environmentally benign pesticide
products. State Cooperative Extension Service specialists and Natural Resources
Conservation Service field staff may be able to assist producers in this selection
process.
Users must apply pesticides in accordance with the requirements on the label of
each pesticide product. Label instructions include the following: allowable use rates;
whether the pesticide is classified as "restricted use" for application only by certified
and trained applicators; safe handling, storage, and disposal requirements.
At a minimum, effective pest management requires evaluating past and current
pest problems and cropping history; evaluating the physical characteristics of the
site; applying pesticides only when an economic benefit to the producer will be
achieved; applying pesticides efficiently and at times when runoff losses are
unlikely; selecting pesticides (when a choice exists) that are the most environ-
mentally benign; using anti-backflow devices on hoses used for filling tank
mixtures and on chemigation systems; and providing suitable mixing, loading,
and storage areas. Other factors which may influence pesticide management
decisions include long-term pest management, resistance management, nutrient
management, and soil conservation.
Pest management practices should be updated whenever the crop rotation is
changed, pest problems change, or the type of pesticide used is changed. Appli-
cation equipment should be calibrated and inspected for wear and damage
frequently and repaired when necessary. Anti-backflow devices should also be
inspected and repaired on a regular basis.
4-70
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4B: Pesticide Management
Pesticides: An Overview
What are pesticides?
Agricultural pesticides are chemicals which are used to protect crops against
damaging organisms. They are generally divided into four categories according
to the target pests:
Insecticides are targeted at insect pests. There are many kinds of insecticides in
use today. They may be applied to the soil to protect roots, seeds, or seedlings.
They may also be applied to the crop to protect stems, leaves, or fruit. Some of
the most common insecticides include chlorpyrifos, diazinon, and carbaryl.
Many insecticides kill the insects by disrupting their nervous system, resulting
in paralysis and death. Unfortunately, they can have the same effect on non-
target insects or fish and animals if enough of the applied product drifts or
washes from the field.
Herbicides are used to control weeds in crops. Up to 80% of all pesticides sold
are herbicides and they are used in most crop production systems. Weed
control is one of the most effective practices to increase yields. Herbicides can
be selective, killing the weeds but not the crop, such as atrazine in corn or
trifluralin in soybeans. Other herbicides, such as glyphosate or paraquat, are
non-selective, killing all plants they contact except those genetically engi-
neered to be resistant to that particular herbicide or those that have developed
resistance due to selection by the herbicide. Many herbicides have relatively
low toxicity to insects, fish, or animals because they target specific enzyme
systems found only in plants (Stevens and Sumner, 1991). This is particularly
true for newer herbicides.
Fungicides are used to control fungi which cause disease in crops. They are
applied to seeds, to soil, or to the crop to prevent or slow disease when condi-
tions are favorable for the fungus. Fungicides are used primarily on high-value
food crops and in turf and ornamental plant maintenance. They generally kill
the fungal spores before they can germinate and infect the plant. Fungicides
such as benomyl, metalaxyl, and chlorothalonil are used for a wide variety of
crops, turf, and ornamental plants.
Nematicides are targeted at nematodes which infect plant roots and stunt or kill
the crop. They are always applied to the soil as that is where the target occurs.
Nematicides are generally non-selective, killing most everything they contact
in the soil.
Why are pesticides used in agriculture?
Pests have affected crop production since man first started planting seeds. Crop
damage from insects, fungi, and weeds can reduce yields and crop quality or even
kill the crop in some cases. As a result, farmers have always sought ways to reduce
this damage. Pest control using chemicals such as sulfur or plant extracts has been
around for thousands of years. The first synthetic pesticides were discovered in
the late 1930s and early 1940s and thousands have been developed since.
Pesticide use became widespread in part because the early results were so
promising. Pests which farmers had battled for centuries seemed to be elimi-
nated quickly and easily with these sprays. In many cases, less labor was re-
National Management Measures to Control Nonpoint Pollution from Agriculture 4-71
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Chapter 4: Management Measures
quired to produce a crop since hand or mechanical weeding was no longer
necessary. As a result, yields increased and more acres could be managed by a
farmer.
What are the risks associated with pesticides?
One problem which became evident in the early years of pesticide application
was that pests developed resistance to the chemicals; this in turn devastated
crops. When large areas are regularly sprayed with a pesticide, a population of
pests resistant to the applied chemical can develop. It was learned later that this
problem can be reduced by spraying only when necessary and using different
pesticides when possible.
Another problem was the effect of pesticides on non-target organisms, which
were inadvertently exposed through the food chain. Many of the first pesticides
were persistent in the environment and accumulated in animals which consumed
contaminated insects or fish. As a result of this problem, most modern pesticides
are much less persistent and do not accumulate in the food chain.
There are several potential problems caused by pesticides reaching surface or
ground water. The most severe occurrences involve acute toxicity. Acute toxicity
occurs when negative effects are seen after exposure to relatively high doses of a
pollutant over a short period of time, measured in hours or days. An amount of
pesticide reaching a water body and killing fish or other nontarget species would
be an example of acute toxicity. Most cases of pesticide acute toxicity are caused
by insecticides which drift or wash from fields soon after application. As noted
above, insecticides tend to be much more acutely toxic than other pesticides.
The most widespread problem is the occurrence of pesticides in surface and
ground water used for drinking water. Because this may result in many people
being exposed to the pesticide through their drinking water, there are concerns
about chronic toxicity in these groups. Chronic exposure is when the exposure
occurs over many years at concentrations which cause no outward effects, but
which may increase cancer or other disease risks. Studies have shown that it is
highly improbable that the types and concentrations of pesticides found in
drinking water pose significant risks. However, most agree that it is prudent to
minimize or eliminate pesticide occurrence in drinking water supplies.
The U.S. Geological Survey's (USGS) National Water Quality Assessment
Program (NAWQA) has shown widespread herbicide occurrence in agricultural
streams and shallow ground water. The presence of insecticides was also fre-
quently detected in streams draining high insecticide use watersheds. The
concentrations of these pesticides were measured at levels well below EPA
drinking water standards 99% of the time. However, water quality standards are
based on exposure to a single chemical or pesticide. In the NAWQA studies,
where pesticide contamination of waters was found, there were generally two or
more pesticides present (USGS, 1999).
In recent years, research on pesticides in water supplies, including the NAWQA
studies, has included the study of pesticide degradation products. Degradation
products are the compounds found in the environment as a result of the natural
breakdown of the original pesticide or parent compound. They are usually less
toxic than the original pesticide. While this document does not directly address
4-72 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4B: Pesticide Management
pesticide breakdown products or their effects, the issue is an emerging concern
and will likely receive more attention in the future.
Pesticide Movement into Surface and Ground Water
Pesticides can reach ground and surface water in a number of ways. Surveys of
ground and surface water have found pesticides in many areas of the country.
The extent of the contamination is often well defined, but the source or sources
of contamination can be quite elusive in some cases. Figures 4b-2 to 4b-4
illustrate the major environmental fates of pesticides and are indicative of how
difficult it is to quantitatively assess pesticide fate. However, the sources and
problems associated with ground and surface water contamination are described
in the following section.
Movement to Surface Water
Importance of pesticide contamination of surface water: About half of the
population in the United States gets its water from surface sources. Therefore,
pesticide contamination of surface water is of great concern to many. Several
studies have shown that water supply reservoirs in the Midwest routinely exceed
the health limits for pesticides, although these levels often only occur briefly in
late spring after the main application season.
Losses of pesticides to runoff generally range from <1 to 5% of applied
amounts, depending on various factors. Losses are usually greatest in the 1 to 2
weeks after application, and are highly dependent on storm events. Often,
pesticide residues are only detectable in the first storm event after application.
Pesticides can enter surface water from the atmosphere in the form of drift or
rainfall. Drift into surface waters can be serious locally if the pesticide is highly
toxic to aquatic organisms, as in the case of many insecticides. Rain and fog
have been shown to contain pesticide residues, particularly during the spring
planting season. However, neither drift nor rain are major contributors to surface
water contamination when compared to runoff.
Most pesticide contamination of streams, lakes, and estuaries occurs as a result
of runoff from agricultural and urban areas. Runoff carries with it a mix of
suspended soil particles and any pesticides which were either attached to the
particles or dissolved in surface moisture just before runoff began. The amount
of pesticide loss due to runoff is affected by the following factors:
Rain Intensity — Heavy downpours result in minimal infiltration and maxi-
mum runoff. If soil is already moist prior to a rainfall event, then runoff will be
greater since the soil's capacity to store additional water is reduced.
Surface Conditions — Recently tilled soil and soil with good ground cover
have the most resistance to runoff, since water infiltrates relatively easily and
the surface is "rough" enough to impede the flow of water. Maximum runoff
potential occurs during the month after planting, since the soil is exposed and
the crop has not grown large enough to intercept rain and reduce its ability to
detach and transport soil particles. Reduced tillage practices that maintain
residue on the surface will decrease runoff relative to conventional tillage
practices that leave the soil bare and smooth at planting.
Good soil and water
management are
also essential for
effective pesticide
management.
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4-73
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Chapter 4B: Pesticide Management
Depth to Ground Water: not exactly a soil property but often
closely related. The farther pesticide residues have to leach to reach
ground water, the greater the chance of biological or chemical
degradation. Although degradation rates decline rapidly below the
root zone, most pesticides will degrade slowly as they move toward
the ground water table.
Weather: The degradation and movement of pesticides in soil is highly
influenced by the weather. Warmer or cooler temperatures will speed up
or slow down degradation, respectively.
Hydrologic Loading: The addition of water to areas of pesticide
application is key to the transport of pesticides toward ground water.
Precipitation or irrigation in excess of evapotranspiration rates and soil
water holding capacity can move pesticides deeper into the soil profile
and increase the likelihood of pesticides leaching into ground water
aquifers.
n Spills — Although some soils are very good at adsorbing and degrading
applied pesticides, high concentrations of pesticides which result from
spills overwhelm all these processes. Highly contaminated soils can be a
long-term source of contamination because percolating water will
continue to carry the pesticide into the ground water. Although the
movement of pesticide residues is through leaching, a spill is still
considered a point source.
n Direct Contamination — Ground water can be contaminated directly
in many ways. Some of the most serious include backsiphoning, surface
water movement into wells, or drainage into limestone channels or sink-
holes. These contamination problems can almost always be prevented.
Once they occur, however, the point of entry becomes a point source for
contamination. A plume of contamination moves slowly away from the
source and can spread to contaminate many downgradient wells.
Well contamination is often the result of a lack of proper backflow
prevention devices or poor well construction. Problems such as a poor or
absent casing, lack of grouting, location in a low spot where water
accumulates, or capping below the soil surface are all invitations for
contaminated surface water to enter the well. High nitrates and bacterial
contamination are often associated with these problems.
Pesticide Management Practices and Their Effectiveness
The practices set forth below have been found by EPA to be representative of
the types of practices that can be applied successfully to achieve the manage-
ment measure described above. Additional information about individual prac-
tices, their purpose, and how they work is presented in Appendix A.
1. Inventory current and historical pest problems, cropping patterns, and
use of pesticides for each field.
The purpose of this procedure is to assist the grower in evaluating the
potential for water contamination at the site and to determine IPM
strategies which may be applied to the operation. Much of this
information is important for many aspects of farm operation beyond
pollution prevention. This inventory can be accomplished by using a
National Management Measures to Control Nonpoint Pollution from Agriculture 4-77
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Chapter 4: Management Measures
farm and field map, and by compiling the following information for each
field:
D Crops to be grown and a history of crop production. Certain IPM
strategies, such as crop rotation, require this information.
O Information on soil types. Different soils can have very different
susceptibility to either runoff or leaching losses of applied pesticides.
O The exact acreage of each field. This information can be used to
check application rates as well as yields.
n Records on past pest problems, pesticide use, and other information
for each field. By keeping these records, the grower can evaluate
options for pest management such as crop rotations and alternative
pesticides.
2. Evaluate the soil and physical characteristics of the site including
mixing, loading, and storage areas for potential for the leaching and/
or runoff of pesticides. The most important types of features for
evaluation include:
O Sinkholes, drainage wells, abandoned wells, and karst topography
which allow direct access to ground water. These allow surface water
carrying sediment, bacteria, and pesticides to quickly enter and
contaminate the ground water.
H Proximity to surface water. Pesticides should not be used directly
adjacent to surface water because of the high potential for pesticide
contamination from runoff and drift. An untreated buffer around the
surface water will provide a measure of protection.
D Runoff potential. Steeper slopes, heavier soils, and conventional
tillage all increase the runoff potential for a field. Greater amounts of
organic matter and clay increase the ability of the soil to bind the
pesticide. Conservation tillage tends to increase infiltration and
decrease the amount of runoff, further reducing potential pesticide
losses.
n Aerial drift. Fields with their longer dimension at 90 degrees to the
prevailing wind direction will have lower drift potential than those
parallel to the wind.
Q Soils with a high risk of erosion. Cropping practices such as no-till
can greatly reduce the runoff potential for pesticides on steep slopes
with heavy soils.
Q Soils with poor adsorptive capacity. Low organic matter (<1%) and
clay content reduces the ability of the soil to bind applied pesticides
and prevent them from leaching through to ground water.
O Highly permeable soils. Often soils with poor adsorptive capacity
also have high sand contents which allow water to percolate rapidly
through them. This allows any pesticides present to move quickly
downward before they are degraded by the more abundant microbes
in the surface horizons.
n Shallow aquifers. A shorter distance between the application zone in
the surface soil to the aquifer means less opportunity for binding and
degradation of the pesticide.
4-78 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4B: Pesticide Management
G Wellhead protection areas. Private wells should have a 100-foot
buffer in which no pesticides or fertilizers are applied. Public water
supply wells may require a larger buffer. The buffer minimizes the
risk of agricultural chemicals leaching into the ground water
immediately adjacent.
Use 1PM strategies to minimize the amount of pesticides applied,
including:
G Scouting fields for pest problems. Most universities have scouting
guides for farmers which will provide guidance for procedures
appropriate to their area. Often county extension staff provide training
for scouting, or a farmer may be able to hire a consultant to provide this
service. Many agricultural retailers also provide scouting services as a
part of their pesticide application contracts. The key is to know how and
where to look for pests and their correct identification. For weeds, a
fanner may rely on problems from the previous year or he may walk
a specified length of row to count weed seedlings. For insects, a
sweep net may be brushed through the crop and the insects identified
and counted to estimate the potential for crop damage.
G Determine the economic threshold for pests. This is also information
that is usually available from local extension offices. The expected
value of the crop and the anticipated losses caused by the pest are
estimated against the cost of an application before any sprays occur.
G Use varieties of crops resistant to pests. Resistant varieties usually
require fewer pesticide applications.
G Use crop rotation. Crop rotations interrupt pest buildup by
eliminating the host plants or by allowing the application of
pesticides which reduce pest populations. An example is a corn-
soybean rotation, in which broadleaf weeds are more easily
controlled in the corn crop and grass weeds are more easily
controlled in the soybean crop.
G Foster biological controls. Identifying the pest properly and
recognizing beneficial insects is key. If a spray is necessary, select a
pesticide which is the most specific to the pest and least toxic to non-
target species. Natural enemies can be introduced and their habitats
preserved. Pheromones can be used to monitor populations, disrupt
mating, or attract predators or parasites.
G Use of improved tillage practices such as ridge tillage.
O Use of cover crops in the system to promote water use and reduce
deep percolation of water that contributes to leaching of pesticides
into ground water.
G Destruction of pest breeding, refuge, and overwintering sites (this
may result in loss of crop residue cover and an increased potential for
erosion).
G Use of mechanical destruction of weed seed through the use of tillage
techniques. Erosion control goals must also be considered when
tillage alternatives are being examined.
G Diversification of habitat. The abundance of pests is greatly
influenced by the environment created by the fanner. Monocultures
National Management Measures to Control Nonpoint Pollution from Agriculture 4-79
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Chapter 4: Management Measures
create a simple environment in which pests may have little or no
competition or predators. Having a broad array of plant species as
crops and in borders diversifies the habitat and dampens pest
populations.
G Use of trap crops, A species or variety of plant which is more
attracted to pests than the main crop can be planted earlier or in an
adjacent area. This will concentrate the pests in a smaller area where
they can be controlled with a pesticide, thus avoiding a wider
pesticide application.
O Use of allelopathic characteristics of crops. There is evidence that
some crops can naturally inhibit the growth of pest populations. For
example, a rye cover crop may reduce weed populations in
subsequent crops.
n Use of timing of field operations (planting, cultivating, irrigation, and
harvesting) to minimize application and/or runoff of pesticides.
D Use of efficient application methods, e.g., spot spraying and banding
of pesticides. Often pest problems occur primarily in one portion of
the field, allowing for targeted pesticide application. Banding may
provide protection of the crop without the entire area being sprayed.
4. When pesticide applications are necessary and a choice of material
exists, consider the persistence, toxicity, and runoff and leaching
potential of products along with other factors, including current label
requirements, in making a selection. This is a complex area and most
pesticide users will not have much of the information necessary to make
such judgements. The leaching potential for many pesticides has been
estimated in several ways and are in general agreement with each other. One
example is the PLP, or Pesticide Leaching Potential, which is an index
of persistence and leaching characteristics of each chemical (Table 4b-l).
Table 4b-l may be useful as a starting point, but other information may
be available from State agencies, NRCS, or universities.
Users must apply pesticides in accordance with the instructions on the
label of each pesticide product and, when required, must be trained and
certified in the proper use of the pesticide. Labels include a number of
requirements including allowable use rates; classification of pesticides
as "restricted use" for application only by certified applicators; safe
handling, storage, and disposal requirements; and other requirements.
Users should contact their state and/or federal pesticide program with
questions concerning specific requirements.
Grower practices can have significant impact on the movement of
pesticides into surface water. Tillage practices, incorporation, and filter
strips all provide significant reductions in pesticide movement from
fields to surface water in most cases (Tables 4b-2, 4b-3). Generally,
practices which slow runoff, increase infiltration, and trap sediment tend
to reduce pesticide losses.
5. Maintain records of application of restricted use pesticides (product
name, amount, approximate date of application, and location of
application of each such pesticide used) for a 2-year period after use,
pursuant to the requirements in section 1491 of the 1990 Farm Bill.
4-80 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4B: Pesticide Management
Table 4b-1. Typical pesticide leaching potential (PLP) index values calculated using commonly reported pesticide
properties, and estimated fraction hitting the soil for six example herbicides (NCCES, 1994).
Common Name
Herbicides:
Acifluoren
Alachlor
Ametryn
Amitrole
Asulam
Atrazine
Trade Name
Blazer
Lasso
Evik
Amitrole-T
Asulox
AAtrex
Application Method3
f
s
s
f
f
f
f, ph7
s, ph7
s, ph5
s, ph7, noncrop
s, ph5, noncrop
PLP Index"
40
52
50
46
53
51
56
60
52
66
57
as = soil application and f = foliar application of pesticide. pH is given where differences have a known effect and data are
available. Noncrop indicates difference in rates, usually higher than crop uses.
bPLP values range from 0 (no leaching potential) to 100 (maximum leaching potential).
Source: North Carolina Cooperative Extension Service. 1994. Soil Facts: Protecting Groundwater in
and Soil Ranking System. North Carolina State University. AG-439-31.
North Carolina, a Pesticide
Table 4b-2. Effect of BMPs on pesticide losses compared to conventional tillage or no filter strips.
Practice
Ridge Till
No-Till
Contour Ridges
Incorporation
Filter Strips
Range of Reductions
-33 - 65
-98-9
29-100
64- 100
85-99
6-41
41
100
53-100
26-75
24-36
7-79
28-31
4-14
9-35
40-72
50-74
15-72
Average
30
51
77
86
92
21
—
—
79
—
30
52
—
—
22
56
63
45
Reference
Baker and Johnson, 1979
Baker and Johnson, 1979
Glenn and Angle, 1987
Halletal., 1991
Halletal., 1984
Franti et al., 1995
Setaetal., 1993
Isensee and Sadeghi, 1993
Ritteretal., 1974
Halletal., 1983
Baker and Laflen, 1979
Franti et al., 1995
Asmussen et al., 1977
Rhode et al., 1980
Halletal., 1983
Mickelson and Baker, 1993
Misra et al., 1994
Misra, 1994
National Management Measures to Control Nonpoint Pollution from Agriculture
4-81
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Chapter 4: Management Measures
Table 4b-3. Summary of buffer studies measuring trapping efficiencies for specific pesticides. Ku( values listed for H
each pesticide are from the NRCS Field Office Technical Guide, Section II Pesticide Property data base ^
(USDA-NRCS, 2000).
Pesticide Koc
Highly adsorbed pesticides
Chlorpyrifos 6,070
Diflufenican 1.990
Lindane 1,100
Trifluralin 8,000
Moderately adsorbed pesticides
Acetochior 150
Alachlor 170
Atrazine 100
Cyanazine 190
2.4-D 20
Dicamba 2
Fluormeturon 100
Isoproturon 120
Mecoprop 20
Metolachlor 200
Metribuzin 60
Norflurazon 600
Study reference
Boyd, etal., 1999
Cole, et at.. 1997
Patty, etal., 1997
Patty, etal., 1997
Rhode, etal., 1980
Boyd, etal., 1999
Lowrance, et al., 1997
Arora, et al., 1996
Boyd. etal.. 1999
Hall, eta!. ,1983
Hoffman 1995
Lowrance, et al., 1997
Mickelson and Baker 1993
Misra.etal., 1996
Patty, etal., 1997
Arora, etal., 1996
Misra.etal., 1996
Asmussen, et al., 1977
Cole, et al.. 1997
Cole, etal., 1997
Rankins, et al., 1998
Patty, etal., 1997
Cole, etal., 1997
Arora, et al., 1996
Misra.etal., 1996
Webster and Shaw 1996
Tingle, et al., 1998
Webster and Shaw 1996
Tingle, etal.. 1998
Rankins, etal., 1998
•
Percent pesticide trapped
57-79
62-99
97
72-100
86-96
56-67
91
11-100
52-69
91
30-57
97
35-60
26-50
44-100
80-100
30-47
70
89-98
90-100
60
99
89-95
16-100
32-47
55-74
67-97
50-76
73-97
65
4-82
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4B: Pesticide Management
Section 1491 requires that such pesticide records shall be made
available to any Federal or State agency that deals with pesticide use or
any health or environmental issue related to the use of pesticides, on the
request of such agency. Section 1491 also provides that Federal or State
agencies may conduct surveys and record the data from individual
applicators to facilitate statistical analysis for environmental and
agronomic purposes; however, in no case may a government agency
release data, including the location from which the data was derived,
that would directly or indirectly reveal the identity of individual
producers. Section 1491 provides that in the case of Federal agencies,
access to records maintained under section 1491 shall be through the
Secretary of Agriculture or the Secretary's designee. This section also
provides that State agency requests for access to records maintained
under section 1491 shall be through the lead State agency so designated
by the State.
Section 1491 includes special access provisions for health care
personnel. Specifically, when a health professional determines that
pesticide information maintained under this section is necessary to
provide medical treatment or first aid to an individual who may have
been exposed to pesticides for which the information is maintained,
upon request persons required to maintain records under section 1491
shall promptly provide records and available label information to that
health professional. In the case of an emergency, such record
information shall be provided immediately.
Operators should consider maintaining records beyond those required by
section 1491 of the 1990 Farm Bill. For example, operators may want to
maintain records of all pesticides used for each field, i.e., not just
restricted use pesticides. These records will be useful in setting up IPM
programs and in crop rotation and management decisions. In addition,
operators may want to maintain records of other pesticide management
activities such as scouting records or other IPM techniques used and
procedures used for disposal of remaining pesticides after application.
Operators should also check with state and local agencies regarding
record keeping requirements.
6. Use only the recommended amount of pesticide for the problem you or
a professional have identified and determined to merit pesticide
application.
1. Recalibrate and repair application equipment, including chemigation
equipment, at least each spray season. Use anti-backflow devices on
hoses used for filling tank mixtures and on chemigation systems.
Calibration of pesticide spray equipment at least once each spray season
is critical to ensuring that proper application rates are maintained.
As replacement equipment is needed, purchase new, more precise
application equipment and other related farm equipment (including
improved nozzles, computer sensing to control flow rates, radar speed
determination, electrostatic applicators, and precision equipment for
banding and cultivating).
8. Solid pad for mixing and loading pesticides.
National Management Measures to Control Nonpoint Pollution from Agriculture 4-83
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Chapter 4: Management Measures
EPA's Office of Pesticide Programs Promotes
Registration of Lower Risk Pesticides
Since 1993 EPArs Pffic^ of Pgstioide Programs lias '^ijcbumged pesticide, coififai^s to register lower ri$c"
pesticides. The Agency expanded fflis pto|£a&i In4ftf | fp fttrtnef encbt^fei^laceo^fe^r brjajaophos*
phate,(0?) pesticides, B class of'neufototfis^, BMW kedueed-rfs^ Iiittiattve ^cj^it^s.the registration' of
•'eqnventionGl pesticides that the^gwy-bel^ves po^el^s risk^htB^heMtti an^theienvlronmerit than
existing alternatives; The "goal of •the'program jis & qo&My tegister.cdmmeriaai^-viable alternatives, to •
'riskier pesticite §uchtas neTOtijxdns^cajclnog^iSi rejwdduotiy^ and-developffieritaLtoxidailts, and ground
" non-target tarrestrial an4 aquatic p^s; and ^l«i!^
low potential to contaminate' gjoi^^^taface; waters ami work>eli wfiji in^grated^pest iRH^agement ^
programs..&'ote#fcal l^sticides w>ich ali^Jm^-Msany of theW derfmbteeh^a^t@fii§tics are dqsciibed,B ,
below. [' ' "*• '*ff \*'^ '' '. " ' ^ ; \ r- . •'" • -'"^ :.s "
' • The mj& incentive for' pestic54e 'epn^tfos t<) ^^^p
sdes is a om to
duced into foe ratrketfttyi eafSes
also aHowittie rt^Mi^^V^^vM
Qffice
cides
to^c to insects
plant p^sficide j^oc^ots,
that 'destroy cfdpi
4-84
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4B: Pesticide Management
Factors in the Selection of Management Practices
The best way to control pests in crops is to know the crop and pest well enough
to determine a control plan which maximizes crop production while minimizing
environmental impacts. This is often a combination of cultural, biological, and
chemical practices. Cultural controls include tillage, crop rotations, resistant
varieties, and varying planting or harvest dates. Biological controls involve
encouraging or introducing natural enemies of the pest and managing the crop
environment to the disadvantage of the pest. Chemical controls should involve a
selection process which selects a pesticide which results in the greatest eco-
nomic benefit for the least environmental cost. Such a determination requires
knowledge and information which are beyond the average grower. However,
many states have guides to assist in pesticide selection.
Relationship of Pesticide Management Measures to Other
Programs
Under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), EPA
registers pesticides on the basis of evaluation of test data showing whether a
pesticide has the potential to cause unreasonable adverse effects on humans,
animals, or the environment. Data requirements include environmental fate data
showing how the pesticide behaves in the environment, which are used to deter-
mine whether the pesticide poses a threat to ground water or surface water. If the
pesticide is registered, EPA imposes enforceable label requirements, which can
include, among other things, maximum rates of application, classification of the
pesticide as a "restricted use" pesticide (which indicates that a pesticide may have
adverse effects on the environment and/or the applicator and restricts use to
certified applicators trained to handle such pesticides), or restrictions on use
practices. FIFRA allows States to develop more stringent pesticide requirements
than those required under FIFRA, and some States have chosen to do this. The
EPA and the U.S. Department of Agriculture Cooperative Extension Service
provide assistance for pesticide applicator and certification training in each State.
Cost and Savings of Practices
Cosfs
In general, most of the costs of implementing the pesticide management measure
are program costs associated with providing additional educational programs
and technical assistance to producers to evaluate pest management needs and for
field scouting during the growing season.
One of the most important IPM practices is scouting, which carries with it a cost
to the producer. High and low scouting costs are given for major crops in each of
the coastal regions (Table 4b-4). These costs reflect variations in the level of
service provided by various crop consultants. For example, in the Great Lakes
region, the relatively low cost of $4.95 per acre is based on five visits per season
at the request of the producer. Higher cost services include scouting and weekly
written reports during the growing seasons. Cost differences may also reflect
differences in the size of farms (i.e., number of acres) and distance between
farms.
National Management Measures to Control Nonpoint Pollution from Agriculture 4-85
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Chapter 4: Management Measures
The variations in scouting costs between regions and within regions also occur
because of differences in the provider of the service. For example, in some states
the Cooperative Extension Service provides scouting services and training at no
cost or for a nominal fee. In other areas, farmer cooperatives have formed crop
management associations to provide scouting and crop fertility/pest management
recommendations. There are also consulting firms and agricultural retailers with
scouting expertise.
Scouting costs also vary by crop type. Scouting services for high-value cash
crops, such as fruits and vegetables, must be very intensive given that pest
damage is permanent and may make the crop unmarketable.
Another issue regarding the cost of pesticide management practices is selection
of the tillage system and direct and indirect costs associated with that system.
Conservation tillage or no-till practices often rely on the use of herbicides to
control weeds rather than multiple passes with a cultivator employed in conven-
tional tillage, which mechanically destroy the weeds. When deciding between
conservation versus conventional tillage, the direct costs of buying more pesti-
cides (and specific pesticides) for no-till must be weighed against the cost of
running more equipment in the field for conventional tillage. Corn production
under conventional tillage requires an average of more than three passes through
the field to cultivate, while no-till may only require one pass to plant and spray
herbicides. Since each cultivation pass costs nearly seven dollars per acre,
production costs may increase by more than $l4/acre for conventional tillage
compared to no-till, minus any additional costs of herbicides.
Savings
Most of the savings of implementing the pesticide management measure are
associated with a reduction in the amount of pesticides used. IPM usually
requires less pesticide use, thereby reducing the cost of production and increas-
ing the profitability of the crop. In a review of 61 studies of IPM impacts on
crop yield, pesticide use, and economics, pesticide use declined in seven of the
eight commodities evaluated (Norton and Mullen, 1994; Table 4b-5). Some
studies found increased use of pesticides with IPM due to increased awareness
of pest problems, but the majority found reductions.
An additional benefit is associated with the use of no-till practices. Soil losses
are reduced by up to 90% in no-till compared to conventional tillage, reducing
both the indirect costs of erosion and consequent crop yield losses and also
adverse environmental impacts of sedimentation of surface water bodies. Yields
with conservation tillage are often reduced when a farmer first experiments with
it, as it is a new practice which requires new skills and equipment. However, this
situation usually changes with time. An added benefit of no-till is that consider-
able time is saved by only needing to work the field once instead of three or
more times.
4.86 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4B: Pesticide Management
Table 4b-4. Estimated scouting costs (dollars/acre) by coastal region and crop in the coastal zone in 1992 (EPA, 1992a).
COASTAL
REGION
Northeast
Low
High
Southeast
Low
High
Gulf Coast
Low
High
Great Lakes
Low
High
West Coast
Low
High
NA = not available
— = not applicable
a Most fresh market
Corn
5.50
6.25
5.00
6.00
6.00
8.00
4.95
5.50
NA
NA
vegetables
Soybean
NA
NA
3.25
4.00
4.50
6.50
4.25
5.00
NA
NA
are produced
b Scouting costs for hay are based on alfalfa
Wheat
3.75
4.50
3.00
3.50
—
—
3.75
4.00
3.50
5.50
Rice
—
—
8.00
12.00
5.00
9.00
—
—
NA
NA
under a regular spraying
insect inspection
Cotton
—
—
6.00
8.00
6.00
9.00
—
—
6.75
9.30
schedule.
The higher cost in the
Fresh Market
Vegetables3
25.00
28.00
30.00
35.00
35.00
40.00
—
—
32.00
38.00
Great Lakes region
Hayb
2.50
2.75
2.00
3.00
—
—
4.75
5.25
NA
NA
includes
pesticide and soil sampling.
Table 4b-5
. Summary of results of farm-level economic evaluations of IPM programs.
Average Percent Percent
Percent
Number Change In
of Pesticide
Commodity States Studies Use"
Cotton
Soybeans
Corn
Vegetables
and
Flowers
Fruits
Peanuts
Tobacco
Alfalfa
Unweightec
Averageb
TX, GA, MS,
NC, SC, LA,
MO, TN, AZ,
NM, CA, AR
NC, VA, MD
GA, IN
IN, IL, and 10
other states
CT, CA, MA,
TX, FL, OH,
NY, HI
NY, MA, WA,
NJ, CA, CT
GA, TX, OK,
NC
NC
OK, Wl,
Northwest
18
7
3
15
8
5
2
3
-15
-35
+20
-43
-20
-5
-19
-2
-14.9
Change in Percent Change
Production Yield In Net Level of
Cost with Change with Returns Risk with
IPM" IPM* Per Acre" IPM
-7 +29 +79
-5 +6 +45
+3 +7 +54
Quality increased in 4 studies and
same in others
0 +12 +19
-5 +13 +100
— 0 +1
— +13 +37
-2.8 +11.4 +47.8
decreased
decreased
—
remained the
—
—
—
decreased
decreased
B For those producers that adopted the specified IPM practices compared to those that did not.
b Weighting is not possible without an accurate accounting of the acreage affected for each commodity in each state.
Source: Norton, G.W. and J. Mullen. 1 994. Economic evaluation of integrated pest management programs: a literature review.
Va. Coop. Ext. Pub. 448-120, Virginia Tech, Blacksburg, VA 24061.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-87
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Chapter 4: Management Measures
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4C: Erosion and Sediment Control
4C: Erosion and Sediment Control
Apply the erosion-component of a
minimise the delivery of jMimeftt&bm «iciiturat l$*4l to SOstt? 'ywfakj
• , '".. S. * ' •> *" + * 4 ° Jt,l.t»4
' ' *
to •
the contrbuting area f0r$ldmt& of if to'su
* ** • i *.44
24-hte
I't
Management Measure for Erosion and Sediment:
Description
Application of this management measure will preserve soil and reduce the mass
of sediment reaching a water body, protecting both agricultural land and water
quality.
This management measure can be implemented by using one of two general
strategies, or a combination of both. The first, and most desirable, strategy is to
implement practices on the field to minimize soil detachment, erosion, and
transport of sediment from the field. Effective practices include those that
maintain crop residue or vegetative cover on the soil; improve soil properties;
reduce slope length, steepness, or unsheltered distance; and reduce effective
water and/or wind velocities. The second strategy is to route field runoff through
practices that filter, trap, or settle soil particles. Examples of effective manage-
ment strategies include vegetated filter strips, field borders, sediment retention
ponds, and terraces. Site conditions will dictate the appropriate combination of
practices for any given situation. The United States Department of Agriculture
(USDA)-Natural Resources Conservation Service (NRCS) or the local Soil and
Water Conservation District (SWCD) can assist with planning and application of
erosion control practices. Two useful references are the USDA-NRCS Field
Office Technical Guide (FOTG) and the textbook "Soil and Water Conservation
Engineering" by Schwab et al. (1993).
Resource management systems (RMS) include any combination of conservation
practices and management that achieves a level of treatment of the five natural
resources (i.e., soil, water, air, plants, and animals) that satisfies criteria con-
tained in the Natural Resources Conservation Service Field Office Technical
Guide (FOTG). These criteria are developed at the State level. The criteria are
then applied in the provision of field office technical assistance.
The erosion component of an RMS addresses sheet and rill erosion, wind
erosion, concentrated flow, streambank erosion, soil mass movements, road bank
erosion, construction site erosion, and irrigation-induced erosion. National
(minimum) criteria pertaining to erosion and sediment control under an RMS
will be applied to prevent long-term soil degradation and to resolve existing or
potential off-site deposition problems. National criteria pertaining to the water
Sedimentation
causes widespread
damage to our
waterways. Water
supplies and wildlife
resources can be
lost, lakes and
reservoirs can be
filled in, and
streambeds can be
blanketed with soil
lost from cropland.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-E
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Chapter 4: Management Measures
resource will be applied to control sediment movement to minimize contamina-
tion of receiving waters. The combined effects of these criteria will be to both
reduce upland soil erosion and minimize sediment delivery to receiving waters.
The practical limits of resource protection under an RMS within any given area
are determined through the application of national social, cultural, and economic
criteria. With respect to economics, landowners should implement an RMS that
is economically feasible to employ. In addition, landowner constraints may be
such that an RMS cannot be implemented quickly. In these situations, a "pro-
gressive planning approach" may be used to ultimately achieve planning and
application of an RMS. Progressive planning is the incremental process of
building a plan on part or all of the planning unit over a period of time. For
additional details regarding RMS, see Appendix B.
Sediment Movement into Surface and Ground Water
Sedimentation is the process of soil and rock detachment (erosion), transport,
and deposition of soil and rock by the action of moving water or wind. Move-
ment of soil and rock by water or wind occurs in three stages. First, particles or
aggregates are eroded or detached from the soil or rock surface. Second, de-
tached particles or aggregates are transported by moving water or wind. Third,
when the water velocity slows or the wind velocity decreases, the soil and rock
being transported are deposited as sediment at a new site.
Sheet, rill, and gully
erosion can occur on
cropland fields.
Streambank and
streambed erosion
can occur in
intermittent and
perennial streams.
It is not possible to completely prevent all erosion, but erosion can be reduced to
tolerable rates. In general terms, tolerable soil loss is the maximum rate of soil
erosion that will permit indefinite maintenance of soil productivity, i.e., erosion
less than or equal to the rate of soil development. The USDA-NRCS uses five
levels of erosion tolerance ("T") based on factors such as soil depth and texture,
parent material, productivity, and previous erosion rates. These T levels are
expressed as annual losses and range from about 1-5 tons/acre/year (2-11 t/ha/
year), with minimum rates for shallow soils with unfavorable subsoils and
maximum rates for deep, well-drained productive soils.
Water Erosion
Water erosion is generally recognized in several different forms. Sheet erosion is
a process in which detached soil is moved across the soil surface by sheet flow,
often in the early stages of runoff. Rill erosion occurs as runoff water begins to
concentrate in small channels or streamlets. Sheet and rill erosion carry mostly
fine-textured, small particles and aggregates. These sediments will contain
higher proportions of nutrients, pesticides, or other adsorbed pollutants than are
contained in the surface soil as a whole. This process of preferential movement
of fine particulates carrying high concentrations of adsorbed pollutants is called
sediment enrichment.
Gully erosion results from water moving in rills which concentrate to form larger
and more persistent erosion channels. Gullies are classified as either ephemeral
or classic. Ephemeral gullies occur on crop land and are temporarily filled in by
field operations, only to recur after concentrated flow runoff. This filling and
recurrence of the ephemeral gully can happen numerous times throughout the
year if untreated. Classic gullies may occur in agricultural fields but are so large
they cannot be crossed by farming equipment, are not in production nor planted
4-90
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4C: Erosion and Sediment Control
to crops, and are fanned around. Classic gullies are characterized by headward
migration and enlargement through a combination of headcut erosion and
gravitational slumping, as well as the tractive stress of concentrated flows.
Streambank and streambed erosion typically increase in streams during runoff
events. Within a stream, the force of moving water on bare or undercut banks
causes streambank erosion. Streambank erosion is usually most intense along
outside bends of streams, although inside meanders can be scoured during severe
floods. Stream power can detach, move, and carry large soil particles, gravel,
and small rocks. After large precipitation events, high gradient streams can
detach and move large boulders and chunks of sedimentary stone. Streambank
and shoreline erosion are addressed in greater detail in EPA's guidance for the
coastal nonpoint source pollution control program (EPA, 1993a).
Gully and streambank erosion can move and carry large soil particles that often
contain a much lower proportion of adsorbed pollutants than the finer sediments
from sheet and rill erosion. Sheet and rill erosion are generally active only
during or immediately after rainstorms or snowmelt. Gullies that intercept
groundwork may continue to erode without storm events.
Irrigation may also contribute to erosion if water application rates are excessive.
Erosion may also occur from water transport through unlined earthen ditches.
See the Practices for Irrigation Erosion Control discussion in Chapter 4F: Irrigation
Water Management for additional information regarding erosion from irrigation.
Water erosion rates are affected by rainfall energy, soil properties, slope, slope
length, vegetative and residue cover, and land management practices. Rainfall
impacts provide the energy that causes initial detachment of soil particles. Soil
properties like particle size distribution, texture, and composition influence the
susceptibility of soil particles to be moved by flowing water. Vegetative cover and
residue may protect the soil surface from rainfall impact or the force of moving
water. These factors are used in the Revised Universal Soil Loss Equation (RUSLE),
an empirical formula widely used to predict soil loss in sheet and rill erosion
from agricultural fields, primarily crop land and pasture, and construction sites:
Revised Universal Soil Loss Equation (RUSLE)
A = R * K * LS * C * P
where
A = estimated average annual soil loss (tons/acre/year)
R = rainfall/runoff factor, quantifying the effect of raindrop impact and
the amount and rate of runoff associated with the rain, based on
long term rainfall record
K = soil erodibility factor based on the combined effects of soil
properties influencing erosion rates
LS = slope length factor, a combination of slope gradient and
continuous extent
C = cover and management factor, incorporating influences of crop
sequence, residue management, and tillage
P = practice factor, incorporating influences of conservation practices
such as contouring or terraces
Excessive irrigation
water application can
detach and transport
soil particles.
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4: Management Measures
Prediction equations
such as the RUSLE
and WEQ help
planners make
quantitative
assessments of soil
loss and BMP
effectiveness.
RUSLE may be used as a framework for considering the principal factors
affecting sheet and rill erosion: climate (R), soil characteristics (K), topography
(LS), and land use and management (C and P). Except for climate, these factors
suggest areas where changes in management can influence soil loss from water
erosion. Although soil characteristics (K) may be changed slightly over a long
period of good management practices by an increase in organic matter, it should
generally not be considered changed by management.
It is important to note that the RUSLE predicts soil loss, not sediment delivery to
receiving waters. Even without erosion control practices, delivery of soil lost
from a field to surface water is usually substantially less than 100%. Sediment
delivery ratios (percent of gross soil erosion delivered to a watershed outlet) are
often on the order of 15^0% (Novotny and Olem, 1994). Numerous factors
influence the sediment delivery ratio, including watershed size, hydrology, and
topography.
Ephemeral gully erosion can be predicted by the Ephemeral Gully Erosion
Model (EGEM), (http://www.wcc.nrcs.usda.gov/water/quality/common/
h2oqual.html). EGEM has two major components: hydrology and erosion. The
hydrology component is a physical process model that uses the soil, vegetative
cover and condition, farming practices, drainage area, watershed flow length,
average watershed slope, 24-hour rainfall, and rainfall distribution to estimate
peak discharge and runoff volume. Estimates of peak discharge and runoff
volume drive the erosion process in the model. The erosion component uses a
combination of empirical relationships and physical process equations to com-
pute the width and depth of the ephemeral gully based on hydrology outputs.
The model may be used to estimate ephemeral gully erosion for a single 24-hour
storm or for average annual conditions.
Erosion control in humid tropical areas like Hawaii and Puerto Rico may present
special problems. Soil loss by water erosion may be drastically higher than in
temperate regions, especially in areas of steep slopes (El-Swaify and Cooley,
1980). High annual rainfall and the energy of intense storms often result in high
erosion rates. Sediment yields of up to 3000 t/sq km/yr from montane basins in
Puerto Rico have been reported, where mass wasting contributed most of the
sediment to the receiving streams (Simon and Guzman-Rio, 1990). Land clear-
ing and changes in soil characteristics (e.g. exhaustion of soil organic matter)
can result in catastrophic soil erosion in tropical regions.
Erosion control practices that succeed in temperate regions are often less effec-
tive in the tropics. Engineered practices like terracing, contour ridging, diver-
sions, terraces, and grassed waterways are frequently overwhelmed by torrential
rains (Troeh et al., 1980; Lai, 1983). Agronomic practices that conserve the soil,
such as mulch farming, reduced tillage, mixed cropping with multistorey canopy
structure, and strip cropping with perennial sod crops are more likely to be
successful (Troeh et al., 1980; Lai, 1983). El-Swaify and Cooley (1980) reported
that pineapple and sugarcane provided adequate protection from soil erosion
only a few months after planting.
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4C: Erosion and Sediment Control
Wind Erosion
Wind detaches soil particles when, at one foot above the ground surface, wind
velocity exceeds 12 mph. Detached soil is moved by wind in one of three ways
(Figure 4c-l):
1. Soil particles and aggregates smaller than 0.05 mm in diameter may be
picked up by wind and carried in suspension. Suspended dust may be
moved great distances, but does not drop out of the air unless rain
washes it out or the velocity of the wind is dramatically reduced.
2. Intermediate sized grains — 0.05 to 0.5 mm (very fine to medium sand)
— move in the wind in a series of steps, rising into the air and falling
after a short flight in a motion called saltation.
3. Soil grains larger than 0.5 mm cannot be lifted into the wind stream, but
particles up to about 1 mm may be pushed along the soil surface by
saltating grains or by direct wind action. This type of movement is
called surface creep.
Wind can erode and
transport soil
particles of various
sizes causing
damage to land and
waterways.
Figure 4c-1. The different ways soil can move during wind erosion.
Source: Soft Erosion by Wind. 1994. USDA-SCS, Agriculture Information
Bulletin Number 555.
Wind erosion rates are determined by factors similar to those affecting water
erosion rates, including the detachment and transport capacity of the wind, soil
cloddiness, soil stability, surface roughness, residue or vegetative cover, and
length of exposed area. These factors are expressed in the Wind Erosion Equa-
tion (WEQ). The WEQ is an empirical wind erosion prediction equation that is
National Management Measures to Control Nonpoint Pollution from Agriculture
4-93
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Chapter 4: Management Measures
currently the most widely used method for estimating average annual soil loss by
wind for agricultural fields. The equation is expressed in the general form of:
Wind Erosion Equation (WEQ)
E = f(l,K,C,L,V)
where E is the potential average annual soil loss (tons/acre/year},
a function of:
I, the soil erodibility index;
K, the soil ridge roughness factor;
C, the climate factor;
L, the unsheltered distance across the field; and
V, the vegetative cover.
Ground Water Protection
Although sediment movement into ground water is generally not an issue in
most locations, there are places, such as areas of karst topography, where
sediment and sediment-borne pollutants can enter ground water through direct
links to the surface. More important from a national perspective, however, is the
potential for increased movement of water and soluble pollutants through the
soil profile to ground water as a result of implementing erosion and sediment
control practices.
It is not the intent of this measure to correct a surface water problem at the
expense of ground water. Erosion and sediment control systems can and should
be designed to protect against the contamination of ground water. Ground water
protection will also be provided through implementation of the nutrient and
pesticide management measures.
Erosion and Sediment Control Practices and Their
Effectiveness
The strategies for controlling erosion and sedimentation involve reducing soil
detachment, reducing sediment transport, and trapping sediment before it
reaches water. Combinations of the following practices can be used to satisfy the
requirements of this management measure. The NRCS practice number and
definition are provided for each management practice, where available. Addi-
tional information about the purpose and function of individual practices is
provided in Appendix A.
Practices to Reduce Detachment
For both water and wind erosion, the first objective is to keep soil on the field.
The easiest and often most effective strategy to accomplish this is to reduce soil
detachment. Detachment occurs when water splashes onto the soil surface and
dislodges soil particles, or when wind reaches sufficient velocity to dislodge soil
particles on the surface.
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Chapter 4C: Erosion and Sediment Control
Crop residues (e.g. straw) or living vegetative cover (e.g. grasses) on the soil
surface protect against detachment by intercepting and/or dissipating the energy
of falling raindrops. A layer of plant material also creates a thick layer of still air
next to the soil to buffer against wind erosion. Keeping sufficient cover on the
soil is therefore a key erosion control practice.
The implementation of practices such as conservation tillage also preserves or
increases organic matter and soil structure, resulting in improved water infiltra-
tion and surface stability. In addition, creation of a rough soil surface through
practices such as surface roughening will break the force of raindrops and trap
water, reducing runoff velocity and erosive forces. This benefit is short-lived,
however, as rainfall rapidly decreases effectiveness of surface roughness.
Reducing effective wind velocities through increased surface roughness or the
use of barriers or changes in field topography will reduce the potential of wind
to detach soil particles. Practices which increase the size of soil aggregates
increase a soil's resistance to wind erosion.
The following practices can be used to reduce soil detachment:
D Chiseling and subsoiling (324): Loosening the soil without inverting
and with a minimum of mixing of the surface soil to improve water and
root penetration and aeration.
O Conservation cover (327): Establishing and maintaining perennial
vegetative cover to protect soil and water resources on land retired from
agricultural production.
D Conservation crop rotation (328): An adapted sequence of crops
designed to provide adequate organic residue for maintenance or
improvement of soil tilth.
D Residue Management (329): Any tillage or planting system that
maintains at least 30% of the soil surface covered by residue after
planting to reduce soil erosion by water; or, where soil erosion by wind
is the primary concern, maintains at least 1,000 pounds of flat, small-
grain residue equivalent on the surface during the critical erosion period.
D Contour orchard and other fruit area (331): Planting orchards,
vineyards, or small fruits so that all cultural operations are done on the
contour.
n Cover crop (340): A crop of close-growing grasses, legumes, or small
grain grown primarily for seasonal protection and soil improvement. It
usually is grown for 1 year or less, except where there is permanent
cover as in orchards.
G Critical area planting (342): Planting vegetation, such as trees, shrubs,
vines, grasses, or legumes, on highly erodible or critically eroding areas
(does not include tree planting mainly for wood products).
n Seasonal Residue Management (344): Using plant residues to protect
cultivated fields during critical erosion periods.
D Diversion (362): A channel constructed across the slope with a
supporting ridge on the lower side (Figure 4c-2).
01 Windbreak/shelterbelt establishment (380): Linear plantings of single
or multiple rows of trees or shrubs established next to farmstead,
feedlots, and rural residences as a barrier to wind.
Source area
stabilization is
fundamental to
erosion and
sediment control.
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4C: Erosion and Sediment Control
Table 4c-1. Relative Gross Effectivenessa of Sediment" Control Measures Pennsylvania State University, 1992b).
Practice Category0
Reduced Tillage Systems6
Diversion Systemsf
Terrace Systems9
Filter Strips'1
Runoff
Volume
reduced
reduced
reduced
reduced
Total PhosphorusTotal Nitrogen Sediment
45
30
70
75
-(% reduction)-
55
10
20
70
75
35
85
65
a Actual effectiveness depends on site-specific conditions. Values are not cumulative between practice categories.
b Includes data where land application of manure has occurred.
c Each category includes several specific types of practices.
d Total phosphorus includes total and dissolved phosphorus; total nitrogen includes surface-delivered organic-N, ammonia-N,
and nitrate-N.
e Includes practices such as conservation tillage, no-till, and crop residue use.
f Includes practices such as grassed waterways and grade stabilization structures.
g Includes several types of terraces with safe outlet structures where appropriate.
h Includes all practices that reduce contaminant losses using vegetative control methods.
Conservation tillage is now promoted widely by a large number of groups and
organizations because it is both profitable and effective in controlling erosion.
For example, researchers at Louisiana State University have shown that the use
of no-till with or without a cover crop (2-6 tons of soil loss per acre per year) is
much more effective at controlling erosion on cotton fields than is use of con-
ventional tillage with or without a cover crop (13-16 tons per acre per year)
(Zeneca, 1994). It is reported that the top three reasons soybean farmers adopt
no-till are reduced soil erosion, increased profit potential, and time and labor
savings (Alesii, 1998). The percentage of soybeans planted in no-till has in-
creased from 1992 to 1997 at an average annual rate of 11.6 percent, ranging
from 4 percent (Minnesota) to 25 percent (North Dakota) in the Upper Midwest
(CTIC, 1997). According to some of the leading authorities on conservation
tillage, the economic and environmental benefits of farming with conversation
tillage are simply too numerous to ignore (CTIC, ca. 1997). CTIC reported that,
on average, no-till resulted in 93 percent less erosion and 69 percent less water
runoff than moldboard plowing.
Factors in the Selection of Management Practices
Two fundamental options exist to minimize water and wind erosion from agri-
cultural land and the delivery of sediment to receiving waters: (1) Controlling
soil loss from fields or streambanks by reducing detachment and transport of
sediment, and (2) Encouraging deposition of eroded sediment to prevent deliv-
ery to surface waters. Different management strategies are employed with the
different options. Preventing initial soil loss (option "(1)") is generally the most
desirable option because it not only minimizes the delivery of sediment to
receiving waters but also provides an agronomic benefit by preserving soil
resources. Option "(2)" minimizes the delivery of sediment to receiving waters,
but does not necessarily provide the agronomic benefits of upland erosion
control. In addition, practices encouraging sediment deposition require mainte-
Site conditions, cost,
and maintenance
requirements are
considered for
practice selection.
Local
demonstrations are
also needed to refine
practices and
encourage adoption.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-103
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Chapter 4: Management Measures
nance to retain their effectiveness over time. In some cases, for example, man-
agement or economic constraints may prevent full installation of all practices
needed to adequately reduce field soil loss, and additional practices to prevent
delivery of eroded sediment may be needed. In other cases, even if field soil loss
can be reduced to "T" level, additional practices may be needed to prevent
delivery of sediment to critical or sensitive water bodies. Using one or both of
these options, planners have the flexibility to address erosion and sediment
problems in a manner that best reflects State, local, and land owner/operator
needs and preferences.
Management practices for a given site should not result in undue economic
impact on the operator. Many of the practices that could be used to implement
this measure may already be encouraged or required by Federal, State, or local
programs (e.g., filter strips or field borders along streams) or may otherwise be
in use on agricultural fields. By building upon existing erosion and sediment
control efforts, the time, effort, and cost of implementing this measure will be
reduced.
It should be noted that basic erosion control measures will not always provide
adequate control of nutrients, pesticides, or other sediment-attached pollutants.
Erosion control practices tend to be most effective on larger particles, which
tend to carry a lower proportion of adsorbed pollutants than do finer particles
like clays. Many erosion control practices or structures may not effectively
control the majority of pollutants that are attached to fine soil particles. If
pollutants attached to soil particles are the primary concern, practices specifi-
cally designed to control fine sediments should be applied.
Conversely, some nutrient or irrigation management practices may contribute to
erosion control, even though their primary purpose is not erosion control. Waste
utilization, for example, may help reduce soil erodibility by both water and wind
through improvements in soil organic matter content. Improved irrigation water
management may help reduce wind erosion potential by maintaining adequate
soil moisture during critical periods.
Continued performance of this measure will be ensured through supporting
maintenance operations where appropriate. Although some practices are de-
signed to be effective and withstand a design storm, they may suffer damage
when larger storms occur. It is expected that damage will be repaired after such
storms and that practices will be inspected periodically. To ensure that practices
selected to implement this measure will continue to function as designed and
installed, some operational functions and maintenance will be necessary over the
life of the practices.
Most structural practices for erosion and sediment control are designed to
operate without human intervention. Management practices such as conservation
tillage, however, do require some attention each time they are used. Field
operations should be conducted with practices like contouring or terraces in
mind to ensure that the practices or structures are not damaged or destroyed by
the operations. For example, non-selective herbicides should not be applied to
areas of permanent vegetative cover that are used as part of erosion control
practices, such as waterways and filter strips.
Structural practices such as diversions, grassed waterways, and filter strips may
require grading, shaping, and reseeding. Trees and brush should not be allowed
4-104 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4C: Erosion and Sediment Control
to grow on berms, dams, or other structural embankments. Cleaning of sediment
retention basins will be needed to maintain their original design capacity and
trapping efficiency.
Filter strips and field borders must be maintained to prevent channelization of
flow and the resulting short-circuiting of filtering mechanisms. Reseeding of
filter strips may be required on a frequent basis. Periodic removal of vegetative
growth will help keep filter strips actively growing and remove nutrients and
other potential pollutants that have been taken up by the plants or attached to the
vegetative growth. Grazing and other livestock activities should be managed to
avoid damage to vegetation cover, especially near streams.
Finally, conditions sometimes occur when serious wind erosion is imminent or
has just begun, and immediate action is needed to protect soil and crops. Several
emergency techniques can lessen or slow wind erosion. Emergency measures are
not as effective as long-term planned erosion control; they are last resort options
and should not be relied on for primary erosion control or continued use. The
following emergency control methods can reduce damage from anticipated wind
erosion (Smith et al., 1991).
D Emergency tillage to produce surface roughness, ridges, and clods
n Addition of crop residue
H Application of manure
D Irrigation to increase soil moisture
d Temporary, artificial wind barriers
d Soil additives or spray-on adhesives
Choice of specific methods depends on severity of erosion, soil type, crop type
and growth stage, and equipment available.
Cost and Savings of Practices
Costs
Reliable and current
information on cost
of initial investment,
along with
annualized cost
throughout practice
life, helps planners
and farmers make
sound decisions.
Both national and selected State costs for a number of common erosion control
practices are presented in Table 4c-2. The variability in costs for practices can be
accounted for primarily through differences in site-specific applications and
costs, differences in the reporting units used, and differences in the interpreta-
tion of reporting units.
The cost estimates for control of erosion and sediment transport from agricul-
tural lands in Table 4c-3 are based on experiences in the Chesapeake Bay
Program.
Savings
It is important to note that for some practices, such as conservation tillage, the
net costs often approach zero and in some cases can be negative because of the
savings in labor and energy. In fact, it is reported that cotton growers can lower
their cost per acre by $24.32 due to lower fixed costs associated with conserva-
tion tillage (Zeneca, 1994).
National Management Measures to Control Nonpoint Pollution from Agriculture
4-105
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Chapter 4: Management Measures
Table 4c-2. Representative costs of selected erosion control practices.
Practice
Unit
Range of Capital Costs1
References
Diversions
Terraces
Waterways
Permanent
Vegetative Cover
Conservation
Tillage
ft
ac
a.e.3
ac
ac
1.97 - 5.51
3.32 - 14.79
24.15-66.77
5.88 - 8.87
113 - 4257
1250 - 2174
69 - 270
9.50 - 63.35
Sanders et al., 1991
Smolen and Humenik, 1989
Smolen and Humenik, 1989
Russell and Christiansen, 1984
Sanders et al., 1991
Barbarika, 1987; NCAES, 1982;
Smolen and Humenik, 1989
Russell and Christiansen, 1984
Barbarika, 1987; Russell and
Christiansen, 1984; Sanders et al.,
1991; Smolen and Humenik, 1989
NCAES, 1982; Russell and
Christiansen, 1984; Smolen and
Humenik, 1989
1 Reported costs inflated to 1998 dollars by the ratio of indices of prices paid by farmers for all production items, 1991=100.
2 acre served
3 acre established
[Note: 1991 dollars from CZARA were adjusted by +15%, based on ratio of 1998 Prices Paid by Farmers/1991 Prices
Paid by Farmers, according to USDA National Agricultural Statistics Service, http://www.usda.gov/nass/
sources.htm, 28 September, 1998]
Table 4c-3. Annualized cost estimates and life spans for selected management practices from Chesapeake Bay
Installations1' (Camacho, 1991).
Practice
Practice Life Span
(Years)
Median Annual Costs')
(EACc)($/acre/yr)
Nutrient Management
Strip-cropping
Terraces
Diversions
Sediment Retention Water Control Structures
Grassed Filter Strips
Cover Crops
Permanent Vegetative Cover on Critical Areas
Conservation Tillage"
Reforestation of Crop and Pastured
Grassed Waterways6
Animal Waste System'
3
5
10
10
10
5
1
5
1
10
10
10
2.40
11.60
84.53
52.09
89.22
7.31
10.00
70.70
17.34
46.66
1.00/LF/yr
3.76/ton/yr
a Median costs (1990 dollars) obtained from the Chesapeake Bay Program Office (CBPO) BMP tracking data base and
Chesapeake Bay Agreement Juristictions' unit data cost. Costs per acre are for acres benefited by the practice.
b Annualized BMP total cost including O&M, planning, and technical assistance costs.
c EAC = Equivalent annual cost: annualized total; costs for the life span. Interest rate = 10%.
d Government incentive costs.
e Annualized unit cost per linear foot of constructed waterway.
f Units for animal waste are given as $/ton of manure treated.
4-106
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4D: Animal Feeding Operations (AFOs)
4D: Animal Feeding Operations (AFOs)
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be designed and
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waste storage, waste
utilization, and
nutrient
management.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-107
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Chapter 4: Management Measures
USDA-EPA Unified National Strategy for Animal
Feeding Operations
i . , M'^ , - j 14'
^^af^^^'yixftf ^WajMy and public health, mainly
^l^a^l^gfene^te. ,fo,n1iftimize water quality and
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the Unified National Strategy
, ;-,;,-.,. w . ,.ia] performance expectation
a^ll^it technically souml and Economically feasible
'.'f _ _J . *M i. ^ .. y^Wufc-rm afunt.-v i . ^AfiA
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a
P Land Application of Manure; &tUi!ztn$ ihe .nutrients and organic mattetin manure while
minimising the rislc to
G Lamd Management; jnstallitt| ;ljest mstnag^ment practices to minimize movement of potential
pollutants to surface or ground wa,ter
O Record Keeping: residing the quantity of manure produced and how the manure was Utilized
3 Other Utilization Options; fading a&eiiativ© $&& oc jnarJ^ts (e^.^ompostlag, sale to other
, power generation) for manttre wheff land ajpllcal|on is not feasible
Voluntary and regulatory, programs serve compl^inenta roles in providing APO owners and operators
and the animal agricultural tndus^cy witti tto,e as$i
business and personal goalsl and in en
majority of AFGs, voluntary efforts wi
developing and. 'implementing site-specific CHMP$
risks associated with AFOs. While CJNM am no
programs* they are strongly encourages! as
and public health impacts from $hese,ow$ationss
and public health, For the vast
assist ownets and operators in
aod infeciacmg w^ter poiMtlon and public health
j ^qalrfid foi1 AFOs participating only in voluntary
ble means of managing potential water quality
Impacts from certain higher rM^AFQ^ &i address^ j taroafh National Pollutant Discharge Elimination
System (NPOBS) permits ua^r the* auttoiity of,the Gles^n ,Wat«t Act, AFOs tfeat meet certain specified
criteria in the KPDtS regulations are relkre<| ^o as concentrated animal feeding operations or CAFOs,
NPDES permits wttl rajuie CAFQs to develop CNM^s and ^ meet other conditions that minimise the
threat to water quality, and public health and otherwise $as$te compliance with the requirements of the
Clean Water Act.
4-108
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4D: Animal Feeding Operations (AFOs)
|y identifies tfiree categories of ,p^0s that are, priorities &tr th§ pjgi
*/, "(3 Sianiilcant Manure froduelfetfiVlEa'g^ ^pttbsXJ^^ater^St lO^amm^uni^l
•t* 34 , *' i > j , * j ^ 4 TT ** v X **ff ^ <• J •- p f-J.^*?**-*
' / O Unacceptable Conditions:^ ^qiilt|^sir4j)M discharge tferdurgh a M^-ma^£oiiveyanc^ k> ^atejra
;f;H, Significant Contributors to Water Quality Inipairincnt: factlMes-tiiat.are significanfly ,• 4
4-'-V;' 4coi|tiibutiagtothe4ii^ajnri^t^ft^^^b^', , , , „ ,
^^^ttti^j the ^fpiilid AFp Jtet^y;ad3i^se^ str^iegic issues to be addressed by ^fe agencies. The
' JjftM$itiej!pii|| tnei5>tt'ai^gy>4'wC|nT^'Joji ttiese a0t|oi!isi^'6: listewj'^eiow. 4 • 4 * , # * t • *, t
/'" ^/«%", -V't- ' 4I ' '4 ''*' ' ' ''"'.'"' . 4* ,'° '' ' 4'^ * S '" * 4 ^ '*' 4 4 ", '
4 / ri aetmrs* tlrPt^siwaiTaHiliff^f rt'F/inaliTiA^ cif\tWMi*Iti£f'E "rVinm tHA timl^li^ iSr rti^watfi'i cArtfrtihc tt\ accisfl' in tfeA
f * t~|. inySi&JJ;!.*! L^J,ista.v^iiijt)ilIvy'UJl ^^«ill^*3J"•a|^C;vlt^|sstati^\lil^ IftK pUWilt^ Wt UliVaw;' acSUIVts if ',^4
research technical irniova|io», ^id te'ckft^>Iogy,Cfaksfer activities ., ;
of the Mnjal^ajricultitte^mdastry(in GNMP kdoptio|i *• . :
mte data sharj-ftg while protecting the fektionS-h^Of trtist ^We^ US0A,and farmers
^^!";-L ^tii0formatioGthatkmerMJa'|)i'c^ctiiig\^^ —-i-—--
>r measarmg tne etrecGveness or etrorts" to miijiji^ze the' water quality1 and
jl""" ^ 4 * 4 ^ 4 , , (• 4 • 4 , ^ ^ ^ • ^ ^ 4 ^ f ^
4 ' \ _ For additional information on the Strategy, see www.i'pa.gov/owm/afo.htm
National Management Measures to Control Nonpoint Pollution from Agriculture
4-109
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Chapter 4: Management Measures
AFOs, CAFOs, and CZARA
Existing regulatory definitions of AFOs and concentrated animal feeding
operations (CAFOs) are given at 40 CFR 122.23 and Part 122, Appendix B (as
revised February 12, 2003). These regulations define an AFO as a facility that
meets the following criteria:
1. Animals (other than aquatic animals) have been, are, or will be stabled
or confined and fed or maintained for a total of 45 days or more in any
12-month period, and
2. Crops, vegetation forage growth, or post-harvest residues are not sustained
in the normal growing season over any portion of the lot or facility.
As described in Chapter 1, EPA published guidance specifying management
measures for sources of nonpoint pollution in coastal waters as required under
section 6217(g) of CZARA. With regard to the management measures for
livestock operations (EPA, 1993a), EPA defined a confined animal facility as a
lot or facility that meet the same two criteria d and 2) specified above for AFOs.
AFOs include the areas used to grow or house the animals, areas used for
processing and storage of product, manure and runoff storage areas, and silage
storage areas.
The subset of AFOs within the section 6217 coastal management areas that are
subject to the CZARA management measures for confined animal facilities is
determined by the number of head at the operation and whether or not the
operation is designated as a CAFO. Those facilities that are required by Federal
regulation 40 CFR 122.23(c) to apply for and receive discharge permits, are
NOT covered by section 6217 since they are CAFOs. CAFOs are defined
generally as an AFO that:
D Confines the number of animals presented in the second column of
Table 4d-l: or
D Confines the number of animals presented in the third column of Table
4d-l and discharges pollutants:
• Into waters of the U.S. through a man-made ditch, flushing system, or
similar man-made device; or
• Directly into waters of the U.S. that originate outside of and pass
over, across, or through the facility or otherwise come into direct
contact with the animals confined in the operation.
In addition, 40 CFR 122.23(c) provides that the Director of a National Pollutant
Discharge Elimination System (NPDES) permit program may designate any
AFO as a CAFO upon determining that it is a significant contributor of water
pollution. AFOs containing fewer than the number of head listed in Table 4d-l
for small confined animal facilities are not subject to the CZARA management
measures for confined animal facilities. Figure 4d-l shows the relationship between
AFOs, CAFOs, and large and small confined animal facilities under the NPDES and
CZARA programs. Operators of confined animal facilities should contact their state
or federal NPDES permitting authority for information on permit application
procedures.
It is important to note that in December 2002 EPA finalized revised regulations
for concentrated animal feeding operations under 40 CFR 122. The final regula-
tions changed some of the definitions. Readers are encouraged to contact EPA's
4-110 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4D: Animal Feeding Operations (AFOs)
Table 4d-1. Comparison of CAFO and AFO Size Difinitions under the NPDES and CZARA Programs.
Animal Type
Defined as a
CAFO by Size
and must have a
NPDES Permit
Defined as CAFO Large Animal
by Size and Site Feeding Operations
Conditions* and under CZARA (that
must have a do not have a
NPDES Permit NPDES Permit)
Small Animal
Feeding Operations
under CZARA
Number of Head
Beef cattle or heifers
Veal calves
Mature dairy cattle
Swine
Swine
Turkeys
Chickens with liquid
manure handling
Chickens (except
laying hens) with dry
manure handling
Laying hens with dry
manure handling
Horses
Sheep or lambs
Ducks with liquid
manure handling
Ducks with dry
manure handling
>1,000
>1,000
>700
>2,500
(each 55 Ibs or more)
>10,000
(each under 55 Ibs)
>55,000
>30,000
£1 25,000
>82,000
£500
>10,000
£5,000
£30,000
<1,000&>300
< 1 ,000 & >300
< 700 & >200
< 2,500 & >750
(each 55 Ibs or more)
< 1,000&>300
(each under 55 Ibs)
<55,000 & >1 6,500
< 30,000 & >9,000
< 1 25,000 & £37,500
< 82,000 & >25,000
< 500 & £150
< 1 0,000 & £3,000
< 5,000 & £1,500
< 30,000 & £10,000
£300
ND**
£70
£200
ND
£13,750
ND
£15,000
(all broilers)
>1 5,000
(all laying hens)
£200
ND
ND
ND
51 - 299
ND
20-69
100- 199
ND
5,000- 13,749
ND
5,000 - 14,999
(all broilers)
5,000- 14,999
(all laying hens)
100- 199
ND
ND
ND
*AFOs are defined as CAFOs if they have the number of animals shown above AND have a man-made ditch or pipe that carries
manure or wastewater from the operation to surface waters OR the animals come into contact with surface water running through
the area where they are confined,
**Not defined.
Office of Wastewater Management (www.epa.gov/owm) or their state NPDES
permitting authority for the latest information on the final CAFO regulations.
Management Measure for Animal Feeding Operations:
Description
The water quality problems associated with confined animal facilities result
from accumulated animal wastes, facility wastewater, and storm runoff, all of
which may be controlled under this management measure (Figure 4d-2). The
goal of this management measure is to minimize the discharge of contaminants
in facility wastewater, runoff, and seepage to ground water, while at the same
time preventing any other negative environmental impacts such as increased air
pollution. Accumulated animal wastes include manure, litter, or other waste
products that are deposited within the confinement area and are periodically
removed by scraping, flushing, or other means and can be conveyed to a storage
or treatment facility. Facility wastewater is water generated in the operation of
an animal facility as a result of animal or poultry watering; washing, cleaning, or
National Management Measures to Control Nonpoint Pollution from Agriculture
4-111
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Chapter 4: Management Measures
Management of Soil Phosphorus Levels to
Protect Water Quality
Phosphorus to Agr&utero
, Phosphorus (P) is iiiiportant$<3 &id wed ..exteipvely in both the crey production and confined livestock
segments of agriculture, making it one of the most common elements used in agriculture today.
One of the most important functions of P in- piant§> fy fhe storage and tr^sfer of energy. Phosphorus is
essential for seed production* promotes Increased root growth,* stalk strength and early plant maturity, and
aids in resistance to root rot diseases 'and .WpjterJdll. ' , ' •
la the confined livestock segment, producers use P as a diet supplement, in addition to the P already
contained m feeds, to improve animal perioi;raa0c$, To avoid, excessive buildup Of soil-P on the lands
surrounding confined animal operations, considemtipn must be given to the amount of land available to
absorb P ten livestock, <,',•, ';• "/,,!,.
In areas of intense crop and, livestock prb$aetioi continued .inputs of fertilizer and manure P in excess of
crop requirements have led to a >bui|d-u|j of soil P levels. This increases the potential for nonpoim source
runoff to carry excess phosphorus to surrounding streams and lakes.
Phosphorus is usually the limiting nutrient in freshwater aquatic systems. When excess phosphorus enters
streams and lakes, creating P concentrations, between the critical values of 0.01 and 0,02 ppm (Sawyer,
1947; Vollenweider, 1968), accelerated eutrophicatlon occurs. Butrophication, a natural process that
usually occurs over a long period of time,', is characterized by increased aquatic plant growth, oxygen
depletion, and pH variability. It eventually leacjs to a decline in plant species quality and adverse food
chain effects (Sharpley et al; 1994), 41 of which ma^ reduce water Duality.
Transport UwHani&m ,.„„.;,, ',..,.,. ',' ' '....:....,, ,„ ' •
Phosphorus enters the soil trough min^al 4^olutiob» desorption |rdm clay and mineral surfaces, and
biological conversion from1 'organic matedti* to Inbrg^iic for^is. As,raihfaH or irrigation water interacts
with' a thin layer of surface soil, P is either mpyed into agriculture runoff through dissolution from the soil
and plant material, or is transported fry 'erosion, remaining e,i$ier attached to soil or in vegetation. The
dissolved P is immediately available for uptake by aquatic biota (bioavailable); while the paniculate P is
available only after all of the dissolved P is consumed. Once bioayailable P moves from the field into
receiving waters, it can contribute, to ;©utro|ihication (Wood et #1
Another mechamsmfocP transport occurs when .large accumulations of P occupy all available sites on the
soil1 surface, causing additional P to'leach downward through the so|l Column. When this leaching is
followed by lateral movement of water wfytec ifte soil surface, especially under high- water table condi-
4-112
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4D: Animal Feeding Operations (AFOs)
$$ttTesting, - :/ [ ,. > . . -
I -----------'----_...__*?....... ^ ... .....!..._.v^.._...... -^-:-_i-_^.^)-vTT--im, . ,. ---.--- ^ -^;Av;^-^v^-;^-^-;^^-^'-;-v::^v-^-::^-:-'-::^-:-t::r'r:--- * ! , * ,
the prime goal of soil testing meJKods have aMo° been developed gtyd tested Jq determine if .they n»ght'
more accurately $t&$et the wrioff an$ dr&inage P levels. Some oj tfj^ most |>romising new methods are;
(1) BreeiBwma«t at,1995v de^oped to determine,*^ degree of ^satwration in soils.
" " (2}!Ahajcdiii et at., 19^64 A|M I
=•: * .ffltieasw'fe^lieamowit.ijfFlasoil^fliat is subject
4 f < ' , 4 • " ' ; ' : ' f H ,, ^ * ' ^ ^ ;
(3) Poteetal, 1996-usingdistilled%^terte'extf^f£fad%4@sOtb^fe&^
, release of P to-rawtfff water. ; ,'V » , , \ ,'';',-'-
gaH mft extractaais now aseclfta' ghosphorttsiri the y.S..(Kat^ra^^ Wato, 19SO);
ory ; C*jiHiw0pif Keg!otts;iii the U.&.
P . SoilTeM v : *!/ Co»|i«ttettlyll
. vegt aature of acids, , ,, M^iiichl° Sovitost sad Mid-
primarily extracts AI and Fe boa»d ?,pi^ some <^*P,' Best for , 4 '. - /. '!
soilswi^|>H<7.0' -, , '' % s 4 \\- 4 • . ,
pito& eonceatmticm? M.strong acids vim .a.cpmpk!jdBg iofl: ; • gpiyPl — ,
BxiraciasfsTefflOVePbysolvem^tionofac^aRd^ott^lexini ^ ,Mehiicfe3 _
ability of flitotide iofl for A1*B B^lhor«s leyejs in nuioif ifom fields JEMlteed
these aniinais lack-j>hytase enzymes, Aaian^ most of tfee ph^tate?{^^ of ^dF)k com ^ soybeans.
unavailable to these iraimals. In ofdef Cor normal growth Bftd;deveiopmeHti otter, torins of P inu^t b@ }., r
ad^ed to th$ diet. This addition of ino:qpnie P xesiilts in mifeh M^her levels of Pin tt&nufev \ ' f \
PhytetsfptoduGts * 6ae way to redace the level of inpTganic P fed 1o these animals/ tius lowering tie \+ "
IbVel t?f P in manor^; is 'to add phytMe enzyme to {he Jeed aiding the bfeakdj3Wn <>f jShytate P/ ;.% / -;;: * %
low ptyttetxMl af'high ay&lfa&te p (HAP) corn j MOtKer way to reduce the amount of addjfiionftlP, *: * /
needed in the animal diets, thus reducing amount$ "of P in .naantjre. Is! to fed the £njma& a com
containing lower amoftflts of phytateP or higher attiOUats'of Bailable E-
While some studio have shown that P levels in rm®$ decrease with.me us& Of these
diets, more
National Management Measures to Control Nonpoint Pollution from Agriculture
4-113
-------
Chapter 4: Management Measures
Figure 4d-1. Management of Animal Feeding Operations
ANIMAL FEEDING OPERATION
Over 1,000 animal untts
(•• described In 40 CFR
122, Appendix B)
Potential to
discharge through
any means of conveyance
301-1,000 animal units )
(ae deacrlbed In 40 CFR
122, Appendix B) j
«- - -f
• Fewer than 300 animal j
unit! (as described In 40
CFR 122, Appendix D J
Potential to
discharge through
man-made devlte
or directly to
waters of the U.S.
Potential to
discharge through
men-made device
or directly to
waters of the U.S.
Potential to
discharge through
any other means of
conveyance
Case-by-oase
designation
ICaae-by-caee
designation
^
f '
YES
'
| NO
NPDES PERMIT
NOT
REQUIRED
NPDES PERMIT
REQUIRED FOR
DISCHARGE
'
NPDES PERMIT
NOT
REQUIRED
' '
NPDES permit
requirements: BAT
or BCT based on BPJ
'
CZARA and/or
Stata Requirement*
may apply
NPDES PERMIT
REQUIRED FOR
DISCHARGE
i
'
NPDES permit
requirements: BAT
or BCT baaed on BPJ
NPDES PERMIT
NOT
REQUIRED
i
>
CZARA and/or
State Requirements
may apply
Source: Guide Manual on NPDES Regulations For Concentrated Animal Feeding Operations. Final. 1995.
US Environmental Protection Agency, Office of Water. EPA833-B-95-001.
Diverting clean water
from upslope areas
and roof runoff away
from the animal lot
and waste storage
structure can reduce
waste volume and
storage
requirements.
flushing pens, barns, manure pits, or other facilities; washing or spray cooling of
animals; and dust control. Animal lot runoff includes any precipitation (rain or
snow) that comes into contact with manure, feed, litter, or bedding and may
potentially leave the facility either by overland flow or by infiltration.
Implementation of this management measure greatly reduces the volume of
runoff, manure, and facility wastewater reaching a water body due to structural
practices such as solids separation basins in combination with vegetative prac-
tices and other techniques that reduce runoff while also protecting ground water.
The measure can be implemented by using practices that divert clean runoff
water from upslope sites and roofs away from the facility, thereby minimizing
the amount of contaminated water to be stored and managed. Accumulated
animal wastes should be protected as much as possible from runoff and stored in
such a way that any runoff water, seepage, or leachate can be captured and
managed with runoff and wastewater. Runoff water and facility wastewater
should be routed through a settling structure or debris basin to remove solids',
and then stored in a pit, pond, or lagoon for application on agricultural land in
accordance with the Nutrient Management Measure. If manure is managed as a
4-114
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4D: Animal Feeding Operations (AFOs)
Figure 4d-2. Management measure for animal feeding operations (large units) (EPA, 1993a).
(A) Runoff from enclosed confined facilities
(H) Runoff from silage storage areas
(c) Runoff from open confined areas
(o) Runoff from manure storage areas
E Facilities wastewater
Storage for up to & including
a 25-yr, 24-hr frequency storm
Minimize contamination of groundwater
Manage stored runoff
and accumulated
sol Ids from facility
through an
appropriate waste
utilization system
liquid, all manure, runoff, and facility wastewater can be stored in the same
structure and there is no need for an additional debris basin. In some areas,
certain systems may be preferred over others due to competing environmental
concerns (e.g., liquid systems may raise concerns regarding air quality), and
innovative alternatives that achieve the management measure goals should be
considered.
This management measure is consistent with, yet more specific than the CZARA
management measure for large confined animal facilities, and it goes beyond the
expectation for small confined animal facilities under CZARA by calling for
storage. This does NOT change, however, the performance expectations for
either large or small facilities that are subject to the CZARA management
measures.
Contaminant Movement from Animal Feeding Operations
into Surface and Ground Water
The concentration of livestock production and housing in large systems has
resulted in large accumulations of animal wastes with the potential to contribute
nutrients, suspended solids, pathogens, oxygen-demanding materials, and heavy
metals to surface and ground waters. Animal operations can also be a source of
atmospherically transported pollutants, particularly ammonia, via volatilization
(Harper and Sharpe, 1997). The pollution potential of such accumulations is
influenced by the number and type of animals in the operation, the facilities and
practices used to collect and store the wastes, and the methods chosen to manage
the wastes (e.g., application to the land).
Animal feeding
operations have the
potential to
contribute large
pollutant loads to
waterways. Because
they may be located
near streams and
water supplies, AFOs
require well-planned
and maintained
systems of practices
to minimize human
health and aquatic
ecosystem impacts.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-115
-------
Chapter 4: Management Measures
Movement to Surface Waters
The volume of runoff from animal facilities is influenced by several major
factors including: (1) water inputs, dependent on rain storm intensity and
duration, time since last runoff, snowpack accumulation and melting, and runoff
entering from outside the facility and (2) runoff generation from impervious
surfaces such as roofs and paved areas. While precipitation inputs cannot usually
be managed, the diversion of clean water from upgradient areas, and the reduc-
tion and diversion of runoff from impervious areas (e.g. installation of roof
gutters on facility buildings) to avoid contact with pollutants can affect the
volume of runoff that needs to be controlled. In regions of the country with very
high rainfall, some animal facilities are entirely roofed to prevent precipitation
from coming into contact with animal wastes and to minimize the total volume
of stored wastes that must be managed.
The pollutant load carried in runoff from animal facilities is affected by several
additional factors, including: (1) pollutants available for transport in the facility;
(2) the rate and path of runoff-movement through the facility; and (3) passage of
runoff through settling or filtering practices before exiting the facility. Manage-
ment activities like scraping manure from pavement areas or proper storage of
feeds and bedding can significantly reduce the availability of pollutants for
transport. Structures such as detention basins can affect pollutant transport by
regulating runoff movement and increasing settling within the facility. Vegetated
filter strips, riparian buffers, or other vegetated areas located around animal
facilities can reduce delivery of pollutants to surface waters by infiltrating,
settling, trapping, or transforming nutrients, sediment, and pathogens in runoff
leaving the facility.
The ranges in concentrations of pollutants from some typical sources on a dairy
farm are shown in Table 4d-2. The total pounds of pollutants that could come
from a typical 100-cow dairy is shown in Table 4d-3. These values were ob-
tained by multiplying the concentrations by the typical volume in Table 4d-2.
The pounds per year from these concentrated sources may be small but represent
significant pollutant sources if not controlled. Each farm is different, as shown
by the range in concentration and amount of pollutants from the various sources.
Some of the variation is under the control and management of the farmer and
their day-to-day operations, while some of it is due to the type and layout of the
facility.
Facility wastewater volumes and pollutant loads are controlled primarily through
the design and operation of the facilities involved in watering, washing, and
cleaning. Frequency of wash-downs and the volume of water used, for example,
will influence both total volume of wastewater to be managed and the concentra-
tions of pollutants in the wastewater. In dairy milking center wastewater, both
volume and concentrations of pollutants in the wastewater are controlled by the
type of milking and plumbing systems and the formulation of cleaning com-
pounds used.
An important part of the management of milking center waste is to reduce the
volume of water and the amount of material that must be handled. The amount
of waste can be affected by management as shown by the variability of both the
flows and the concentrations in Tables 4d-2 and 4d-3. Reducing the volume of
wastewater to be treated will reduce the cost of wastewater treatment. Energy
4-116 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4D: Animal Feeding Operations (AFOs)
Table 4d-2. Waste characteristics from dairy farms (Wright, 1996).
Potential
Pollutant
Source
Milking Center
Waste
Silage Leachate
Barnyard
Runoff
Dairy Manure
Domestic Waste
a 5 day BOD
b yearly volumes
Biochemical
Oxygen
Demand8 ppm
400-10,000
12,000-90,000
1,000-10,000
20,000°
150-250
Nitrogen
ppm
80-900
4,400°
50-2,100
5,600C
20-30
assuming: 2 gallons/cow/day milking center
bunk silo,
70 ft2/cow
25% DM, no drainage
Phosphorus
ppm
25-170
500°
5-500
900°
5-10
waste
Volume
gallons per
100 cows"
73,000
105,000
80,000
660,000
365,000
water, 36" precipitation
36" precip., scraped daily, good solid retention
22,000 LB/cow/yr. milk production, 18 gal./cow/day
0 Typical values
10 people
producing 100 gal. /day/person
Table 4d-3. Annual waste production on a typical11100 cow dairy (Wright, 1996).
Potential
Pollutant
Source
Biochemical
Oxygen
Demand9 Ib.
Nitrogen
Ib.
Phosphorus
Ib.
Milking Center
Waste
Silage Leachate
Barnyard
Runoff
Dairy Manure
Domestic Waste
250-6,100
10,500-79,000
670-6,700
110,000°
450-760
50-550
3900C
30-1,400
31,000°
60-90
15-100
440°
3-330
5,000C
15-30
a 5 day BOD
D yearly volumes assuming:
Typical values
2 gallons/cow/day milking center waste
bunk silo, 25% DM, no drainage water, 36" precipitation
70 ft2/cow, 36" precip., scraped daily, good solid retention
22,000 LB/cow/yr. milk production, 18 gal./cow/day
10 people producing 100 gal./day/person
savings for reduced pumping costs and water heating can also be realized. Using
only the amount of cleaners that are necessary and using low phosphorus deter-
gents can significantly decrease the amount of phosphorus in the wastewater.
Using automated systems appropriately and water treatment where needed can
result in a cost savings. Manure reduction methods for milking centers are
shown in Table 4d-4 and methods for phosphorus reduction are described in
Table 4d-5.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-117
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Chapter 4: Management Measures
Table 4d-4. Manure reduction methods and costs for milking centers (Wright, 1996).
Manure Reduction Methods
Reduction
Potential
Estimated Cost
Schedule the cleaning of alleys and holding High
areas to minimize the amount of manure
tracked into parlors
Scrape the cow platforms before hosing down High
parlors
Don't install drains in the cow platform High
Slope the floors of the parlor to facilitate High
scraping to the holding area
Install deep traps in drains Low
Keep traffic from manure areas out of the milk house Low
<$300to >$1,200
<$300
>$1,200
>$300
$300-$1,200
<$300
Table 4d-5. Phosphorus reduction methods and costs (Springman, 1992).
Phosphorus Reduction Methods
Reduction
Potential
Estimated Cost
Install water softener and/or increase softening High
time
Install an iron filter if needed Low
Install automatic, programmable CIP Medium
dispensing system
Use low or no phosphorus containing High
detergents and acid rinses
Reuse CIP detergent and/or acid rinse water Medium
Install water conservation methods in CIP Medium
<$1,200
<$300
>$1,200
<$300
>$300
>$300
Movement to Ground Water
Implementation of some surface runoff controls may increase the potential for
movement of water and soluble pollutants through the soil profile to the ground
water. The intent of this measure is not to address a surface water problem at the
expense of ground water. Facility wastewater and runoff control systems can and
should be designed to protect against the contamination of ground water. Ground
water protection will also be provided by minimizing seepage of stored, con-
taminated water to ground water, and by implementing the nutrient and pesticide
management measures.
Most parts of AFOs are either paved or highly compacted, and therefore rela-
tively impervious. Thus, in most cases, threats to ground water by infiltration at
the feedlot are low, and most actions for ground water protection will occur on
4-118
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4D: Animal Feeding Operations (AFOs)
land application sites and should be approached through the Nutrient Manage-
ment Measure. There are, however, a few important concerns within the feedlot
and storage areas. Unpaved feedlots and earthen impoundments are generally
believed to be "self-sealing" through compaction or with fine organic matter and
bacterial cells after a few months of operation. The rate and effectiveness of
sealing varies with waste and soil type. Cattle manure generally seals better than
swine waste; fine-textured soils generally seal more quickly and effectively than
do more porous soils. This sealing, however, is neither immediate nor 100%
effective. Significant leaching of pathogens or soluble pollutants such as nitrate
may occur early in the life of a facility, and the very slow seepage after "sealing"
may still pose a long-term threat to ground water. Additional sealing by compac-
tion, soil additives, or impermeable membranes is often required over porous
soils or fractured bedrock. Whenever possible, liners made of clay or synthetic
materials should be used in the original design and construction of the facility.
Construction with concrete or use of closed storage tanks are effective means of
preventing seepage.
Vegetated filter strips located within or adjacent to the facility may sometimes
represent an additional ground water concern. When such areas receive a high
pollutant load and infiltration occurs, ground water levels of nitrate may be
increased. While it may not be necessary to implement a nutrient management plan
on the vegetative control practices themselves, ground water should be protected by
taking care to not exceed the capacity of the practices to assimilate nutrients.
Finally, wells within the facility represent a direct path to ground water and may
be vulnerable to direct contamination by runoff water or by accidental spills of
wastes. Wells are a particular concern where drinking water may be threatened
by nitrates, bacteria, viruses, or other pathogens. Care should be taken to protect
wells from routine or accidental contamination. Wells should be properly cased,
grouted, and sealed, and abandoned wells should be properly filled and sealed.
Participation in Farm*A*Syst, a voluntary farmstead pollution risk assessment
program, is an excellent way to identify ways to prevent contamination of wells
(Jackson et al., undated).
Animal Feeding Operation Management Practices and
Their Effectiveness
AFO Management Practices
One of the most important considerations in preventing water pollution from
AFOs is the location of the facility. For new facilities and expansions to existing
facilities, consideration should be given to siting the facility:
H Away from surface waters;
O Away from areas of shallow ground water;
G Away from areas with high leaching potential;
G Away from sinkholes and other critical or sensitive areas;
d To avoid odor drift to homes, churches, and communities; and
n In areas where adequate land is available; to apply animal wastes in
accordance with the nutrient management measure.
National Management Measures to Control Nonpoint Pollution from Agriculture 4-119
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Chapter 4: Management Measures
Combinations of the following practices can be used to satisfy the requirements
of this management measure. The Natural Resources Conservation Service
(NRCS) practice number and definition are provided for each management
practice, where available. Additional information about the purpose and function
of individual practices is provided in Appendix A. In some emergency situations,
such as extreme animal mortality or structure failure, certain management
methods such as commercial rendering, incineration, or approved burial sites
may be necessary.
Practices to Divert Clean Water
n Diversions (362): A channel constructed across the slope with a
supporting ridge on the lower side.
CD Field Border (386): A strip of perennial vegetation established at the
edge of a field by planting or by converting it from trees to herbaceous
vegetation or shrubs.
D Filter strip (393): A strip or area of vegetation for removing sediment,
organic matter, and other contaminants from runoff and wastewater.
n Grassed waterway (412): A natural or constructed channel that is
shaped or graded to required dimensions and established in suitable
vegetation for the stable conveyance of runoff.
O Lined waterway or outlet (468): A waterway or outlet having an
erosion-resistant lining of concrete, stone, or other permanent material.
The lined section extends up the side slopes to a designed depth. The
earth above the permanent lining may be vegetated or otherwise
protected.
O Roof runoff management (558): A facility for controlling and
disposing of runoff water from roofs.
D Terrace (600): An earthen embankment, a channel, or combination ridge
and channel constructed across the slope.
A large set of
management
practices are
available to custom
fit most facilities for
an effective pollution
prevention system.
Practices for Waste Storage
D Dikes (356): An embankment constructed of earth or other suitable
materials to protect land against overflow or to regulate water.
D Sediment basin (350): A basin constructed to collect and store debris or
sediment.
D Water and sediment control basin (638): An earth embankment or a
combination ridge and channel generally constructed across the slope and
minor water courses to form a sediment trap and a water detention basin.
D Waste storage facility (313): A waste impoundment made by
constructing an embankment and/or excavating a pit or dugout, or by
fabricating a structure.
n Waste treatment lagoon (359): An impoundment made by excavation
or earth fill for biological treatment of animal or other agricultural
wastes.
Practices for Waste Management
O Constructed wetlands (656): A wetland that has been constructed for
the primary purpose of water quality improvement.
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Chapter 4D: Animal Feeding Operations (AFOs)
n Heavy use area protection (561): Protecting heavily used areas by
establishing vegetative cover, by surfacing with suitable materials, or by
installing needed structures.
H Waste utilization (633): Using agricultural wastes or other wastes on
land in an environmentally acceptable manner while maintaining or
improving soil and plant resources.
G Composting facility (317): A facility for the biological stabilization of
waste organic material.
D Application of manure and/or runoff water to agricultural land:
Manure and runoff water are applied to agricultural lands and
incorporated into the soil in accordance with the Nutrient Management
Measure.
Practices for Mortality Management
CJ Composting facility (317): A facility for the biological stabilization of
waste organic material.
Practice Effectiveness
The effectiveness of practices to control contaminant losses from confined
livestock facilities depends on several factors including:
D The contaminants to be controlled and their likely pathways in surface,
subsurface, and ground water flows;
d The types of practices and how these practices control surface,
subsurface, and ground water contaminant pathways; and
n Site-specific variables such as soil type, topography, precipitation
characteristics, type of animal housing and waste storage facilities,
method of waste collection, handling and disposal, and seasonal
variations. The site-specific conditions must be considered in system
design, thus having a large effect on practice effectiveness levels.
The gross effectiveness estimates reported in Table 4d-6 simply indicate sum-
mary literature values. For specific cases, a wide range of effectiveness can be
expected depending on the value and interaction of the site-specific variables
cited above. When runoff from storms up to and including the 24-hour, 25-year
frequency storm is stored, there should be no release of pollutants from an AFO
via surface runoff. Rare storms of a greater magnitude or sequential storms of
combined greater magnitude may produce runoff, however.
Table 4d-7 shows reductions in pollutant concentrations that are achievable with
solids separation basins that receive runoff from small barnyards and feedlots.
Concentration reductions may differ from the load reductions presented in Table
4d-6 since loads are determined by both concentration and discharge volume.
Solids separation basins combined with drained infiltration beds and vegetated
filter strips (VFS) provide additional reductions in contaminant concentrations.
The effectiveness of solids separation basins is highly dependent on site vari-
ables. Solids separation; basin sizing and management (clean-out); characteris-
tics of VFS areas such as soil type, land slope, length, vegetation type,
vegetation quality; and storm amounts and intensities all play important roles in
the performance of the system.
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Chapter 4: Management Measures
Table 4d-6. Relative gross effectiveness'' (load reduction) of animal feeding operation control measures
(Pennsylvania State University, 1992b).
Practice11
Category
Runoff
Volume
Total"
Phosphorus
Total"
Nitrogen
Sediment
Fecal
Coliform
Animal Waste reduced
Systems6
Diversion Systems' reduced
Filter Strips9 reduced
Terrace System reduced
Containment reduced
Structures'1
90
70
85
85
60
80
45
NA
55
65
60
NA
60
80
70
85
NA
55
NA
90
NA= not available.
a Actual effectiveness depends on site-specific conditions. Values are not cumulative between practice categories.
b Each category includes several specific types of practices.
d Total phosphorus includes total and dissolved phosphorus; total nitrogen includes organic-N, ammonia -N, and
nitrate-N.
6 Includes methods for collecting, storing, and disposing of runoff and process-generated wastewater.
f Specific practices include diversion of uncontaminated water from confinement facilities.
9 Includes all practices that reduce contaminant losses using vegetative control measures.
h Includes such practices as waste storage ponds, waste storage structures, waste treatment lagoons.
Table 4d-7. Concentration reductions in barnyard and feedlot runoff treated with solids separation.
Site Location
TS
Ohio - basin onlya'b 49-54
Ohio - basin combined w/infiltration 82
bed8
VFSb 87
Canada - basin only0 56
Canada - basin w/VFS°
Ilinois - basin w/VFSd 73
a Edwards el al., 1986.
b Edwards etal., 1983.
GAdametal., 1986.
d Dickey, 1981.
Constituent Reduction (%)
COD Nitrogen
51-56 35
85 —
89 83
38 14(TKN)
(High 90's in fall and spring)
80(TKN)
TP
21-41
80
84
—
78
Constructed wetlands have been developed and evaluated for animal waste
treatment. These constructed wetlands use the same plants, soils and microor-
ganisms as natural wetlands to remove contaminants, nutrients and solids from
the wastewater. Constructed wetlands have been used for years to treat munici-
pal wastewater, industrial wastewater, and stormwater. More recently, they have
been used for animal wastewater treatment. A literature review cited in Con-
structed Wetlands and Wastewater Management for Confined Feeding Opera-
tions published by the Gulf of Mexico program (Alabama Soil and Water
Conservation Committee et al., 1997) identified 68 different sites using con-
structed wetlands to treat wastewater from confined animal feeding operations.
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Chapter 4D: Animal Feeding Operations (AFOs)
Overall, the wetlands reduced the concentration of wastewater constituents such
as 5-day biochemical oxygen demand, total suspended solids, ammonia nitrogen,
total nitrogen, and total phosphorus. Table 4d-8 shows the average treatment
performance.
Of the 68 sites identified, 46 were at dairy and cattle feeding operations. The
herd sizes ranged from 25 to 330, with an average of 85 head. Dairy wastewater
often included water from milking barns and from feeding/loafing yards with
varying characteristics. Cattle feeding wastewater typically came from areas
where animals were confined. Usually, dairy and cattle wastewaters were
pretreated or diluted before being discharged to constructed wetlands.
Swine operations accounted for 19 of the wetland systems in the study. Swine wastes
were collected using flush water from solid floor barns and paved lots, or they were
collected directly from slatted floors in farrowing or nursery barns. In many cases,
the wastewater was pretreated in lagoons and then discharged to a wetland
system to further reduce concentrations to a level that could be applied to the land.
Constructed wetland systems which provided high levels of nitrogen removal for
swine wastewater was recently reported by Rice et al. 1998. Three sets of two 3.6
x 33.5 m wetlands received lagoon liquid from a 2600-pig nursery operation. In
these wetlands, mass reduction of total nitrogen was 94% when the low nitrogen
loading rate of 3 kg/ha specified for advanced treatment for stream discharge was
used. However, discharge requirements for nitrogen and phosphorus could not
consistently be achieved at this low loading rate, so the goal was changed to
determine the maximum loading and nitrogen removal that could be achieved. At
the current loading rate of approximately 25 kg/ha/day, the mean nitrogen
removal efficiency was 87%. The nitrogen loading rates and mass removal
efficiencies for these investigated loading rates are shown in Table 4d-9.
It was determined that there was not enough nitrate in the wetlands for denitrifi-
cation; hence, treatment experiments were also conducted with nitrified waste-
water, for which the nitrogen removal rate was 4 to 5 times higher than when
non-nitrified wastewater was added. Also, wetlands with plants were more
effective than those with bare soil. These results suggest that vegetative wet-
Table 4d-8, Summary of average performance of wetlands treating wastewater from
confined animal feeding operations".
Wastewater Constituent
Average Concentration (mg/L)b
Inflow Outflow
Average Reduction (%)
5-Day biochemical oxygen demand (BOD5) 263
Total suspended solids (TSS) 585
Ammonium nitrogen (NH4-N) 122
Total nitrogen (TN) 254
Total phosphorus (TP) 24
93
273
64
148
14
65
53
48
42
42
6 Data from the Livestock Wastewater Treatment Wetland Database (LWDB), which includes wetland
systems at dairy, cattle, swine, poultry, and aquaculture sites (Knight et al., 1996).
b Average concentration is based on a hydraulic loading rate of 1.9 inches per day (50,000 gallons
per day per acre [gpd/ac]). Averages were calculated from data for 30 to 86 systems.
mg/L = milligrams per liter
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Chapter 4; Management Measures
Table 4cl-9. Nitrogen loading rates and mass removal efficiencies for the constructed wetlands,
Duplin Co, NC (June 1993-November 1997) (Rice et al, 199}.
Nitrogen
3 kg/ha/day
8 kg/ha/day
15 kg/ha/day
25 kg/ha/day
% Mass Removal = %
nutrient mass inflow.
System
Rush/bulrush
Cattails/bur- reed
Rush/bulrush
Cattails/bur-reed
Rush/bulrush
Cattail/bur- reed
Rush/bulrush
Cattail/bur- reed
mass reduction of N (NH3-N + NO3-N)
% Mass Removal
94
94
88
86
85
81
90
84
in the effluent with respect to the
It is appropriate to
evaluate the waste
management
capabilities and
interests of the
grower, herdsman,
or stock manager.
Factor this
information into the
daily and periodic
site operation
requirements for
facility design.
lands with nitrification pretreatment is a viable treatment alternative for the
removal of large quantities of nitrogen from swine wastewater.
Major conclusions of these studies were that wetlands by themselves cannot
remove sufficient amounts of nitrogen and phosphorus to meet stream discharge
requirements but do show promise for high rates of nitrogen mass removal.
Since wetlands are nitrate limited, the mass removal rate can be increased by
nitrifying the wastewater prior to wetland application. With nitrification pre-
treatment, wetlands have the potential to annually remove more than 14,000 kg
N/ha. By sequencing nitrification and denitrification unit processes, advanced
wastewater treatment levels can be achieved. Such systems could provide a safer
alternative to anaerobic lagoons, with reduced ammonia volatilization and odor.
Operation and Maintenance
Appropriate operation and maintenance are critical to achieving the full environ-
mental benefits of this management measure. Holding ponds and treatment
lagoons should be operated such that the design storm volume is available for
storage of runoff. Facilities filled to or near capacity should be pumped. Solid
separation basins should be pumped or cleaned out according to design specifi-
cations. Pollutant loads can be reduced by managing manure to prevent or
minimize accumulation on open lots.
It is appropriate to evaluate the waste management capabilities and interests of
the grower, herdsman, or stock manager. Factor this information into the daily
and periodic site operation requirements for facility design.
Diversions will need periodic reshaping and should be free of trees and brush
growth. Gutters and downspouts should be inspected annually and repaired
when needed. Established grades for lot surfaces and conveyance channels
should be maintained at all times.
Channels should be free of trees and brush growth. Periodic cleaning of debris
basins, holding ponds, and lagoons will be needed to ensure that design volumes
are maintained. Clean water should be excluded from the storage structure
unless it is needed for further dilution in a liquid system.
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Chapter 4D: Animal Feeding Operations (AFOs)
Infiltration areas or vegetative filter areas need to be maintained in permanent
vegetative cover, with vegetation harvested when conditions permit. Where
possible, runoff should be alternated between two infiltration areas to provide
alternating use and rest periods.
To protect ground water, it is important to avoid disturbing the manure-soil seal
when cleaning or emptying a feedlot, barnyard, or waste storage structure.
Factors in the Selection of Management Practices
The first priority in the selection of management practices should be clean water
diversion. Diverting as much precipitation, snowmelt, and overland flow as
possible away from the facility before the water can come into contact with
wastes will greatly reduce the volumes of contaminated runoff and wastewater
requiring later management. Once all clean water sources are diverted, facility
runoff and wastewater should be collected and conveyed to the management
systems. Simple facilities may have a single outlet that makes collection rela-
tively easy; large facilities with complex topography and layout may require
regrading, curbs, diversions, dikes, channels, or pipes to effectively collect and
convey runoff and wastewater.
Proper design and construction are essential to the performance of settling
basins, storage structures, and filter strips. Management practices and compo-
nents must be physically compatible with the functional layout of the facility
itself. Impoundments should always be located so that gravity flow can be
employed; however, clean water or runoff should be diverted from the site as a
precaution. It is also desirable to position buildings and waste treatment systems
so that prevailing winds do not immediately transport dust and odors to sensitive
areas. Distance and topography play a major role in determining what portions
of the site will receive direct land application of waste or irrigation of lagoon
liquid. State and local NRCS offices, Cooperative Extension Service offices,
State agriculture departments, State Land Grant Universities, and the American
Society of Agricultural Engineers are good sources of information for size and
layout requirements for management practices.
Wastewater management systems must protect water, soil and air quality.
Therefore, consideration also needs to be directed to storage, treatment and land
application techniques that minimize odor and ammonia volatilization. Nitrogen
loss during land application of manure by ammonia volatilization for various
waste management techniques is shown in Table 4d-10. Concerns also exist
regarding uncontrolled methane released from animal waste because it is consid-
ered to be an important factor in gases that cause global wanning. Odor has
become one of the major concerns of the general public and livestock producers.
Therefore, techniques to reduce in-house odors, such as alternative manure
collection and emptying techniques and dietary studies which reduce waste
volume and odor have received increased attention. Major soil quality concerns
include the buildup of phosphorus. Concern also exists about other constituents
that accumulate in the soil, such as copper and zinc. Therefore, management
practices should be selected that are both compatible with a given facility and
protective of water, air and soil quality.
Soil and manure testing data must be considered along with fertilizer recommen-
dations to be sure that the proper amount of manure is applied to land. Land
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Chapter 4: Management Measures
Table 4d-10. Nitrogen volatilization losses during land application of manure
(percent of nitrogen applied that is lost within 4 days of application).
Application method
Type of waste
Percent of
nitrogen lost
Broadcast
Broadcast with
immediate cultivation
Injection
Drag-hose injection
Sprinkler irrigation
Solid
Liquid
Solid
Liquid
Liquid
Liquid
Liquid
15 to 30
10 to 25
1 to 5
1 to 5
Oto2
Oto2
15 to 35
This table shows typical nitrogen losses due to volatilization—evaporation into the air.
Remember, practices that reduce volatilization losses will also reduce surface runoff losses.
Source: Hirschi et al., 1997, adapted from Livestock Waste Facilities handbook, MWPS-18,
3rd edition, 1993. ©MidWest Plan Service, Ames, IA 50011-3080.
application techniques which minimize ammonia volatilization and thus loss of
fertilizer value need to be employed. These techniques will also protect air quality
so that ammonia volatilization and odor are minimized. Calibration methods to
assist in the proper land application of manure are given in Table 4d-ll.
The management of stored runoff and accumulated solids through an appropriate
waste utilization system can be achieved under a range of options, including
land application, composting, biogas generation, recycling as feedstuffs, aquac-
ulture, and biomass production (Hauck, 1995). Early efforts to conserve animal
waste nutrients and other valuable components for fertilizer are directing re-
newed interest to conserve and process waste into value-added products. These
strategies involve using manure and dead animals in conjunction with other
materials such as sawdust, soybean and com products, culled sweet potatoes,
soybean hulls, and other organic waste products processed by rendering, extru-
sion, fluid bed cook-dehydration procedures and other techniques to produce
value-added products. Crab bait is one successful value-added byproduct pro-
duced from animal waste at the North Carolina State University Animal and
Poultry Waste Processing Center which has successfully utilized these waste
nutrients and reduced the use of bait fish. Any stored water, accumulated solids,
processed dead animals, or manure should be applied in accordance with the
Nutrient Management Measure.
Cost of Practices
Construction costs for control of runoff and manure from confined animal
facilities are provided in Table 4d-12. The annual operation and maintenance
costs average 4% of construction costs for diversions, 3% of construction costs
for settlement basins, and 5% of construction costs for retention ponds (DPRA,
1992). Annual costs for repairs, maintenance, taxes, and insurance are estimated
to be 5% of investment costs for irrigation systems (DPRA, 1992).
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4D: Animal Feeding Operations (AFOs)
Table 4d-11. Calibration methods (some common ways to calculate the application rate of manure
spreaders) (Hirschi et al., 1997).
Manure
source
What you need
to know
Calculations
Liquid manure
in a tank
Liquid manure
in spreader:
volume method
Liquid manure
in spreader:
weight method*
Solid manure
in spreader:
spreader volume
method**
Solid manure
in spreader:
plastic sheet
weight method
Shortcut method #1
with plastic sheet:
for lighter application
rates (use a 9' x 12' sheet)
Shortcut method #2
with plastic sheet:
for heavier application
rates (use a 4'8" x 4'8"
sheet or 87" x 3' sheet)
1. Tank load size
(gallons of manure)
2. Acreage over which
manure is spread at
even rate
1. Spreader load size
(gallons of manure)
2. Distance driven and
width spread (feet)
1. Spreader load size
(pounds of manure)
2. Distance driven and
width spread (feet)
1. Spreader struck-level
load size
(bushels of manure)
2. Distance driven and
width spread (feet)
1. Pounds of manure on
the sheet after drive-over
2. Square footage of
plastic sheet
1. Pounds of manure on
the sheet after drive-over
1. Pounds of manure on
the sheet after drive-over
gallons
acreage
application rate
(gallons per acre)
gallons x 43.560
distance x width
pounds x 5.248
distance x width
bushels x 1.688
distance x width
application rate
(gallons per acre)
application rate
(gallons per acre)
application rate
(tons per acre)
pounds x 21.78 _ application rate
square footage ~ (tons per acre)
of plastic sheet
pounds •+• 5
application rate
(tons per acre)
pounds of manure
collected on the sheet
application rate
(tons per acre)
*The calculation for this method assumes that a gallon of manure will weigh a certain number of pounds.
An average figure is used.
**The calculation for this method assumes that a bushel of manure will weigh a certain number of pounds.
An average figure is used.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-127
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Chapter 4: Management Measures
Table 4d-12. Costs for runoff control systems (DPRA, 1992; USDA, 1998).
Practice
Unit
Cost/Unit
Construction in 1997
DollarsblC'd
Diversion
Irrigation
- Piping (4-inch)
- Piping (6-inch)
- Pumps (10 hp)
-Pumps (15 hp)
- Pumps (30 hp)
- Pumps (45 hp)
- Sprinkler/gun (150 gpm)
- Sprinkler/gun (250 gpm)
- Sprinkler/gun (400 gpm)
- Contracted service to empty retention pond
Infiltration6
Manure Hauling
Dead Animal Composting Facility
Retention Pond
- 241 cubic feet in size
- 2,678 cubic feet in size
- 28,638 cubic feet in size
- 267,123 cubic feet in size
Settling Basin
- 53 cubic feet in size
-488 cubic feet in size
- 5,088 cubic feet in size
- 49,950 cubic feet in size
foot
foot
foot
unit
unit
unit
unit
unit
unit
unit
1,000 gallon
acre
mile per 4.5-ton load
cubic foot
cubic foot
cubic foot
cubic foot
cubic foot
cubic foot
cubic foot
cubic foot
cubic foot
2.38
2.35
3.02
2,350
2,690
4,030
4,700
1,180
2,350
4,300
3.68
2980
2.64
5.96
3.08
1.48
0.72
0.37
5.08
3.27
2.04
1.29
a Expected lifetimes of practices are 20 years for diversions, settling basins, retention ponds, and filtration areas and
15 years for irrigation equipment.
b Table is derived from DPRA estimates presented in an earlier edition adjusted by USDA price indices.
c Table does not present annualized costs.
d Costs for pumps, sprinklers, and infiltration are rounded to the nearest 10 dollars.
e Does not include land costs.
Sources:
* DPRA. Draft Economic Impact Analysis of Coastal Zone Management Measures Affecting Confined Animal Facilities,
DPRA, Inc., Manhattan, KS, 1992.
* United States Department of Agriculture (USDA), Agricultural Prices-1997 Summary, National Agricultural Statistics
Service, July 1998,
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4E: Grazing Management
4E: Grazing Management
' 0 preyeitt acceler^;e4 soil ©rosjoit H
* . dilute-wind and Water; . ,, a, r, /,' ,',\*'"
- such a manner that the Impacts to vegetative %&d wato quality will 7 *.
! .heoog&ive: ' - *'. ,, _^ ^ . ^ ' "'- ^ • , / - \; ^
;tllpj livestock: - ^
access to and'^use of sensitiye areas, sach as4 streambanlts, weJ^Rd%
> e"sfiiarie$* p>ndSj lake ^ore§,^ofts f^oiie to etosioti* and jipaiia|i2;|)^
thrp«gbthe;^bfoneof^bieoft«followlng|>r^t^ t| .
a. «.se of improved grazing management system^ (e,g,,feding):tq
. , f educe pbysical disturbance of «oi! and vegetaSonanrfrninimi^ •
' . direct loading of animal waste and sediMeJit losansitlve areas;-. -
b.' 'installationofaltenjatlve^•inldngwat^'sources; v/
-' c, instaliation 6f hardened assess points for driiilcing watetconsumpi
wljere altematives^arenot-feasible; • ' ' - - ,*
' ,d. placement of salt and additional sha-fe.ineJkdingattiWal shelters;
at legations and-distartces adequate; to pi^tec* 'sensitive ,areasr '-
e. provide stream crossings, where jajecessar^in afeak selected to
minimize ^e impacts of tfe erosslRgiS on w^r qmitey aiwJ labitat
and, ' * ' ' • ,4 \\ ' , '•* • -.' '\..:
f. use of exclusionary practices* suc& as-fencing (conwnfjDrtai amj
electric), hedgerows, molats and other, practices as appropriate ,
The restoration or
protection of
designated water
uses (e.g. fisheries)
is the goal of BMP
systems designed to
minimize the water
quality impact of
grazing and
browsing activities
on pasture and
range lands.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-129
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Chapter 4: Management Measures
3. achieving either of the following on all ran$qland> pasture, and other
grazing lands not addressed above;: , , ,
a, apply the planning approach of the U.S. pe|mrtment of Agriculture
(US0A), Natuftl Resources Conservation Service (NRCS) to
implement the gracing land components in accordance with one or
more of the following from N&CS; a Orating Land Resource
Management System (KMS); National Rattge and Pasture
Handbook (USDA-NRCS, IttWb); and NftlS Field Office
Tephnical Guide^ including f^CS Pre/Sg&bei <&&2$ng 52&\;
b. maintain or improve gracing -lands in accordance with activity platt$!
or gracing pe&nit retirements established by the Bwreau of JLand.
Management, tfcje National Fark Service* or &e Bureail of Indian
Affairs of thei U.S, I>epartm$tt of Interior, or tiie USt)A forest -
Service; or other federal land manager.
Management Measure for Grazing: Description
The management measure is intended to be applied to activities on rangeland,
irrigated and non-irrigated pasture, and other grazing lands used by domestic
livestock. This management measure applies to both public and private range
and pasture lands. A grazing management plan/system should be used to plan
and achieve implementation of this management measure.
The goals of this management measure are to protect water quality and quantity
and sensitive areas. The grazing management plan/system is the primary mecha-
nism through which these goals are achieved. A grazing management plan/
system may include management strategies and practices such as herding,
alternative water sources, livestock exclusion, and conservation of range,
pasture, and other grazing lands. Grazing management systems are intended to
achieve specified objectives and ensure "proper use." Proper use can be defined
as grazing managed so that the total vegetation available is grazed at a time and
intensity that does not degrade the existing-riverine/aquatic-riparian-upland
systems or in the case of degraded rangelands, inhibit system response to a more
desirable state (adapted from Platts, 1990). As such, a clear understanding of
plants and their ecology are key to good grazing management.
It is recognized that livestock exclusion is more practicable on pasture than
rangeland in many cases, but livestock exclusion can be used for the protection
of water quality in key sensitive areas on rangelands. In grazing systems, major
environmental improvements can be achieved by minimizing livestock access to
streambanks and riparian areas during periods of streambank instability and
regrowth of key riparian vegetation.
To meet the objectives of the management measure, a comprehensive manage-
ment system should be employed to manage the entire grazing area. This grazing
area may include uplands, riparian areas, and wetlands. Special attention should
be given to grazing management in riparian and wetland areas due to their
sensitivity to disturbance and the tendency of many grazing animals to favor
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Chapter 4E: Grazing Management
these areas for foraging and loafing. Riparian areas are defined by Mitsch and
Gosselink (1986) and Lowrance et al. (1988) as:
vegetated ecosystems along a water body through which
energy, materials, and water pass. Riparian areas
characteristically have a high water table and are subject
to periodic flooding and influence from the adjacent water
body.
Riparian area and wetland protection strategies should be integrated with upland
management strategies. The health of the riparian and wetland ecosystems,
receiving waterbody quality, and stream base flow levels are often dependent on
the use, management and condition of adjacent uplands. Proper management of
uplands can reduce grazing pressure on riparian areas and also increase forage
productivity due to increased water table height and stream base flow. Increased
forage productivity and overall upland health can result in increased economic
benefits to the landowner or grazing management entity.
This management measure also contains recommendations under 3a and 3b that
USDA/NRCS methodologies and guidance and/or other federal agency require-
ments should be employed in addition to the management elements listed in la-g
and 2a-f to provide the requisite level of natural resource protection. Resource
management systems (RMS) include any combination of conservation practices
and management that achieves a level of treatment of the five natural resources
(i.e., soil, water, air, plants, and animals) that satisfies criteria contained in the
Natural Resources Conservation Service (NRCS) Field Office Technical Guide
(FOTG). The rangeland and pasture components of a RMS address erosion
control, proper grazing, adequate pasture stand density, and rangeland condition.
National (minimum) criteria pertaining to rangeland and pasture under an RMS
are applied to achieve environmental objectives, conserve natural resources, and
prevent soil degradation.
Recommendations for Grazing Management
in Riparian Areas
O tailor the gracing approach to,the specific riparian area under consideration,
*£3 Incorporate management of riparian areas into the overall management-plan for the whole
operation. . * ;
*, P Select a season or seasons of use so grazing occurs, as often as possible, daring .periods- compatible
','- • with aaim4 behavior 'and conditions in $ie Ep,anari area, '' " ^tt\
'• O ' Control the distribution of livestock vifithinthe targeted pasture.
*. 'P Ensure'adequate residual vegetative cover. • ' - >
- 'P Provide adequate regro.wth time and rest for plants • *' ;. t
0 'Be prepared to pjay-an active role in managing riparian-areas. • ' -
Source: &e$t Management'Pryqticps for grazing Montana, Montana Waters^ Cpo^inatioft Council's
/ • - • Grazing Prances Work Group;
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter4: Management Measures
Grazing and Pasturing: An Overview
In addressing nonpoint source pollution concerns, producers must balance
production and water quality objectives. This section explores some of the
production-oriented resources management decisions confronting livestock
producers.
Livestock can obtain their needed nutrients through feed supplied to them in a
confined livestock facility, through forage, or through a combination of forage
and feed supplements. Forage systems can be pasture-based or rangeland-based.
It is important for the reader to be aware of the difference between rangeland
and pasture. Rangeland refers to those lands on which the native or introduced
vegetation (climax or natural potential plant community) is predominantly
grasses, grasslike plants, forbs, or shrubs suitable for grazing or browsing.
Rangeland includes natural grassland, savannas, many wetlands, some deserts,
tundra, and certain forb and shrub communities. Pastures are those improved
lands that have been seeded, irrigated, and fertilized and are primarily used for
the production of adapted, domesticated forage plants for livestock. Other
grazing lands include grazable forests, native pastures, and crop lands producing
forage.
The major differences between rangeland and pasture are the kind of vegetation
and level of management that each land area receives. In most cases, range
supports native vegetation that is extensively managed through the control of
livestock rather than by agronomy practices, such as fertilization, mowing, or
irrigation. Rangeland also includes areas that have been seeded to introduced
species (e.g., clover or crested wheatgrass) but are managed with the same
methods as native range. For both rangeland and pasture, the key to good
grazing practice is vegetative management, i.e., timing of grazing should be
managed to ensure adequate vegetative regrowth and soil stability.
Pastures are represented by those lands that have been seeded, usually to intro-
duced species (e.g., legumes or tall fescue) or in some cases to native plants
(e.g., switchgrass or needle grass), and which are intensively managed using
agronomy practices and control of livestock. Permanent pastures are typically
based on perennial warm-season (e.g., bermudagrass) or cool-season (e.g., tall
fescue) grasses and legumes (e.g., warm-season alfalfa, cool-season red clover),
while temporary pastures are generally plowed and seeded each year with annual
legumes (e.g., warm-season lespedezas, cool-season crimson clover) and grasses
such as warm-season pearl millet and cool-season rye (Johnson et al., 1997).
Plant selection for pastures should be based upon consideration of climate, soil
type, soil condition, drainage, livestock type and expected forage intake rates,
and the type of pasture management to be used. Management of pH and soil
fertility is essential to both the establishment and maintenance of pastures
(Johnson et al., 1997). In some climates (e.g., Georgia), overseeding of summer
perennials with winter annuals is done to provide adequate forage for the period
from mid-winter to the following summer.
Factors Affecting Animal Performance on Grazed Lands
The manager of a forage system must be concerned with care and management
of the livestock, control of noxious plants, and the quality of forage (McGinty,
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Chapter 4E: Grazing Management
1996). Both forage quality and forage intake must be managed to ensure the
performance, or quality, of livestock on pasture and grazing lands.
Forage quality
Forage quality is generally measured in terms of its nutritional value and digest-
ibility. Nutritional value can be assessed based on the amount of protein, phos-
phorus, and energy the plants contain (Ruyle, 1993). The nutritional value of
rangeland forage varies with season (e.g., higher in spring and summer), and
differs among forage types. For example, protein availability from grasses
decreases rapidly as the grasses mature, while shrubs are good sources of protein
even at full maturity. The protein content of forbs (e.g., weeds, wildflowers) falls
between that of grasses and shrubs. Grasses are generally considered to be good
sources of energy, shrubs are good energy sources before fruit development, and
the value of forbs is intermediate between that of grasses and shrubs for live-
stock.
Rangeland condition also affects the nutritive value of forage plants, with better
rangeland condition yielding more digestible plants (Ruyle, 1993). Other factors
affecting the quality of forage include the plant parts eaten (e.g., leaves versus
stem), the presence of secondary compounds (e.g., lignin, tannins, terpenes) in
the plants (Lyons et al., 1996b), and pests (Johnson et al., 1997). The stocking
rate and the type of grazing system can affect grazing animal nutrition as well.
Over-stocking will cause a shift toward less productive and less palatable forage
plants, resulting in decreased forage intake due to less total forage and less
desirable forage (Lyons et al., 1996b). The preservation of some of the forage on
grazed lands is necessary to protect the resource, but forage quality may suffer if
too much old growth is maintained. Closely-grazed forage is generally good for
animal performance since it results in younger forage that is higher in nutrient
value and more digestible (Johnson et al., 1997). The quality of regrowth in
pastures is improved with intensive grazing, but the rate of regrowth, and
therefore the yield, is reduced (Cannon et al., 1993). Grazing management
decisions should allow for plant vigor and regrowth and maintenance of soil
stability. Growing season factors should be considered when evaluating the
potential for plant regrowth.
Many practitioners currently use forage utilization or stubble height as a man-
agement tool to gauge the acceptable level of grazing. Stubble height measure-
ments can be used successfully as one component of a comprehensive grazing
management strategy. Stubble height measurements are a good tool to help
practitioners begin to focus on stream ecology and forage availability for animal
production. However, the exclusive and continuing use of stubble height as the
only or primary indicator of riparian health can be problematic. As a result
stubble height measurements are sometimes improperly used. Stubble height
measurements often are conducted at the wrong time or intervals, in the wrong
places, and based on measurements of the wrong plant species. To properly use
stubble height as an effective grazing management tool, stubble height must be
measured frequently during the grazing period to ensure that adequate vegetative
cover and soil stability are maintained at the end of both the growing season and
grazing period. The proper use of stubble height measurements can benefit
animal production and help ensure the stability of the riparian area, however, the
practicality and expense of frequent stubble height measurements may be
burdensome, and, as a result, this technique may be improperly applied.
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Chapter4: Management Measures
In Oregon, it is recommended that pastures be grazed from about 2,400 to 2,800
pounds of dry matter growth per acre down to about 1,500-1,600 pounds of dry
matter growth per acre, maintaining a height of 2-6 inches for clover and grasses
(Cannon et al., 1993). Guidelines for Texas ranchers recommend minimum
stubble height and plant residue as follows: 1.5 inches and 300-550 pounds per
acre for short grass; 4-6 inches and 750-1,000 pounds per acre for mid-grass;
and 840 inches and 1,200-1,500 pounds per acre for tall grass (McGinty, 1996).
However, these stubble height strategies may oversimplify the complexity and
site specificity of herbage dynamics under grazing, and it has been argued that
these assessments are qualitative, subjective, and not truly quantitative
(Scarnecchia, 1999).
The Montana Watershed Coordination Council's Grazing Practices Work Group
publication, Best Management Practices for Grazing Montana (1999) recom-
mends that rangeland managers set target levels for grazing use based on ani-
mals' nutritional needs balanced against the need to maintain a healthy plant
community. This approach is based on setting target levels for key species and
evaluating on a site level basis rangeland condition and trends. As a general rule
of thumb, the Council advises that the planned grazing target should be to use no
more than 50-60% of the key species.
Forage intake
Forage intake generally increases as forage quality increases (Lyons et al.,
1995). As illustrated in Figure 4e-l, forage intake increases with digestibility
since digestion creates room for additional forage. Livestock do not generally
stop eating once their nutrient requirements are met. Because of this, ranchers
cannot assume that higher quality forage alone will result in adequate resource
protection. Grazing management systems will still be needed to protect the
Figure 4e-1. Relationship between forage digestibility, the amount of forage ruminants can
eat, and the amount of forage needed to meet nutrient requirements as a
percentage of body weight (BW) (Lyons et al., 1995).
5
ACO
5?
1
o
o>
S
o
LJ_
0
Potential
X Intake
Required
Intake
40 80
Forage Digestibility, %
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Chapter 4E: Grazing Management
resource from improper grazing. With low-quality forage, more forage is needed
to meet nutrient needs, but the lower digestibility makes it much more difficult for
the livestock to meet their nutrient needs since the forage does not pass through
the rumen as quickly.
Forage intake is also affected by herbivore species and size, foraging behavior
(e.g., preference for certain forage types, preference for specific areas), physi-
ological status, animal production potential, supplemental feed, forage availabil-
ity, and environmental factors (Lyons et al., 1995). Smaller herbivore species
(e.g., sheep) have greater intake rates when measured as a percentage of live
weight than do larger species (e.g., beef cattle). Sheep and goats tend to be more
selective of the plants they graze than are cattle, and tend to have higher forage
intake rates due to their consumption of a readily digestible mixture of grass,
forbs, and browse (young twigs, leaves, and tender shoots of plants or shrubs
suitable for animal consumption). Horses may consume up to 70 percent more
forage than a cow of similar size due mostly to the rapid passage rate of horses.
The forage selected by herbivore species varies, and is determined largely by their
mouth parts and the anatomy of their digestive systems (Lyons et al., 1996a). For
example, horses eat more grass than cattle, sheep, and goats as a percentage of
their annual diet, while goats eat the most browse, and sheep eat the greatest share
of forbs. Diet also varies across season within a given species. Browse constitutes
34 percent of the diet of Texas-raised goats in spring and 53 percent in fall and
winter, while forbs account for 6 percent of the diet of cattle in fall and 25 percent
in spring. Management strategies should control animal distribution and plant
harvest timing to counter the effects of preference (Platts, 1990).
The importance of physiological status is evidenced by the fact that lactating
animals generally have a higher nutrient demand and greater forage intake rate
than animals that are dry, open, or pregnant (Lyons et al., 1995). In fact, an
animal can eat 35 to 50 percent more when lactating than when dry, open, or
pregnant. Highly productive cows early in lactation require the highest quality
feed to maintain production (Cannon et al., 1993). Thus, the good farm manager
gives high priority to the provision of adequate forage to lactating dairy herds in
order to avoid a drop in milk production.
Producers may need to provide feed nutrient supplements to ensure suitable
livestock production on rangeland (Ruyle, 1993) and other grazing lands. Protein
supplements are often given to livestock grazing on low-protein forage, and the
quantity and timing of the supplemental feeding can affect forage intake (Lyons et
al., 1995). For example, supplemental protein can increase forage intake to a point,
beyond which forage intake is reduced with increasing supplemental protein.
Forage availability is often measured in terms of stocking rates, or the number of
animals that use a unit of land for a specified period of time (White, 1995;
Sedivec, 1992). Forage growth and production can vary greatly over any given
land area, as seasons change, and as a function of weather conditions, so match-
ing stocking rates with forage availability is dependent upon assumptions
regarding forage production. Further, since forage intake is dependent upon
forage quality, it becomes necessary to carefully monitor forage quality and
quantity to determine if stocking rates need to be adjusted. A general rule-of-
thumb for grazing is to allow livestock to use 50 percent of the forage (Sedivec,
1992). USDA encourages development of a feed, forage, livestock balance sheet
National Management Measures to Control Nonpoint Pollution from Agriculture 4-135
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Chapter 4: Management Measures
to assist in management of grazing lands, and provides procedures and
worksheets to assist managers (USDA-NRCS, 1997b).
An alternative approach to addressing forage availability in management decisions
is based on the concept of a forage allowance, which is the weight of forage
allocated per unit of animal demand at any instance (Cropper, 1998). Forage
allowance is expressed as a percentage of live body weight or as pounds of forage
per animal per day, and generally averages 2.5-3% for beef and sheep, 2% for
horses, and 3-4% for lactating cows (Cropper, 1998). Research has shown that
forage intake increases with forage allowance, reaching a maximum level at a
forage allowance of about 6.5% of herd live weight (Figure 4e-2). Forage utiliza-
tion rate, however, decreases as forage allowance is increased, meaning that more
forage is potentially wasted since it is not consumed by livestock. With knowl-
edge of the number of animals on the pasture, the percentage of forage intake
derived from the pasture, forage intake per animal, and the desired forage utiliza-
tion rate, one can manage forage and livestock to achieve desired animal perfor-
mance without wasting or degrading pasture (Cropper, 1998).
Figure 4e-2. Relationship of forage allowance to forage intake and utilization (after Cropper, 1998).
(Lyons et al., 1995).
100
80
Forage Intake
(% of maximum)
50
100
80
Utilization
(% of available storage)
50
40
Forage Allowance
(% of live weight)
Environmental factors, including air temperature, soil moisture, and snowcover,
also affect forage intake. Each species of herbivore has a temperature-based
comfort zone, the thermoneutral zone, within which forage intake is not affected
(Lyons et al., 1995). Above and below the thermoneutral zone, however, intake
may increase or decrease depending upon outside conditions.
There is also a need to assess and compensate for wildlife forage utilization
when managing livestock to protect water quality. In many areas, wildlife con-
sumes a significant portion of available forage and wildlife ungulates (i.e., mam-
mals with hooves) may have a major impact on riparian areas and woody
vegetation. Land managers should take these impacts into account when plan-
ning and managing grazing management programs and setting grazing use levels
for each grazing unit.
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Chapter 4E: Grazing Management
Because of the many sources of variability in forage quality, forage availability,
and forage intake, the rancher faces a significant challenge in providing an
appropriate mix of forage to ensure that livestock receive adequate nutrition
throughout the year.
Water
Water is essential to the survival, growth, and productivity of livestock. Insuffi-
cient water supply will result in reductions in feed intake, production, and
profits (Paries et al., 1998). High salinity, high nitrate and nitrite levels, bacterial
contamination, excessive growth of blue-green algae, and spills of petroleum,
pesticides, and fertilizers are the water quality problems that most affect live-
stock production.
Research in Missouri has shown that water consumption of pastured beef cow-
calf pairs increased almost linearly as the temperature increased from 50 degrees
to 95 degrees Fahrenheit (Gerrish, 1998). At 50 degrees F, water consumption
was approximately 6 gallons per day, increasing to about 24 gallons per day at
95 degrees F. Cattle in Texas drink from 7 to 16 gallons per day, while horses (8-
12 gallons per day) and sheep and goats (1-4 gallons per day) drink less
(McGinty, 1996). Dry cows drink 8-10 gallons of water per day, while cows in
their last three months of pregnancy need up to 15 gallons of water per day
(Paries et al., 1998). The frequency with which livestock seek water varies,
ranging from 3-5 times per day for beef cows in the Midwest, to less frequent
visits in drier climates (Gerrish, 1998). A recent study showed that distance from
water supply had a large effect on water consumption, as cows within 800 feet of
water drank 15 percent more water than cows further than 800 feet from water
(Gerrish, 1998). The maximum distance that livestock will travel to water in
Texas ranges from 0.5 miles in rough terrain to 2.0 miles in smooth, flat terrain
(McGinty, 1996).
Minerals
Sodium, chloride, and other minerals are essential to the bodily functions of
animals, and livestock on the rangeland should consume about 20 pounds of salt
per year (Schwennesen, 1994). Well managed vegetation can provide the needed
minerals for healthy animals, but mineral supplements can benefit animals if
they are developed to meet local deficiencies. Livestock are attracted to salt and
other mineral supplements, and will remain with it as long as it remains, making
mineral supplements a very useful grazing land management tool. By placing
measured quantities of minerals at various locations throughout the year, livestock
operators can manage the location of livestock to control grazing, help manage the
grazing land condition, and keep livestock away from sensitive areas.
Weed and Brush Management
Weeds can reduce forage production and lower forage quality (Johnson et al.,
1997). Well-managed pastures present fewer weed problems as grasses can
outcompete most weeds. Weed management on rangeland may involve pre-
scribed burning or the use of herbicides (McGinty, 1996). The grazing of cattle,
sheep, and goats can also be used as a weed management tool.
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Chapter4: Management Measures
Grazing Systems
There is a wide range of grazing systems for rangeland and pastures that manag-
ers may select from (Table 4e-l). Specific terms and definitions used may vary
considerably across the nation. In all cases, however, the key management
parameters are:
d grazing frequency
O livestock stocking rates
O livestock distribution
C5 timing and duration of each rest and grazing period
d livestock kind and class
d forage use allocation for livestock and wildlife.
Factors to consider in determining the appropriate grazing system for any
individual farm or ranch include the availability of water in each pasture, the
type of livestock operation, the kind and type of forage available, the relative
location of pastures, the terrain, the number and size of different pasture units
available (Sedivec, 1992), and producer objectives.
While many systems may be derived from combinations of the key management
parameters, the basic choice is between continuous and rotational grazing. Under
continuous grazing, the livestock remain on the same grazing unit for extended
periods, while rotational grazing involves moving the livestock from unit to unit
during the growing season (Johnson et al., 1997). A prescribed grazing schedule
for rangeland is a system in which two or more grazing units are alternately
deferred or rested and grazed in a planned sequence over a period of years
(USDA-NRCS, 1997b). Rest periods are generally non-grazing periods of a full
year or longer, while deferment typically involves a non-grazing period of less
than twelve months.
Continuous, season-long grazing is typically done on larger pastures, with less
fencing and less livestock management than required for rotational grazing
(Johnson et al., 1997). A central problem with this approach is the difficulty of
matching the stocking rate with the changing forage growth rate during the
grazing season. For example, forages may grow at a rate of 90 pounds per acre
per day in spring, followed by summer growth rates of as little as 5 pounds per
acre per day, resulting in a mismatch of supply and demand if the stocking rate is
kept constant (Cropper, 1998).
Rotational grazing generally involves smaller pastures or paddocks, more
fencing, and more livestock management than required for continuous grazing
(Johnson et al., 1997). If forage growth exceeds forage intake, forage from some
paddocks may be harvested and stored for winter grazing. Rotational grazing
provides opportunities to better manage the available forage to meet livestock
needs (Johnson et al., 1997). In some cases, the additional costs for fencing and
supplying water in each paddock may be prohibitive. Options exist, however, for
designing paddocks such that drinking water sources can be shared by more than
one paddock, thus eliminating the need for additional water development (Drake
and Oltjen, 1994). In addition, affordable, portable fencing is often used in
management-intensive grazing systems (SARE, 1997).
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Chapter 4E: Grazing Management
Table 4e-1. Some commonly used grazing systems (Sedivec, 1992; McGinty, 1996; Frost and Ruyle, 1993; USDA-NRCS,
1997b).1995).
Grazing
System
Continuous
Description
Unrestricted livestock access to any part
of the range during the entire grazing
season. No rotation or resting.
Rotation
Intensive grazing followed by resting.
Livestock are rotated among 2 or more
pastures during grazing season.
Switchback
Rest-rotation
Livestock are rotated back and forth
between 2 pastures.
One pasture rested for an entire grazing
year or longer. Others grazed on
rotation. Multiple pastures with multiple
or single herd.
Deferred rotation Grazing discontinued on different parts
of range in succeeding years to allow
resting and re-growth. Generally
involves multiple herds and pastures.
Twice-over Variation of deferred rotation, with faster
rotation rotation. Uses 3-5 pastures.
Short-duration Grazing for 14 days or less. Large herd,
grazing many small pastures (4-8 cells), high
stocking density.
High intensity- Heavy, short duration grazing of all
tow frequency animals on one pasture at a time. Rotate
to another pasture after forage use goal is
met. Multiple pastures with single herds.
Comments
Difficult to match stocking rate to forage growth
rate. Severe overgrazing occurs where cattle
congregate. Other areas underutilized. Long-
term productivity depends upon moderate levels
of stocking. Can be year-long or seasonal
continuous grazing. Less fence and labor than
for rotation.
Each pasture may be alternately grazed and
rested several times during a grazing season.
Cattle are moved to different grazing area after
desired stubble height or forage allowance is
reached.
Every 2-3 weeks in ND. In TX, graze 3 months
on pasture 1, 3 months on pasture 2, then 6
months on pasture 1, etc.
In ND, 4 pastures used with 1 rested, one each
grazed in spring, summer, and fall. Rest periods
are generally longer than grazing periods.
Length of grazing period is generally longer than
the deferment period.
Long period of rest between rotations. Sequence
alternates from year to year.
Rest period is 30-90 days. Allows 4-5 grazing
cycles. Requires a high level of grass and herd
management skills. Similar to high intensity-low
frequency, but length of grazing and rest periods
are both shorter for short-duration grazing.
Grazing period is shorter than rest period, and
grazing periods for each pasture change each
year. In TX, grazing period is more than 14 days,
and resting period is more than 90 days. TX
typically has single herd on 4 or more pastures.
Three herds.
Merrill Each of 4 pastures grazed 12 months and
rested 4 months.
Season-long No specific number of herds or pastures. No set movement pattern.
Grazing
A number of different stocking methods are used to manage pastures, including
allocation stocking methods (continuous set stocking, continuous variable
stocking, set rotational stocking, variable rotational stocking), nutrition optimi-
zation stocking methods (creep grazing, strip grazing, frontal grazing), and
seasonal stocking methods (deferred stocking, sequence stocking) (USDA-
NRCS, 1997b). Rotational stocking, or top grazing, is an adaptation of rotational
grazing that improves the efficiency with which forage is used. This approach is
based upon the fact that cattle select the highest quality forage available before
grazing lower quality forage (Johnson et al., 1997). In rotational stocking, for
example, a lactating dairy herd might be rotated to a paddock where it can obtain
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Chapter4: Management Measures
The loss of
streambank stability,
riparian vegetation,
stream habitat, and
modification of
hydrologic regime
due to poor grazing
practices has a
devastating effect on
stream life.
100 percent of its forage intake needs at a low forage utilization rate (see Figure
4e-2). Forage allowances for high-producing, lactating diary cattle need to be
generous to maintain milk production, resulting in utilization rates of 50 percent or
less (Cannon et al., 1993). Dry cows and heifers might be rotated to the same
paddock after the lactating dairy herd is removed to increase the forage utiliza-
tion rate (Cropper, 1998).
Potential Environmental Impacts of Grazing
The focus of the grazing management measure is on the protection of water
quality and aquatic and riparian habitat. Riparian areas may need special atten-
tion to achieve water quality and habitat related goals. The entire watershed
should be evaluated to determine the sources and causes of nonpoint source
pollution problems and to develop solutions to those problems. Application of
this management measure will reduce the physical disturbance to sensitive areas
and reduce the discharge of sediment, animal waste, nutrients, pathogens, and
chemicals to surface waters.
More than half the commercial operators with beef cattle herds in the West graze
federal lands. According to a report by the Council for Agricultural Science and
Technology (CAST) (Laycock, 1996), a leading consortium of 33 professional
scientific societies, individuals are becoming increasingly concerned about the
ecological effects of improper grazing on federal lands. Major concerns include
diminished biodiversity, deteriorating rangeland, watershed, and streambank
conditions; soil erosion and desertification; decreased wildlife population and
habitat; and lost recreational opportunities.
Riparian areas constitute important sources of livestock grazing. One acre of
riparian meadow has the potential grazing capacity equal to 10 to 15 acres of
surrounding forested rangeland. In the Pacific Northwest, riparian meadows
often cover only 1 to 2% of the summer rangeland area, but provide about 20%
of the summer forage.
Streambank stability is directly related to the species composition of the riparian
vegetation and the distribution and density of these species (Figure 4e-3). During
high water, riparian vegetation protects the banks from erosion, reducing water
velocity along the stream edge, and causing sediments to settle out. Platts (1991)
has summarized the importance of riparian vegetation in providing cover and
maintaining streambank stability. Trees provide shade and streambank stability
because of their large and massive root systems. Trees that fall into or across
streams create high quality pools and contribute to channel stability. Brush
protects the streambank from water erosion, and its low overhanging height adds
cover that is used by fish. Grasses form the vegetative mats and sod banks that
reduce surface erosion and erosion of streambanks. As well-sodden banks gradu-
ally erode, they create the undercuts important to salmonids as hiding cover. Root
systems of grasses and other plants trap sediment to help rebuild damaged banks.
When animals repeatedly graze directly on erodible streambanks, bank structure
may be weakened causing soil to move directly into the stream. Excessive
grazing on riparian vegetation can result in changes in plant community compo-
sition and density and can negatively impact bank stability and the filtering
capacity of the vegetation. Within the federal government, the Bureau of Land
Management (BLM) and the USDA have experience in and tools for assessing
riparian system function and erodibility.
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Chapter 4E; Grazing Management
Figure 4e-3. Benefits that a riparian buffer can provide. Dosskey, 1997).
Cropland runoff
flood protection
filter agricultural runoff
wildlife habitat
economic products
bank stability
aquatic habitat
visual diversity
The loss of riparian vegetation together with collapsed streambanks increases
stream width and decreases depth, which has the potential to alter stream
temperature. With the loss of riparian vegetation, the stream is exposed to
greater temperature fluctuations, resulting in potentially higher temperatures
during the day and cooler temperatures at night. Riparian vegetation moderates
stream temperatures by absorbing short-wave radiation during the day and
insulating the stream from loss of long-wave radiation at night. Other reports
indicate that keeping the water in the ground longer is also a major contributing
factor to cooler water temperatures (Baschita, 1997).
Improper grazing management can contribute to the removal of most vegetative
cover, soil compaction, exposure of soil, degradation of soil structure, and loss
of infiltration capacity. These impacts can result in soil susceptible to wind and
water erosion. Due to the steep slopes, highly erodible soils, and storm events,
the sediment delivery ratio from rangeland can be very high (Carpenter et al.,
1994), Improper management can also alter the plant species composition by
creating a shift from desirable perennial species to undesirable annual species.
Livestock also generate microorganisms in waste deposits as they graze on
pasture and rangelands. Animal wastes contain fecal coliform and fecal strepto-
cocci in numbers on the order of 10s - 108 organisms per gram of waste, or 109 -
1010 excreted per animal per day (Moore et al., 1988). In addition to such indica-
tor organisms, livestock can serve as an important reservoir of pathogens such as
E. coli O157:H7 (Wang et al., 1996; Pell, 1997). The extent of manure and
microorganism deposition on grazing land typically depends on livestock density
or stocking rate (Carpenter et al., 1994; Fraser et al., 1998; Edwards et al., 2000).
Release of microbes from manure deposited on grazing land is influenced by
time, temperature, moisture, and other variables. Enhanced survival of microor-
ganisms in fecal deposits on grazing land has been documented elsewhere; the
bacterial pollution potential of fecal deposits on grazing land is significant
(Thelin and Gifford, 1983; Kress and Gifford, 1984). Bohn and Buckhouse
(1985) reported that fecal coliforms may survive in soil only 13 days in summer
Compaction and
vegetation loss due
to improper grazing
can increase runoff,
erosion, and
sediment delivery to
streams.
Pathogen impacts on
waterways are a
grazing land use
issue.
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Chapter4: Management Measures
and 20 days in winter, but that cow fecal deposits provide a protective medium
that permit microorganisms to survive for more than a year.
Runoff from grazed land can contain high numbers of indicator microorganisms.
Crane et al. (1983) cited fecal coliform counts of 103 - 105 organisms/100 ml in
pasture runoff. Edwards et al. (2000) reported that FC levels in runoff from
simulated grazing plots were always higher (2.4 x 105 - 1.8 x 106FC/100 ml)
than counts from the ungrazed control plots (1.5 x 103 FC/100 ml). Microorgan-
ism counts in runoff from grazing land are, however, typically several orders of
magnitude lower than numbers from land where manure is deliberately applied.
It should be noted that, because all warm-blooded animals excrete indicator
bacteria in their feces, wildlife inhabiting agricultural land are likely to contrib-
ute to the pool of microorganisms available in a watershed, including both
indicator organisms (Kunkle, 1970; Niemi and Niemi, 1991; Valiela et al., 1991)
and pathogens such as Giardia (Ongerth et al., 1995).
Nutrient inputs from grazing lands to surface water come mainly in the form of
nitrogen and phosphorus from manure and decaying vegetation (Carpenter et al.,
1994). Nutrient impacts on water quality vary considerably in study results, and
are dependent on specific site conditions such as precipitation, runoff, vegetation
cover, grazing density, proximity to the stream, and period of use, The risk of
nutrient enrichment is low in arid rangelands where animal wastes are distrib-
uted and runoff is comparatively light. Studies by the ARS and BLM found little
evidence of nutrient enrichment from unconfined livestock grazing in Reynolds
Creek, an arid watershed in southern Idaho (USDA-ARS, 1983). This risk can
also be low in humid climates if grazing lands are managed correctly. In a humid
site in east-central Ohio (Owens et al., 1989), nutrient concentrations did not
increase significantly with summer grazing of the unimproved pasture, and were
also low when continuously grazed. In another study, Schepers and Francis
(1982) found increases in nutrients in a cow-calf pasture in Nebraska. Nutrient
levels were correlated primarily with grazing density,
Grazing Management Practices and their Effectiveness
The Grazing Management Measure was selected based on an evaluation of
available information that documents the beneficial effects of improved grazing
management. Specifically, the available information shows that
d Riparian habitat conditions are improved with proper livestock
management;
D The amount of time livestock spend drinking and loafing in the riparian
zone is dramatically reduced through the provision of supplemental
water and fencing; and
D Nutrient and sediment delivery is reduced through the proper use of
vegetation, streambank protection, planned grazing systems, and
livestock management.
For any grazing management measure to work, it must be tailored to fit the
needs of the vegetation, terrain, class or kind of livestock, and particular opera-
tion involved,
For both pasture and rangeland, areas should be provided for livestock watering,
supplemental minerals, and shade that are located away from streambanks and
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Chapter 4E: Grazing Management
Five Steps to a Successful Prescribed Grazing
Management Plan
riparian zones where necessary and practical. This will be accomplished by
managing livestock grazing and providing facilities for water, minerals, and
shade as needed.
The rancher may seek technical assistance from Cooperative Extension, NRCS,
Soil and Water Conservation Districts, or other agencies to help identify water
quality problems, develop management measures (statements of water quality
goals or objectives), and select management practices. The amount or extent to
which a practice is applied must be consistent with national, state, and basin
water quality goals and should reflect the relative contribution of that type of
land use activity toward water quality problems within the basin. This technical
assistance will result in a plan, typically known as a ranch plan or conservation
plan.
Additional information on grazing management can be found in the NRCS
National Range and Pasture Handbook (USDA-NRCS, 1997b), as well as the
Bureau of Land Management's (BLM) Technical Reference Series on Grazing.1
The Management Practices set forth below have been found by the U.S. Envi-
ronmental Protection Agency (EPA) to be representative of the types of practices
that can be applied successfully to achieve the management measure for grazing.
The NRCS management practice number and definition are provided for each
management practice, where available. Other practices may be appropriate due
to site specific factors. State and local requirements may apply.
Grazing Management Practices
Appropriate grazing management systems ensure proper grazing use by adjusting
grazing intensity and duration to reflect the availability of forage and feed desig-
nated for livestock uses, and by controlling animal movement through the operat-
Contact your county
Cooperative
Extension agent,
USDA-NRCS district
conservationist, or
the local Soil and
Water Conservation
District.
1 Four key references within the BLM's Technical Reference Series on Grazing include Grazing Management for Riparian-Wetland
Areas (Leonard et al., 1997), Process for Assessing Proper Functioning Condition (Prichard et al., 1993), A User Guide to
Assessing Proper Functioning Condition and the Supporting Science for Lotic Areas (USDOI-BLM, USDA-Forest Service, and
USDA-NRCS, 1998), and A User Guide to Assessing Proper Functioning Condition and the Supporting Science for Lentic Areas
(USDOI-BLM, USDA-Forest Service, and USDA-NRCS, 1999). Other references of similar interest include Successful Strategies
for Grazing Cattle in Riparian Zones, Riparian Tech Bulletin #4, USDOI, Montana BLM, January 1998; and Effective Cattle
Management in Riparian Zones: A Field Survey and Literature Review, Riparian Tech Bulletin #3, USDOI, Montana BLM,
November 1997.
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Chapter 4: Management Measures
Practices have been
developed
for grazing
management,
alternative water
supply, riparian
grazing, and land
stabilization.
ing unit of grazing land. Grazing used as a tool for promoting vegetative vigor can
help maintain live vegetation and litter cover from actively growing grasses and
forbs and help reduce the soil erosion rates below the natural erosion rates for
the soil type and pre-existing vegetative cover. The use of grazing management
systems can help maintain riparian and other resource objectives and can help
meet the specific management objectives of the desired quality, quantity, and age
distribution of vegetation. Practices that accomplish this are:
CD Grazing Management Plan: A strategy or system designed to manage
the timing, intensity, frequency, and duration of grazing to protect and/or
enhance environmental values while maintaining or increasing the
economic viability of the grazing operation. This applies to both upland
and riparian management.
d Pasture and Hay Planting (512): Establishing native or introduced
forage species.
G Rangeland planting (550): Establishment of adapted perennial
vegetation such as grasses, forbs, legumes, shrubs, and trees.
d Forage Harvest Management (511): The timely cutting and removal of
forages from the field as hay, greenchop, or ensilage.
H Prescribed Grazing (528A): The controlled harvest of vegetation with
grazing or browsing animals, managed with the intent to achieve a
specified objective.
n Use Exclusion (472): Exclusion of animals, people, or vehicles from an
area to protect, maintain, or improve the quantity and quality of the
plant, animal, soil, air, water, and aesthetic resources and human health
safety.
n Nutrient Management (590): Managing the amount, source,
placement, form and timing of the application of nutrients and soil
amendments.
Alternate Water Supply Practices
Providing water and mineral supplement facilities away from streams will help
keep livestock away from streambanks and riparian zones. The establishment of
alternate water supplies for livestock is an essential component of this measure
when problems related to the distribution of livestock occur in a grazing unit. In
most western states, securing water rights may be necessary. Access to a devel-
oped or natural water supply that is protective of streambank and riparian zones
can be provided by using the stream crossing (interim) technology to build a
watering site. In some locations, artificial shade may be constructed to encour-
age use of upland sites for shading and loafing. Providing water can be accom-
plished through the following NRCS practices and the stream crossing (interim)
practice of the following section. Practices include:
d Irrigation Water Management (449): Irrigation water management is
the process of determining and controlling the volume, frequency, and
application rate of irrigation water in a planned, efficient manner.
CD Pipeline (516): Pipeline installed for conveying water for livestock or
for recreation.
n Pond (378): A water impoundment made by constructing a dam or an
embankment or by excavation of a pit or dugout.
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Chapter 4E: Grazing Management
D Trough or Tank (614): A trough or tank, with needed devices for
water control and waste water disposal, installed to provide drinking
water for livestock.
n Well (642): A well constructed or improved to provide water for
irrigation, livestock, wildlife, or recreation.
O Spring Development (574): Improving springs and seeps by
excavating, cleaning, capping, or providing collection and storage
facilities.
Riparian Grazing Practices
When implementing a grazing management system (see table 4e-l) within a
riparian area, it may at times be necessary to minimize livestock access to
riparian zones, ponds or lake shores, wetlands, and streambanks to protect these
areas from physical disturbance. The use of management practices for limiting
access should be linked in the overall management plan to proper grazing use
and other water quality goals. Practices include:
n Fence (382): A constructed barrier to livestock, wildlife, or people.
D Animal Trails and Walkways (575): A travel facility for livestock and/
or wildlife to provide movement through difficult or ecologically
sensitive terrain.
d Stream Crossing (Interim): A stabilized area to provide controlled
access across a stream for livestock and farm machinery.
Land and Streambank Stabilization Practices
It may be necessary to improve or reestablish the vegetative cover on rangeland
and pastures or on streambanks to reduce erosion rates. The following practices
can be used to reestablish vegetation:
O Nutrient Management (590): Managing the amount, source,
placement, form and timing of the application of nutrients and soil
amendments.
n Channel Vegetation (322): Establishing and maintaining adequate
plants on channel banks, berms, spoil, and associated areas.
n Pasture and Hay Planting (512): Establishing native or introduced
forage species.
n Rangeland Planting (550): Establishment of adapted perennial
vegetation such as grasses, forbs, legumes, shrubs, and trees.
G Critical Area Planting (342): Planting vegetation, such as trees, shrubs,
vines, grasses, or legumes, on highly erodible or critically eroding areas.
(Does not include tree planting mainly for wood products.)
d Brush Management (314): Removal, reduction, or manipulation of
non-herbaceous plants.
D Grazing Land Mechanical Treatment (548): Modifying physical soil
and/or plant conditions with mechanical tools by treatments such as;
pitting, contour furrowing, and ripping or subsoiling.
G Grade Stabilization Structure (410): A structure used to stabilize the
grade and control erosion in natural or artificial channels, to prevent the
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Chapter 4: Management Measures
formation and advance of gullies, and to enhance environmental quality
and reduce pollution hazards.
n Prescribed Burning (338): Applying controlled fire to predetermined
area.
n Stream Corridor Improvement (interim): Restoration of a modified
or damaged stream to a more natural state using bioengineering
techniques to protect the banks and reestablish the riparian vegetation.
O Land Reclamation Landslide Treatment (453): Treating inplace
materials, mine spoil, mine waste, or overburden to reduce downslope
movement.
n Sediment Basin (350): A basin constructed to collect and store debris or
sediment. Stock water ponds often act as sediment basins.
n Wetland Wildlife Habitat Management (644): Retaining, creating or
managing habitat for wetland wildlife. The construction or restoration of
wetlands.
D Stream Channel Stabilization (584): Using vegetation and structures to
stabilize and prevent scouring and erosion of stream channels.
O Wetland Restoration (657): A rehabilitation of a drained or degraded
wetland where the soils, hydrology, vegetative community, and
biological habitat are returned to the natural condition to the extent
practicable.
G Streambank and Shoreline Protection (580): Using vegetation or
structures to stabilize and protect banks of streams, lakes, or estuaries,
against scour and erosion.
O Riparian Forest Buffer/Herbaceous Cover (391A/390): Establish an
area of trees, shrubs, grasses, or forbs adjacent to and up-gradient from
water bodies.
Monitoring Grazing Land Condition
Monitoring is essential to determining whether grazing management objectives
are being achieved (Chancy et al., 1993). An integrated approach to monitoring
will evaluate nutrient cycling, soil and water quality, and plant community
dynamics. To evaluate and adjust management strategies, monitoring should be
conducted on both a site specific or allotment level and at the watershed or
subwatershed level to determine rangeland condition status and trends. A wide
array of monitoring options exist, including the use of photo points, vegetation
sampling, soil assessments, water quality and quantity analyses and assessments
of watershed, riparian and stream condition. A number of methods are available
for monitoring vegetation and for measuring forage utilization and residuals to
determine the effects of grazing and browsing on rangelands (Interagency
Technical Team, 1996 a, 1996 b; Ruyle and Forst, 1993). To assess vegetative
consumption and assist in the nutritional management of livestock and wildlife,
other methods, such as clipping procedures, have been developed (Brence and
Sheley, 1997).
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Chapter 4E: Grazing Management
Numerous publications aid the rangeland manager in determining the status and
trends of rangeland resources. Recommended publications on rangeland moni-
toring include:
G Monitoring the Vegetation Resources in Riparian Areas (Winward,
2000).
n Interpreting Indicators of Rangeland Health (USDOI-BLM and USGS,
and USDA-NRCS and ARS, 2000).
G Monitoring Rangelands: Interpreting What You See (Rasmussen et al.,
2001)
n Repeat Photography, Monitoring Made Easy (Rasmussen and Voth,
2001)
See page 143 for additional references on rangeland management.
Decisions regarding changes to stocking rates and preservation of an adequate
amount of forage to ensure good rangeland health and minimize water quality
impacts are dependent upon good information. Grazing land should be checked
frequently to ensure that the plants and animals are meeting management objec-
tives, depending on the management techniques being used.
Spreadsheet applications are available to make tracking and management of
grazing cells much easier (Gum and Ruyle, 1993). These spreadsheets address
both growing and dormant seasons, and incorporate such factors as the number
and size of paddocks, the number of days each paddock is to be rested, and the
relative quality of forage in each paddock. Some studies also recommend
monitoring plan implementation (i.e., how well the grazing management plan is
followed) and effectiveness (i.e., have objectives for vegetation condition been
met) (Clary and Leininger, 2000).
Recognizing that the pattern of grazing use varies across an enclosed grazing
area, or management unit, USDA recommends the identification of key grazing
areas and key plant species to aid in grazing land management (USDA-NRCS,
1997b). By protecting and monitoring the key grazing areas and key plant
species, it is believed that the management unit as a whole will be protected.
Practice Effectiveness
Eckert and Spencer (1987) studied the effects of a three-pasture, rest-rotation
management plan on the growth and reproduction of heavily grazed native
bunch grasses in Wyoming. The results indicated that rangeland improvement
under this otherwise appropriate rotation grazing system is hindered by heavy
grazing. Stocking rates on the study plots exceeded the carrying capacity of the
land and would decrease native grasses and increase potential erosion and
sedimentation.
Van Poollen and Lacey (1979) showed that herbage production was greater for
managed grazing versus continuous grazing, greater for moderate versus heavy
intensity grazing, and greater for light- versus moderate-intensity grazing.
Tiedemann et al. (1988) studied the effects of four grazing strategies on bacteria
levels in 13 Oregon watersheds in the summer of 1984. Although wildlife were
believed to be significant sources of bacteria in each of the study watersheds,
results indicate that lower fecal coliform levels can be achieved at stocking rates
National Management Measures to Control Nonpoint Pollution from Agriculture 4-147
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Chapter4: Management Measures
of about 20 ac/AUM (acres per animal unit month) if management for livestock
distribution, fencing, and water developments are used (Table 4e-2). The study
also indicates that, even with various management practices, the highest fecal
coliform levels were associated with the higher stocking rates (6.9 ac/AUM)
employed in strategy D.
Owens et al. (1982) measured nitrogen losses from an Ohio pasture under a
medium-fertility, 12-month pasture program from 1974 to 1979. The results
included no measurable soil loss from three watersheds under summer grazing
only, and increased average TN concentrations and total soluble N loads from
watersheds under summer grazing and winter feeding versus watersheds under
summer grazing only (Table 4e-3).
Data from a comparison of the expected effectiveness of various grazing and
streambank practices in controlling sedimentation in the Molar Flats Pilot Study
Area in Fresno County, California indicate that planned grazing systems are the
most effective single practice for reducing sheet and rill erosion (Fresno Field
Office, 1979).
By switching grazing allotments from continuous, season-long grazing to a
three-pasture, rest-rotation system, the U.S. Forest Service was able to achieve
Table 4e-2. Bacterial water quality responses to four grazing strategies (Tiedemann et al., 1988).
Practice
Geometric Mean Fecal
Coliform Count
Strategy A: Ungrazed
Strategy B: Grazing without management for livestock distribution; 20.3
ac/AUM.
Strategy C: Grazing with management lor livestock distribution: fencing
and water developments; 19.0 ac/AUM.
Strategy D: Intensive grazing management, including practices to attain
uniform livestock distribution and improve forage production
with cultural practices such as seeding, fertilizing, and forest
thinning; 6.9 ac/AUM.
40/L
150/L
90/L
920/L
Table 4e-3. Nitrogen losses from medium-fertility, 12-month pasture program (Owens et al.
Soil Loss
Practice (kg/ha)
Summer Grazing Only
Growing season —
Dormant season —
Year —
Summer Grazing - Winter Feeding
Growing season 251
Dormant season 1 , 1 04
Year 1 ,355
Total Sediment N
Transport (kg/ha)
—
1.4
6.6
8.0
Total N Concentration
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Chapter 4E: Grazing Management
major improvements in the vegetation in the Tonto National Forest in Arizona
(Chancy et al., 1990). For example, cottonwood populations increased from 20 per
100 acres to more than 2,000 per 100 acres in six years, while at the same time the
amount of livestock forage grazed increased by 27 percent. Similar improvements
from improved grazing management were documented through case studies in
Idaho, Nevada, Oregon, South Dakota, Texas, Utah, and Wyoming.
Hubert et al. (1985) showed in plot studies in Wyoming that livestock exclusion
and reductions in stocking rates can result in improved habitat conditions for
brook trout. In this study, the primary vegetation was willows, Pete Creek
stocking density was 7.88 ac/AUM (acres per animal unit month), and Cherry
Creek stocking density was 10 cows per acre (Table 4e-4).
Platts and Nelson (1989) used plot studies in Utah to evaluate the effects of
livestock exclusion on riparian plant communities and streambanks. Several
streambank characteristics that are related to the quality of fish habitat were
measured, including bank stability, stream shore depth, streambank angle,
undercut, overhang, and streambank alteration. The results clearly show better
fish habitat in the areas where livestock were excluded (Table 4e-5).
Kauffman et al. (1983a) showed that fall cattle grazing decreases the standing
crop of some riparian plant communities by as much as 21% versus areas where
cattle are excluded, while causing increases for other plant communities. This
study, conducted in Oregon from 1978 to 1980, incorporated stocking rates of
3.2 to 4.2 ac/AUM.
Buckhouse (1993) did an extensive review of livestock impacts on riparian
systems. Researchers documented many factors interrelated with grazing effects,
primarily dealing with instream ecology, terrestrial wildlife, and riparian vegeta-
Table 4e-4. Grazing management influences on two brook trout streams in Wyoming (Hubert et al., 1985).
Stream Parameter
Width
Depth
Width/depth ratio
Coefficient of variation in depth
Percent greater than 22 cm deep
Percent overhanging bank cover
Percent overhanging vegetation
Percent shaded area
Percent silt substrate
Percent bare soil along banks
Percent litter along banks
a Indicates statistical significance at p<=0,05.
0 Indicates statistical significance at p<=0.1.
Pete
Heavily
Grazed
(mean)
2.9
0.07
43
47.3
9.0
2.7
0
0.7
35
19.7
7.0
Creek (n=3)
Lightly
Grazed
(mean)
2.2a
0.11a
21
66.6a
22.3b
30.0a
11.7"
18.3a
52
13.3
6.0
Cherry
Outside
Exclosure
(mean)
2.9
0.08
37
57
6.7
24.0
8.5
23.5
22
22.8
10.0
Creek (n=4)
Inside
Exclosure
(mean)
2.5"
0.09B
28"
71
21.0"
15.3
18.0
28.0
13a
12.3a
6.8a
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Chapter 4: Management Measures
Table 4e-5. Streambank characteristics for grazed versus rested riparian areas
Streambank Characteristic (unit)
Extent (m)
Bank stability (%)
Stream-short depth (cm)
Bank angle (°)
Undercut (cm)
Overhang (cm)
Streambank alteration (%)
Grazed
4.1
32.0
6.4
127.0
6.4
1.8
72.0
(Platts and Nelson, 1989).
Rested
2.5
88.5
14.9
81.0
16.5
18.3
19.0
Grazing
management
research indicates
that local practices
designed for area
soils, vegetation, and
stocking rates are
more likely to
succeed than
applying one system
of BMPs across the
entire region.
tion. Permanent removal of grazing will not guarantee maximum herbaceous
plant production. Researches found that a protected Kentucky bluegrass meadow
reached peak production in six years and then declined until production was
similar to the adjacent area grazed season-long. The accumulation of litter over a
period of years seems to retard forage production in wetlands. Thus, some
grazing of riparian areas could have beneficial effects. Stoltzfus and Lanyon
(1992) also identified that fencing a riparian zone protects herd health from
infectious bacteria, hoof diseases, poor quality drinking water, and provides a
wildlife habitat.
The effect of grazing on streambanks depends on site conditions, management
practices, timing, and other factors. Kauffman et al. (1983b) found that
late-season grazing increased bank erosion relative to ungrazed areas in Oregon.
If late season grazing is permitted, adequate time for regrowth should be allowed
prior to the next major runoff event. Hallock (1996) found that delaying grazing
in riparian pastures until the soil dries in the late spring did not degrade the
streambanks or change stream morphology significantly in a Coastal California
Watershed.
Lugbill (1990) estimates that stream protection in the Potomac River Basin will
reduce total nitrogen (TN) and total phosphorus (TP) loads by 15%, while
grazing land protection and permanent vegetation improvement will reduce TN
and TP loads by 60%.
Nutrient loss is minimal where the riparian pasture remains in good condition.
Vegetation buffers the stream from direct waste input and assimilates the nutri-
ents into plant tissue. Gary et al. (1983) evaluated the effects on a small stream
in central Colorado of spring cattle grazing on pastures. Nitrate nitrogen did not
increase significantly and ammonia increased significantly only once.
Meals (2001) reported significant water quality improvements in Vermont
streams following livestock exclusion and riparian restoration on dairy
pastureland. Mean total phosphorus concentrations were reduced by 15%, and
total P load was reduced by 49% over a three-year period following riparian
restoration. Indicator bacteria counts in treated streams fell by 29% - 46%.
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Chapter 4E: Grazing Management
Photos have been used to document improvements in riparian condition due to
such practices as rest rotations and exclusion (Chancy et al., 1993). The authors
emphasize the importance, however, of looking beyond the vegetation and
examining whether water quality benefits also accrue. Vegetative response
usually happens in one to five years, however, stream channel changes may take
decades.
Miner et al. (1991) showed that the provision of supplemental water facilities
reduced the time each cow spent in the stream within 4 hours of feeding from
14.5 minutes to 0.17 minutes (8-day average). This pasture study in Oregon
showed that the 90 cows without supplemental water spent a daily average of
25.6 minutes per cow in the stream. For the 60 cows that were provided a
supplemental water tank, the average daily time in the stream was 1.6 minutes
per cow, while 11.6 minutes were spent at the water tank. Based on this study,
the authors expect that a 90% decrease in time spent in the stream will substan-
tially decrease bacterial loading from the cows.
McDougald et al. (1989) tested the effects of moving supplemental feeding
locations on riparian areas of hardwood rangeland in California. With stocking
rates of approximately 1 ac/AUM, they found that moving supplemental feeding
locations away from water sources into areas with high amounts of forage
greatly reduces the impacts of cattle on riparian areas (Table 4e-6).
Plant species
production
management is
central to effective
grazing BMPs.
Consider ecosystem
productivity, harvest
rates by stock and
wildlife, and
regenerative
capacity.
Table 4e-6. The effects of supplemental feeding location on riparian area vegetation (McDougald et al., 1989}.
Percentage of riparian area with the following levels of
residual dry matter In early October
Practice
Low
Moderate
Supplemental feeding located close to riparian areas:
1982-85 Range Unit 1
1982-85 Range Unit 8
1986-87 Range Units
Supplemental feeding moved away from riparian area:
1986-87 Range Unit 1
48
59
54
38
29
33
27
High
13
12
13
72
Factors in the Selection of Management Practices
The selection of grazing management practices for this measure should be based
on an evaluation of current conditions, problems identified, quality criteria, and
management goals. Successful resource management on grazing lands includes
appropriate application of a combination of practices that will meet the needs of
the rangeland and pasture ecosystem (i.e., the soil, water, air, plant, and animal
(including fish and shellfish) resources) and the objectives of the land user.
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter4: Management Measures
For a sound grazing land management system to function properly and to provide
for a sustained level of productivity, the following should be considered:
D Know the key factors of plant species management, their growth habits,
and their response to different seasons and degrees of use by various
kinds and classes of livestock.
n Know the demand for, and seasons of use of, forage and browse by
wildlife species.
n Know the amount of plant residue or grazing height that should be left
to protect grazing land soils from wind and water erosion, provide for
plant health and regrowth, and provide the riparian vegetation height
desired to trap sediment or other pollutants.
n Know the ecological site production capabilities for rangeland and the
forage suitability group capabilities for pasture so an initial stocking rate
can be established.
d Know how to use livestock as a tool (i.e., control timing and duration of
grazing) in the management of the rangeland ecosystems and pastures to
ensure the health and vigor of the plants, soil tilth, proper nutrient
cycling, erosion control, and riparian area management, while at the
same time meeting livestock nutritional requirements.
n Establish grazing unit sizes, watering, shade (where possible) and
mineral locations, etc. to secure optimum livestock distribution and
proper vegetation use.
D Provide for livestock herding, as needed, to protect sensitive areas from
excessive use at critical times.
d Work with state game management agencies to agree on proper stocking
numbers prior to wildlife harvest. Encourage proper wildlife harvesting
to ensure proper population densities and forage balances.
n Know the livestock diet requirements in terms of quantity and quality to
ensure that there are enough grazing units to provide adequate livestock
nutrition for the season and the kind and classes of animals on the farm/
ranch.
n Maintain a flexible grazing system to adjust for unexpected
environmentally and economically generated problems.
G Follow special requirements to protect threatened or endangered species.
To speed up the rehabilitation process of riparian zones, seeding can be used as a
proper management practice. This strategy, however, can be very expensive and
risky. Riparian zones can be rehabilitated positively and at a lower cost through
improving livestock distribution, better watering systems, fencing, or reducing
stock rates. In areas where the desirable native perennial forage plants are nearly
extinct, seeding is essential. Such areas will have a poor to very poor rating of
forage condition and are difficult to restore.
Cost of Practices
Costs
Much of the cost associated with implementing grazing management practices is
due to fencing installation, water development, and seeding. Costs vary accord-
4-152 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4E: Grazing Management
ing to region and type of practice. Generally, the more components or structures
a practice requires, the more expensive it is. However, cost-share is usually
available from the USDA and other federal agencies for most of these practices.
The principal direct costs of providing grazing practices vary from relatively low
variable costs of dispersed salt blocks to higher capital and maintenance costs of
supplementary water supply improvements. Improving the distribution of
grazing pressure by developing a planned grazing system or strategically locat-
ing water troughs, salt, or feeding areas to draw cattle away from riparian zones
can result in improved utilization of existing forage, better water quality, and
improved riparian habitat.
Principal direct costs of excluding livestock from the riparian zone for a period
of time are the capital and maintenance costs for fencing to restrict access to
streamside areas and/or the cost of herders to achieve the same results. In
addition, there may be an indirect cost of the forage that is removed from
grazing by the exclusion.
Principal direct costs of improving or reestablishing grazing land include the
costs of seed, fertilizer, and herbicides needed to establish the new forage stand
and the labor and machinery costs required for preparation, planting, cultivation,
and weed control (Table 4e-7). An indirect cost may be the forage that is re-
moved from grazing during the reestablishment work and rest for seeding
establishment.
Table 4e-7. Cost of forage improvement/reestablishment for grazing management (EPA, 1993a).
Constant Dollar0
Location
Alabama"
Nebraska0
Oregon"
Year
1990
1991
1991
Type Unit
planting acre
(seed, lime &
fertilizer)
establishment acre
seeding acre
establishment acre
a Reported costs inflated to 1991 constant dollars by the ratio
Capital costs are annualized at 8% interest for 10 years.
"Alabama Soil Conservation Service, 1990.
°Hermsmeyer, 1991.
dUSDA-ASCS, 1991b.
Reported
Capital Costs
S/Unit
84- 197
47
45
27
of indices of prices
Capital Costs
1991 S/Unlt
83-195
47
45
27
paid by farmers
Annualized
Costs
1991 $/Unit
12.37 - 29.00
7.00
6.71
4.02
for seed, 1997=100.
Water Development
The availability and feasibility of supplementary water development varies
considerably between arid western areas and humid eastern areas, but costs for
water development, including spring development and pipeline watering, are
similar (Table 4e-8).
National Management Measures to Control Nonpolnt Pollution from Agriculture
4-153
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Chapter 4: Management Measures
Table 4e-8. Cost of water development for grazing management (EPA, 1993a).
Constant Dollar"
Location Year
California" 1979
Kansas0 1989
Maine1' 1988
Alabama9 1990
Nebraska' 1991
Utah" 1968
Oregonh 1991
Type
pipeline
spring
spring
pipeline
spring
pipeline
trough
pipeline
tank
spring
pipeline
tank
a Reported costs inflated to 1991 constant dollars
fencing, 1977=100. Capital costs are annuallzed
b Fresno Field Office, 1979.
Unit
foot
each
each
each
each
foot
each
foot
each
each
foot
each
Reported
Capital Costs
S/Unlt
0.28
1 ,239.00
1,389.00
831.00
1,500.00
1.60
1,000.00
1.31
370.00
200.00
0.20
183.00
by the ratio of indices of prices
at 8% interest for 10 years.
GNorthupetal., 1989.
d Cumberland County Soil and Water Conservation District,
e Alabama Soil Conservation Service, 1990.
'Hermsmeyer, 1991.
° Workman and Hooper, 1 968.
11 USDA-ASCS, 1991b.
undated.
Capital Costs
1991 $/Unlt
0.35
1 ,282.94
1,438.26
879.17
1,520.83
1.62
1,013.89
1.31
370.00
389.33
0.20
183.00
paid by farmers
Annuallzed
Costs
1991 S/Unlt
0.05
191.20
214.34
131.02
226.65
0.24
151.10
0.20
55.14
58.02
0.03
27.27
for building and
Use Exclusion
There is considerable difference between multistrand barbed wire, chiefly used
for perimeter fencing and permanent stream exclusion and diversions, and
single- or double-strand smoothwire electrified fencing used for stream exclu-
sion and temporary divisions within permanent pastures. The latter may be all
that is needed to accomplish most livestock exclusion in a smaller, managed,
riparian pasture (Table 4e-9). In some cases, exclusion of livestock from water-
ways and riparian areas can be accomplished through the use of hedgerows,
intensive herding/grazing management, or provision of feed, water, and shade at
alternative sites.
Overall Costs of the Grazing Management Measure
Since the combination of practices needed to implement the management
measure depends on site-specific conditions that are highly variable, the overall
cost of the measure is best estimated from similar combinations of practices
applied under the Agricultural Conservation Program (ACP), Rural Clean Water
Program (RCWP), and similar activities.
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4E: Grazing Management
Table 4e-9. Cost of livestock exclusion for grazing management (EPA, 1993a).
Constant Dollar"
Location Year
California" 1979
Alabama0 1990
Nebraska' 1991
Great Lakes6 1989
Oregon1 1991
Type
permanent
permanent
net wire
electric
permanent
permanent
permanent
"Reported costs inflated to 1991 constant dollars
fencing, 1977=100. Capital
"Fresno Field Office, 1979.
c Alabama Soil Conservation
d Hermsmeyer, 1991.
"DPRA, 1989.
1USDA-ASCS, 1991b.
costs are annualized
Service, 1990.
Reported
Capital Costs
Unit S/Unit
mile
mile
mile
mile
mile
mile
mile
by the ratio of
2,000
3,960
5,808
2,640
2,478
2,100-
2,400
2,640
indices of prices
Annualized
Capital Costs Costs
1991 $/Unlt 1991 S/Unit
2,474.58
4,015.00
5,888.67
2,676.67
2,478.00
2,174.47 -
2,485.11
2,640.00
paid by farmers for
368.78
598.35
877.58
398.90
369.30
324.06 -
370.35
393.44
building and
at 8% interest for 10 years.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-155
-------
Chapter4: Management Measures
4-156 National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4F: Irrigation Water Management
4F: Irrigation Water Management
ioii system so ttsat the tkmh^ and am^
. This wil
' i '
" * s T; a ,i4fj*&t
/ •%<*?+ v^Wit^jofjrHgatioH water £$blied,ttri4 (b) uniform OTfieSadtt e»f wate&>;
H c ' fi *,*•**',' -e ', 4 , * f -* ' i- , 4 , 4 4. '.
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^^•;:^ei4|e<^'fe lielfl, and^oitrpl dee^°^^oi^Cipa,JJ3 eases «^t^;> fj ^
- ei. B s . , -
' ^>,vs v jpB&ijifcoo^d ti precluded and woold .nm "be considered fan of tite f'. V
•" ,
! ;* -^(2f ,By iiicreasiag the water use eifieienc^, fe disc^ar^e volume ftt»m die,
V'Vt V/i(^stem will asttailybe reduced. Wki|e'ftteloislj)oliiAa^t:load-maybe.-
4f^;^Vifd^ed sonkyiat^there is die potential for aft increase in ifir r%
.SIB
;iti/>iv*(ii3irnf
f aUt_4viii>lJJi
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^ fl-^ t ^: , a&aywvp ilie^axjiaulp 'on^fatJi
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+ ^ \ * ^i'* TT AnVrf^**"*^ p-WJlVt-gp^S'^-.J'*' 'II**^*^ V f*^'**f^h«*^*?-' VJf-J***>"Vf'fft.|^ **.--V ^^f-^^f'^f^ *-** •r»-rft|f|*JY' '^V
'*,' x'' 4;*$|k ^^ cf elBoi^jc^ artd' tfteti: 4t|y^ tfe^a^k v^ter*^ $^ tfet:* ;> /V/
>,;,;: Y W^Iand or sHIdlife r@l"uge,%fe wUl^^v?$& q«^liw otwa^f V, / V\,>
*'r ' / rIWtiixiA>-£i'/4 tA iirorfTon^iu Vs*" "iriJl/'JI'f'fi* Vai'&itvati* t*xt mWo-trniritiWirt- *fi(* Ji**W-eu4timNAM *•-
* pnma1^ conc®rn
irrigation water
ruflnflnpmpnt IQ thp
". r^ ' . "
discharge of salts,
pesticides, and
niltriPntc; tf* fimiinrt
water and discharge
of these pollutants
plus sediment to
surface water.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-157
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Chapter4: Management Measures
Effective irrigation
management reduces
runoff and leachate
losses, controls deep
percolation and,
along with cropland
sediment control,
reduces erosion and
sediment delivery to
waterways.
Management Measure for Irrigation Water: Description
The goal of this management measure is to reduce movement of pollutants from
land into ground or surface water from the practice of irrigation. This goal is
accomplished through consideration of the following aspects of an irrigation
system, which will be discussed in this chapter:
\, Irrigation scheduling
2. Efficient application of irrigation water
3. Efficient transport of irrigation water
4. Use of runoff or tailwater
5. Management of drainage water
A well designed and managed irrigation system reduces water loss to evaporation,
deep percolation, and runoff and minimizes erosion from applied water. Applica-
tion of this management measure will reduce the waste of irrigation water, improve
water use efficiency, and reduce the total pollutant discharge from an irrigation
system. It focuses on components to manage the timing, amount and location of
water applied to match crop water needs, and special precautions (i.e., backflow
preventers, prevent runoff, and control deep percolation) when chemigation is
used.
Irrigation and Irrigation Systems: An Overview
Irrigation, the addition of water to lands via artificial means, is essential to profit-
able crop production in arid climates. Irrigation is also practiced in humid and
sub-humid climates to protect crops during periods of drought. Irrigation is prac-
ticed in all environments to maximize production and, therefore, profit by applying
water when the plant needs it. Figure 4f-l shows the distribution of irrigated
farmland in the U.S. (USDA-ERS, 1997).
Figure 4f-1. Irrigated land in farms, 1992. Source: USDA-ERS, 1997, based on
USDC 1992 Census of Agriculture data.
One dot = 10,000 acres
4-158
National Management Measures to Control Nonpoint Pollution from Agriculture
-------
Chapter 4F: Irrigation Water Management
Soil-Water-plant Relationships
Effective and efficient irrigation begins with a basic understanding of the relation-
ships among soil, water, and plants. Figure 4f-2 illustrates the on-farm hydrologic
cycle for irrigated lands, and Table 4f-l provides definitions of several terms
associated with irrigation. Water can be supplied to the soil through precipitation,
irrigation, or from groundwater (e.g., rising water table due to drainage manage-
ment). Plants take up water that is stored in the soil (soil water), and use this for
growth (e.g., nutrient uptake, photosynthesis) and cooling. Transpiration is the
most important component of the on-farm hydrologic cycle (Duke, 1987), with
the greatest share of transpiration devoted to cooling. Water is also lost via evapo-
ration from leaf surfaces and the soil. The combination of transpiration and
evaporation is evapotranspiration, or ET. ET is influenced by several factors,
including plant temperature, air temperature, solar radiation, wind speed, relative
humidity, and soil water availability (USDA-NRCS, 1997a). The amount of water
the plant needs, its consumptive use, is equal to the quantity of water lost through
ET. Due to inefficiencies in the delivery of irrigated water (e.g., evaporation,
runoff, wind drift, and deep percolation losses), the amount of water needed for
irrigation is greater than the consumptive use. In arid and semi-arid regions,
salinity control may be a consideration, and additional water or "leaching require-
ment" may be needed.
Figure 4f-2. On-farm hydrologic cycle for irrigated lands.
Evaporation
Transpiration
Evaporation
Soil Water Storage
Water Held In
Pore Spaces
Soil Particles
Air In Pore Spaces
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4-159
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Chapter4: Management Measures
Table 4f-1. Soil-water-plant relationship terms.
Temn -
Evaporation
Transpiration
Evapotranspiration (ET)
Soil water
Soil-water potential
Soil-water tension
Soil moisture tension
Gravitational water
Free water
Capillary water
Field capacity
Available water capacity
Water holding capacity
Permanent wilting point
Management allowable depletion
(MAD)
Consumptive use
Soil texture
Soil structure
Bulk density
, BdfMticm
The transformation of water to vapor without passing through the
plant.
The movement of water into plant roots, through the pfant, and out
the stomata as water vapor.
Evaporation + Transpiration
Water stored in the soil.
A measure of the strength with which the soil holds the water. Soil
water potential is the amount of work required per unit quantity of
water to transport water in soil, and is measured in units of bars and
atmospheres or cm. A tension is a negative potential. Water moves
from high to low potential.
Water that moves downward freely in soils under the force of gravity.
Water that moves slowly through smaller pores in soils, due to
surface tension forces in unsaturated conditions.
The amount of soil water stored in the soil after free water
(gravitational water) passes through the soil profile. Sometimes
referred to as 2-3 day drainage or a soil water potential of about -1/3
bar. For a sandy soil, this might occur in less than one day.
The amount of stored soil water that is available to the plant.
The amount of water that can be stored in the soil at field capacity.
The soil-water content at which most plants cannot obtain sufficient
water to prevent permanent tissue damage, about
-15 bars.
The greatest amount of water that can be removed by plants before
irrigation is needed to avoid undesirable crop water stress.
The amount of water that is used by the plant. Is equal to ET.
The proportion of the various sizes of soil particles (sand, silt, and
clay). Defines coarseness or fineness of soil, along with structure,
and controls the hydraulic characteristics of the soil.
The arrangement and organization of soil particles into natural units
of aggregation.
The weight of a unit volume of dry soil.
Build up of salts typically occurs in regions where evapotranspiration exceeds
precipitation. Salts contained in precipitation or dissolved in the soil are left behind
as evaporation and capillary action transports and deposits these salts near the
surface. Salinity is not normally a problem in humid regions, where natural
leaching of salts from rainfall occurs.
Excess salts in the soil have an adverse impact on plant growth. The total concen-
tration of salts in the soil solution exerts an osmotic force, and therefore makes it
4-160
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4F: Irrigation Water Management
more difficult for plants to uptake water. In addition, specific ions, such as
chloride, sodium, boron and others may have a toxic effect on plants at certain
levels. Crops respond differently to both total and specific salts, some being more
sensitive than others.
Plant growth depends upon a renewable supply of soil water, which is governed
by the movement of water in the soil, the soil-water holding capacity, the amount
of soil water that is readily available to plants, and the rate at which soil water can
be replenished (Duke, 1987). Efficient irrigation provides plants with this renew-
able supply of soil water with a minimum of wasted time, energy, and water.
Knowledge and understanding of the factors that affect water movement in the
soil, storage of water in the soil, and the availability of water to plants are essential
to achieving maximum irrigation efficiencies,
Movement of soil water
When water is applied to soils it moves via such pathways as infiltration, runoff,
and evaporation (Figure 4f-2). The ultimate fate and transport of applied water is
determined by various forces, including gravity and capillary force. Gravity pulls
water downward freely in soils with large pores, causing it to move through the
root zone quickly if not taken up by the crop (Duke, 1987). As the water passes
through the soil, the pores are filled again with air, preventing crop damage that
could arise due to excess water. In soils with smaller pores, water moves via
capillary forces. This "capillary water" moves more slowly than gravitational
water, and tends to move from wetter areas to drier areas. The lateral distribution
of capillary water makes it more important to the irrigated crop since it provides
greater wetting of the soil (Duke, 1987). In saturated conditions, gravity is the
primary force causing downward water movement (Watson, et al. 1995), while
capillary action is the primary force in unsaturated soil.
The above discussion uses subjective terms such as "capillary water" and "gravita-
tional water" (see Table 4f-1) to simplify the description of how water moves in
soils. USDA describes this movement in the more technically correct terms of soil-
water potential, measured in units of bars and atmospheres (USDA-NRCS,
1997a). Soil-water potential is the sum of matric, solute, gravitational, and pres-
sure potential, detailed discussions of which are beyond the scope of this docu-
ment. In simple terms, however, water in the soil moves toward decreasing
potential energy, or commonly from higher water content to lower water content
(USDA-NRCS, 1997a).
Storage and availability of soil water
The amount of water that soil can hold, its water holding capacity, is a key factor
in irrigation planning and management since the soil provides the reservoir of
water that the plant draws upon for growth. Water is stored in the soil as a film
around each soil particle, and in the pore spaces between soil particles (Risinger
and Carver, 1987). The magnified area in Figure 4f-2 illustrates how soil water
and air are held in the pore spaces of soils.
All soil water is not equally available for extraction and use by plants. The ability
of plants to take water from the soil depends upon a number of factors, including
soil texture, soil structure, and the layering of soils (Duke, 1987). Texture is
classified based upon the proportion of sand, silt, and clay particles in the soil
(Figure 4f-3). Structure refers to how the soil particles are arranged in groups or
National Management Measures to Control Nonpoint Pollution from Agriculture 4-161
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Chapter4: Management Measures
Figure 4f-3, Soil textural triangle for determining textural class (Duke, 1987).
100%
CLAY
*_, v .
CLAY LOAM \8ILTY CLAY\ 70 /
' \ LOAM V
/ \50 ^
'SILTYX %
fLAX \ 60 <>
100%
SAND
100%
SILT
90
20
10
\ Percent SAND
aggregates, while layering refers to the vertical distribution of soils in the soil
profile (e.g., clay soils underlying a sandy loam layer). The type and extent of
layering can influence the percolation and lateral distribution of applied water.
Soil texture and structure affect the size, shape, and quantity of pores in the soil,
and therefore the space available to hold air or water. For example, the available
water capacity of coarse sand ranges from 0.1 to 0.4 inches of water per foot of
soil depth (in/ft), while silt holds 1.9-2.2 in/ft, and clay holds 1.7-1.9 in/ft
(USDA-NRCS, 1997a). The structure of some volcanic ash soils allows them to
carry very high water content at field capacity levels, but pumice and cinder
fragments may contain some trapped water that is not available to plants (USDA-
NRCS, 1997a). In fine-textured soils and soils affected by salinity, sodicity, or
other chemicals, a considerable volume of soil water may not be available for plant
use due to greater soil water tension (USDA-NRCS, 1997a).
Field capacity is the amount of water a soil holds after "free" water has drained
because of gravity (USDA-NRCS, 1997a). "Free" water, which is conceptually
similar to "gravitational" water, can drain from coarse-textured (e.g., sandy) soils
in a few hours from the time of rainfall or irrigation, from medium-textured (e.g.,
loamy) soils in about 24 hours, and from fine-textured (e.g., clay) soils in several
days. Soil properties that affect field capacity are texture, structure, bulk density,
and strata within the soil profile that restrict water movement. Available water
capacity is the difference between the amount of water held at field capacity and
the amount held at the permanent wilting point (Hurt, 1995).
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4F: Irrigation Water Management
Uptake of soil water by plants
Water stored in soil pore spaces is the easiest for the plant to extract, while
water stored in the film around soil particles is much more difficult for the plant
to withdraw (Risinger and Carver, 1987). As evapotranspiration draws water
from the soil, the remaining water is held more closely and tightly by the soil. Soil
moisture tension increases as soils become drier, making it more difficult for the
plant to extract the soil water. Figure 4f-4 is a soil moisture release curve that
shows how greater energy (tension measured in bars, or potential measured in
negative (-) bars) is needed to extract water from the soil as soil-water content
decreases (USDA-NRCS, 1997a). This figure also illustrates the greater soil-water
tension (or lesser soil-water potential) in clays versus loam and sand for any given
soil-water content. Because clay holds water at greater tension than medium-
textured soils (e.g., loam) at similar water contents, it has less available water
capacity despite its greater water holding capacity (USDA-NRCS, 1997a).
Wilting occurs when the plant cannot overcome the forces holding the water to the
soil particles (i.e., the soil-water tension). Irrigation is needed at this point to save
the plant. The permanent wilting point (represented as -15 bars in Figure 4f-4) is
the soil-water content at which most plants cannot obtain sufficient water to
prevent permanent tissue damage (USDA-NRCS, 1997a). Based upon yield and
Figure 4f-4. Typical water release curves for sand, loam, and clay (USDA-NRCS,
1997a).
456 8 10 12
Soil water tension (bars)
Texture Tension level (atmospheres or bars)
@field capacity @Perm. wilting point
Course
Medium & fine
0.1
0.33
15.0
15.0
National Management Measures to Control Nonpoint Pollution from Agriculture
4-163
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Chapter 4: Management Measures
product quality objectives, growers decide how much water to allow plants to
remove from the soil before irrigation. This amount, the Management Allowable
Depletion (MAD), is expressed as a percentage of the available water-holding
capacity and varies for different crops and irrigation methods. As a general rule of
thumb, MAD is 50%. Smaller MAD values, which result in more frequent irriga-
tions, may be desirable where micro-irrigation is practiced, when saline water is
used, for shallow root zones, and in cases where the water supply is uncertain
(Hurt, 1995). Large MAD values might be desirable when hand-move and hose-
pull sprinklers are used, where furrows are long and soils are sandy, or for crops
such as some varieties of cotton that need to be stressed on heavy soil to develop
a sufficient number of cotton bolls (Burt, 1995).
Irrigation Methods and System Designs
Irrigation systems consist of two basic elements: (1) the transport of water from its
source to the field, and (2) the distribution of transported water to the crops in the
field. A number of soil properties and qualities are important to the design, opera-
tion, and management of irrigation systems, including water holding capacity, soil
intake characteristics, permeability, soil condition, organic matter, slope, water
table depth, soil erodibility, chemical properties, salinity, sodicity, and pH (USDA-
NRCS, 1997a). Some soils cannot be irrigated due to various physical problems,
such as low infiltration rates and poor internal drainage which may cause salt
buildup. The chemical characteristics of the soil and the quantity and quality of the
irrigation water will determine whether irrigation is a suitable management practice
that can be sustained without degrading the soil or water resources (Franzen et al.,
1996; Scherer et al., 1996; and Seelig and Richardson, 1991).
Water supply and demand
Producers need to factor the availability of good quality water (in terms of
amount, timing, and rate) into their irrigation management decisions. Both surface
water and ground water can be used to supply irrigation water. An assessment of
the total amount of water available during an irrigation season is essential to
determining the types and amounts of irrigated crops that can be grown on the
farm.
The quality of some water is not suitable for irrigating crops. Irrigation water must
be compatible with both the crops and soils to which it will be applied (Scherer
andWeigel, 1993; Seelig and Richardson, 1991). The quality of water for irriga-
tion purposes is generally determined by its salt content, bicarbonate concentra-
tion, and the presence of potentially toxic elements. Irrigation water can also
contain appreciable amounts of nutrients that should be factored into the overall
nutrient management plan.
Efficient irrigation scheduling depends upon knowledge of when water will be
available to the producer. In some areas, particularly west of the Mississippi River,
irrigation districts or some other outside entities may manage the distribution of
water to farms, while farmers in other areas have direct access to and control over
their water supplies. An irrigation district is defined as blocks of irrigated land
within a defined boundary, developed or administered by a group or agency
(USDA-NRCS, 1997a). Water is delivered from a source to individual turnouts via
a system of canals, laterals, or pipelines. Figure 4f-5 depicts the Ainsworth Unit in
northern Nebraska within which water from the Merritt Reservoir is distributed to
4-164 National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4F: Irrigation Water Management
the Ainsworth Irrigation District via the 53-mile long, concrete-lined Ainsworth
Canal (Hermsmeyer, 1991). A system of laterals and drains serves approximately
35,000 acres of cropland in the irrigation district. Irrigation districts that deliver
water to farms on a rotational basis control when the farmer can irrigate, leaving
the farmer to choose only the rate and methods of irrigation. In cases where
farmers are able to control the availability of irrigation water it is possible, how-
ever, to develop a predetermined irrigation schedule.
Figure 4f-5. Ainsworth Unit in northern Nebraska.
M
*'*>
**,
%fc^
MERRITT DAM
'and RESERVOIR
AINSWORTH UNIT
Long
Pine
The amount of water that is needed for adequate irrigation depends upon climate
and crop growth stage. Different crops require different amounts of water, and the
water demand for any particular crop varies throughout the growing season.
Producers need to factor the peak-use rates, the amount of water used by a crop
during its period of greatest water demand (usually during period of peak growth),
into both the initial design of an irrigation system and annual irrigation planning.
Irrigation methods
There are four basic methods of applying irrigation water: (1) surface (or flood),
(2) sprinkler, (3) trickle, and (4) subsurface. Types of surface irrigation are
furrow, basin, border, contour levee or contour ditch. Factors that are typically
considered in selecting the appropriate irrigation method include land slope, water
intake rate of the soil (i.e., how fast the soil can absorb applied water), water
tolerance of the crops, and wind. For example, sprinkler, surface, or trickle
methods may be used on soils (e.g., fine soils) with low water intake rates, but
surface irrigation may not be appropriate for soils (e.g., coarse soils) with high
water intake rates. Key factors that determine water intake rates are soil texture,
surface sealing due to compaction and sodium content of the soil and/or irrigation
water, and electrical conductivity of the irrigation water.
Water available to the farm from either on-site or off-site sources can be trans-
ported to fields via gravity (e.g. canals and ditches) or under pressure (pipeline).
Pressure for sprinkler systems is usually provided by pumping, but gravity can be
used to create pressure where sufficient elevation drops are available.
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Chapter 4: Management Measures
Figure 4f-6. Water infiltration characteristics for sprinkler, border, and furrow irrigation systems
Sprinkler
Raindrop action
Water movement vertically downward
Border
Completely flooded
Water movement vertically downward
Furrow
Water movement downward and outward from furrow
Gravity-based, or surface irrigation systems, rely on the ponding of water on the
surface for delivery through the soil profile (Figure 4f-6), whereas pressure-based
sprinkler systems are generally operated to avoid ponding for all but very short
time periods (USDA-NRCS, 1997a).
Irrigation systems
There are several irrigation system options for each irrigation method selected for
the farm. The options for irrigation by gravity include level basins or borders,
contour levees, level furrows, graded borders, graded furrows, and contour ditches
(Figure 4f-7) (USDA-NRCS, 1997a). Pressure-based irrigation systems include
periodic move, fixed or solid-set, continuous (self) move, traveling gun, and
traveling boom sprinkler systems, as well as micro-irrigation and subirrigation
systems. Operational modifications to center pivot and linear move systems,
including Low Energy Precision Application (LEPA) and Low Pressure In Canopy
(LPIC), increase the range of pressure-based options to select from (USDA-
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Chapter 4F: Irrigation Water Management
Figure 4f-7. Irrigation system options for irrigation by gravity (Turner, 1980).
STRIP
LEVEE
FLOOD
GATE
STRIP
LEVEE
HEAD DITCH
FLOOD
GATE
Level border type of surface system.
HEAD
PIPELINE
Contour levee type of surface system.
Level furrow type of surface system.
Graded border type of graded surface system.
Graded furrow type of graded surface system. Contour ditch type of graded surface system.
NRCS, 1997a). Figure 4f-8 illustrates a range of sprinkler systems.
Micro-irrigation systems (Figure 4f-9) include point-source emitters (drip, trickle,
or bubbler emitters), surface or subsurface line-source emitters (e.g., porous
tubing), basin bubblers (Figure 4f-10), and spray or mini-sprinklers. Table 4f-2
summarizes the basic features of each type of irrigation system (USDA-NRCS,
1997a), and Figure 4f-11 shows typical layouts of graded-furrow with tailwater
recovery and reuse, solid-set, center pivot, traveling gun, and micro-irrigation
systems (USDA-NRCS, 1997a; Turner, 1980).
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Chapter 4: Management Measures
Figure 4f-8. Typical types of sprinkler irrigation systems (Turner, 1980).
SINGLE-SPRINKLER
SELF-PROPELLED
OR WINCH
Figure 4f-9. Micro-irrigation system components (USDA-NRCS, 1997a).
Controls
Drain
(where
Solenoid / / / needed)
valve / / / Submainline
/ Backflow
Pump / Prevention
' valve
Lateral lines
with emitters
Secondary
filter
Flow
rnntrnl
Submain line
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Chapter 4F: Irrigation Water Management
Figure 4f-10. Basin bubbler system (USDA-NRCS,
1997a).
Buried lateral
The advantages and disadvantages of the various
types of irrigation systems are described in a number
of existing documents and manuals (USDA-NRCS,
1997a; EduSelf Multimedia Publishers Ltd., 1994).
A comprehensive set of publications, videos, interac-
tive software, and slides on irrigation has been
assembled by the U.S. Department of Agriculture to
train its employees (USDA-NRCS, 1996a). This
irrigation "toolbox" covers soil-water-plant relation-
ships, irrigation systems planning and design, water
measurement, irrigation scheduling, soil moisture
measurement, irrigation water management planning,
and irrigation system evaluation. Updated material is
provided periodically as it becomes available. Other
sources of material may be found in USDA-NRCS,
1997a, Sec. 652-1502.
Pollutant Transport from Irrigated Lands
Return flows, runoff, and leachate from irrigated lands may transport the follow-
ing types of pollutants to surface or ground waters:
n Sediment and paniculate organic solids;
G Particulate-bound nutrients, chemicals, and metals, such as phosphorus,
organic nitrogen, a portion of applied pesticides, and a portion of the
metals applied with some organic wastes;
G Soluble nutrients, such as nitrogen, soluble phosphorus, a portion of the
applied pesticides, soluble metals, salts, and many other major and minor
nutrients; and
d Bacteria, viruses, and other pathogens.
G If soils or drainage in the irrigated area contain toxic substances that may
concentrate in the drainage or reuse system, this factor must be
considered in any decisions about use of the water and design of the reuse
system. Discharge of drainage water containing selenium into wetlands is
an example of where this type of problem can occur.
The movement of pollutants from irrigated lands is affected by the timing and
amount of applied water and precipitation; the physical, chemical, and biological
characteristics of the irrigated land; the type and efficiency of the irrigation system
used; crop type; the degree to which erosion and sediment control, nutrient
management, and pesticide management are employed; and the management of
the irrigation system.
Transport of irrigation water from the source of supply to the irrigated field via
open canals and laterals can be a source of water loss if the canals and laterals are
not lined. Water is also transported through the lower ends of canals and laterals
as part of flow-through requirements to maintain water levels. In many soils,
unlined canals and laterals lose water via evaporation and seepage in bottom and
side walls. Seepage water either moves into the ground water through percolation
or forms wet areas near the canal or lateral. This water will carry with it any
soluble pollutants in the soil, thereby creating the potential for pollution of ground
or surface water (Figure 4f-12).
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Chapter4; Management Measures
Figure 4f-11. Typical irrigation system layouts (USDA-NRCS, 1997a; Turner, 1980).
Collector
ditch
I
Return
pipeline;
OH M H M M H
i
j
^-
-------
Chapter 4F: Irrigation Water Management
Figure 4f-11. Typical irrigation system layouts (USDA-NRCS, 1997a; Turner, 1980). Continued
Field layout for self-propelled, center-pivot system.
Traveling gun type sprinkler system layout.
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Chapter 4: Management Measures
Figure 4M1. Typical irrigation system layouts (USDA-NRCS, 1997a; Turner, 1980). Continued
Fertilizer Fertilizer
solution injector
tank pump
Typical orchard micro-system layout.
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Chapter 4F: Irrigation Water Management
Table 4f-2. Types of Irrigation Systems.
s
3* a^BwfflPlBp^CT^n^^A'iliR?
Gravity-Level Basins
Gravity-Contour Levees
Gravity-Level Furrows
Gravity-Graded Borders
Gravity-Graded Furrows
Gravity-Contour Ditches
Pressure-Periodic Move
Sprinkler
Pressure- Fixed or
Solid-Set Sprinkler
Pressure-Continous Move
Sprinkler
Pressure-Traveling Gun
Sprinkler
Pressure-Traveling Boom
Sprinkler
Micro/Pressure -Point
Source Emitters
Micro/Pressure-Line
Source Emitters
Micro/Pressure-Basin
Bubblers
Micro/Pressure -Spray or
Mini-Sprinklers
Subirrigation
Large flow rates over short periods to flood entire field or basin. Level fields surrounded
by low dike or levee. Best for soils with low to medium water intake rate.
Similar to level basins except for rice. Small dikes or levees constructed on contour. For
rice, ponding is maintained. Best for soils with very low intake rate.
Large flow rates over short periods. Level fields. End of furrow or field is blocked to
contain water. Best for soils with moderate to low water intake rate and moderate to
high available water capacity.
Controlled surface flooding. Field divided into strips bordered by parallel dikes or border
ridges. Water introduced at upper end.
Like graded borders, but only furrows are covered with water. Water distribution via
vertical and lateral infiltration. Water application amount is a function of intake rate of
soil, spacing of furrows, and length of field. Heavy soils (small pores sizes) provide
slower infiltration and greater lateral movement.
Controlled surface flooding. Water discharged with siphon tubes, over ditch banks, or
from gated pipes located upgradient and positioned across the slope on contour. Sheet
flow is goal.
Sprinkler is operated in a fixed location for a specified period of time, then moved to the
next location. Many design options including hand-moved laterals, side-roll laterals,
end-tow laterals, hose-fed (pull) laterals, guns, booms, and perforated pipe.
Laterals are not moved, but one or more sections of sprinklers are cycled on and off to
provide coverage of entire field over time.
Center pivot (irrigates in circular patterns, or rectangular with end guns or swing lines)
or linear (straight lateral irrigates in rectangular patterns) move continuously to irrigated
field. Multiple sprinklers located along the laterals.
High-capacity, single-nozzle sprinkler fed by flexible hose. Hose is dragged or on a
reel. Gun is guided by cable, and moved from field to field. Best for soils with high water
intake rates.
Similar to traveling gun, except a boom with several nozzles is used.
Frequent, low-volume, low-pressure applications through small tubes and drop, trickle,
or bubbler emitters. Water must be filtered. Used for orchards, vineyards, ornamental
landscaping. Emitters discharge from 0.5 to 30 gallons per hour.
Frequent, low-volume, low-pressure applications through surface or buried tubing that
is porous or has uniformly spaced emitter points. For permanent crops, but also
vegetables, cotton, melons.
Water applied via risers into small basins adjacent to plant. Bubblers discharge less
than 60 gallons per hour. Water filtration not required. Orchards and vineyards. Best for
medium to fine textured soils.
Water applied as spray droplets from small, low-pressure heads. Wets a greater area
(2 to 7 feet in diameter) than drop emitters. Discharges less than 30 gallons per hour.
Manage water table by providing subsurface drainage, providing controlled drainage,
and irrigating via buried laterals.
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Chapter 4: Management Measures
Figure 4f-12. Fate of water and pollutants in an irrigated hydrologic system.
Ground Wai
Recharge
SoU Water
Storage
Since irrigation is a consumptive use of water, any pollutants in the source waters
that are not consumed by the crop (e.g., salts, pesticides, nutrients) can be con-
centrated in the soil, concentrated in the leachate or seepage, or concentrated in
the runoff or return flow from the system. Salts that concentrate in the soil profile
must be managed in order to sustain crop production. In such cases, a carefully
calculated additional amount of water may be applied to leach the salts below the
root zone. The application of this "leaching requirement" should be timed to
prevent the leaching of other potential pollutants when possible (e.g., after the
growing season when nutrients are low, or after a cover crop that has used excess
nutrients).
Irrigation Scheduling
Both long-term and short-term irrigation decisions must be made by the producer.
Long-term decisions, which are associated with system design and the allocation of
limited seasonal water supplies among crops, rely on average water use determined
from historical data (Duke, 1987) and average water availability. Particularly in arid
areas, long-term irrigation decisions are needed to determine seasonal water
requirements of different possible crops, determine which crops to grow based
upon crop adaptability and water availability, and in some cases to determine when
and how much to stress the various crops to maximize economic return. Short-
term decisions determine when and how much to irrigate, and are based upon
daily water use. In areas where rainfall is either insignificant or falls predictably
during the growing season, long-term decisions can be used to construct an
irrigation schedule at the beginning of the growing season (Duke, 1987), although
better water management is obtained by constant updating of information. In semi-
arid and humid areas where weather varies significantly on a daily basis, short-
term irrigation decisions are used in lieu of pre-determined irrigation schedules.
The emphasis of this guidance is placed on short-term irrigation decisions.
Irrigation scheduling is the use of water management strategies to prevent over-
application of water while minimizing yield loss from water shortage or drought
stress (Evans et al., 1991c). Irrigation scheduling will ensure that water is applied
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Chapter 4F: Irrigation Water Management
to the crop when needed and in the amount needed (USDA-NRCS, 1997a).
Effective scheduling requires knowledge of the following factors (Evans et al.,
1991b; Evans etal., 1991c):
D Soil properties
G Soil variability within the field
G Soil-water relationships and status
G Type of crop and its sensitivity to drought stress
D The stage of crop development and associated water use
G The status of crop stress
G The potential yield reduction if the crop remains in a stressed condition
G Availability of a water supply
G Climatic factors such as rainfall and temperature
Much of the above information can be found in Natural Resources Conservation
Service soil surveys and Extension literature. However, all information should be
site-specific and verified in the field.
In environments where salts tend to concentrate in the soil profile, additional
information is needed to sustain crop production, including:
D Salt tolerance of the crop
G Salinity of the soil
G Salinity of the irrigation water
G Leaching requirement of the soil
Deciding when to irrigate
There are three ways to determine when irrigation is needed (Evans et al., 1991c):
G Measuring soil water
G Estimating soil water using an accounting approach
CJ Measuring crop stress
Soil water can be measured directly by sampling the soil and determining the water
content through gravimetric analysis. The distribution of plant roots and their
pattern of development during the growing season are very important consider-
ations in deciding where and at what depth to take soil samples to determine soil
water content (USDA-NRCS, 1997a). For example, all plants have very shallow
roots early in their development, and the concentration of moisture-absorbing
roots of most plants is usually greatest in the upper quarter of the root zone.
Further, since roots will not grow into a dry soil, it may be important to measure
soil moisture beyond the current root zone to determine irrigation needs associated
with full root development. Figure 4f-13 illustrates the typical water extraction
pattern in a uniform soil, again pointing out the need to relate soil sampling deci-
sions to crop development.
Soil moisture can also be determined indirectly using a range of devices (Evans et
al., 1991a; Werner, 1992), including tensiometers (Figure 4f-14), electrical resistance
blocks (Figure 4f-14), neutron probes, heat dissipation sensors, time domain reflec-
tometers, and carbide soil moisture testers (USDA-NRCS, 1997a). Table 4f-3
Research in irrigation
scheduling indicates
the need for specific
site-dependent data
for plan development.
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Chapter4: Management Measures
Figure 4f-13. Typical water extraction pattern in uniform soil profile (USDA-NRCS,
1997a).
40% extraction here
Figure 4f-14. Soil moisture measurement devices: (a) tensiometer and (b) electrical resistance block.
Reservoir
Digital
display
Meter
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Chapter 4F: Irrigation Water Management
Table 4f-3. Devices and methods to measure soil moisture.
Tensiometer
Measures soil suction which is
related to soil water content.
Available in lengths from 6 to 72 inches.
Requires careful installation and field
maintenance. Most applicable when soil
moisture is between 50-75 percent of field
capacity, and on medium to fine-textured soils
with frequent irrigation.
Electrical Resistance Block
(Gypsum or Moisture or
Porous Block)
Measures electrical resistance which
is related to soil water content via a
calibration curve.
Inexpensive. Simple to use. Gives accurate
readings over wider moisture range than
tensiometers, but limited to medium to coarse-
textured soils. Most accurate when soil
moisture is below field capacity. Sodic soils
problematic. Gypsum blocks need replacement
each growing season; nylon, plastic, fiberglass
more durable.
Neutron Probe (Neutron
Scattering)
Measures thermalized neutrons (fast
neutrons that are slowed by collisions
with hydrogen molecules in water)
which are related to volumetric soil
water content by a calibration curve.
Can be most accurate and precise method.
Requires calibration using gravimetric
procedures, especially if used for top 6 inches
of soil profile, in clay soils, soils with high
organic matter content, and soils with boron
ions. Requires licensed operator since
radioactive. Expensive.
Thermal Dissipation Block
(Heat Dissipation Sensor)
Estimates soil water based upon the
relationship between heat
conductance and soil water content.
Requires calibration. Work across wide range
of soil-water content.
Time Domain Reflectometer
(TDR) & Frequency Domain
Reflectometer (FDR)
(Dialectric Constant Method)
Senses the dielectric property of soil
which is related to water content.
Requires careful installation. TDR works across
wide range of soil texture, bulk density, and
salinity. FDR results may be skewed as salinity
increases.
Carbide Soil Moisture Tester
(Speedy Moisture Tester)
Measures gas pressure from reaction
of calcium carbide with water in soil
sample.
Provides percent water content of soil. Works in
field. Practice necessary for reliable results.
Feel and Appearance
Method
Soil samples are compared to tables
or pictures that give moisture
characteristics of different soil
textures.
Experienced individuals can estimate soil
moisture within 10 percent of true value, but
tables and pictures use ranges of 25 percent.
Gravimetric Method (Oven
Dry)
Soil samples from field are weighed,
dried, and weighed again in the lab.
Accurate measure of water content. Requires
sensitive scales, drying method, and known or
estimated bulk density value to calculate %
volume of water.
provides an overview of these devices. The appropriate device for any given
situation is a function of the acreage of irrigated land, soils, cost, available trained
labor, and other site-specific factors.
Direct measurement of soil water status or crop status is always more accurate than
estimating its magnitude, but because of the cost associated with obtaining represen-
tative samples in some situations, it may be more appropriate to use estimation
techniques (Duke, 1987). Accounting approaches estimate the quantity of plant-
available water remaining in the effective root zone. A variety of methods can be
used to estimate and predict the root zone water balance, including a simple check-
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Chapter 4; Management Measures
book method (USDA-NRCS, 1997a), computer-assisted methods (Hill, 1997 and
Allen, 1991), graphical methods (Figure 4f-15), and tabular methods. In essence,
these methods begin with an estimate of initial soil-water depletion and use measure-
ments or estimates of daily water inputs (rain, irrigation) and outputs (evapotrans-
piration) to determine the current soil-water depletion volume (Equation 4f-1).
Net irrigation depth is the depth of water applied multiplied by the irrigation
efficiency, which ranges from 75-100% for drip systems to 20-60% for furrow
irrigation on sandy soils (Duke, 1987). Effective precipitation is the amount of
precipitation minus losses due to runoff or unnecessary deep percolation. At some
pre-determined moisture deficit (e.g., the MAD value), irrigation must be started
(Figure 4f-15). The water balance must be updated at least weekly, including field
checks on estimated parameters, to be useful for scheduling irrigations (Duke,
1987).
Potential sources of data for Equation 4f-l include field measurements to deter-
mine the initial soil-water content, field measurements to determine effective
rooting depth as the plant matures, ET measurements or estimates based upon
data from weather stations, irrigation depth measurements, measured precipitation,
Figure 4M5. Graphical format for irrigation scheduling (Duke, 1987).
FIELD CAPACITY
V
MAXIMUM ALLOWABLE DEPLETION
PLANT
EFFECTIVE COVER
DATE
HARVEST
Equation 4f-1. Soil-water depletion volume (Duke, 1987).
D = D0 + ET - IR - R - WT
where D = soil-water depletion at end of day (D=0 at field capacity)
D0 = soil-water depletion for previous day
ET = ET for the day
IR = net irrigation depth (depth of applied water which is stored in soil root zone)
for the day
R = effective precipitation during the day
WT = upward movement of water during the day from water table close to bottom
of root zone
If the water table is not near the root zone, the last term (WT) may be dropped.
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Chapter 4F: Irrigation Water Management
and estimates of water table contributions. Clearly, good estimates or measure-
ments of ET are essential to successful accounting approaches since crop water
use can vary considerably with crop type, stage of growth, temperature, sunshine,
wind speed, relative humidity, and soil moisture content (Figure 4f-16). Direct
measurement of ET with lysimeters may not be practical for most farms, but
evaporation pans and atmometers can be used effectively. There is also, however,
a wide range of computational techniques for estimating ET from weather data
(Doorenbos and Pruitt, 1975; Jensen et al., 1990; USDA-SCS, 1993). Crop ET
data are often available in newspapers, through telephone dial-up service, or on
television, and some farms have on-site weather stations that provide the neces-
sary ET data (USDA-NRCS, 1997a). There is also a growing number of computer
programs that aid the irrigation decisionmaker, including the NRCS Scheduler
(Figure 4f-17) and others (Smith, 1992; Allen, 1991; and Hill, 1991).
Figure 4f-16. Crop water use for corn, wheat, soybean, and potato based on
average climatic conditions for North Dakota (Lundstrom and
Stegman, 1991).
46 8 10 12
Weeks After Emergence
16
Figure 4M7. NRCS (SCS) Scheduler - seasonal crop ET (USDA-NRCS, 1997a).
Personal Computer Irrigation Scheduler
Farm home: XFARM
Crop type: CORN
Emergence Date: May 21,1998
Growing Season: 119 days
Reference ET0
Calculated Crop ET0
Cumulative ET0: 12.28 inches
Cum. Calc. ET,,: 12.14 Inches
05/21
06/15
07/10
08/04
08/29
09/23
Date
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Chapter 4: Management Measures
Measuring crop stress is another way to determine when irrigation is needed.
Unavailability of water during crop stress periods could result in crop failure or
reduced yields that leave unused nutrients vulnerable to runoff and deep percola-
tion. Devices and methods used to measure crop stress include the crop water
stress gun, leaf moisture stress as measured in a pressure chamber, and infrared
photography (USDA-NRCS, 1997a). However, infrared photography is typically
not an option for "real time" water management due to slow turnaround times.
The crop water stress gun calculates plant water stress and expresses it as an index
value based on measurements of plant canopy temperature, ambient air tempera-
ture, relative humidity, and a range of solar radiation. Using a crop water stress
index, irrigation can be scheduled depending on the severity of moisture stress.
Threshold values must be developed for each crop.
Deciding how much water to apply
Once the decision to irrigate has been made, the amount of water to apply must be
determined. A decision rule should be established to determine how much water to
apply, with the basic choices being full irrigation to replenish the root zone to field
capacity or partial irrigation. Partial irrigation, which is more easily achieved via
sprinkler systems, may be preferred if there is opportunity for rainfall to provide
some of the water needed to reach field capacity.
Factors in determining the amount of irrigation water to apply include the soil-
water depletion volume in the effective root zone and local weather forecasts for
rain. The application rate should not exceed the water intake rate of the soil when
using sprinkler systems, and the application depth should not exceed the soil-water
depletion volume, except as necessary for leaching of salts (Duke, 1987). Local
weather forecasts for rain should be considered before irrigating to avoid over-
application.
The relationship between irrigation system capacity, irrigated area, and time of
irrigation may be expressed as
where Q is system discharge capacity (gpm), A is irrigated area (acres), d is gross
application depth (in),/is time allowed for completion of one irrigation (days), and
Tis actual operating time (hr/day) (USDA, 1983). Normally A, T, and d are fixed
in a design process. The time allowed for completion of one irrigation should be
set to insure that the area initially irrigated does not become stressed before the
next irrigation is applied. Note that a system design that just meets the peak crop
water demand may be determined as illustrated in Table 4f-4. Partial irrigations
may facilitate covering a larger area to prevent immediate crop damage, but they
increase the frequency of irrigation necessary, and could impede root growth or
harm a crop that will be stressed if the soil is not adequately saturated.
Deep percolation of irrigation water can be greatly reduced by limiting the amount
of applied water to the amount that can be stored in the plant root zone. The deep
percolation that is necessary for salt management can be accomplished with a
sprinkler system by using longer sets or very slow pivot speeds or by applying
water during the non-growing season. Salt management by surface irrigation
methods is much less efficient than other irrigation methods, and water used to
leach salts should be applied when nutrients or pesticides are least vulnerable to
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Chapter 4F: Irrigation Water Management
Table 4f-4. System capacity needed in gal/min-acre for different soil textures and
crops to supply sufficient water in 9 out of 10 years (Scherer, 1994).
Crop
Potatoes3
Dry beans
Soybeans
Corn
Sugarbeets
Small grains
Alfalfa
Root
Zone
Depth
(«)
2.0"
2.0
2.0
3.0
3.0
3.0
4.0
Coarse
Sand
and
Gravel
8.2
7.9
7.9
7.3
7.3
7.3
6.8
Sand
7.5
7.1
7.1
6.6
6.6
6.6
5.9
Loamy
Sand
7.0
6.4
6.4
5.9
5.9
5.9
5.6
Sandy
Loam
6.4
6.1
6.1
5.5
5.5
5.5
5.1
Fine
Sandy
Loam
6.1
5.7
5.7
5.3
5.3
5.3
5.0
Loam
and
Silt
Loam
5.7
5.4
5.4
4.9
4.9
4.9
4.5
a Adjusted for 40% depletion of available water.
b An application efficiency of 80% and a 50% depletion of available soil water were used for calculations.
leaching, such as when maximum uptake or dissipation of the chemical has
occurred.
Accurate measurements of the amount of water applied are essential to maximiz-
ing irrigation efficiency. A wide range of water measurement devices is available
(USDA-NRCS, 1997a). For example, the quantity of water applied can be mea-
sured by such devices as a totalizing flow meter that is installed in the delivery
pipe or calibrated canal gates. If water is supplied by ditch or canal, weirs or
flumes in the ditch can be used to measure the rate of flow. Rain gauges should
also be used in the field to determine the quantity of water added through rainfall.
Such gauges are also a valuable tool for checking uniformity of application of
sprinkler systems.
Efficient Transport and Application of Irrigation Water
There are several measures of irrigation efficiency, including conveyance effi-
ciency (Table 4f-5), irrigation efficiency, application efficiency, project application
efficiency, potential or design application efficiency, uniformity of application,
distribution uniformity, and Christiansen's uniformity (USDA-NRCS, 1997a).
Project water conveyance and control facility losses can be as high as 50% or
more in long, unlined, open channels in alluvial soils (USDA-NRCS, 1997a).
Seepage losses associated with canals and laterals can be reduced by lining them,
or can be eliminated by conversion from open canals and laterals to pipelines.
Flow-through losses or spill, however, will not be changed by lining canals and
laterals, but can be eliminated or greatly reduced by conversion to pipelines or
through changes in operation and management. Flow-through water constitutes
over 30% of canal capacity in some water districts, but simple automatic gate/
valve control devices can limit flow-through water to less than 5% (USDA-NRCS,
1997a). Conversion to pipelines may in some cases cause impacts to wildlife due
to loss of beneficial wet areas, and an environmental assessment or environmental
impact statement may be needed before the conversion is made (USDA-NRCS,
1997a).
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4: Management Measures
Table 4f-5. Measures of irrigation efficiency.
Conveyance Efficiency
(to farm)
W.
Delivered
w,
*100
Dl varied
Irrigation Efficiency
(on farm)
'Beneficial
'Applied
*100
Application Efficiency
(on farm)
W
*100
Applied
Project Application Efficiency
(to and on farm)
IV,.
*100
Where
Wdeiivered = Water delivered
= Total water diverted or pumped into an open channel or pipeline at upstream end
= Avg. depth of water beneficially used
Wappiied = Av9- depth of applied water
Wstored = Avg. depth of water infiltrated and stored in the plant root zone
Water application efficiency can vary considerably by method of application.
Increased application efficiency reduces erosion, deep percolation, and return
flows. In general, trickle and sprinkler application methods are more efficient than
surface and subsurface methods. Two major hydraulic distinctions between
surface irrigation methods and sprinkler and micro irrigation are key to this
difference in efficiencies (Burt, 1995):
1. The soil surface conveys the water along border strips or furrows in
surface irrigation, whereas the water infiltrates into the soil very near to
the point of delivery from sprinkler and micro irrigation systems.
2. Water application rate exceeds soil water infiltration rate in surface
irrigation, and the soil controls the amount of water that will infiltrate. In
properly designed and managed sprinkler and micro irrigation systems, the
application rate is equal to the soil water infiltration rate.
The type of irrigation system used will dictate which practices can be employed to
improve water use efficiency and to obtain the most benefit from scheduling.
Flood systems will generally infiltrate more water at the upper end of the field than
at the lower end because water is applied to the upper end of the field first and
remains on that portion of the field longer. This will cause the upper end of the
field to have greater deep percolation losses than the lower end. This situation can
sometimes be improved by changing slope throughout the length of the field or
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Chapter 4F: Irrigation Water Management
shortening the length of run. For example, furrow length can be reduced by
cutting the field in half and applying water in the middle of the field. This will
require more pipe or ditches to distribute the water across the middle of the field.
Other methods used to improve application efficiency in surface systems are
surge and cut-back irrigation. In surge irrigation, flow is pulsed into the furrow
allowing for wet and dry cycles, while in cut-back irrigation, the furrow inflow
rate is reduced after a period of time. Both of these methods improve irrigation
efficiency by allowing for a more uniform time of infiltration. A wide range of
options exist for manipulating field lengths, slopes, flow rate, irrigation time, and
other management variables to increase surface irrigation efficiency (Burt, 1995;
USDA-NRCS, 1997a).
A properly designed, operated, and maintained sprinkler irrigation system should
have a uniform distribution pattern. The volume of water applied can be changed
by altering the total time the sprinkler runs; by altering the pressure at which the
sprinkler operates; or, in the case of a center pivot, by adjusting the speed of travel
of the system. There should be no irrigation runoff or tailwater from most well-
designed and well-operated sprinkler systems (USDA-NRCS, 1997a). Operating
outside of design pressures and using worn equipment can greatly affect irrigation
uniformity.
Use of Runoff or Tailwater
Surface irrigation systems are usually designed to have a percentage (up to 30%)
of the applied water lost as tailwater. The volume and peak runoff rate of tailwater
will depend upon both the irrigation method and its management. Tailwater
recovery and reuse facilities collect irrigation runoff and return it to the same,
adjacent, or lower fields for irrigation use (USDA-NRCS, 1997a). If the water is
pumped to a field at higher elevation, the facility is a return-flow or pumpback
facility. Sequence-use facilities deliver the water to adjacent or lower-elevation
fields. Those facilities that store runoff and precipitation for later use are reservoir
systems, while cycling-sump facilities have limited storage and pump the water
automatically to irrigate fields.
The components of a tailwater reuse or pumpback facility include tailwater
collection ditches to collect the runoff; drainageways, waterways, or pipelines to
convey the water to a central collection area; a sump (cycling-sump facilities) or
reservoir (reservoir systems); a pump and power unit for pumpback facilities; and
pipelines or ditches to deliver the recovered water (USDA-NRCS, 1997a). A
typical pumpback facility plan is illustrated in Figure 4f-18. For new facilities,
runoff flows must be measured or estimated to properly size tailwater reuse
sumps, reservoirs, and pumping facilities. Capacity should be provided to handle
concurrent peak runoff events from both precipitation and tailwater, unexpected
interruption of power, and other uncertainties.
Tailwater management is needed to reduce the discharge of pollutants such as
suspended sediment and farm chemicals which can be found in the runoff. In
reservoir systems, tailwater is typically stored until it can be either pumped back to
the head of the field and reused or delivered to additional irrigated land. The
quality of tailwater, including nutrient concentrations, should be considered in
reuse systems. Water quality testing may be necessary. In some locations, there
may be downstream water rights that are dependent upon tailwater, or tailwater
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Chapter4: Management Measures
Figure 4f-18. Typical tailwater collection and reuse facility for quick-cycling pump
and reservoir (USDA-NRCS 1997a).
Water
t
Head
ditch
Inlet
Regulating
reservoir
JL**I
M
Sump&
pump
I'i'l
Collector ditch
I" '""I . '" ' I
Return
pipeline
may be used to maintain flow in streams. These requirements may take legal
precedence over the reuse of tailwater.
If a tailwater recovery system is used, it should be designed to allow storm runoff
to flow through the system without damage. Where reservoir systems are used,
storm runoff containing a large sediment volume should bypass or be trapped
before entering the storage reservoir to prevent rapid loss of storage capacity
(USDA-NRCS, 1997a). Additional surface drainage structures such as filter
strips, field drainage ditches, subsurface drains, and water table control may also
be used to control runoff and leachate if site conditions warrant their use.
Management of Drainage Water
Drainage of agricultural lands is intended to control and manage soil moisture in
the crop root zone, provide for improved soil conditions, and improve plant root
development (USDA-NRCS, 1997a). In cases where the water table impinges
upon the root zone, water table control is an essential element of irrigation water
management. However, installation of subsurface drainage should only be consid-
ered when good irrigation water management, good nutrient management, and
good pesticide management are being conducted. Further, impacts to wetlands,
wildlife habitat, and water quality must be thoroughly investigated, and relevant
federal, state, and local laws fully considered prior to installation of drainage
practices.
Drainage increases water infiltration, which reduces soil erosion and also allows
application of excess water to keep salts leached below the root zone. Drainage
also provides more available soil moisture and plant food by increasing the depth
of the root zone. Subsurface drainage may concentrate soluble nutrients in irriga-
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National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4F: Irrigation Water Management
tion return flows. Properly installed subsurface drainage systems can be used
successfully as a supplemental source of irrigation water if the water is of good
quality (USDA-NRCS, 1997a).
Irrigation Water Management Practices and Their
Effectiveness
The practices that can be used to implement this management measure on a given
site are commonly used and are recommended by NRCS for general use on
irrigated lands. Many of the practices that can be used to implement this measure
(e.g., water-measuring devices, tailwater recovery systems, and backflow
preventers) may already be required by State or local rules or may otherwise be in
use on irrigated fields.
The NRCS practice number and definition are provided for each management
practice, where available. Additional information about the purpose and function of
individual practices is presented in Appendix A. Another useful reference is
"Irrigation Management Practices to Protect Ground Water and Surface Water
Quality-State of Washington" (WSU Cooperative Extension, 1995).
Irrigation Scheduling Practices
Proper irrigation scheduling is a key element in irrigation water management.
Irrigation scheduling should be based on knowing the daily water use of the crop,
the water-holding capacity of the soil, and the lower limit of soil moisture for each
crop and soil, and measuring the amount of water applied to the field. Also, natural
precipitation should be considered and adjustments made in the scheduled
irrigations.
Whether the irrigation source is surface or ground water, water availability during the
growing season should be adequate to support the most water sensitive crop in the
rotation. The design capacity of the irrigation system depends on regional climate,
irrigation efficiency, crop, and soil (USDA-SCS, 1993; USDA-SCS, 1970). See
Table 4f-4 for typical required system capacities for various crops and soils.
A practice that may be used to accomplish proper irrigation scheduling is:
n Irrigation Water Management (449): Determining and controlling the
rate, amount, and timing of irrigation water in a planned and efficient
manner.
Tools to assist in achieving proper irrigation scheduling include:
D Water-Measuring Device: An irrigation water meter, flume, weir, or other
water-measuring device installed in a pipeline or ditch.
O Soil and Crop Water Use Data: From soils information the available
water-holding capacity of the soil can be determined along with the
amount of water that the plant can extract from the soil before additional
irrigation is needed (MAD). Water use information for various crops can
be obtained from various United States Department of Agriculture
(USDA) publications. Crop water use for some selected irrigated crops is
shown in Figure 4f-16.
Daily accounting for
the cropland field
water budget helps
determine irrigation
scheduling.
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Chapter 4: Management Measures
Drainage Systems: An Overview
sometimes used as field drains
Outlets
There-are generally tws types ©:
name implies, in a gravity outlet wajej ftmlty\
phy is-limiting, pumped outlets itiay be rtf$s*
age water from the field' drains, ani
**i*
,* **«^
'!»J"1
l";I5'^ *<''!
' ;As^rj;5;
ia^6l,*I|fee$^i)|j^",
4-186
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4F: Irrigation Water Management
On sprinkler irrigated land, the design rate of application should be within a range
established by the minimum practical application rate under local climatic condi-
tions and the maximum rate consistent with the intake rate of the soil and the
conservation practices used on the land. Sprinkler systems should be designed for
zero runoff so no water leaves the point of application. The effects on erosion and
the movement of sediment, and soluble and sediment-attached substances carried
by runoff should be considered whether surface or sprinkler irrigation systems are
employed.
Practices for Use of Runoff Water or Tailwater
The use of runoff water to provide additional irrigation or to reduce the amount of
water diverted increases the efficiency of use of irrigation water. For surface
irrigation systems that require runoff or tailwater as part of the design and opera-
tion, a tailwater management practice is needed. The practice is described as
follows:
Cl Irrigation System, Tailwater Recovery (447): A facility to collect, store,
and transport irrigation tailwater for reuse in the farm irrigation distribution
system.
Practices for Drainage Water Management
Drainage water from an irrigation system should be managed to reduce deep perco-
lation, move tailwater to the reuse system, reduce erosion, and help control adverse
impacts on surface water and ground water. A total drainage system should be an
integral part of the planning and design of an efficient irrigation system.
There are several practices to accomplish this:
G Filter Strip (393): A strip or area of vegetation for removing sediment,
organic matter, and other pollutants from runoff and waste water.
G Surface Drainage Field Ditch (607): A graded ditch for collecting excess
water in a field.
H Subsurface Drain (606): A conduit, such as corrugated plastic tile, or
pipe, installed beneath the ground surface to collect and/or convey
drainage water.
G Water Table Control (641): Water table control through proper use of
subsurface drains, water control structures, and water conveyance
facilities for the efficient removal of drainage water and distribution of
irrigation water.
G Controlled Drainage (335): Control of surface and subsurface water
through use of drainage facilities and water control structures.
Practices for Backflow Prevention
The American Society of Agricultural Engineers recommends, in standard EP409,
safety devices to prevent backflow when injecting liquid chemicals into pressur-
ized irrigation systems (ASAE, 1989).
The process of supplying fertilizers, herbicides, insecticides, fungicides,
nematicides, and other chemicals through irrigation systems is known as
chemigation. A backflow prevention system will "prevent chemical backflow to the
water source" in cases when the irrigation pump shuts down (ASAE, 1989).
National Management Measures to Control Nonpoint Pollution from Agriculture 4-191
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Chapter 4: Management Measures
Three factors an operator must take into account when selecting a backflow
prevention system are the characteristics of the chemical that can backflow, the
water source, and the geometry of the irrigation system. Areas of concern include
whether injected material is toxic and whether there can be backpressure or
backsiphonage (ASAE, 1989; EPA, 1991b). Several different systems used as
backflow preventers are:
O Air gap. A physical separation in the pipeline resulting in a loss of water
pressure. Effective at end of line service where reservoirs or storage tanks
are desired.
D
CJ
Check valve with vacuum relief and low pressure drain. Primarily
used as an antisiphon device (Figure 4f-20).
Double check valve. Consists of two single check valves coupled within
one body and can handle both backsiphonage and backpressure.
Reduced pressure principle backflow preventer. This device can be
used for both backsiphonage and backpressure. It consists of a pressure
differential relief valve located between two independently acting check
valves.
Atmospheric vacuum breaker. Used mainly in lawn and turf irrigation
systems that are connected to potable water supplies. This system cannot
be installed where backpressure persists and can be used only to prevent
backsiphonage.
Pump interlocking. Application of chemicals in sprinkler systems require
an injection pump. By interlocking the injection pump with the water pump,
the injection pump is only powered when the water pump is operating.
Figure 4f-20. Backflow prevention device using check valve with vacuum relief and low
pressure drain (USDA-NRCS, 1997a).
From chemical tank
To
irrigation
system
Solenoid valve
Injection port
with check valve
Pressure
gauge
Injection
pump
Flow
Vacuum breaker
and inspection
port
From water
supply
Coupler
Gate
valve
Low
8 res sure
rain
Practice Effectiveness
The following is information on pollution reductions that can be expected from
installation of the management practices outlined within this management measure.
However, it should be noted that practice effectiveness is determined through
experience and evaluations based on system limitations, topography, climate, etc.,
and cannot merely be selected from a chart. The efficiency and effectiveness
figures given below are for illustrative purposes.
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Chapter 4F: Irrigation Water Management
In a review of a wide range of agricultural control practices, EPA (1982a)
determined that increased use of call periods, on-demand water ordering, irriga-
tion scheduling, and flow measurement and control would all result in decreased
losses of salts, sediment, and nutrients. Various alterations to existing furrow
irrigation systems were also determined to be beneficial to water quality, as were
tailwater management and seepage control.
Logan (1990) reported that chemical backsiphon devices are highly effective at
preventing the introduction of pesticides and nitrogen to ground water. The
American Society of Agricultural Engineers (ASAE) specifies safety devices for
chemigation that will prevent the pollution of a water supply used solely for
irrigation (ASAE, 1989).
Properly designed sprinkler irrigation systems will have little runoff (Boyle Engi-
neering Corp., 1986). Furrow irrigation and border check or border strip irrigation
systems typically produce tailwater, and tailwater recovery systems may be
needed to manage tailwater losses (Boyle Engineering Corp., 1986). Tailwater can
be managed by applying the water to additional fields, by treating and releasing the
tailwater, or by reapplying the tailwater to upslope cropland.
The Rock Creek Rural Clean Water Program (RCWP) project in Idaho is the
source of much information regarding the benefits of irrigation water management
(USDA, 1991). Crops in the Rock Creek watershed are irrigated with water
diverted from the Snake River and delivered through a network of canals and
laterals. The combined implementation of irrigation management practices,
sediment control practices, and conservation tillage resulted in measured reduc-
tions in suspended sediment loadings ranging from 61% to 95% at six stations in
Rock Creek (1981-1988). Similarly, 8 of 10 sub-basins showed reductions in
suspended sediment loadings over the same time period. The sediment removal
efficiencies of selected practices used in the project are given in Table 4f-6.
Normally, drip irrigation will have the greatest irrigation efficiency and contour
ditch irrigation will have the lowest irrigation efficiency. See Table 4f-7 for appli-
cation efficiencies of various systems and Table 4f-8 for a range of deep percola-
tion and runoff losses from surface and sprinkler methods. Tailwater recovery
irrigation systems are expected to have the greatest percolation rate. USDA
projects significant increases in overall irrigation efficiencies when tailwater
recovery facilities are used (Table 4f-9).
Plot studies in California have shown that in-season irrigation efficiencies for drip
irrigation and Low Energy Precision Application (LEPA) are greater than those for
improved furrow and conventional furrow systems (Table 4f-10). LEPAis a linear
move sprinkler system in which the sprinkler heads have been removed and
replaced with tubes that supply water to individual furrows (Univ. Calif., 1988).
Dikes are placed in the furrows to prevent water flow and reduce soil effects on
infiltrated water uniformity.
Mielke and Leavitt (1981) studied the effects of tillage practice and type of center
pivot irrigation on herbicide (atrazine and alachlor) losses in runoff and sediment.
Study results clearly show that, for each of three tillage practices studied, low-
pressure spray nozzles result in much greater herbicide loss in runoff than either
high-pressure or low-pressure impact heads.
Irrigation
management practice
systems can reduce
suspended sediment
loading to streams.
National Management Measures to Control Nonpoint Pollution from Agriculture
4-193
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Chapter 4: Management Measures
Table 4f-6. Sediment removal efficiencies and comments on BMPs evaluated (USDA, 1991).
Sediment Removal
Practice Efficiency (%)
Average Range
Sediment basins: field, farm, subbasin 87 75-95
Mini-basins 86a 0-95
Buried pipe systems (incorporating 83 75-95
mini-basins with individual outlets
into a buried drain)
Vegetative filters 50a 35-70
Placing straw in furrows 50 40-80
Comment
Cleaning costly.
Controlled outlets essential. Many
failed. Careful management required.
High installation cost. Potential for
increased production to offset costs.
Eliminates tailwater ditch. Good
control of tailwater.
Simple. Proper installation and
management needed.
Labor-intensive without special
equipment. Careful management
required.
a Mean of those that did not fail.
Table 4f-7. Ranges of irrigation application efficiencies from various sources.
Application Efficiency. %
Irrigation System Duke, 19871 USDA-NRCS, 1997a HIM, 19942
Center Pivot 70-90
Linear Move
LEPA
Solid Set Sprinklers
Periodic Move Lateral
Drip 75-100
Level Basin 70-90
Border
Furrow
Furrow - sandy soil 20-60
Furrow - clay soil 50-90
Contour Ditch
75-85
80-87
90-95
60-75
60-75
35-60
80
80
70-80
70-80
80-90
80
60-75
60-70
40-50
65
45-55
1 Typical single event efficiencies
2 Possible values for various systems with good design and above average management practices
Table 4f-8. Ranges of Application Efficiency E_( and runoff, deep percolation, and
evaporation losses (Hill, 1994).'
Method
Surface Irrigation
E
a
Runoff Losses
Deep Percolation Losses
Sprinkler Irrigation
E
a
Evaporation Losses
Deep Percolation Losses
HI
72
55
65
84
45
37
Low
24
5
20
52
8
8
Typical
50
20
X
70
12
18
'determined from field evaluations in Utah
4-194
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter 4F: Irrigation Water Management
Table 4f-9.
Overall efficiencies obtainable by using tailwater recovery and reuse facility (USDA-NRCS, 1997a).
Original %of
appllc water
efflc reused
%
60
50
40
X
20
40
60
80
40
60
80
40
60
80
40
60
60
40
60
80
%of
orlg
water
used
16
24
32
20
30
40
24
36
48
28
42
56
32
48
64
First reuse —
Effect Accum
use - effect
%of
orlg %
9.6
14.4
19.2
10.0
15.0
20.0
9.6
14.4
19.2
8.4
12.6
16.8
6.4
9.6
12.8
69.6
74.4
79.2
60.0
65.0
70.0
49.6
54.4
59.2
38.4
42.6
46.8
26.4
29.6
32.8
— Second reuse —
%of Effect Accum
orlg use • effect
water %of
used orlg %
2,6
5.8
10.2
4.0
9.0
16.0
5.8
13.0
23.0
7.8
17.8
31.4
10.2
23.0
41.0
1.5
3.5
6.1
2.0
4.5
8.0
2.3
5.2
9.2
2.4
5.3
9.4
2.1
4.6
8.2
71.1
77.9
85.3
62.0
69.5
78.0
52.9
59.6
68.4
40.8
49.9
56.2
28.5
34.2
41.0
— Third reuse —
%of Effect Accum
orlg use - effect
water %of
used orlg %
1.1
1.4
3.3
0.8
2.7
6.4
1.4
4.7
11.0
2.2
7.5
17.6
3.2
11.0
26.2
0.7
0.8
2,0
0.4
1.4
3.2
0.6
1.9
4.4
0.7
2.3
5.3
0.7
2.2
5.3
71.8
78.7
87.3
62.4
70.9
81.2
53.5
61.5
72.8
41.5
52.2
61.5
29.2
36.4
46.3
Fourth reuse —
%of Effect Accum
orlg use - effect
water %of
used orlg %
0.2
0.4
1.0
0.2
0.8
2.6
0.3
1.7
5.3
0.6
3.1
9.8
1.0
5.3
17.5
0.1
0.2
0.6
0.1
0.4
1.3
0.1
0.7
2.1
0,2
0.9
3,0
0.2
1.1
3.5
71.9
78.9
87.9
62.5
71.3
82.5
53.6
62.2
74.9
41.7
53.1
64.5
29.4
37.5
49.8
Table 4f-10. Irrigation efficiencies of selected irrigation systems for cotton (California SWRCB, 1992).
System
Subsurface Drip Irrigation
LEPA (Low Energy
Precision Application)
Improved Furrow
Conventional Furrow
Year
19891
19901
1989
1990
1988
1990
1989
1990
Seasonal
Irrigation (In.)
23.54
24.04
19.89
26.55
29.77
20.19
30.75
28.76
Distribution
Uniformity (%)
79
76
80
92
60
82
61
72
Irrigation
Efficiency (%)
86
81
82
74
35
66
35
62
Deep
Percolation (In.)
2.43
3.98
2.88
6.13
18.9
6.06
19.39
9.85
1 includes one preirrlgation with hand move sprinklers
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Chapter 4: Management Measures
Factors in Selection of Management Practices
Irrigation Scheduling
Selecting a water scheduling method will depend on the availability of climatic
data. Crop water use depends on the type of crop, stage of growth, temperature,
sunshine, wind speed, relative humidity and soil moisture content. Water use can
be estimated based on maximum daily temperatures and the growth stage of the
crop. If climatic data cannot be measured on site or is not available nearby, it may
be more appropriate to schedule irrigation from representative field soil water
measurements.
Determining water holding capacity for the field is critical in water scheduling.
Where large differences in soil texture are found in an irrigated field, particular
attention should be paid to the coarsest textures. Coarse textures will hold less
available water than finer textured soils and will reach depletion sooner. Knowl-
edge of soil texture and soil moisture status will help determine the appropriate
application rate and depth, so runoff and deep percolation are minimized. Variable
rate application of water should be considered if water holding capacities range
significantly.
Efficient Irrigation Water Application
The selection of an appropriate irrigation system should be based on having
sufficient capacity to adequately meet peak crop water demands for the crop with
the highest peak water demand in the rotation. The system capacity is dependent
on the peak period evapotranspiration rate, crop rooting depth, available water
holding capacity of the soil, and irrigation efficiency. Other potentially limiting
factors are water delivery capacity and permitted water allocation (Table 4f-4).
Other factors that should be considered when selecting an irrigation system are the
shape and size (acres) of the field and the topography. Field slope and steepness
will determine whether surface or sprinkler irrigation can be used. If surface
application of water is chosen, land leveling may be required to more efficiently
spread water over the field.
A sprinkler system can and should be designed to apply water uniformly without
runoff or erosion. The application rate of the sprinkler system should be matched
to the intake rate of the most restrictive soil in the field. If the application rate
exceeds the soil intake rate, the water will run off the field or relocate within the
field resulting in areas of over application that could percolate soluble chemicals to
ground water. Care should be taken in a pivot system to match endguns with soil
water intake rates.
If secondary salinization from irrigation is a problem, an application method must
be chosen to keep salts leached below the root zone.
The selected water application method will also depend on whether chemigation is
to be used. Coverage, timing, and type of chemical application will determine
which application method will be most efficient. Chemigation with surface irriga-
tion should be avoided when alternative methods are available for the application
of fertilizers and pesticides. Additional costs for pollution prevention may be
incurred when chemigating.
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Chapter 4F: Irrigation Water Management
Tailwater recovery may be required if surface chemigation is practiced, and
backflow prevention is needed if sprinkler chemigation is used.
Cost and Savings of Practices
Costs
Costs to install, operate and maintain an irrigation system will depend on the type
of irrigation system used. In order to efficiently irrigate and prevent pollution of
surface and ground waters, the irrigation system must be properly maintained and
water measuring devices used to estimate water use.
A cost of $10 per irrigated acre is estimated to cover investments in flow meters,
tensiometers, and soil moisture probes (EPA, 1992a; Evans, 1992). The cost of
devices to measure soil water ranges from $3 to $4,900 (Table 4f-ll). Gypsum
blocks and tensiometers are the two most commonly used devices. A more
expensive and instantaneous device is a neutron probe. It uses a radioactive
source of neutrons and a probe to measure the amount of moisture in the soil.
The probe is inserted into the soil through a tube and the energy, produced by
neutons colliding with hydrogen and oxygen atoms that make up water, is mea-
sured in the probe indicating the soil moisture content.
For quarter-section center pivot systems, backflow prevention devices cost about
$416 per well (Stolzenburg, 1992). This cost (1992 dollars) is for: (1) an
8-inch, 2-foot-long unit with a check valve inside ($386); and (2) a one-way
injection point valve ($30). Assuming that each well will provide about 800-1,000
gallons per minute, approximately 130 acres will be served by each well. The cost
for backflow prevention for center pivot systems then becomes approximately
$3.20 per acre. In South Dakota, the cost for an 8-inch standard check valve is
about $300, while an 8-inch check valve with inspection points and vacuum
release costs about $800 (Goodman, 1992). The latter are required by State law.
For quarter-section center pivot systems, the cost for standard check valves ranges
from about $1.88 per acre (corners irrigated, covering 160 acres) to $2.31 per acre
(circular pattern, covering about 130 acres). To maintain existing equipment so
that water delivery is efficient, annual maintenance costs can be figured at 1.5%
of the new equipment cost (Scherer, 1994).
Table 4f-11. Cost of soil water measuring devices.
Device
Approximate Cost
Tensiometers3
Gypsum blocks'3
Neutron Probe0
PheneCell3
Tensiometers and soil moisture probesd
$50 and up, depending on size
$3-4, $200-400 for meter
$4,900
$4,000-4,500
$10 per irrigated acre
aHydratec, 1998.
bSneed,1992.
cCambell Pacific Nuclear, 1998.
d Evans, 1992.
National Management Measures to Control Nonpoint Pollution from Agriculture
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Chapter4: Management Measures
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-------
Chapter 4F: Irrigation Water Management
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-------
Chapter 4: Management Measures
Tailwater can be prevented in sprinkler irrigation systems through effective
irrigation scheduling, but may need to be managed in furrow systems. The reuse
of tailwater downslope on adjacent fields is a low-cost alternative to tailwater
recovery and upslope reuse (Boyle Engineering Corp., 1986). Tailwater recovery
systems require a suitable drainage water receiving facility such as a sump or a
holding pond, and a pump and pipelines to return the tailwater for reapplication
(Boyle Engineering Corp., 1986). The cost to install a tailwater recovery system
was about $125/acre in California (California SWRCB, 1987) and $97.00/acre in
the Long Pine Creek, Nebraska, RCWP (Hermsmeyer, 1991). Additional costs
may be incurred to maintain the tailwater recovery system.
The cost associated with surface and subsurface drains is largely dependent upon
the design of the drainage system. In finer textured soils, subsurface drains may
need to be placed at close intervals to adequately lower the water table. To convey
water to a distant outlet, land area must be taken out of production for surface
drains to remove seeping ground water and for collection of subsurface drainage.
The Agricultural Conservation Program (ACP) has been phased out and replaced
by the Environmental Quality Incentive Program (EQIP) in the 1996 Farm Bill.
However, the Statistical Summaries (USDA-FSA, 1996) from the ACP contain
reliable cost-share estimates. The following cost information is taken from these
summaries and assumes a 50% cost-share to obtain capital cost estimates. The
ACP program has a unique set of practice codes that are linked to a conservation
practice. The cost to install irrigation water conservation systems (FSA practice
WC4) for the primary purpose of water conservation in the 33 States that used the
practice was about $73.00 per acre served in 1995. Practice WC4 increased the
average irrigation system efficiency from 47% to 64% at an amortized cost of
$10.41 per acre foot of water conserved. The components of practice WC4 are
critical area planting, canal or lateral, structure for water control, field ditch,
sediment basin, grassed waterway or outlet, land leveling, water conveyance ditch
and canal lining, water conveyance pipeline, trickle (drip) system, sprinkler
system, surface and subsurface system, tailwater recovery, land smoothing, pit or
regulation reservoir, subsurface drainage for salinity, and toxic salt reduction.
When installed for the primary purpose of water quality, the average installation
cost for WC4 was about $67 per acre served. For erosion control, practice WC4
averaged approximately $82 per acre served. Specific cost data for each compo-
nent of WC4 are not available.
Water management systems for pollution control, practice SP35, cost about $94
per acre served when installed for the primary purpose of water quality. When
installed for erosion control, SP35 costs about $72 per acre served. The compo-
nents of SP35 are grass and legumes in rotation, underground outlets, land
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Chapter 4F: Irrigation Water Management
smoothing, structures for water control, subsurface drains, field ditches, mains or
laterals, and toxic salt reduction.
The design lifetimes for a range of salt load reduction measures are presented in
Table 4f-12 (USDA-ASCS, 1988).
Sawngs
Savings associated with irrigation water management generally come from
reduced water and fertilizer use.
Steele et al. (1996) found that improved methods of irrigation scheduling can
produce significant savings in seasonal irrigation water totals without yield reduc-
tions. In a six-year continuous corn field study, a 31 % savings in seasonal irriga-
tion totals was realized compared to the average commercial grower in the same
irrigation district. Corn grain yields were maintained at 3% above average corn
grain yields in the irrigation district.
Table 4f-12. Design lifetime for selected salt load reduction measures (USDA-ASCS, 1988).
Practice/Structure
Design Life (Years)
Irrigation Land Leveling
Irrigation Pipelines-Aluminum Pipe
Irrigation Pipelines - Rigid Gated Pipe
Irrigation Canal and Ditch Lining
Irrigation Head Ditches
Water Control Structure
Trickle Irrigation System
Sprinkler Irrigation System
Surface Irrigation System
Irrigation Pit or Regulation Reservoir
Subsurface Drain
Toxic Salt Reduction
Irrigation Tailwater Recovery System
Irrigation Water Management
Underground Outlet
Pump Plant for Water Control
10
20
15
20
1
20
10
15
15
20
20
1
20
1
20
15
National Management Measures to Control Nonpoint Pollution from Agriculture
4-201
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Chapter 4: Management Measures
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Using Management Measures to
Prevent and Solve Nonpoint
Source Problems in Watersheds
Watershed Approach
Watersheds are areas of land that drain to a single stream or other water re-
source. Watersheds are defined solely by drainage areas and not by land owner-
ship or political boundaries. The watershed approach is a coordinating
framework for environmental management that focuses public and private sector
efforts to address priority problems within hydrologically defined geographic
areas (e.g., watersheds), taking into consideration both ground and surface water
flow (EPA, 1995b).
EPA supports watershed approaches that aim to prevent pollution, achieve and
sustain environmental improvements and meet other goals important to the
community. Although watershed approaches may vary in terms of specific
objectives, priorities, elements, timing, and resources, all should be based on the
following guiding principles.
D Partnerships: Those people most affected by management decisions are
involved throughout and shape key decisions.
This ensures that environmental objectives are well integrated with
those for economic stability and other social and cultural goals. It also
provides that the people who depend upon the natural resources within
the watersheds are well informed of and participate in planning and
implementation activities.
D Geographic Focus: Activities are directed within specific geographic
areas, typically the areas that drain to surface water bodies or that
recharge or overlay ground waters or a combination of both.
n Sound Management Techniques based on Strong Science and Data:
Collectively, watershed stakeholders employ sound scientific data,
tools, and techniques in an iterative decision making process. This
includes:
i. assessment and characterization of natural resources and the
communities that depend upon them;
ii. goal setting and identification of environmental objectives based on
the condition or vulnerability of resources and the needs of the
aquatic ecosystem and the people within the community;
hi. identification of priority problems;
iv. development of specific management options and action plans;
v. implementation; and
vi. evaluation of effectiveness and revision of plans, as needed.
National Management Measures to Control Nonpoint Pollution from Agriculture 5-203
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Chapter 5: Using Management Measures to Prevent and Solve Nonpoint Source Problems in Watersheds
Because stakeholders work together, actions are based upon shared information
and a common understanding of the roles, priorities, and responsibilities of all
involved parties. Concerns about environmental justice are addressed and, when
possible, pollution prevention techniques are adopted. The iterative nature of the
watershed approach encourages partners to set goals and targets and to make
maximum progress based on available information while continuing analysis and
verification in areas where information is incomplete.
Watershed projects should have a strong monitoring and evaluation component.
Using monitoring data, stakeholders identify and prioritize stressors that may
pose health and ecological risk in the watershed and any related aquifers.
Monitoring is also essential to determining the effectiveness of management
options chosen by stakeholders to address high priority stressors. Because many
watershed protection activities require longterm commitments from stakehold-
ers, stakeholders need to know whether their efforts are achieving real improve-
ments in water quality. Monitoring is described in greater detail in Chapter 6.
Watershed projects should also be consistent with state regulatory programs
such as development and implementation of total maximum daily loads
(TMDLs) and basinwide water quality assessments. In fact, a watershed may be
selected for special attention because of the need for a complex TMDL involv-
ing point and nonpoint sources (see Chapter 7 for a discussion of TMDLs).
Operating and coordinating programs on a watershed basis makes good sense for
environmental, financial, social, and administrative reasons. For example, by
jointly reviewing the results of assessment efforts for drinking water protection,
point and nonpoint source pollution control, fish and wildlife habitat protection
and other resource protection programs, managers from all levels of government
can better understand the cumulative impacts of various human activities and
determine the most critical problems within each watershed. Using this informa-
tion to set priorities for action allows public and private managers from all levels
to allocate limited financial and human resources to address the most critical
needs. Establishing environmental indicators helps guide activities toward
solving those priority problems and measuring success.
The final result of the watershed planning process is a plan that is a clear de-
scription of resource problems, goals to be attained, and identification of sources
for technical, educational, and funding assistance needed. A comprehensive plan
will provide a basis for seeking support and for maximizing the benefits of that
support.
Implementing Management Measures in
Watersheds
Management measures can be implemented in either a preventive or restorative
mode depending upon the State and local needs identified through the watershed
planning process. Similarly, although management measures are generally
considered to be technology-based, they can also be used as key elements of a
water quality-based approach to solving identified water quality problems.
Technology-based pollution control measures are identified based upon technical
and economic achievability rather than on the cause-and-effect linkages between
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Chapter 5: Using Management Measures to Prevent and Solve Nonpoint Source Problems in Watersheds
particular land use activities and particular water quality problems that drive
water quality-based approaches.
Technology-based Implementation
As noted earlier, a clear assessment of the problem is essential to identifying
appropriate solutions. For example, the Section 6217 management measures
were specified to address water quality problems in the Nation's coastal areas.
These management measures were developed as affordable technology-based
controls that could be implemented broadly within coastal drainage areas to
improve and protect the quality of coastal waters. The Section 6217 program
also includes provisions for implementing additional control measures where
water quality problems are not solved through implementation of the manage-
ment measures alone (USDOC and EPA, 1993). This iterative approach to
solving coastal problems is consistent with the guiding principles of the water-
shed approach.
Primary justification for applying management measures through a technology-
based approach is that the measures are known to reduce pollution and are
generally acceptable and affordable. Therefore, the measures should be applied
to as much land as possible, regardless of location. This has been the approach
of most USDA and state agencies for many years. For example, Vermont's
Accepted Agricultural Practices are "basic practices that all farmers must follow
as part of their normal operations" (Vermont Department of Agriculture, 1995).
They "are intended to reduce, not eliminate, pollutants associated with nonpoint
sources." By implementing management measures or practices in a technology-
based approach, a level of water quality protection can be achieved which makes
it easier to then focus on remaining sources that need additional control.
The means by which management measures are implemented in a technology-
based approach can range from voluntary to regulatory. All States have some
form of voluntary program for addressing agricultural nonpoint source pollution.
These programs include USDA's Farm Bill programs (Chapter 1) and State and
local cost-share and assistance programs. Cost-share programs are very often
technology-based and can be directed to high-priority watersheds in much the
same way that Section 6217 is focused within coastal drainage areas. Private
sector efforts are also technology-based in many cases, including, for example,
precision farming techniques.
Water Quality-based Implementation
In areas where specific water quality problems have been identified and charac-
terized in detail, it is possible to tailor implementation to achieve well-defined
goals. For example, TMDLs result in allocations of the quantity of pollution that
can be discharged from point sources (wasteload allocation) and nonpoint
sources (load allocation) to ensure that water quality standards are achieved
within a specified margin of safety (see Chapter 7). Management measures can
be applied to achieve all or part of the pollution control needed by agricultural
sources to achieve the load allocation. Management measures can also be used
National Management Measures to Control Nonpoint Pollution from Agriculture 5-205
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Chapter 5; Using Management Measures to Prevent and Solve Nonpoint Source Problems in Watersheds
in permits to address the portion of a wasteload allocation assigned to animal
operations designated as point sources.
Understanding Hydrology
Understanding site and watershed hydrology is essential to understanding
nonpoint source problems and the impacts that management measure implemen-
tation may have on water quality. Each action taken on a farm has the potential
to impact hydrology (see Garen et al., 1999). For example, diversions and
buffers clearly affect water movement, and even grazing management affects
hydrology through its changes to grazing land quality and/or riparian condition.
Nutrient management can also affect hydrology directly if the application of
nutrients includes liquids, and indirectly through its effects on crop growth
which control plant water and nutrient uptake. The extent to which management
decisions affect hydrology needs to be understood and estimated since hydrol-
ogy is so important to the detachment, transport, and delivery of pollutants.
In agricultural watersheds, hydrology can be affected by a number of factors
including the use of tile drains and irrigation practices, installation of grassed
waterways and diversions, field buffers and buffer strips, crop type, and tillage
type. The combined effects on hydrology of all management measures and
management practices implemented should be considered both at the farm level
and at the watershed scale in order to estimate the impacts on receiving water
quality. Field-scale and watershed-scale models can aid analysis of the impacts
on hydrology, and thus decisions on appropriate selection and placement of
measures and practices in the watershed. In some cases, a thoughtful discussion
or simple analysis will provide the answers regarding impacts to hydrology, but
some form of modeling will usually be needed to integrate the various small and
large impacts that management measures and practices are likely to have on
watershed hydrology. However, models often have many limitations. Therefore,
a thorough understanding of the hydrology of the area gained through monitor-
ing or experience is usually needed to properly interpret model results.
If the watershed within which agricultural management measures will be imple-
mented includes land uses other than agriculture, then planners will need to
consider agriculture's role within the watershed. In other words, the degree to
which agricultural lands control watershed hydrology should be investigated and
understood to enable analysis of the potential impacts that management mea-
sures and practices will have on watershed hydrology. Once again, some sort of
watershed modeling capability will usually be needed to aid this analysis.
Assessing On-Site Treatment Needs
Once watershed hydrology is understood, analysis of on-site treatment needs and
the impacts of management measures on pollutant sources and delivery patterns
can be conducted. At a particular farm it may be simple to determine which
management measures are needed. For example, if nutrients and pesticides are
applied, then nutrient and pesticide management should be implemented. If
runoff from a confined animal facility leaves the farm without any attenuation or
treatment, then storage and treatment of runoff is probably needed. More diffi-
cult cases will be those in which some management is practiced, but not enough
to fully achieve the management measures. Even more difficult may be the cases
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Chapter 5: Using Management Measures to Prevent and Solve Nonpoint Source Problems in Watersheds
where management measures are fully achieved but water quality goals or
standards are still not being met.
On-site assessments should be performed to determine the needs on any indi-
vidual farm. USDA-NRCS, soil and water conservation districts, state coopera-
tive extension, and other public and private organizations have expertise in
performing on-site assessments. EPA has developed guidance for tracking and
evaluating the implementation of nonpoint source control measures (EPA,
1997b). Tools such as Farm*A*Syst (Jackston et al., undated) can be helpful
when performing self-assessments of on-farm conditions.
It is usually beneficial to examine the water resource (e.g., to perform a stream
walk) to view the watershed from the perspective of the receiving water body.
This may lead to discovery of sources that would not be found from a typical on-
site assessment. USDA's Stream Visual Assessment Protocol (USDA-NRCS,
1998) is a potential tool for stream assessment. In some watershed projects
upland erosion control and riparian protection have been implemented with the
expectation that sedimentation problems would be solved. Results, however,
indicated that sedimentation problems persisted. For example, in the Rock
Creek, Idaho, Rural Clean Water Program project, improved irrigation, sediment
retention structures, filter strips, and conservation tillage were implemented to
address sediment problems impacting a cold-water fishery (EPA, 1990a). The
project did achieve and measure reduced levels of suspended sediment, but it
was concluded that the project should have included the contribution of sedi-
ment from streambanks and the effects of hydromodification to fully achieve
water quality objectives. A thorough examination of the water resource could
have helped in the initial planning stages for this project.
Targeting
Even properly designed management practice systems constitute only part of an
effective land treatment strategy. In order for a land treatment strategy to be
most effective, properly designed management practice systems must be placed
in the correct locations in the watershed (i.e., "critical areas") and the extent of
land treatment must be sufficient to achieve water quality improvements (Line
and Spooner, 1995). RCWP results indicate that 75% of the critical areas (as
designated in that program) need to be treated to achieve water quality goals.
For livestock-related water quality problems, generally 100% of the critical area
should be treated with BMP systems (Meals, 1993). "Critical areas" are gener-
ally considered to be sub-areas within a watershed or recharge area that encom-
pass the major pollutant sources that have a direct impact on the impaired water
resource (Gale et al., 1993). The discussion below and in Chapter 7 provides
information related to the delineation of critical areas. Although the term "criti-
cal area" is not generally used in TMDLs, the allocation of loads to sources in
the watershed is entirely consistent with the concept.
In cases where implementation of management measures is water-quality based
or voluntary, the implementation should be prioritized based upon the water
quality benefits to be derived. Phased implementation on a priority basis may be
best if financial resources are limited.
National Management Measures to Control Nonpoint Pollution from Agriculture 5-207
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Chapter 5: Using Management Measures to Prevent and Solve Nonpoint Source Problems in Watersheds
Estimating On-Site and Off-Site Impacts
On-site benefits are highly desirable, yet unless the needed off-site benefits are
derived from the collective implementation of management measures and
practices across the watershed, then implementation has not been fully success-
ful. It is important to estimate the collective impacts of all management activities
in the watershed to gage whether water quality goals will be achieved. In water-
sheds with easily characterized problems (e.g., bacterial contamination is due to
a few obviously polluting animal operations in a watershed that has no other
identifiable sources of pathogens) it may be very easy to project that water
quality benefits will be achieved through implementation of the management
measures for nutrient management, erosion and sediment control, and facility
wastewater and runoff, for example. However, in a watershed with multiple land
uses where agriculture is considered to contribute about one-third or so of the
pollutants, it is more complicated to estimate the combined impacts of a variety
of management measures and practices on a fairly large number of diverse
farming operations. Further complicating the assessment may be that historic
loading of pollutants has caused the water quality impairment and several years
are required for the water resource to recover or cleanse itself (i.e., current
loading may be low). In this type of situation, computer modeling may be
needed.
A variety of models exist to help assess the relative benefits of implementing
practices at the field and watershed level. However, an understanding of the
model's limitations and assumptions is necessary for appropriate interpretation
of modeling results. It is also important that models be adequately validated and
calibrated for a range of circumstances. The following are some models that
have been evaluated for a relatively wide range of conditions and have been
shown to be appropriate for the farm or field:
O GLEAMS (Knisel et al., 1991) simulates the effects of management
practices and irrigation options on edge of field surface runoff,
sediment, and dissolved and sediment attached nitrogen, phosphorus,
and pesticides. The model considers the effects of crop planting date,
irrigation, drainage, crop rotation, tillage, residue, commercial nitrogen
and phosphorus applications, animal waste applications, and pesticides
on pollutant movement. The model has been used to predict the
movement of pesticides (Zacharias et al., 1992) and nutrients and
sediment from various combinations of land uses and management
(Knisel and Leonard, 1989; Smith et al., 1991).
D EPIC (Sharpley and Williams, 1990) simulates the effect of management
strategies on edge of field water quality and nitrate nitrogen and
pesticide leaching to the bottom of the soil profile. The model considers
the effect of crop type, planting date, irrigation, drainage, rotations,
tillage, residue, commercial fertilizer, animal waste, and pesticides on
surface and shallow ground water quality. The EPIC model has been
used to evaluate various cropland management practices (Sugiharto et
al., 1994; Edwards et al., 1994).
D NLEAP (Follet et al., 1991) evaluates the potential of nitrate nitrogen
leaching due to land use and management practices. The NLEAP model
has been used to predict the potential for nitrogen leaching under
various management scenarios (Wylie et al., 1994; Wylie et al., 1995).
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Chapter 5: Using Management Measures to Prevent and Solve Nonpoint Source Problems in Watersheds
D PRZM (Mullens et al. 1993) simulates the movement of pesticides in
unsaturated soils within and immediately below the root zone. Several
different field crops can be simulated and up to three pesticides are
modeled simultaneously as separate parent compounds or metabolites.
The PRZM model has been used under various conditions to assess
pesticide leaching under fields (Zacharias et al., 1992; Smith et al.,
1991).
O DRAINMOD (Skaggs, 1980) simulates the hydrology of poorly drained,
high water table soils. Breve et al. (1997) developed DRAINMOD-N, a
nitrogen version of the model to evaluate nitrogen dynamics in
artificially drained soils. The DRAINMOD model has been used to
predict pollutant losses associated with various drainage management
scenarios (Deal et al., 1986). Website is http://www.bae.ncsu.edu/bae/
research/soil_water/www/watmngmnt/drainmod/index.htm.
G REMM (Riparian Ecosystem Management Model) is a computer
simulation model used to simulate hydrology, nutrient dynamics and
plant growth for land areas between the edge of fields and a water body.
Output from REMM allows designers to develop buffer systems to help
control non-point source pollution. REMM was developed by ARS at
the Southeast Watershed Research Laboratory, Coastal Plain Experiment
Station, Tifton, GA. Web site is http://www.cpes.peachnet.edu/
remmwww/.
n NTRM (Shaffer and Larson, 1985) simulates the impact of soil erosion on
the short and long-term productivity of soil, and is intended to assist with
evaluation of existing and proposed soil management practices in the
subject areas of erosion, soil fertility, tillage, crop residues, and irrigation.
The NTRM model has been applied to evaluate effects of conservation
tillage, supplemental nitrogen and irrigation practices (Shaffer, 1985) and
moldboard plow and chisel plow tillage (Shaffer et al., 1986) on soil
erosion and productivity. This model has had limited use.
The following models can be used for either farm field or small watershed scale
analysis:
D WEPP (Flanagan and Nearing, 1995) simulates water runoff, erosion,
and sediment delivery from fields or small watersheds. Management
practices including crop rotation, planting and harvest date, tillage,
compaction, stripcropping, row arrangement, terraces, field borders, and
windbreaks can be simulated. The WEPP model has been applied to
various land use and management conditions (Tiscareno-Lopez et al.,
1993; Liu et al., 1997). Web site is http://topsoil.nserl.purdue.edu/
nserlweb/weppmain/wepp.html.
D SWAT (which incorporates SWRRBWQ) (Arnold et al., 1990) simulates
the effect of agricultural management practices such as crop rotation,
conservation tillage, residue, nutrient, and pesticide management; and
improved animal waste application methods on water quality. The
SWRRB model has been used on several watersheds to assess
management practices and to test its validity (Arnold and Williams,
1987; Bingner et al., 1987). Web site is http://www.brc.tamus.edu/swat.
d AnnAGNPS (Cronshey and Theurer, 1998) is a spatially-distributed
model for estimating pollutant runoff from agricultural watersheds.
National Management Measures to Control Nonpoint Pollution from Agriculture 5-209
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Chapter 5: Using Management Measures to Prevent and Solve Nonpoint Source Problems in Watersheds
HAS/MS 3M: A Powerful and Improved Tool for Managing Watersheds
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5-210
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Chapter 5: Using Management Measures to Prevent and Solve Nonpoint Source Problems in Watersheds
Within cells, the model can evaluate practices such as feedlot
management, terraces, vegetative buffers, grassed waterways, and farm
ponds. Simulated nutrient, sediment, and pesticide concentrations and
yields are available for any cell within the watershed. The AnnAGNPS
model has been applied to many field and watershed size areas to
estimate pollutant runoff from various land uses and management
practices (Bosch et al., 1998; Line et al., 1997; Young et al., 1994;
Sugiharto et al., 1994; Bingner et al., 1987). Web site is http://
www.sedlab.olemiss.edu/AGNPS.html.
O ANSWERS (Beasley et al., 1980) is a spatially-distributed watershed
model. The model is primarily a runoff and sediment model as soil
nutrient processes are not simulated. The ANSWERS model has been
applied to several small field-sized areas with various management
practices (Griffin et al., 1988; Bingner et al., 1987).
n BASINS (EPA, 2001d) is a user-friendly GIS-based program containing
several models capable of simulating watershed loadings and receiving
water impacts at various levels of complexity. This new version allows
you to subdivide large watersheds into very small watershed segments
using either an automated delineation tool or a manual delineation tool.
BASINS 3.0 includes three watershed models. The HSPF model, present
in earlier versions, is supported by a new Windows interface that makes
it easier to run the urban and rural watershed simulations. A rural
watershed model called Soil Water Assessment Tool (SWAT), developed
by the U.S. Department of Agriculture's Agricultural Research Service,
has been added to BASINS. It is anticipated that this model will be
widely used in agricultural watersheds. A third very simple model called
PLOAD has also been added. PLOAD is most applicable for screening
analyses. In addition, there is a new model postprocessor and scenario
generator called GenScn that allows users to manage, visualize, analyze,
and compare the results of several HSPF and/or SWAT simulations. Web
site is www.epa.gov/ostftasins.
A series of pollutant specific protocols has been developed by EPA to assist in
the development of TMDLs and implementation plans to achieve the TMDLs
(EPA, 1997d; 1999b; 1999c; 2001c). These protocols focus primarily on the
application of computer models that simulate watershed conditions and the
changes that could result from implementation of various land management
scenarios. Some models contain default values for the quantity of pollutants that
are delivered in runoff from various sources (e.g., cropland deliver X pounds of
nitrogen per acre per inch of runoff). These default values can generally be
replaced with better information that is available for a particular watershed.
Models should have functions that are intended to simulate the implementation
of management practices, enabling modelers to estimate changes due to a range
of land management options. Such models can be helpful tools for planning the
implementation of management measures to achieve water quality goals, but the
limitations of models and appropriate interpretation of modeling results should
be fully understood before implementation decisions are made. The application
of models to estimate pollutant loads is discussed further in Chapter 7.
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Chapter 5: Using Management Measures to Prevent and Solve Nonpoint Source Problems in Watersheds
Adaptive Management
Because many of the decisions made regarding the appropriate type, extent, and
location of management measures and practices are based upon estimates and
partial information, it is highly likely that changes will be needed. If progress is
monitored (see Chapter 6) adequately, managers and landowners will be able to
adjust implementation plans, schedules, and models as needed to ensure more
cost-efficient achievement of water quality objectives. One of the major findings
from the Rural Clean Water Program is that water quality monitoring can
provide valuable feedback for defining areas needing priority treatment (Gale et
al., 1993).
Preventing Unintended Adverse Environmental Effects
As noted in Chapter 2, this guidance does not address all environmental consid-
erations at a particular site or within a watershed. Resource management systems
(RMS) are more broad, yet planners and managers should even go beyond the
scope of an RMS to consider whether management measure or practice imple-
mentation at the site or watershed scale will have any unintended environmental
impacts. For example, methane generation from structures implemented to store
runoff and facility wastewater from confined animal facilities may be problem-
atic in certain areas. Alternatives to conventional storage structures might be
needed.
Similarly, extensive changes to water management could impact baseflows in
streams. Different configurations and design specifications for diversions and
storage devices might be able to provide needed water quality improvement
without causing negative impacts to baseflow patterns. Whole-farm planning
approaches such as those specified in Chapter 2 (e.g., Idaho One Plan) can go a
long way toward preventing these types of unintended environmental impacts at
the farm level, but potential watershed-wide or landscape-scale impacts need to
considered from a more global perspective.
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Estimating the Effectiveness of Management Measures and Management
Practice Systems
It is very difficult to estimate the effectiveness of management practice systems. Some researchers
have proposed that the effectiveness of management practice systems should be calculated by
adding the average relative effectiveness of individual practices. As an example of this approach,
assume a system to control sediment is composed of surface drainage, terraces, and conservation
tillage. Based upon data in the literature (Foster et al., 1996), the average sediment load reductions
achieved by these practices are 36% for surface drainage, 91% for terraces, and 69% for conserva-
tion tillage. Under this approach, the average pollutant load reduction for surface drainage is
subtracted from the total load of 100% (100% - 36% = 64%). Thus, 64% of the sediment remains
after surface drainage is accounted for. If terraces reduce sediment loads by 91%, then the remain-
ing pollutant load after surface drainage and terraces is about 6% (.64 x [1.00 - .91] = .058 = 5.8%).
The remaining practice in the system, conservation tillage, reduces sediment loads by 69%, result-
ing in a final sediment delivery of approximately 2% (.058 x [1.00 - .69] = .018 = 1.8%).
The Idaho RCWP project, however, demonstrated that the effectiveness of individual practices in a
system of practices are not additive. The effectiveness of some of the BMPs used in the project was
measured by the USDA-Agricultural Research Service, and the results are given in Table 5-1
(Maretetal., 1991).
Table 5-1. Sediment removal effectiveness of selected individual
BMPs used in the Snake River RCWP Project (Idaho).
Individual BMP
Sediment Basins
Mini-basin
Buried Pipe Systems
Vegetative Filters
Straw Mulch
Mean %
Effectiveness
87
86
83
50
50
% Effectiveness
Range
75-95
0-95
75-95
35-70
40-80
Sediment loads in the Idaho RCWP project were reduced by 75%. Even though the effectiveness of
only five of the nineteen BMPs used in the project was measured (Table 5-1), it can be seen that the
overall reduction of 75% would not have been estimated accurately by using the above approach in
which average effectiveness of practices was considered to be additive. Using the additive approach,
the sediment delivery would have been reduced to essentially zero if the mean effectiveness values
for the five practices in Table 5-1 were used in the analysis.
In summary, the aggregate effectiveness of any system of management practices is a function of not
only the mean effectiveness of individual practices, but also the interactions between the individual
practices within the range of site-specific conditions experienced.
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5-214 National Management Measures to Control Nonpoint Pollution from Agriculture
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Monitoring and Tracking
Techniques
Knowledge of land management activities and water quality conditions is
important in many ways to efforts involving implementation of management
measures and practices. As discussed in Chapter 5, the watershed planning
process includes an understanding of the hydrologic resources, an assessment of
environmental problems, goal setting, and priority setting. The development of
action plans and implementation follow, with evaluation of effectiveness and
revisions of plans as needed. Good water quality data are essential to problem
identification and characterization, goal setting, priority setting, development of
implementation plans, and evaluation. In order to have an understanding of what
goals have to be met, a baseline must be established. Without good data regard-
ing land management activities, including the control of point sources, accurate
interpretation of the causes of water quality problems and improvements is not
possible.
Water Quality Monitoring
Since the relationship between public health and water quality began to influ-
ence legislation in the early 1900s, water quality management and its related
information needs have evolved considerably. Today, the Intergovernmental Task
Force on Monitoring Water Quality (ITFM, 1995) defines water quality monitor-
ing as an integrated activity for evaluating the physical, chemical, and biological
character of water in relation to human health, ecological conditions, and
designated water uses. Water quality monitoring for nonpoint sources (NFS) of
pollution facilitates the important element of relating the physical, chemical, and
biological characteristics of receiving waters to land use characteristics. Without
current information on water quality conditions and pollutant sources, effects of
land-based activities on water quality cannot be assessed, effective management
and remediation programs cannot be implemented, and program success cannot
be evaluated.
The most fundamental step in the development of a monitoring plan is to define
the goals and objectives, or purpose, of the monitoring program. In general,
monitoring goals are broad statements such as "to measure improvements in
Hojnacki Creek" or "to verify nutrient load reductions into Stumpe Lake." In the
past, numerous monitoring programs did not document this aspect of the design
process and the resulting data collection efforts led to little useful information
for decision making (GAO, 1986; MacDonald et al., 1991; National Research
Council, 1986; Ward et al., 1990). As a result, the identification of monitoring
goals is the first component of the design framework outlined by the ITFM
(1995). Figure 6-1 presents one approach for developing a monitoring plan.
Monitoring programs can be grouped according to the following general pur-
poses or expectations (ITFM, 1995; MacDonald et al., 1991):
n Describing and ranking existing and emerging problems
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Chapter 6: Monitoring and Tracking Techniques
Figure 6-1. Development of a monitoring project (after MacDonald et al., 1991).
QA Planning
QA Implementation
&
QA Assessment
Define personnel and budgetary constraints
Define monitoring parameters,
sampling frequency, sampling location
and analytical procedures
Evaluate hypothetical
or. If available, real data
Will the data meet the
proposed monitoring objectives?
Yea
No
Revise the
objectives
or the
monitoring
procedures
Is the proposed monitoring
program compatible with
available resources?
Yes
No
Initiate monitoring activities on a pilot basis
Analyze and evaluate data
Does the pilot project meet
the monitoring objectives?
Yes
No
Continue monitoring and data analysis
Reports and recommendations
Revise
monitoring
plan as
needed
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Chapter 6: Monitoring and Tracking Techniques
d Describing status and trends
n Designing management and regulatory programs
n Evaluating program effectiveness
D Responding to emergencies
n Describing the implementation of best management practices
d Validating a proposed water quality model
D Performing research
The importance of problem identification can not be underestimated. The water
quality impairment (e.g., algal growth, sediment deposition, turbidity) must first
be documented. Second, the pollutant(s) causing the impairments should be
identified (e.g., nitrogen, phosphorus, soil erosion or streambank instability).
This information can be used to facilitate the identification of pollutant sources.
Water quality assessments and land use information are useful in identification
of pollutant sources.
Unlike monitoring goals, monitoring objectives are more specific statements that
can be used to complete the monitoring design process including scale, variable
selection, methods, and sample size (Plafkin et al., 1989; USDA-NRCS, 1996b).
Monitoring program objectives must be detailed enough to allow the designer to
define precisely what data will be gathered and how the resulting information
will be used. An example objective which would facilitate quantitative evalua-
tions is "To detect a decrease in total phosphorus loading to Stumpe Lake via
Hajnacki Creek by 50% over the next 6 years." Vague or inaccurate statements
of objectives lead to program designs that provide too little or too much data,
thereby failing to meet management needs or costing too much.
The remainder of the design framework outlined by the ITFM (1995) includes
coordination and collaboration, design, implementation, interpretation, evaluation
of the monitoring program, and communication. Numerous guidance documents
have been developed, or are in development, to assist resource managers in
developing and implementing monitoring programs that address all aspects of the
ITFM's design framework. Appendix A in Monitoring Guidance for Determining
the Effectiveness of Nonpoint Source Controls (EPA, 1997a) presents a review of
more than 40 monitoring guidances for both point and NPS pollution. These
guidances discuss virtually every aspect of NPS pollution monitoring, including
monitoring program design and objectives, sample types and sampling methods,
chemical and physical water quality variables, biological monitoring, data
analysis and management, and quality assurance and quality control.
Once the monitoring goals and objectives have been established, existing data
and constraints should be considered. A thorough review of literature pertaining
to water quality studies previously conducted in the geographic region of interest
should be completed before starting a new study. The review should help
determine whether existing data provide sufficient information to address the
monitoring goals and what data gaps exist.
Identification of project constraints should address financial, staffing, and
temporal elements. Clear and detailed information should be obtained in the
time frame within which management decisions need to be made, the amounts
and types of data that must be collected, the level of effort required to collect the
Appendix A in
Monitoring Guidance
for Determining the
Effectiveness of
Nonpoint Source
Controls (EPA,
1997a) presents a
review of more than
40 monitoring
guidances for both
point and NPS
pollution.
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Chapter 6: Monitoring and Tracking Techniques
necessary data, and equipment and personnel needed to conduct the monitoring.
From this information it can be determined whether available personnel and
budget are sufficient to implement or expand the monitoring program.
As with monitoring program design, the level of monitoring that will be con-
ducted is largely determined when goals and objectives are set for a monitoring
program, although there is some flexibility for achieving most monitoring
objectives. Table 6-1 provides a summary of general characteristics of various
types of monitoring.
The overall scale of a monitoring program has two components—a temporal
scale and a geographic scale. The temporal scale is the amount of time required
to accomplish the program objectives. It can vary from an afternoon to many
years. The geographic scale can also vary from quite small, such as plots along a
single stream reach, to very large, such as an entire river basin. The temporal and
geographic scales, like a program's design and monitoring level, are primarily
determined by the program's objectives.
If the main objective is to determine the current biological condition of a stream,
sampling at a few stations in a stream reach over 1 or 2 days might suffice.
Similarly, if the monitoring objective is to determine the presence or absence of
a NFS impact, a synoptic survey might be conducted in a few select locations. If
the objective is to determine the effectiveness of a nutrient management program
for reducing nutrient inputs to a downstream lake, however, monitoring a
subwatershed for 5 years or longer might be necessary. Collection of baseline
information prior to implementation of improved management practices is
important so that an improvement can be quantified. If the objective is to cali-
brate or verify a model, more intensive sampling might be necessary.
Depending on the objectives of the monitoring program, it might be necessary to
monitor only the waterbody with the water quality problem or it might be
Table 6-1. General characteristics of monitoring types (Mac Dona Id et al., 1991).
Type of
Monitoring
Trend
Baseline
Implementation
Effectiveness
Project
Validation
Compliance
Number and Type
of Water Quality
Parameters
Usually water
column
Variable
None
Near activity
Variable
Few
Few
Frequency of
Measurements
Low
Low
Variable
Medium to high
Medium to high
High
Variable
Duration of
Monitoring
Long
Short to
medium
Duration of
project
Usually short
to medium
Greater than
project duration
Usually medium
to long
Dependent on
project
Intensity of
Data Analysis
Low to
moderate
Low to
moderate
Low
Medium
Medium
High
Moderate to
high
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Chapter 6: Monitoring and Tracking Techniques
necessary to include areas that have contributed to the problem in the past, areas
containing suspected sources of the problem, or a combination of these areas. A
monitoring program conducted on a watershed scale must include a decision
about a watershed's size. The effective size of a watershed is influenced by
drainage patterns, stream order, stream permanence, climate, number of land-
owners in the area, homogeneity of land uses, watershed geology, and geomor-
phology. Each factor is important because each has an influence on stream
characteristics.
There is no formula for determining appropriate geographic and temporal scales
for any particular monitoring program. Rather, once the objectives of the moni-
toring program have been determined, a combined analysis of them and any
background information on the water quality problem being addressed should
make it clear what overall monitoring scale is necessary to reach the objectives.
Other factors that should be considered to determine appropriate temporal and
geographic scales include the type of water resource being monitored and the
complexity of the NFS problem. Some of the constraints mentioned earlier, such
as the availability of resources (staff and money) and the time frame within
which managers require monitoring information, will also contribute to determi-
nation of the scales of the monitoring program.
For additional details regarding NFS monitoring techniques, including chemical
and biological monitoring, the reader is referred to Monitoring Guidance for
Determining the Effectiveness ofNonpoint Source Controls (EPA, 1997a). This
technical document focuses on monitoring to evaluate the effectiveness of
management practices, but also includes approximately 300 references and
summaries of more than 40 other monitoring guides. In addition, Chapter 8 of
EPA's management measures guidance for Section 6217 contains a detailed
discussion of monitoring with emphasis on coastal areas (EPA, 1993a). Another
useful reference for monitoring design is the National Handbook of Water
Quality Monitoring (USDA-NRCS, 1996b).
Tracking Implementation of Management
Measures
The implementation of management measures may be tracked to determine the
extent to which management measures are implemented in a watershed, recharge
area, or other geographic area.
Implementation and trend monitoring can be used to address the following goals:
O Determine the extent to which management measures and practices are
implemented in accordance with relevant standards and specifications.
[] Determine whether there has been a change in the extent to which
management measures and practices are being implemented.
G Establish a baseline from which decisions can be made regarding the
need for additional incentives for implementation of management
measures,
O Measure the extent of voluntary implementation efforts,
See EPA's
Monitoring Guidance
for Determining
Effectiveness of
Nonpoint Source
Controls for details
on NPS monitoring
techniques.
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Chapter 6: Monitoring and Tracking Techniques
£J Support work-load and costing analyses for assistance or regulatory
programs,
O Determine the relative adoption rates of various management measures
across different geographic areas,
O Determine the extent to which management measures are properly
maintained and operated.
Methods to assess the implementation of management measures are a key focus
of technical assistance provided by EPA and NOAA.
Implementation assessments can be performed on several scales. Site-specific
assessments can be used to assess individual management measures or practices,
and watershed assessments can be used to look at the cumulative effects of
implementing multiple management measures. With regard to "site-specific"
assessments, individual practices must be assessed at the appropriate scale for
the practice of interest. For example, to assess the implementation of manage-
ment measures and practices for animal waste handling and disposal on a farm,
only the structures, areas, and practices implemented specifically for animal
waste management (e.g., dikes, diversions, storage ponds, composting facility,
and manure application records) would need to be inspected. In this instance, the
animal waste storage facility would be the appropriate scale and "site." To assess
erosion control, the proper scale might be fields over 10 acres and the site could
be 100-meter transect measurements of crop residue. For nutrient management,
the scale and site might be an entire farm. Site-specific measurements can then
be used to extrapolate to a watershed or statewide assessment. It is recognized
that some studies might require a complete inventory of management measures
and practice implementation across an entire watershed or other geographic area.
Sampling design, approaches to conducting the evaluation, data analysis tech-
niques, and ways to present evaluation results are described in EPA's Techniques
for Tracking, Evaluating, and Reporting the Implementation ofNonpoint Source
Control Measures - Agriculture (EPA, 1997b). Chapter 8 of EPA's management
measures guidance for Section 6217 contains a detailed discussion of techniques
and procedures to assess implementation, operation, and maintenance of man-
agement measures (EPA, 1993a).
Determining Effectiveness of
Implemented Management Measures
By tracking management measures and water quality simultaneously, analysts
will be in a position to evaluate the performance of those management measures
implemented. Management measure tracking will provide the necessary informa-
tion to determine whether pollution controls have been implemented, operated,
and maintained adequately. Without this information, analysts will not be able to
fully interpret their water quality monitoring data. For example, analysts cannot
determine whether the management measures have been effective unless they
know the extent to which these controls were implemented, maintained, and
operated.
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Chapter 6: Monitoring and Tracking Techniques
A major challenge in attempting to relate implementation of management
measures to water quality changes is determining the appropriate land manage-
ment attributes to track. For example, a "bean count" of the number of manage-
ment measures implemented in a watershed has little chance of being useful in
statistical analyses that relate water quality to land treatment since the count will
be only remotely related (i.e., a mechanism is lacking) to the measured water
quality parameter (e.g., phosphorus concentration). Land treatment and land use
monitoring should relate directly to the pollutants or impacts monitored at the
water quality station (Coffey and Smolen, 1990). For example, the tons of
animal waste managed may be a much more useful parameter to track than the
number of confined animal facilities constructed. Since the impact of manage-
ment measures on water quality may not be immediate or implementation may
not be sustained, information on other relevant watershed activities (e.g., urban-
ization, growth in animal numbers) will be essential for the final analysis.
Figure 6-2. Land treatment and water quality monitoring program design (Coffey et al., 1995).
Define monitoring objective
Determine experimental design
WATER QUALITY
LAND TREATMENT
Locate treatment and
control (or reference)
monitoring sites
Develop a land treatment
tracking system for each
subwatershed draining
to a water quality
monitoring site
Gather baseline water
quality (2 years)
Gather baseline,
land treatment, and land
use data
Link water quality and land
treatment data bases
Continued water quality
monitoring during treatment
Start land treatment
Monitor post-implementation
water quality (2-5 years)
Continued tracking of land
treatment and land use
Link water quality and land
treatment data bases
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Chapter 6: Monitoring and Tracking Techniques
Water quality and land treatment monitoring must be coordinated to maximize
the chance of meaningful results. In order to provide the manager with a sense of
the nature of the coordination needed, an overview of monitoring program
design is provided in Figure 6-2.
Monitoring program design, as shown in Figure 6-2, begins by defining the
monitoring objective. Once the objective is defined, the experimental design
(e.g., upstream/downstream, pre- and post-BMP, and paired watershed) is
determined. Based on the experimental design, separate but coordinated parallel
water quality and land treatment activities are specified.
Appropriately collected water quality information can be evaluated with trend
analysis to determine whether pollutant loads have been reduced or whether
water quality has improved. Valid statistical associations drawn between imple-
mentation and water quality data can be used to indicate:
(1) Whether management measures have been successful in improving
water quality in a watershed or recharge area, and
(2) The need for additional management measures to meet water quality
objectives in the watershed or recharge area.
Greater detail regarding methods to evaluate the effectiveness of land treatment
efforts can be found in EPA's NPS monitoring guidance (EPA, 1997a) and
management measures guidance for section 6217 (EPA, 1993a).
Quality Assurance and Quality Control
Introduction
Quality assurance (QA) and quality control (QC) are commonly thought of as
procedures used in the laboratory to ensure that all analytical measurements
made are accurate. Yet QA and QC extend beyond the laboratory and are essen-
tial components of all phases and all activities within each phase of a NPS
monitoring project. This section defines QA and QC, discusses their value in
NPS monitoring programs, and explains EPA's policy on these topics. The
following sections provide detailed information and recent references for
planning and ensuring quality data and deliverables that can be used to support
specific decisions involving NPS pollution.
Definitions of Quality Assurance and Quality Control
Quality assurance is
an integrated system of management procedures and
activities used to verify that the quality control system is
operating within acceptable limits and to evaluate the
quality of data (Taylor, 1993; EPA, 1994a).
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Chapter 6: Monitoring and Tracking Techniques
Quality control is
a system of technical procedures and activities developed
and implemented to produce measurements of requisite
quality (Taylor, 1993; EPA, 1994a).
Quality control procedures include proper collection, handling, and storage of
samples; analysis of blank, duplicate, and spiked samples; and use of standard
reference materials to ensure the integrity of analyses. QC procedures also
include regular inspection of equipment to ensure proper operation. Quality
assurance activities are more managerial in nature and include assignment of
roles and responsibilities to project staff, staff training, development of data
quality objectives, data validation, and laboratory audits. Table 6-2 lists some
common activities that fall under the headings of QA and QC. Such procedures
and activities are planned and executed by diverse organizations through care-
fully designed quality management programs that reflect the importance of the
work and the degree of confidence needed in the quality of the results.
Table 6-2. Common quality management activities (adapted from Drouse et al., 1986, and Erickson et al., 1991).
Quality Assurance
Organization of project into component parts
Assignment of roles and responsibilities to project staff
Use of statistics to determine the number of samples and sampling sites needed to obtain
data of a required confidence level
Tracking of sample custody from field collection through final analysis
Development and use of data quality objectives to guide data collection efforts
Audits of field and laboratory operations
Maintenance of accurate and complete records of all project activities
Personnel training to ensure consistency of sample collection techniques and equipment use
Quality Control
Collection of duplicate samples for analysis
Analysis of blank and spike samples
Replicate sample analysis
Regular inspection and calibration of analytical equipment
Regular inspection of reagents and water for contamination
Regular inspection of refrigerators, ovens, etc. for proper operation
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Chapter 6: Monitoring and Tracking Techniques
Importance of Quality Management Programs
Although the value of a quality management program might seem questionable
while a project is under way, its value should be quite clear after a project is
completed. If the objectives of the project were used to design an appropriate
data collection and analysis plan, all procedures were followed for all project
activities, and accurate and complete records were kept throughout the project,
the data and information collected from the project will be adequate to support a
choice from among alternative courses of action. In addition, the course of
action chosen will be defensible based on the data and information collected.
Development and implementation of a quality management program can require
up to 10 to 20% of project resources (Cross-Smiecinski and Stetzenback, 1994),
but this cost can be recaptured in lower overall costs due to the project's being
well planned and executed. Likely problems are anticipated and accounted for
before they arise, eliminating the need to spend countless hours and dollars
resampling, reanalyzing data, or mentally reconstructing portions of the project
to determine where an error was introduced. QA procedures and QC activities
are cost-effective measures used to determine how to allocate project energies
and resources toward improving the quality of research and the usefulness of
project results (Erickson et al., 1991).
EPA Quality Policy
EPA has established a quality policy that requires the implementation of a
quality system by EPA and by non-EPA organizations receiving financial assis-
tance from EPA to ensure that data used in research and monitoring are of
known and documented quality to satisfy project objectives. A quality system is
developed by an organization and documented in writing. The system provides
the policies, objectives, responsibilities, and procedures to be followed to ensure
the quality of work processes, services, or products. A quality system is typically
documented in a quality management plan (QMP). When conducting monitoring
or tracking the implementation of management measures by collecting environ-
mental data, site-specific written plans are needed to describe the quality objec-
tives (acceptance or performance criteria) to be met so that the data can be used
to support the particular decision(s) for which the data are being collected. Such
site-specific plans are known as quality assurance project plans (QAPPs). The
use of different methodologies, lack of data comparability, unknown data
quality, and poor coordination of sampling and analysis efforts can delay the
progress of a project or render the data and information collected from it insuffi-
cient for decision making. Whether or not EPA funding is involved, quality
practices should be used as an integral part of the development, design, and
implementation of an NPS monitoring project to minimize or eliminate these
problems (Erickson et al., 1991; Pritt and Raese, 1992; EPA, 1997a).
Additional information on developing quality programs can be found in EPA
publications (e.g., EPA, 2000; 2001a, b;), available on the Internet at http://
www.epa.gov/quality/qa_tools.html.
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Chapter 7: Load Estimation Techniques
pollutants such as fecal coliform can vary by several orders of magnitude during
a week depending on hydrologic and other conditions. The vast majority of
nonpoint source load estimations will require storm event sampling. The choice
of sampling frequency for load estimation is a complex function of watershed
hydrology, pollutant(s) of interest, land use/management, the duration of moni-
toring and the water resource type. Periodic measurements in the field (in situ or
sample analysis with a field kit) or laboratory measurements performed on
collected water samples are typically used to provide the pollutant concentration
values that will be used in load estimation.
Water sampling approaches have been categorized in several ways, some based
more upon the equipment used, and others based more upon the statistical design
employed (USDA-NRCS, 1996b; EPA, 1979; EPA, 1991c). Grab, point, com-
posite, integrated, continuous, random, systematic, and stratified sampling are
frequently described in the literature. In practice, sampling involves a decision
regarding the population and population units to be sampled (e.g., instantaneous
concentration at single point or integrated over depth, average concentration at
single point or integrated over depth for a specified time interval or flow inter-
val), a determination of the statistical approach to be used (e.g., simple random
sampling, stratified random sampling, systematic sampling), and a choice of
sampling equipment and configuration (e.g., grab sample taken manually or
automatically with a mechanical sampler, time-weighted or flow-weighted
sampling with a programmed mechanical sampler).
For any given watershed, the best approach for estimating loads will be deter-
mined based upon the needs and characteristics of the watershed. Still, some
general rules-of-thumb should be considered (USDA-NRCS, 1996b; Richards,
1997).
G Accuracy and precision increase with increased frequency of sam-
pling.
G Grab, Point, or Instantaneous Samples — may be insufficient to
determine loads unless concentrations are correlated to discharge which
is measured continuously.
G Depth-Integrated and Width-Integrated Grab Samples — can
account for stratification in concentration with depth or horizontally
across a stream, but still depends upon correlation to discharge for
suitability in load estimation.
G Time-Weighted Composite Samples — not generally sufficient for
load estimation since they may not adequately reflect changes in dis-
charge and concentration during the period over which samples are
composited.
G Flow-Weighted Composite Samples — well-suited to load estimation,
but difficult to collect since stage-discharge relationship is needed and a
"smart sampler" is needed to trigger sampling as a function of flow rate.
Projecting sample size and number of bottles needed is difficult.
G Systematic Sampling — as efficient as, or more efficient than, simple
random sampling if the sampling interval is not equal to a multiple of
any strong period of fluctuation in the sampled population (e.g., sam-
pling weekly on the day when a particular pollutant is always at its peak
level due to scheduling by a discharger).
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Chapter 7: Load Estimation Techniques
Stratified Random Sampling — with most samples taken during
periods of high flow, can be of great importance in providing increased
precision for a given number of samples.
Types of Water Samples
Grab Sample — A single sample taken at one place a single
time.
Composite Sample — A series of grab samples, usually
collected in the same location but at different times, combined to
form one sample for analysis. Composite samples are usually:
Flow-Weighted - Sample is taken after a specified quantity of
water has passed the monitoring station (e.g., draw 10 ml sample
every 750,000 liters of flow); or
Time-Weighted - A pre-determined sample volume is taken at a
predetermined time interval (e.g., draw 10 ml sample every 15
minutes).
Integrated Sample — Subsamples are taken at various depths or
distances from the stream bank, and integrated into a single
sample.
Continuous Sample — Probes are used to continuously record
contaminant concentration in stream. Not widely applicable to
nonpoint source programs.
For many TMDLs, the daily pollutant load may be the population unit of great-
est importance. In these cases, sampling should emphasize obtaining accurate
estimates of daily loads for the pollutant of interest. Since TMDLs establish
maximum wasteload and load allocations that can be discharged without violat-
ing water quality standards, the monitoring effort should provide the data
necessary for determining whether or not quality standards are met. For ex-
ample, if water quality standards are more likely violated under low-flow (dry
weather) conditions, then the monitoring should provide reliable data regarding
low-flow loads. Conversely, in cases where water quality standards are violated
during high-flows (wet weather or snowmelt) or as a result of loads from high
flows, the monitoring should emphasize high-flow monitoring. In other cases,
such as those in which annual or seasonal loads are critical, high quality esti-
mates of low-flow and high-flow loads may be equally important.
Sampling location should be determined based upon the monitoring objectives,
water resource characteristics, and source characteristics. For example, it may be
appropriate to sample at the outlets of tributaries to a lake, or above and below a
farm or set of farms, depending upon whether the objective is to estimate lake
loading from tributary watersheds or stream loading from an individual farm or
farms. Additional information regarding sampling location can be found in
existing guides (EPA, 1997a; USDA-NRCS, 1996b; Ponce, 1980).
Detailed discussions of statistical sampling approaches (e.g., random sampling)
can be found in several sources (EPA, 1997a; Richards, 1997; USDA-NRCS,
1996b; Gilbert, 1987). Older sampling equipment is described by Brakensiek, et
al. (1979), while USDA-NRCS (1996b) provides an overview of more current
devices, including a helpful list of references regarding sampling equipment.
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Calculating Pollutant Loads
The pollutant load is the integral of flux over time, but flux cannot be measured
directly (Richards, 1997). In Figure 7-1 the flux is calculated as the product of
concentration and discharge, with appropriate conversion units. Each calculated
flux is a discrete value that is assumed to apply across the sampling interval,
which is 24 hours in this hypothetical example (daily composites). The cumula-
tive load in Figure 7-1 is determined by adding the calculated fluxes over all
sampling intervals.
Because there will be more discharge data than concentration data in almost all
chemical monitoring efforts, there will be a need to make estimates of concentra-
tion, and therefore pollutant flux, for periods between water quality observations
(Richards, 1997). Figure 7-2 illustrates how missing values can greatly affect the
calculated load estimates. Load A is the same load as shown in Figure 7-1,
whereas Load B was calculated after deleting every other concentration value
used to calculate Load A.
Data gaps can be filled by estimating missing concentration values for pairing
with the flow data, or by adjusting the load estimate made from the observations
where both flow and concentration were measured (Richards, 1997). Flow data
typically form the basis for making flux estimates for periods during which
water quality (concentration) data are lacking.
Some of the methods for estimating pollutant loads include numeric integration,
the worked record procedure, averaging approaches, the flow interval technique,
ratio estimators, regression approaches, and flow-proportional sampling
(Richards, 1997). A review of evaluative studies of loading approaches has
resulted in the following points of consensus (Richards, 1997):
O Averaging methods (e.g., for monthly or quarterly loads) are generally
biased, and the bias increases as the size of the averaging window
increases and/or the number of samples decreases. For example, an
annual load determined by adding four quarterly loads will generally be
Figure 7-1. Flux and cumulative load overtime.
Load (tons)
Pollutant
Concentration
Stream Discharge
(cfs)
Flux (Ib/min)
Time —>
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Chapter 7: Load Estimation Techniques
Figure 7-2. Effect of missing concentration data.
Load A (tons)
• Load B (tons)
I—I Discharge (cfs)
more biased than an annual load determined by adding 12 monthly
loads.
n In most studies, ratio approaches performed better than regression
approaches, and both performed better than averaging approaches.
G Regression approaches can perform well if the relationship between
flow and concentration is well-defined, linear throughout the range of
flows, and constant throughout the year.
Greater detail and illustrative examples regarding averaging approaches, regres-
sion approaches, ratio estimators, and sampling approaches can be found in
Richards (1997).
Water runoff,
sediment delivery,
and nutrient loading
can be estimated
using watershed
models. Match
modeling objectives,
staff expertise, data
requirements, and
available budget for
proper model
selection.
Estimating Pollutant Loads Through Modeling
Types of Models Available
Loading models include techniques primarily designed to predict pollutant
movement from the land surface to waterbodies (EPA, 1997d). Watershed
loading models range from simple loading rate assessments in which loads are a
function of land use type only, to complex simulation techniques that more
explicitly describe the processes of rainfall, runoff, sediment detachment, and
transport to receiving waters. Some loading models operate on a watershed
scale, integrating all loads within a watershed, and some allow for the subdivi-
sion of the watershed into contributing subbasins.
Field-scale models, which have traditionally specialized in agricultural systems,
are loading models that are designed to operate on a smaller, more localized
scale. Field-scale models have often been employed to aid in the selection of
management measures and practices. For example, a dynamic simulation model
was used to predict the long-term patterns of phosphorus export from fields
under a variety of management scenarios (Cassell and Clausen, 1993). The
process model simulated the annual inputs and outputs of phosphorus, and was
determined by the authors to be useful for simulating long-term patterns. Process
models such as this one, however, are dependent upon local export coefficients
and a thorough understanding of pollutant transport processes.
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Chapter 7: Load Estimation Techniques
Methods for Estimating Pollutant Loads (Richards, 1997)
Numeric Integration — Total load is calculated as the sum of the individual loads calculated for
each sample.
Worked Record Procedure — Chemical observations are plotted onto a detailed hydrograph, and
smooth curves are drawn through chemical data points based upon analyst's experience with the
relationship of concentration and flow.
Averaging Approaches — Calculation that uses averaging of concentration and/or flow to
estimate loads. For example, analyst might multiply average weekly suspended solids
concentration by daily flow to estimate daily loads for the week.
Flow Interval Technique — Semi-graphical technique that calculates "interval loads" as the
product of average flux for a range of daily flow values times the number of days in which flows
were within the particular flow range.
Ratio Estimators — Total loads are estimated using a known relationship between the less-
frequently sampled parameter of interest and a more-frequently sampled parameter (e.g.,
discharge) to fill gaps in the data record for the parameter of interest.
Regression Approaches — Relationship is established between concentration and flow based on
samples taken, and then applied to estimate concentration for days not sampled.
Flow-Proportional Sampling — Mechanical approach in which representative samples are taken
to determine concentration for a known discharge. Pollutant load is calculated as the sum of the
sample concentrations multiplied by the measured discharge.
Other types of models include receiving-water models, which emphasize the
response of a waterbody to pollutant loadings, flows, and ambient conditions,
and ecological models that simulate biological communities and their response
to stressors such as toxics and habitat modification (EPA, 1997d). Integrated
modeling systems link models, data, and a user interface within a single system.
The advent of geographic information systems (GIS) has facilitated the develop-
ment of and expanded the capabilities of integrated modeling systems.
The emphasis of this section will be on watershed loading models. The reader is
encouraged to seek additional information regarding field-scale, ecological, and
integrated models in existing documents (EPA, 1997d; EPA, 1992b). The reader
can also consult Chapter 5 of this manual for information on field- and water-
shed-scale models.
Watershed Loading Models
Watershed loading models are configured and characterized in several ways (see
Modeling Jargon), but they can be grouped into three general categories: simple
methods, mid-range models, and detailed models (EPA, 1997d). The defining
characteristics of models are the degree to which processes (and complexities of
systems) are simplified and the time scale that is used for analysis and display of
output information.
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Chapter 7: Load Estimation Techniques
Simple methods are generally used to provide quick and easy identification of
critical pollutant sources in the watershed. Detailed watershed models represent
the other extreme, featuring costly and time-consuming efforts to provide
quantitative estimates of pollutant loads from a range of management alterna-
tives. Richards (1997) cautions that modeling of agricultural settings is often
inadequate to evaluate the success of management practices in reducing loads
because there are mixed land uses that change annually and these land uses have
different loading rates. An additional concern is that most models fail to ad-
equately address stream channel and bank dynamics, including the impact of
management practices on these factors. Some detailed models such as
GLEAMS, however, attempt to capture the variability associated with cropping
practices and rotations in the agricultural setting.
Mid-range watershed models are generally midway between the cost, complex-
ity, and accuracy of simple methods and detailed watershed models. Mid-range
models provide qualitative estimates of management alternatives (EPA, 1997d).
Figure 7-3 shows examples of models and integrated modeling systems for load
estimation. EPA's Compendium of Tools for Watershed Assessment and TMDL
Development has additional details regarding the capabilities, limitations, and
data requirements for these and other models (EPA, 1997d).
Simple Watershed Methods
Uses
d Support assessment of relative significance of sources
n Guide decisions for management plans
D Focus continuing monitoring efforts
Features
n Typically derived from empirical relationships between physiographic characteristics of the
watershed and pollutant export
G Often applied using a spreadsheet or hand-held calculator
Pros
O Rapid
CJ Minimal data requirements (large-scale aggregation; low resolution)
n Minimal effort
Cons
O Output is typically mean annual values or storm loads
G Rough estimates of loadings
n Very limited predictive capability
D Low transferability to other regions due to empirical basis
D Do not consider degradation and transformation processes
n Few incorporate detailed representation of pollutant transport within and from watershed
n Cannot adequately account for most management practices
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Chapter 7: Load Estimation Techniques
Figure 7-3. Load estimation models.
Simple Methods
EPA Screening
Simple Method
Regression Method
SLOSS-PHOSPH
Federal Highway
Administration Model
Watershed Mangement
Model
Field-Scale Loading Models
• CREAM/GLEAMS
• Opus
• WEPP
Mid-Range Models
SITEMAP
GWLF
Urban Catchment Model
Automated Q-ILLUDAS
AnnAGNPS
SLAMM
Detailed Models
STORM
DR3M-QUAL
SWRRBWQ
SWMM
HSPF
Integrated Modeling Systems
PC-VIRGIS
WSTT
LWMM
GISPLM
BASINS
Mid-Range Watershed Models
Uses
D Assist in defining target areas for pollution mitigation programs on watershed basis
O Support relative comparisons of management alternatives
Features
n Compromise between empiricism of simple methods and complexity of detailed mechanistic models
• Use simplified relationships for the generation and transport of pollutants
• Greater reliance on site-specific data than for simple methods
• Can address land use patterns and landscape configurations in watersheds
O Typically require some calibration with additional data sets
n Often tailored to site-specific applications (e.g., agriculture only)
Pros
n Can assess seasonal or inter-annual variability of loadings, and long-term water quality trends
n Those with continuous simulation can compare storm-driven loads over a range of storm events
or conditions
n Those with GIS interface facilitate parameter estimation
D Relatively broad range of regional applicability
O Usually include detailed input-output features to simplify processing
D Often have built-in graphical and statistical capabilities
Cons
d Use of simplifying assumptions can limit accuracy of predictions
O Most do not consider degradation and transformation processes
D Few incorporate detailed representation of pollutant transport within and from watershed
D Can not account for most management practices
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Chapter 7: Load Estimation Techniques
Detailed Watershed Models
Uses
G If properly applied, can provide accurate estimates of pollutant loads and impacts on water
G Identify causes of problems rather than simply describing overall conditions
Features
G Use storm event or continuous simulation to predict flow and pollutant concentrations for a range
of flow conditions (small calculation time steps)
n Algorithms more closely simulate the physical processes of infiltration, runoff, pollutant accumula-
tion, instream effects, and ground/surface water interaction
Pros
G Input/output have greater spatial and temporal resolution than simple and mid-range models
D Detailed hydrologic simulations can be used to design potential control actions
G Linkage to biological modeling is possible
G Those with new interfaces and GIS linkages facilitate use of models
G Provide relatively accurate predictions of variable flows and water quality at any point in a water-
shed if properly applied and calibrated
Cons
H Considerable time and expenditure required for data collection and model application
G Complex — not easily utilized by untrained staff
G Require rate parameters for flow velocities, settling, decay, and other processes
G Input data file preparation and calibration require professional training and adequate resources
Planning and Selection of Models
Setting modeling objectives should be the first step in developing a modeling
approach. In some cases, the objectives may be achievable using a simple model,
but in other cases it may be necessary to perform complex modeling involving
more than one model. Criteria that apply in selecting a model may include the
value of the resource under consideration, data needs, hardware needs, cost,
accuracy required, type of pollutants/stressors, management considerations such
as long-term commitment to the modeling effort, availability of trained person-
nel, user experience with the model, and acceptance of the model (EPA, 1997d).
It is also important in many cases to involve stakeholders from the outset of
modeling exercises to increase the potential for broad acceptance of modeling
results.
The following steps can be used to define the modeling approach (EPA, 1997e):
1. Use available information to develop a good understanding of watershed
characteristics, watershed problems, and watershed hydrology.
2. Consult with program and project managers to develop a clear under-
standing of project needs and modeling objectives.
3. Select a model or models that best meet the project needs and modeling
objectives.
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Chapter 7: Load Estimation Techniques
4. Choose the processes to be simulated and the level of complexity, and
focus on
the processes that govern the problems of concern.
5. Segment the watershed to the desired degree of complexity including the
number of sub water sheds, reaches, and land use categories.
6. Choose a simulation process such as single-event or continuous simula-
tion based upon the specified modeling objectives and the system being
modeled.
7. Select the time step and imulation time frame necessary to meet the
modeling
objectives.
Modeling Jargon
Terms You Should Know When Communicating With Modelers
Deterministic models — Mathematical relationships based on physical or mechanistic
processes are represented in the model. For example, runoff output is produced in response
to precipitation input.
Empirical models — Mathematical relationships in the model (i.e., coefficients for
parameters) are based upon measured data rather than theoretical relationships. Must be
calibrated.
Steady-state models — Mathematical model of fate and transport that uses constant values
of input variables to predict constant values (e.g., receiving water quality concentrations).
Dynamic models — Mathematical model describing the physical behavior of a system or
process and its temporal variability.
Hydrodynamic models — Mathematical model that describes circulation, transport, and
deposition processes in receiving waters.
Physical models — The building of a scale model of the system and testing it.
Distributed parameter models — Incorporate the influences of the spatially variable,
controlling parameters (e.g., topography, soils, land use) in a manner internal to its
computational algorithms (EPA, 1982b). Allows simultaneous simulation of conditions at all
points within the watershed. Also facilitates incorporation of equations that represent unique
processes that occur at only specific points in the watershed.
Lumped parameter models — Use average values for characterizing the influence of
specific, non-uniform distributions of each parameter (e.g., soil type, cover, slope steepness).
Calibrated models — Require calibration with measured data for each site-specific
application.
"Uncalibrated" or measured-parameter models — Can be used without calibration. Use
measured or estimated parameters.
Event-based simulation — Modeling of individual storms. Does not simulate, or account for,
periods between storms.
Annualized — Modeling of a longer time series than individual storms. Event-based model
outputs can be annualized.
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Chapter 7: Load Estimation Techniques
8. Design a model calibration and validation process, including data
requirements.
9. Evaluate the assumptions and limitations of the modeling approach.
10. Develop a post-processing data analysis and data interpretation plan.
For applications to nonpoint source problems, the key features of nonpoint
sources of pollution need to be fully considered, including but not limited to the
following:
1. Hydrology (i.e., rainfall, snowmelt, and sometimes irrigation) drives the
process.
2. Pollutant sources are land-based and distributed, with pollutant loads
often highly variable in both space and time.
3. Land use types range from highly urbanized to undisturbed forest.
4. Management measures and practices vary from non-structural (e.g.,
nutrient management) to structural (e.g., waste storage ponds).
5. Land management and land cover change over time, including seasonal
fertilization, tillage, crop growth, road maintenance, and off-season
inactivity.
Additional considerations and details regarding modeling approach, model
selection, and data requirements can be found in existing guidance documents
(EPA, 1997d; EPA, 1985).
Model Calibration and Validation
The analyst must evaluate how the model will be used to address management or
future conditions- The adequacy of the calibration and validation can be evalu-
ated based on consideration of the type of changes expected to occur, the types
of management expected, and the loading and assimilation processes that
dominate the system. In some cases, changes in land use distribution can be
modeled well by a calibrated system. In other cases, a new land use, such as a
new crop, may require that supplemental calibration be performed to account for
its unique features. Detailed discussions of model calibration and validation
steps and procedures can be found in existing documents (EPA, 1997d; EPA,
1993b; EPA, 1989b; EPA, 1985; ASCE, 1993; Haan et al., 1995; Donigian,
1983).
A very important consideration in estimating nonpoint source loads is the quality
and representativeness of the water quality data used in model calibration. A
water quality data set that does not include a representative sample of high-flow
events is unlikely to yield a calibration that is relevant to the concern addressed
in the modeling effort. For example, if the goal is to determine the extent to
which phosphorus loads are reduced through the implementation of management
measures in a watershed dominated by agricultural nonpoint source impacts, it is
important that runoff conditions are represented adequately in the calibration.
It is also important that the water quality data used in model calibration cover
the same range of wet and dry conditions that are to be used in model validation
and prediction. For example, measured loads to New York's Owasco Lake were
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greater than estimates generated by a simple unit-area
loading method due largely to the fact that the measured
loads were based on sampling during wet years (Heidtke
and Auer, 1993). The simple model used in this example
does not explicitly represent rainfall runoff processes,
and is therefore very sensitive to the conditions under
,. . .. . , , , A ,. f_ . f, ,. ff. with an independent data set (without further
which it is developed. An adjustment of loading coeffi- adjustment)
cients based upon data from the wet years would likely
result in over-prediction of long-term average annual
loads.
Successful model validation should not be blindly
Calibration — process of adjusting model
input parameters to cause mode! output
values to more closely agree with
corresponding observed values.
Validation — comparison of model results
Verification — examination of the numerical
technique in the computer code to ascertain
that it truly represents the conceptual model
and that there are not inherent numerical
interpreted to prove that a model has predictive capabili-
ties. In some cases, the calibration and validation data
sets may come from the same period prior to implementation of control mea-
sures and practices. For example, if a data set from a period prior to implementa-
tion of measures or practices is arbitrarily split in half, with half of the data used
for calibration and the other half used for validation, then validation merely
confirms that the model can represent conditions prior to implementation of
controls. If the measures and practices are intended to change pollutant loads
through source reduction, delivery reduction, and/or runoff attenuation, then
post-implementation water quality and flow may (and are expected to) respond
very differently to precipitation events as compared to pre-implementation
conditions. Thus, the model has not really been proven as a predictive tool
because the ability to forecast a change in water quality and flow has not been
tested with a data set that reflects the changed response to precipitation. Even if
the calibration and validation data sets are determined to be independent through
statistical analyses, the predictive capabilities are not proven through successful
validation unless the validation data set is derived from or reflects conditions of
the modeled "future" condition. This is not to say, however, that validation is not
important. Successful validation will increase the credibility of modeling results,
but the results must be interpreted with care.
Model Calibration and Validation
A good calibration using bad data is a bad calibration.
D Ensure that the water quality data used in the calibration and validation process are
representative of the true distribution of water quality conditions in the watershed.
• Don't use data sets with only low-flow concentrations to simulate high-flow conditions.
• Do use data sets with concentration values covering the range of flow and land
management conditions in the watershed.
n Land use and land management data should be logically linked both to the water quality
parameters simulated and to the sources and management measures and practices that
will be implemented.
• Don't calibrate nutrient concentrations against general land use variables that cannot be
logically linked to nutrient management.
• Do incorporate to the extent possible data that reflect long-term crop rotations, erosion
control, nutrient control, management at other significant sources, and the control of
other pollutants that will be managed and simulated in the modeling.
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Chapter 7: Load Estimation Techniques
Unit Loads
Several simple methods (see "Simple Watershed Methods" on p. 234) for
watershed loading determination use unit loads, or unit-area loads, to represent
pollutant contributions from various land uses. Unit loads are expressed as mass
per unit area per unit time. One concern associated with unit-load approaches is
the availability of good local data regarding the unit loads for watershed-specific
physical, chemical, and climatological conditions (Heidtke and Auer, 1993). In
the absence of local data, unit loads are approximated using values that may
come from nearby studies or studies conducted in distant regions, thus introduc-
ing error to the analysis.
Scale should be considered when selecting unit loads, or export coefficients. A
study of 210 paired observations of total phosphorus (TP) export taken from 38
studies showed that TP export in agricultural catchments is not a linear function
of catchment area, but instead varies as the 0.77 power of drainage basin area
(TVPrairie and Kalff, 1986). This decline in unit-area export was attributable to
the TP export from row crops and pasture catchments. However, the study found
that the unit-area export of TP from forested catchments did not change as
catchment size increased.
Addressing Uncertainty in Modeling
Predictions
Because models simplify the real world, the predictions from a model are
uncertain, and quantification of the prediction uncertainty should be included in
the modeling approach (EPA, 1980). Prediction uncertainty is caused by natural
process variability, and bias and error in sampling, measurement, and modeling.
Reliably estimated prediction uncertainty can be useful to the planner as a means
for judging the value of the prediction and assessing the risk of not achieving
management objectives (e.g., meeting the load allocation of a TMDL). Modeling
may also result in "unqualified supplemental uncertainty," which is uncertainty
introduced through such things as the use of inappropriate export coefficients.
This uncertainty, which is unknown to the analyst, is unquantified, and therefore
introduces hidden planning risks.
To address the high variability of pesticide loads, a Monte Carlo simulation
approach was developed and applied to estimate atrazine and carbofuran loads
from hypothetical corn fields in Georgia and Iowa (Haith, 1985). The approach
incorporated mathematical models of weather, hydrology, and soil chemistry.
One advantage of this approach is the ability to generate a frequency distribution
of pollutant loads rather than just a single value, thus allowing an assessment of
the probability that any given single value for the pollutant load will occur.
Because of the complexity of quantifying modeling uncertainty, modelers are
encouraged to consult with trained statisticians to devise the best approach for
their modeling applications. Detailed examples of uncertainty analyses can be
found in existing documents (EPA, 1980; EPA, 1989b; Haan, 1989; Beck, 1987).
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Model Applications Using GIS Technology
A unit-load approach for estimating phosphorus loads to Owasco Lake in New
York used geographic information system (GIS) technology to distribute land-
based attributes within the watershed (Heidtke and Auer, 1993). The GIS en-
abled the modelers to match unit loads with the appropriate areas within the
watershed in a distributed manner. GIS technology was also used to facilitate
watershed modeling with models such as AGNPS (Agricultural Non-Point
Source Pollution) (Line et al., 1997) and SWAT (Soil and Water Assessment
Tool) (Engel et al. 1993).
EPA's BASINS (Better Assessment Science Integrating Point and Nonpoint
Sources) is an integrated modeling system for performing watershed- and water-
quality-based studies (EPA, 2001d). BASINS is intended to facilitate examina-
tion of environmental information, support analysis of environmental systems,
and provide a framework for examining management alternatives. BASINS
includes assessment tools, spatial data, and watershed and water quality model-
ing components, with GIS providing the integrating framework. An example
illustrating the application of BASINS to estimating the impacts of agricultural
management measures and practices is given in the BASINS Highlight.
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Using BASINS to Develop a TMDL for Fecal Coliform Bacteria
Problem: The Lost River in the state of West Virginia exhibits water quality impairment
due to elevated levels of fecal coliform bacteria. Suspected sources of contamination
include cattle grazing and feedlots, poultry houses, failing septic systems, geese, wild
turkey, and deer, as well as point source dischargers. Section 303(d) of the Clean Water
Act and EPA's Water Quality Planning and Management Regulations (40 CFR Part 130)
require states to develop Total Maximum Daily Loads (TMDLs) for waterbodies that are
not meeting designated uses under technology-based controls. The TMDL process
establishes the allowable loadings of pollutants or other quantifiable parameters for a
waterbody based on the relationship between pollution sources and instream water
quality conditions.
Approach: The U.S. EPA Better Assessment Science Integrating Point and Nonpoint
Sources (BASINS) system Version 2.0 (EPA, 1998) and the Nonpoint Source Model
(NPSM) were selected to predict the significance of fecal coliform sources and fecal
coliform levels in the Lost River watershed. To obtain a spatial variation of the
concentration of bacteria along the Lost River, the watershed was subdivided into 11
subwatersheds. This allowed analysts to address the relative contribution of sources
within each subwatershed to the different segments of the river. The watershed
subdivision was based on a number of factors, including the locations of flow monitoring
stations, the locations of stream sampling stations, the locations of feedlots and poultry
houses, and land use coverage. To develop a representative linkage between the
sources and the instream water quality response in the 11 reaches of the Lost River,
model parameters were adjusted to the extent possible for both hydrology and bacteria
loading.
Results: Output from NPSM indicates violations of the 200 cfu/100 mL geometric mean
standard throughout the Lost River watershed for the existing conditions using the
representative time period (October 1990 through September 1991). After applying the
load allocations, the NPSM model indicated that all 11 subwatersheds were in
compliance with the fecal coliform bacteria standard. The model analysis indicates that
water quality standards will be achieved if fecal coliform loads from pastureland are
reduced by 38 percent, loads from forestland are reduced 12.8 percent, and loads from
cropland are reduced by 37 percent. No change in the point source load was required.
The load reductions at the source are expected to be sufficient to meet the 30-day
geometric mean, on a daily basis, throughout the year. The margin of safety, an
evaluation of the uncertainty in the TMDL, was included implicitly in the model setup and
formulation. Conservative assumptions included loads associated with wildlife, septic
systems, and existing BMP implementation. Further refinement and corresponding
higher accuracy in the analysis could be achieved by more detailed source
characterization (actual daily or monthly manure application rates), further evaluation of
the viability and dieoff of fecal coliform in the various types of manure, and continued
data collection and calibration.
Attainment of the load reductions is expected through implementation of manure storage
and application guidelines, crop and pasture management, and wildlife management. No
explicit modeling of the BMP effectiveness was performed. Follow-up monitoring is
expected to track water quality improvements.
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Glossary
10-year, 24-hour storm — A rainfall event of 24-hour duration and 10-year
frequency that is used to calculate the runoff volume and peak discharge rate to
a BMP.
25-year, 24-hour storm — A rainfall event of 24-hour duration and 25-year
frequency that is used to calculate the runoff volume and peak discharge rate to
a BMP.
ACP — Agricultural Conservation Program (the ACP is no longer an active
USDA program; it was replaced by EQIP).
Adsorption — The adhesion of one substance to the surface of another.
Allelopathy — The inhibition of growth in one species of plants by chemicals
produced in another species.
Animal unit (au) — A unit of measurement for any animal feeding operation
calculated by adding the following numbers: the number of slaughter and feeder
cattle multiplied by 1.0, plus the number of mature dairy cattle multiplied by
1.4, plus the number of swine weighing over 25 kilograms (approximately 55
pounds) multiplied by 0.4, plus the number of sheep multiplied by 0.1, plus the
number of horses multiplied by 2.0.
Aquifer — A saturated, permeable geologic unit of sediment or rock that can
transmit significant quantities of water under hydraulic gradients.
ASCS — Agricultural Stabilization and Conservation Service of USDA (now
called Farm Service Agency).
AUM — Animal unit month. A measure of average monthly stocking rate that is
the tenure of one animal unit for a period of 1 month. With respect to the
literature reviewed for the grazing management measure, an animal unit is a
mature, 1,000-pound cow or the equivalent based on average daily forage
consumption of 26 pounds of dry matter per day (Platts, 1990). Alternatively, an
AUM is the amount of forage that is required to maintain a mature, 1,000-pound
cow or the equivalent for a one-month period. See animal unit for the NPDES
definition.
Best management practice (BMP) — A practice or combination of practices
that are determined to be the most effective and practicable (including techno-
logical, economic, and institutional considerations) means of controlling point
and nonpoint pollutants at levels compatible with economic and environmental
quality goals.
BMP system — A combination of two or more individual BMPs into a "sys-
tem" that functions to reduce the same pollutant.
Biochemical oxygen demand (BOD) — A quantitative measure of the strength
of contamination by organic carbon materials.
National Management Measures to Control Nonpoint Pollution from Agriculture 8-243
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Chapter 8: Glossary
Chemigation — The addition of one or more chemicals to the irrigation water.
Conservation management system (CMS) — a generic term used by the
NRCS that includes any combination of conservation practices and management
that achieves a level of treatment of the five natural resources that satisfies
criteria contained in the USDA-Natural Resources Conservation Service Na-
tional Handbook of Conservation Practices, such as a resource management
system or an acceptable management system.
Critical area — An area identified in a watershed or project area as having a
significant impact on the impaired use of the receiving waters.
Conservation Reserve Enhancement Program (CREP) — A new initiative of
CRP which uses financial incentives to encourage farmers and ranchers to
voluntarily protect soil, water, and wildlife resources.
Conservation Reserve Program (CRP) — A volunteer program offering
annual rental payments, incentive payments, and cost-share assistance for
establishing long-term, resource-conserving cover crops on highly erodible land.
CZARA — Coastal Zone Act Reauthorization Amendments of 1990.
De nitrification — The chemical or biochemical reduction of nitrate or nitrite to
gaseous nitrogen, either as molecular nitrogen or as an oxide of nitrogen.
Deposition — The accumulation of material left in a new position by a natural
transporting agent such as water, wind, ice, or gravity, or by the activity of man.
Designated use — A beneficial use type established by a State for each water
resource and specified in water quality standards, whether or not it is being
attained.
Drainage area — Watershed; an area of land that drains to one point.
Ecosystem — A network of interactions between biological communities and
the associated physical environment.
EPA — United States Environmental Protection Agency
Environmental Quality Incentives Program (EQIP) — A voluntary conserva-
tion program for farmers and ranchers, offering financial, technical, and educa-
tional help to install or implement practices to conserve soil and other natural
resources.
Erosion — Wearing away of the land surface by running water, glaciers, winds,
and waves. The term erosion is usually preceded by a definitive term denoting
the type or source of erosion such as gully erosion, sheet erosion, or bank
erosion.
Eutrophication — The natural process whereby a lake or other body of water
evolves from low productivity and low nutrient concentrations to high produc-
tivity and high nutrient levels that is greatly accelerated by nutrient enrichment
from human activities. Results of eutrophication can include algal blooms, low
dissolved oxygen, and changes in community composition.
Fertigation — Application of plant nutrients in irrigation water.
FOTG — USDA-NRCS's Field Office Technical Guide.
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Chapter 8: Glossary
FSA — Farm Service Agency, part of the U.S. Department of Agriculture.
Integrated Pest Management (IPM) — A pest population management system
that anticipates and prevents pests from reaching damaging levels by using all
suitable tactics including natural enemies, pest-resistant plants, cultural manage-
ment, and the judicious use of pesticides, leading to an economically sound and
environmentally safe agriculture.
Lateral — Secondary or side channel, ditch, or conduit.
Leachate — Liquids that have percolated through a soil and that contain sub-
stances in solution or suspension.
Management measures — As defined in section 6217(g)(5) of CZARA;
"economically achievable measures for the control of the addition of pollutants
from existing and new categories and classes of nonpoint sources of pollution,
which reflect the greatest degree of pollutant reduction achievable through the
application of the best available nonpoint source control practices, technologies,
processes, siting criteria, operating methods, and other alternatives."
MCL — Maximum contaminant level. The enforceable standard or number
against which a system's treated water samples are judged for compliance with
U.S. Environmental Protection Agency regulations.
Micronutrient — A plant nutrient found in relatively small amounts (<100 mg
kg'1) in plants. These are usually B, Cl, Cu, Fe, Mn, Mo, Ni, Co, and Zn.
Natural Resources Conservation Service (NRCS) — An agency of the U.S.
Department of Agriculture.
Nitrogen (N) — An element occurring in manure and chemical fertilizer that is
essential to the growth and development of plants, but which, in excess, can
cause water to become polluted and threaten aquatic animals.
NFS pollution — Nonpoint source pollution; pollution originating from diffuse
areas (land surface or atmosphere) having no well-defined source.
Nutrients — Elements or compounds essential as raw materials for organism
growth and development, such as carbon, nitrogen, phosphorus, etc.
Pasture — Those improved lands that are primarily used for the production of
adapted domesticated forage plants for livestock.
Phosphorus (P) — An element occurring in manure and chemical fertilizer that
is essential to the growth and development of plants, but which, in excess, can
cause water to become polluted and threaten aquatic animals.
— Those lands on which the native or introduced vegetation (climax or
natural potential plant community ) is predominantly grasses, grasslike plants,
forbs, or shrubs suitable for grazing or browsing use. Range includes natural
grassland, savannas, many wetlands, some deserts, tundra, and certain forb and
shrub communities.
Return flow — That portion or the water diverted from a stream that finds its
way back to the stream channel either as surface or underground flow.
National Management Measures to Control Nonpoint Pollution from Agriculture 8-245
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Chapter 8: Glossary
Resource management system (RMS) — A term used by NRCS defined as a
combination of NRCS conservation practices and management identified by land
or water uses that, when installed, will prevent resource degradation and permit
sustained use by meeting criteria established in the FOTG for treatment of soil,
water, air, plant, and animal resources.
Riparian areas — Vegetated ecosystems along a water body through which
energy, materials, and water pass. Riparian areas characteristically have a high
water table and are subject to periodic flooding and influence from the adjacent
water body.
Runoff — The portion of rainfall or snow melt that drains off the land into
ditches and streams by overland flow.
Rural Clean Water Program (RCWP) — A 15-year federally sponsored
nonpoint source pollution control program initiated in 1980 as an experimental
effort to address agricultural nonpoint source pollution problems in watersheds
throughout the United States. The program concluded in 1995.
Sediment — The solid material, both mineral and organic, that is in suspension,
is being transported, or has been moved from its site or origin by air, water,
gravity, or ice.
Sedimentation — The process of sediment deposition.
Tailwater — Irrigation water that reaches the lower end of a field.
Tillage — The mechanical manipulation of the soil profile for any purpose; but
in agriculture, it is usually restricted to modifying soil conditions, managing
crop residues and/or weeds, or incorporating chemicals for crop production.
Total Maximum Daily Load (TMDL) — The maximum amount of pollution
that a water body can receive without violating water quality standards. Total
Maximum Daily Loads are the sum of point and nonpoint source loads.
Watershed — A geographic area in which water, sediments, and dissolved
materials drain to a common outlet- a point on a larger stream, a lake, an under-
lying aquifer, an estuary, or an ocean. This area is also called the drainage basin
of the receiving water body.
Watershed approach — A coordinating framework for environmental manage-
ment that focuses public and private sector efforts to address the highest priority
problems within hydrologically defined geographic areas, taking into consider-
ation both ground and surface water.
8-246 National Management Measures to Control Nonpoint Pollution from Agriculture
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Appendix
Appendix A: Best Management Practices —
Definitions and Descriptions
Best management practices mentioned in this guidance are listed in alphabetical
order below. This is not a complete list of all the management practices for
agricultural nonpoint source pollution control; there are others that may be in
use or are under development. The NRCS or other code number, if any, is given
for each BMP, followed by a short definition. Additional explanatory text about
selected BMPs is presented in italicized text below the practice, code, and
definition.
Access Road (560): A travelway constructed as part of a conservation plan.
Animal Trails and Walkways (575): A livestock trail or walkway constructed
to improve grazing distribution and access to forage and water.
Bedding (310): Plowing, blading, or otherwise elevating the surface of flat land
into a series of broad, low ridges separated by shallow, parallel channels.
Brush Management (314): Removal, reduction, or manipulation of non-
herbaceous plants.
Improved vegetation quality and the decrease in runoff from the practice will
reduce the amount of erosion and sediment yield. Improved vegetative cover acts
as a filter strip to trap the movement of dissolved and sediment attached sub-
stances, such as nutrients and chemicals from entering downstream water
courses. Mechanical brush management may initially increase sediment yields
because of soil disturbances and reduced vegetative cover. This is temporary
until revegetation occurs.
Channel Vegetation (322): Establishing and maintaining adequate plants on
channel banks, berms, spoil, and associated areas.
Chiseling and Subsoiling (324): Loosening the soil, without inverting and with
a minimum of mixing of the surface soil, to shatter restrictive layers below
normal plow depth that inhibit water movement or root development.
Composting Facility (317): A facility for the biological stabilization of waste
organic material.
The purpose is to treat waste organic material biologically by producing a
humus-like material that can be recycled as a soil amendment and fertilizer
substitute or otherwise utilized in compliance with all laws, rules, and
regulations.
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Conservation Cover (327): Establishing and maintaining perennial vegetative
cover to protect soil and water resources on land retired from agricultural
production.
Agricultural chemicals are usually not applied to this cover in large quantities
and surface and ground water quality may improve where these material are not
used. Ground cover and crop residue will be increased with this practice.
Erosion and yields of sediment and sediment related stream pollutants should
decrease. Temperatures of the soil, surface runoff and receiving water may be
reduced. Effects will vary during the establishment period and include increases
in runoff, erosion and sediment yield. Due to the reduction of deep percolation,
the leaching of soluble material will be reduced, as will be the potential for
causing saline seeps. Long-term effects of the practice would reduce agricul-
tural nonpoint sources of pollution to all water resources.
Conservation Crop Rotation (328): An adapted sequence of crops designed to
provide adequate organic residue for maintenance or improvement of soil tilth.
This practice reduces erosion by increasing organic matter, resulting in a
reduction of sediment and associated pollutants to surface waters. Crop rota-
tions that improve soil tilth may also disrupt disease, insect and weed reproduc-
tion cycles, reducing the need for pesticides. This removes or reduces the
availability of some pollutants in the watershed. Deep percolation may carry
soluble nutrients and pesticides to the ground water. Underlying soil layers, rock
and unconsolidated parent material may block, delay, or enhance the delivery of
these pollutants to ground water. The fate of these pollutants will be site specific,
depending on the crop management, the soil and geologic conditions.
Constructed Wetland (656): A wetland that has been constructed for the
primary purpose of water quality improvement.
This practice is applied to treat waste waters from confined animal operations,
sewage, surface runoff, milkhouse wastewater, silage leachate, and mine drain-
age by the biological, chemical and physical activities of a constructed wetland.
Contour Buffer Strips (332): Narrow strips of permanent, herbaceous vegeta-
tive cover established across the slope and alternated down the slope with
parallel, wider cropped strips.
Contour Farming (330): Farming sloping land in such a way that preparing
land, planting, and cultivating are done on the contour. This includes following
established grades of terraces or diversions.
This practice reduces erosion and sediment production. Less sediment and
related pollutants may be transported to the receiving waters.
Increased infiltration may increase the transportation potential for soluble
substances to the ground water.
Contour Orchard and Other Fruit Area (331): Planting orchards, vineyards,
or small fruits so that all cultural operations are done on the contour.
Contour orchards and fruit areas may reduce erosion, sediment yield, and
pesticide concentration in the water lost. Where inward sloping benches are
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Chapter 10: Appendix
used, the sediment and chemicals will be trapped against the slope. With annual
events, the bench may provide 100 percent trap efficiency. Outward sloping
benches may allow greater sediment and chemical loss.
The amount of retention depends on the slope of the bench and the amount of
cover. In addition, outward sloping benches are subject to erosion from runoff
from benches immediately above them. Contouring allows better access to rills,
permitting maintenance that reduces additional erosion. Immediately after
establishment, contour orchards may be subject to erosion and sedimentation in
excess of the now contoured orchard. Contour orchards require more fertiliza-
tion and pesticide application than did the native grasses that frequently covered
the slopes before orchards were started. Sediment leaving the site may carry
more adsorbed nutrients and pesticides than did the sediment before the benches
were established from uncultivated slopes. If contoured orchards replace other
crop or intensive land use, the increase or decrease in chemical transport from
the site may be determined by examining the types and amounts of chemicals
used on the prior land use as compared to the contour orchard condition.
Soluble pesticides and nutrients may be delivered to and possibly through the
root zone in an amount proportional to the amount of soluble pesticides applied,
the increase in infiltration, the chemistry of the pesticides, organic and clay
content of the soil, and amounts of surface residues. Percolating water below the
root zone may carry excess solutes or may dissolve potential pollutants as they
move. In either case, these solutes could reach ground water supplies and/or
surface downslope from the contour orchard area. The amount depends on soil
type, surface water quality, and the availability of soluble material (natural or
applied).
Contour Stripcropping (585): Growing crops in a systematic arrangement of
strips or bands on the contour to reduce water erosion. The crops are arranged so
that a strip of grass or close-growing crop is alternated with a strip of clean-tilled
crop or fallow or a strip of grass is alternated with a close-growing crop.
This practice may reduce erosion and the amount of sediment and related
substances delivered to the surface waters. The practice may increase the
amount of water that infiltrates into the root zone, and, at the time there is an
overabundance of soil water, this water may percolate and leach soluble sub-
stances into the ground water.
Controlled Drainage (335): Control of surface and subsurface water through
use of drainage facilities and water control structures.
The purpose is to conserve water and maintain optimum soil moisture to (1)
store and manage infiltrated rainfall for more efficient crop production; (2)
improve surface water quality by increasing infiltration, thereby reducing runoff,
which may carry sediment and undesirable chemicals; (3) reduce nitrates in the
drainage water by enhancing conditions for denitriflcation; (4) reduce subsid-
ence and wind erosion of organic soils; (5) hold water in channels in forest areas
to act as ground fire breaks; and (6) provide water for wildlife and a resting and
feeding place for waterfowl.
Cover Crop (340): A crop of close-growing grasses, legumes, or small grain
grown primarily for seasonal protection and soil improvement. It usually is
grown for 1 year or less, except where there is permanent cover as in orchards.
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Erosion, sediment and adsorbed chemical yields could be decreased in conven-
tional tillage systems because of the increased period of vegetal cover. Plants
will take up available nitrogen and prevent its undesired movement. Organic
nutrients may be added to the nutrient budget reducing the need to supply more
soluble forms. Overall volume of chemical application may decrease because
the vegetation will supply nutrients and there may be allelopathic effects of some
of the types of cover vegetation on weeds. Temperatures of ground and surface
waters could slightly decrease.
Critical Area Planting (342): Planting vegetation, such as trees, shrubs, vines,
grasses, or legumes, on highly credible or critically eroding areas. (Does not
include tree planting mainly for wood products.)
This practice may reduce soil erosion and sediment delivery to surface waters.
Plants may take up more of the nutrients in the soil, reducing the amount that
can be washed into surface waters or leached into ground water.
During grading, seedbed preparation, seeding, and mulching, large quantities of
sediment and associated chemicals may be washed into surface waters prior to
plant establishment.
Cross Wind Ridges/StripCropping/Trap Strips (589): Ridges formed by
tillage or planting, crops grown in strips, or herbaceous cover aligned perpen-
dicular to the prevailing wind direction.
Dikes (356): An embankment constructed of earth or other suitable materials to
protect land against overflow or to regulate water.
Where dikes are used to prevent water from flowing onto the floodplain, the
pollution dispersion effect of the temporary wetlands and backwater are de-
creased. The sediment, sediment-attached, and soluble materials being trans-
ported by the water are carried farther downstream. The final fate of these
materials must be investigated on site. Where dikes are used to retain runoff on
the floodplain or in wetlands, the pollution dispersion effects of these areas may
be enhanced. Sediment and related materials may be deposited, and the quality
of the water flowing into the stream from this area will be improved.
Dikes are used to prevent wetlands and to form wetlands. The formed areas may
be fresh, brackish, or saltwater wetlands. In tidal areas, dikes are used to stop
saltwater intrusion, and to increase the hydraulic head of fresh water which will
force intruded salt water out of the aquifer. During construction there is a
potential of heavy sediment loadings to the surface waters. When pesticides are
used to control the brush on the dikes and fertilizers are used for the establish-
ment and maintenance of vegetation, there is the possibility for these materials
to be washed into the surface waters.
Diversion (362): A channel constructed across the slope with a supporting ridge
on the lower side.
This practice will assist in the stabilization of a watershed, resulting in the
reduction of sheet and rill erosion by reducing the length of slope. Sediment may
be reduced by the elimination of ephemeral and large gullies. This may reduce
the amount of sediment and related pollutants delivered to the surface waters.
Fence (382): A constructed barrier to livestock, wildlife, or people.
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Chapter 10: Appendix
Fencing is a facilitating practice to implement a prescribed grazing system
which would improve vegetation and reduce erosion, sediment and nutrient
delivery.
Fencing is a practice that can be on the contour or up and down slope. Often a
fence line has grass and some shrubs in it. When a fence is built across the
slope, the grasses and shrubs that may line the fence will slow down runoff and
cause deposition of coarser grained materials, reducing the amount of sediment
delivered downslope. Fencing may protect riparian areas which act as sediment
traps and filters along water channels and impoundments.
Livestock have a tendency to walk along fences in search of forage when the
grazing land is poorly managed or has inadequate forage. The paths become
bare channels which concentrate and accelerate runoff causing a greater
amount of erosion within the path and where the path/channel outlets into
another channel. This can deliver more sediment and associated pollutants to
surface waters. Fencing can have the effect of concentrating livestock in small
areas, causing a concentration of manure which may wash off into the stream,
thus causing surface water pollution.
Field Stripcropping (586): Growing crops in a systematic arrangement of strips
or bands across the general slope (not on the contour) to reduce water erosion.
The crops are arranged so that a strip of grass or a close-growing crop is alter-
nated with a clean-tilled crop or fallow.
This practice may reduce erosion and the delivery of sediment and related
substances to the surface waters. The practice may increase infiltration and,
when there is sufficient water available, may increase the amount of leachable
pollutants moved toward the ground water.
Since this practice is not on the contour there will be areas of concentrated flow,
from which detached sediment, adsorbed chemicals and dissolved substances
will be delivered more rapidly to the receiving waters. The sod strips will not be
efficient filter areas in these areas of concentrated flow.
Field Border (386): A strip of perennial vegetation established at the edge of a
^eld by planting or by converting it from trees to herbaceous vegetation or
shrubs.
This practice reduces erosion by having perennial vegetation on an area of the
field. Field borders serve as "anchoring points" for contour rows, terraces,
diversions, and contour strip cropping. By elimination of the practice of tilling
and planting the ends up and down slopes, erosion from concentrated flow in
furrows and long rows may be reduced. This use may reduce the quantity of
sediment and related pollutants transported to the surface waters.
Field windbreak (392): A strip or belt of trees or shrubs established in or
adjacent to a field as a barrier to wind.
Filter Strip (393): A strip or area of vegetation for removing sediment, organic
matter, and other pollutants from runoff and wastewater.
Filter strips for sediment and related pollutants meeting minimum requirements
may trap the coarser grained sediment. They may not filter out soluble or
suspended fine-grained materials. When a storm causes runoff in excess of the
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Chapter 10: Appendix
design runoff, the filter may be flooded and may cause large loads of pollutants
to be released to the surface water. This type of filter requires high maintenance
and has a relative short service life and is effective only as long as the flow
through the filter is shallow sheet flow.
Filter strips for runoff from concentrated livestock areas may trap organic
material, solids, materials which become adsorbed to the vegetation or the soil
within the filter. Often they will not filter out soluble materials. This type of filter
is often wet and is difficult to maintain.
Filter strips for controlled overland flow treatment of liquid wastes may effec-
tively filter out pollutants. The filter must be properly managed and maintained,
including the proper resting time. Filter strips on forest land may trap coarse
sediment, timbering debris, and other deleterious material being transported by
runoff. This may improve the quality of surface water and has little effect on
soluble material in runoff or on the quality of ground water.
All types of filters may reduce erosion in the area on which they are constructed.
Filter strips trap solids from the runoff flowing in sheet flow through the filter.
Coarse-grained and fibrous materials are filtered more efficiently than fine-
grained and soluble substances. Filter strips work for design conditions, but
when flooded or overloaded they may release a slug load of pollutants into the
surface water.
Floodwater Diversion (400): A graded channel with a supporting embankment
or dike on the lower side constructed on lowland subject to flood damage.
Forage Harvest Management (511): The timely cutting and removal of forages
from the field as hay, greenchop, or ensillage.
Forest Land Erosion Control System (408): Application of one or more
erosion control measures on forest land. Erosion control system includes the use
of conservation plants, cultural practices, and erosion control structures on
disturbed forest land for the control of sheet and rill erosion, gully formation,
and mass soil movement.
Grade Stabilization Structure (410): A structure used to control the grade and
head cutting in natural or artificial channels.
Where reduced stream velocities occur upstream and downstream from the
structure, streambank and streambed erosion will be reduced. This will decrease
the yield of sediment and sediment-attached substances. Structures that trap
sediment will improve downstream water quality. The sediment yield change will
be a function of the sediment yield to the structure, reservoir trap efficiency and
of velocities of released water. Ground water recharge may affect aquifer quality
depending on the quality of the recharging water. If the stored water contains
only sediment and chemical with low water solubility, the ground water quality
should not be affected.
Grassed Waterway (412): A natural or constructed channel that is shaped or
graded to required dimensions and established in suitable vegetation for the
stable conveyance of runoff.
This practice may reduce the erosion in a concentrated flow area, such as in a
gully or in ephemeral gullies. This may result in the reduction of sediment and
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Chapter 10: Appendix
substances delivered to receiving waters. Vegetation may act as a filter in
removing some of the sediment delivered to the waterway, although this is not
the primary function of a grassed waterway.
Any chemicals applied to the waterway in the course of treatment of the adjacent
cropland may wash directly into the surface waters in the case where there is a
runoff event shortly after spraying.
When used as a stable outlet for another practice, waterways may increase the
likelihood of dissolved and suspended pollutants being transported to surface
waters when these pollutants are delivered to the waterway.
Grazing Land Mechanical Treatment (548): Modifying physical soil and/or
plant conditions with mechanical tools by treatments such as; pitting, contour
furrowing, and ripping or subsoiling.
Heavy Use Area Protection (561): Protecting heavily used areas by establishing
vegetative cover, by surfacing with suitable materials, or by installing needed
structures.
Protection may result in a general improvement of surface water quality through
the reduction of erosion and the resulting sedimentation. Some increase in
erosion may occur during and immediately after construction until the disturbed
areas are fully stabilized.
Some increase in chemicals in surface water may occur due to the introduction
of fertilizers for vegetated areas and oils and chemicals associated with paved
areas. Fertilizers and pesticides used during operation and maintenance may be a
source of water pollution.
Paved areas installed for livestock use will increase organic, bacteria, and
nutrient loading to surface waters. Changes in ground water quality will be
minor. Nitrate nitrogen applied as fertilizer in excess of vegetation needs may
move with infiltrating waters. The extent of the problem, if any, may depend on
the actual amount of water percolating below the root zone.
Hedgerow Planting (422): Establishing a living fence of shrubs or trees in,
across, or around a field.
Herbaceous Wind Bathers (422A): Herbaceous vegetation established in rows
or narrow strips across the prevailing wind direction.
Hillside Ditch (423): A channel that has a supporting ridge on the lower side
constructed across the slope at definite vertical intervals and gradient, with or
without a vegetative barrier.
Irrigation Canal or Lateral (320): A permanent irrigation canal or lateral
constructed to convey water from the source of supply to one or more farms.
Irrigation Field Ditch (388): A permanent irrigation ditch constructed to
convey water from the source of supply to a field or fields in a farm distribution
system.
The standard for this practice applies to open channels and elevated ditches of
25ft3/second or less capacity formed in and with earth materials.
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Irrigation field ditches typically carry irrigation water from the source of
supplying to afield or fields. Salinity changes may occur in both the soil and
water. This will depend on the irrigation water quality, the level of water man-
agement, and the geologic materials of the area. The quality of ground and
surface water may be altered depending on environmental conditions. Water lost
from the irrigation system to downstream runoff may contain dissolved sub-
stances, sediment, and sediment-attached substances that may degrade water
quality and increase water temperature. This practice may make water available
for wildlife, but may not significantly increase habitat.
Irrigation Land Leveling (464): Reshaping the surface of land to be irrigated to
planned grades.
The effects of this practice depend on the level of irrigation water management.
If plant root zone soil water is properly managed, then quality decreases of
surface and ground water may be avoided. Under poor management, ground
and surface water quality may deteriorate. Deep percolation and recharge with
poor quality water may lower aquifer quality. Land leveling may minimize
erosion and when runoff occurs concurrent sediment yield reduction. Poor
management may cause an increase in salinity of soil, ground and surface
waters. High efficiency surface irrigation is more probable when earth moving
elevations are laser controlled.
Irrigation Pit or Regulating Reservoir, Irrigation Pit (552A): A small storage
reservoir constructed to regulate or store a supply of water for irrigation.
Irrigation Pit or Regulating Reservoir, Regulating Reservoir (552B): A small
storage reservoir constructed to regulate or store a supply of water for irrigation.
Irrigation Storage Reservoir (436): An irrigation water storage structure made
by constructing a dam.
Irrigation System, Microirrigation (441): A planned irrigation system in which
all necessary facilities are installed for efficiently applying water directly to the
root zone of plants by means of applicators (orifices, emitters, porous tubing, or
perforated pipe) operated under low pressure (Figure 2-20). The applicators can
be placed on or below the surface of the ground (Figure 2-21).
Surface water quality may not be significantly affected by transported sub-
stances because runoff is largely controlled by the system components (prac-
tices). Chemical applications may be applied through the system. Reduction of
runoff will result in less sediment and chemical losses from the field during
irrigation. If excessive, local, deep percolation should occur, a chemical hazard
may exist to shallow ground water or to areas where geologic materials provide
easy access to the aquifer.
Irrigation System, Sprinkler (422): A planned irrigation system in which all
necessary facilities are installed for efficiently applying water by means of
perforated pipes or nozzles operated under pressure.
Proper irrigation management controls runoff and prevents downstream surface
water deterioration from sediment and sediment attached substances. Over
irrigation through poor management can produce impaired water quality in
runoff as well as ground water through increased percolation. Chemigation with
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this system allows the operator the opportunity to mange nutrients, wastewater
and pesticides. For example, nutrients applied in several incremental applica-
tions based on the plant needs may reduce ground water contamination consid-
erably, compared to one application during planting. Poor management may
cause pollution of surface and ground water. Pesticide drift from chemigation
may also be hazardous to vegetation, animals, and surface water resources.
Appropriate safety equipment, operation and maintenance of the system is
needed with chemigation to prevent accidental environmental pollution or
backflows to water sources.
Irrigation System, Surface and Subsurface (443): A planned irrigation system
in which all necessary water control structures have been installed for efficient
distribution of irrigation water by surface means, such as furrows, borders,
contour levees, or contour ditches, or by subsurface means.
Operation and management of the irrigation system in a manner which allows
little or no runoff may allow small yields of sediment or sediment-attached
substances to downstream waters. Pollutants may increase if irrigation water
management is not adequate. Ground water quality from mobile, dissolved
chemicals may also be a hazard if irrigation water management does not
prevent deep percolation. Subsurface irrigation that requires the drainage and
removal of excess water from the field may discharge increased amounts of
dissolved substances such as nutrients or other salts to surface water. Tempera-
tures of downstream water courses that receive runoff waters may be increased.
Temperatures of downstream waters might be decreased with subsurface systems
when excess water is being pumped from the field to lower the water table.
Downstream temperatures should not be affected by subsurface irrigation
during summer months if lowering the water table is not required. Improved
aquatic habitat may occur if runoff or seepage occurs from surface systems or
from pumping to lower the water table in subsurface systems.
Irrigation System, Tailwater Recovery (447): A facility to collect, store, and
transport irrigation tailwater for reuse in the farm irrigation distribution system.
The reservoir will trap sediment and sediment-attached substances from runoff
waters. Sediment and chemicals will accumulate in the collection facility by
entrapping which would decrease downstream yields of these substances.
Salts, soluble nutrients, and soluble pesticides will be collected with the runoff
and will not be released to surface waters. Recovered irrigation water with high
salt and/or metal content will ultimately have to be disposed of in an environ-
mentally safe manner and location. Disposal of these waters should be part of
the overall management plan. Although some ground water recharge may occur,
little if any pollution hazard is usually expected.
Irrigation Water Conveyance, Ditch and Canal Lining, Flexible Membrane
(428B): A fixed lining of impervious material installed in an existing or newly
constructed irrigation field ditch or irrigation canal or lateral.
Irrigation Water Conveyance, Ditch and Canal Lining, Galvanized Steel
(428C): A fixed lining of impervious material installed in an existing or newly
constructed irrigation field ditch or irrigation canal or lateral.
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Irrigation Water Conveyance, Ditch and Canal Lining, Nonreinforced
Concrete (428A): A fixed lining of impervious material installed in an existing
or newly constructed irrigation field ditch or irrigation canal or lateral.
Irrigation Water Conveyance, High-Pressure, Underground, Plastic
(430DD): A pipeline and appurtenances installed in an irrigation system.
Irrigation Water Conveyance, Low-Pressure, Underground, Plastic
(430EE): A pipeline and appurtenances installed in an irrigation system.
Irrigation Water Conveyance, Pipeline, Aluminum Tubing (430AA); A
pipeline and appurtenances installed in an irrigation system.
Irrigation Water Conveyance, Pipeline, Asbestos-Cement (430BB): A
pipeline and appurtenances installed in an irrigation system.
Irrigation Water Conveyance, Pipeline, Nonreinforced Concrete (430CC): A
pipeline and appurtenances installed in an irrigation system.
Irrigation Water Conveyance, Pipeline, Reinforced Plastic Mortar (430GG):
A pipeline and appurtenances installed in an irrigation system.
Irrigation Water Conveyance, Pipeline, Rigid Gated Pipeline (430HH): A
rigid pipeline, with closely spaced gates, installed as part of a surface irrigation
system.
Irrigation Water Conveyance, Pipeline, Steel (430FF): A pipeline and appur-
tenances installed in an irrigation system.
Irrigation Water Management (449): Determining and controlling the rate,
amount, and timing of irrigation water in a planned and efficient manner.
Management of the irrigation system should provide the control needed to
minimize losses of water, and yields of sediment and sediment-attached and
dissolved substances, such as plant nutrients and herbicides, from the system.
Poor management may allow the loss of dissolved substances from the irrigation
system to surface or ground water. Good management may reduce saline perco-
lation from geologic origins. Returns to the surface water system would increase
downstream water temperature.
The purpose is to effectively use available irrigation water supply in managing
and controlling the moisture environment of crops to promote the desired crop
response, to minimize soil erosion and loss of plant nutrients, to control undesir-
able water loss, and to protect water quality.
To achieve this purpose the irrigator must have knowledge of(l) how to deter-
mine when irrigation water should be applied, based on the rate of water used
by crops and on the stages of plant growth; (2) how to measure or estimate the
amount of water required for each irrigation, including the leaching needs; (3)
the normal time needed for the soil to absorb the required amount of water and
how to detect changes in intake rate; (4) how to adjust water stream size,
application rate, or irrigation time to compensate for changes in such factors as
intake rate or the amount of irrigation runoff from an area; (5) how to recognize
erosion caused by irrigation; (6) how to estimate the amount of irrigation runoff
from an area; and (7) how to evaluate the uniformity of water application.
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Land Reclamation Landslide Treatment (453): Treating in pi ace materials,
mine spoil, mine waste, or overburden to reduce downslope movement.
Lined Waterway or Outlet (468): A waterway or outlet having an erosion-
resistant lining of concrete, stone, or other permanent material.
The lined section extends up the side slopes to a designed depth. The earth
above the permanent lining may be vegetated or otherwise protected.
This practice may reduce the erosion in concentrated flow areas resulting in the
reduction of sediment and substances delivered to the receiving waters.
When used as a stable outlet for another practice, lined waterways may increase
the likelihood of dissolved and suspended substances being transported to
surface waters due to high flow velocities. A lined waterway may also prevent
recharge of the water table as would occur with a natural water body.
Mole Drain (482): An underground conduit constructed by pulling a bullet-
shaped cylinder through the soil.
Mulching (484): Applying plant residues or other suitable materials not pro-
duced on the site to the soil surface.
Nutrient Management (590): Managing the amount, source, placement, form
and timing of applications of nutrients and soil amendments.
Pasture and Hay Planting (512): Establishing native or introduced forage
species.
The long-term effect will be an increase in the quality of the surface water due
to reduced erosion and sediment delivery. Increased infiltration and subsequent
percolation may cause more soluble substances to be carried to ground water.
Pipeline (516): Pipeline installed for conveying water for livestock or for
recreation
Pipelines may decrease sediment, nutrient, organic, and bacteria pollution from
livestock. Pipelines may afford the opportunity for alternative water sources
other than streams and lakes, possibly keeping the animals away from the
stream or impoundment. This will prevent bank destruction with resulting
sedimentation, and will reduce animal waste deposition directly in the water.
The reduction of concentrated livestock areas will reduce manure solids, nutri-
ents, and bacteria that accompany surface runoff.
Pond (378): A water impoundment made by constructing a dam or an embank-
ment or by excavation of a pit or dugout.
Ponds may trap nutrients and sediment which wash into the basin. This removes
these substances from downstream. Chemical concentrations in the pond may be
higher during the summer months. By reducing the amount of water that flows in
the channel downstream, the frequency of flushing of the stream is reduced and
there is a collection of substances held temporarily within the channel. A pond
may cause more leachable substances to be carried into the ground water.
Precision Land Forming (462): Reshaping the surface of land to planned
grades.
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Prescribed Burning (338): Applying controlled fire to predetermined areas.
When the area is burned in accordance with the specifications of this practice
the nitrates with the burned vegetation will be released to the atmosphere. The
ash will contain phosphorous and potassium which will be in a relatively highly
soluble form. If a runoff event occurs soon after the burn there is a probability
that these two materials may be transported into the ground water or into the
surface water. When in a soluble state the phosphorous and potassium will be
more difficult to trap and hold in place. When done on range grasses the growth
of the grasses is increased and there will be an increased tie-up of plant nutrients
as the grasses' growth is accelerated.
Prescribed Grazing (528A): The controlled harvest of vegetation with grazing
or browsing animals, managed with the intent to achieve a specified objective.
Planned grazing systems normally reduce the system time livestock spend in
each pasture. This increases quality and quantity of vegetation, As vegetation
quality increases, fiber content in manure decreases which speeds manure
decomposition and reduces pollution potential. Freeze-thaw, shrink-swell, and
other natural soil mechanisms can reduce compacted layers during the absence
of grazing animals. This increases infiltration, increases vegetative growth,
slows runoff, and improves the nutrient and moisture filtering and trapping
ability of the area.
Decreased runoff will reduce the rate of erosion and movement of sediment and
dissolved and sediment-attached substances to downstream water courses. No
increase in ground water pollution hazard would be anticipated from the use of
this practice.
Increased vegetation slows runoff and acts as a sediment filter for sediments and
sediment attached substances, uses more nutrients, and reduces raindrop splash.
Adverse chemical effects should not be anticipated from the use of this practice.
Pumped Well Drain (532): A well sunk into an aquifer from which water is
pumped to lower the prevailing water table.
Range Planting (Seeding) (550): Establishment of adapted perennial vegetation
such as grasses, forbs, legumes, shrubs, and trees.
Increased erosion and sediment yield may occur during the establishment of this
practice. This is a temporary situation and sediment yields decrease when
reseeded area becomes established. If chemicals are used in the reestablishment
process, chances of chemical runoff into downstream water courses are reduced
if application is applied according to label instructions. After establishment of
the grass cover, grass sod slows runoff, acts as a filter to trap sediment, sedi-
ment attached substances, increases infiltration, and decreases sediment yields.
Regulating Water in Drainage Systems (554): Controlling the removal of
surface or subsurface runoff, primarily through the operation of water-control
structures.
Residue Management (329) (NoTill): Any tillage and planting system in which
at least 30 percent of the soil surface is covered by plant residue after planting to
reduce soil erosion by water; or, where soil erosion by wind is the primary
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concern, at least 1,000 pounds per acre of flat small grain residue-equivalent are
on the surface during the critical erosion period.
This practice reduces soil erosion, detachment and sediment transport by provid-
ing soil cover during critical times in the cropping cycle. Surface residues
reduce soil compaction from raindrops, preventing soil sealing and increasing
infiltration. This action may increase the leaching of agricultural chemicals into
the ground water.
In order to maintain the crop residue on the surface it is difficult to incorporate
fertilizers and pesticides. This may increase the amount of these chemicals in the
runoff and cause more surface water pollution.
The additional organic material on the surface may increase the bacterial action
on and near the soil surface. This may tie-up and then breakdown many pesti-
cides which are surface applied, resulting in less pesticide leaving the field. This
practice is more effective in humid regions.
With a no-till operation, generally the only soil disturbance is from a leading
coulter, followed by the disk openers. Fertilizer may be injected and applied in a
separate operation, including side dressing. The surface applied fertilizers and
chemicals are not incorporated and often are not in direct contact with the soil
surface. This condition may result in a high surface runoff of pollutants (nutrient
and pesticides). Macropores develop under a no-till system. They permit deep
percolation and the transmittal of pollutants, both soluble and insoluble to be
carried into the deeper soil horizons and into the ground water. If rainfall is
relatively light and does not cause rapid runoff, surface applied nutrients and
herbicides move into the soil and are no longer subject to surface runoff losses.
Reduced tillage systems disrupt or break down the macropores, incidentally
incorporate some of the materials applied to the soil surface, and reduce the
effects ofwheeltrack compaction. The results are less runoff and less pollutants
in the runoff.
Riparian Herbaceous Cover (390): Establishing an area of grasses and/or forbs
adjacent to and up-gradient from water bodies.
Riparian Forest Buffer (391A): Establishing an area of trees and or shrubs
adjacent to and up-gradient from water bodies.
Rock Barrier (555): A rock retaining wall constructed across the slope to form
and support a bench terrace that will control the flow of water and check erosion
on sloping land.
Roof Runoff Management (558): A facility for controlling and disposing of
runoff water from roofs.
This practice may reduce erosion and the delivery of sediment and related
substances to surface waters. It will reduce the volume of water polluted by
animal wastes. Loadings of organic waste, nutrients, bacteria, and salts to
surface water will be reduced as water is prevented from flowing across concen-
trated waste areas, barnyards, roads and alleys. Pollution and erosion will be
reduced. Flooding may be prevented and drainage may improve.
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Runoff Management System (570): A system for controlling excess runoff
caused by construction operations at development sites, changes in land use, or
other land disturbances.
Seasonal Residue Management (344): Using plant residues to protect culti-
vated fields during critical erosion periods.
When this practice is employed, raindrops are intercepted by the residue, reduc-
ing detachment, soil dispersion, and soil compaction. Erosion may be reduced
and the delivery of sediment and associated pollutants to surface water may be
reduced. Reduced soil sealing, crusting and compaction allows more water to
infiltrate, resulting in an increased potential for leaching of dissolved pollutants
into the ground water.
Crop residues on the surface increase the microbial and bacterial action on or
near the surface. Nitrates and surface-applied pesticides may be tied-up and less
available to be delivered to surface and ground water. Residues trap sediment
and reduce the amount carried to surface water. Crop residues promote soil
aggregation and improve soil tilth.
Sediment Basin (350): A basin constructed to collect and store debris or sedi-
ment.
Sediment basins will remove sediment, sediment-associated materials and other
debris from the water which is passed on downstream. Due to the detention of
the runoff in the basin, there is an increased opportunity for soluble materials to
be leached toward the ground water.
Soil and Crop Water Use Data: From soils information the available water-
holding capacity of the soil can be determined along with the amount of water
that the plant can extract from the soil before additional irrigation is needed.
Water use information for various crops can be obtained from various USDA
publications.
The purpose is to allow the water user to estimate the amount of available water
remaining in the root zone at any time, thereby indicating when the next irriga-
tion should be scheduled and the amount of water needed. Methods to measure
or estimate the soil moisture should be employed, especially for high-value
crops or where the water-holding capacity of the soil is low.
Spring Development (574): Improving springs and seeps by excavating, clean-
ing, capping, or providing collection and storage facilities.
There will be negligible long-term water quality impacts with spring develop-
ments. Erosion and sedimentation may occur from any disturbed areas during
and immediately after construction, but should be short-lived. These sediments
will have minor amounts of adsorbed nutrients from soil organic matter.
Stream Channel Stabilization (584): Stabilizing the channel of a stream with
suitable structures.
Stream Corridor Improvement (interim): Restoration of a modified or
damaged stream to a more natural state using bioengineering techniques to
protect the banks and reestablish the riparian vegetation.
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Stream Crossing (interim): A stabilized area to provide access across a stream
for livestock and farm machinery.
The purpose is to provide a controlled crossing or watering access point for
livestock along with access for farm equipment, in order to control bank and
streambed erosion, reduce sediment and enhance water quality, and maintain or
improve wildlife habitat.
Streambank and Shoreline Protection (580): Using vegetation or structures to
stabilize and protect banks of streams, lakes, estuaries, or excavated channels
against scour and erosion.
Stripcropping, Contour (585): Growing crops in a systematic arrangement of
strips or bands on the contour to reduce water erosion. The crops are arranged so
that a strip of grass or close-growing crop is alternated with a strip of clean-tilled
crop or fallow or a strip of grass is alternated with a close-growing crop.
Structure for Water Control (587): A structure in an irrigation, drainage, or
other water management systems that conveys water, controls the direction or
rate of flow, or maintains a desired water surface elevation.
Subsurface Drain (606): A conduit, such as corrugated plastic tile, or pipe,
installed beneath the ground surface to collect and/or convey drainage water.
Soil water outlet to surface water courses by this practice may be low in concen-
trations of sediment and sediment-adsorbed substances and that may improve
stream water quality. Sometimes the drained soil water is high in the concentra-
tion of nitrates and other dissolved substances and drinking water standards
may be exceeded. If drainage water that is high in dissolved substances is able
to recharge ground water, the aquifer quality may become impaired. Stream
water temperatures may be reduced by water drainage discharge. Aquatic
habitat may be altered or enhanced with the increased cooler water tempera-
tures.
Surface Drainage Field Ditch (607): A graded ditch for collecting excess water
in a field.
From erosive fields, this practice may increase the yields of sediment and
sediment-attached substances to downstream water courses because of an
increase in runoff. In other fields, the location of the ditches may cause a
reduction in sheet and rill erosion and ephemeral gully erosion. Drainage of
high salinity areas may raise salinity levels temporarily in receiving waters.
Areas of soils with high salinity that are drained by the ditches may increase
receiving waters. Phosphorus loads resulting from this practice may increase
eutrophication problems in ponded receiving waters. Water temperature changes
will probably not be significant. Upland wildlife habitat may be improved or
increased although the habitat formed by standing water and wet areas may be
decreased.
Surface Drainage, Main or Lateral (608): An open drainage ditch constructed
to a designed size and grade.
Surface Roughening (609): Roughening the soil surface by ridge or clod-
forming tillage.
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Terrace (600): An earthen embankment, a channel, or combination ridge and
channel constructed across the slope.
This practice reduces the slope length and the amount of surface runoff which
passes over the area downslope from an individual terrace. This may reduce the
erosion rate and production of sediment within the terrace interval. Terraces
trap sediment and reduce the sediment and associated pollutant content in the
runoff water which enhance surface water quality. Terraces may intercept and
conduct surface runoff at a nonerosive velocity to stable outlets, thus, reducing
the occurrence of ephemeral and classic gullies and the resulting sediment.
Increases in infiltration can cause a greater amount of soluble nutrients and
pesticides to be leached into the soil. Underground outlets may collect highly
soluble nutrient and pesticide leachates and convey runoff directly to an outlet.
Terraces may increase the delivery of pollutants to surface waters. Terraces
increase the opportunity to leach salts below the root zone in the soil. Terraces
may have a detrimental effect on water quality if they concentrate and acceler-
ate delivery of dissolved or suspended nutrient, salt, and pesticide pollutants to
surface or ground waters.
Tree/Shrub Establishing (612): To establish woody plants by planting or
seeding.
Trough or Tank (614): A trough or tank, with needed devices for water control
and waste water disposal, installed to provide drinking water for livestock,
By the installation of a trough or tank, livestock may be better distributed over
the pasture, grazing can be better controlled, and surface runoff reduced, thus
reducing erosion. By itself this practice will have only a minor effect on water
quality; however when coupled with other conservation practices, the beneficial
effects of the combined practices may be large. Each site and application should
be evaluated on its own merits.
Use Exclusion (472): Excluding livestock from an area not intended for grazing.
Livestock exclusion may improve water quality by preventing livestock from
being in the water or walking down the banks, and by preventing manure
deposition in the stream. The amount of sediment and manure may be reduced in
the surface water. This practice prevents compaction of the soil by livestock and
prevents losses of vegetation and undergrowth. This may maintain or increase
evapotranspiration. Increased permeability may reduce erosion and lower
sediment and substance transportation to the surface waters. Shading along
streams and channels resulting from the application of this practice may reduce
surface water temperature.
Waste Management System (312): A planned system in which all necessary
components are installed for managing liquid and solid waste, including runoff
from concentrated waste areas, in a manner that does not degrade air, soil, or
water resources.
Waste Storage Facility (313): A waste storage impoundment made by con-
structing an embankment and/or excavating a pit or dugout, or by fabricating a
structure.
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This practice may reduce the nutrient, pathogen, and organic loading to surface
waters. This is accomplished by intercepting and storing the polluted runoff
from manure stacking areas, barnyards andfeedlots.
Waste Treatment Lagoon (359): An impoundment made by excavation or earth
fill for biological treatment of animal or other agricultural wastes.
This practice may reduce polluted surficial runoff and the loading oforganics,
pathogens, and nutrients into the surface waters. It decreases the nitrogen
content of the surface runoff fromfeedlots by denitrification. Runoff is retained
long enough that the solids and insoluble phosphorus settle and form a sludge in
the bottom of the lagoon. There may be some seepage through the sidewalls and
the bottom of the lagoon. Usually the long-term seepage rate is low enough, so
that the concentration of substances transported into the ground water does not
reach an unacceptable level.
Waste Utilization (633): Using agricultural wastes or other wastes on land in an
environmentally acceptable manner while maintaining or improving soil and
plant resources.
Waste utilization helps reduce the transport of sediment and related pollutants to
the surface water. Proper site selection, timing of application and rate of appli-
cation may reduce the potential for degradation of surface and ground water.
This practice may increase microbial action in the surface layers of the soil,
causing a reaction which assists in controlling pesticides and other pollutants by
keeping them in place in the field.
Mortality and other compost, when applied to agricultural land, will be applied
in accordance with the nutrient management measure. The composting facility
may be subject to State regulations and will have a written operation and man-
agement plan if SCS practice 317 (composting facility) is used.
Water and Sediment Control Basin (638): An earthen embankment or a
combination ridge and channel generally constructed across the slope and minor
watercourses to form a sediment trap and water detention basin.
The practice traps and removes sediment and sediment-attached substances from
runoff. Trap control efficiencies for sediment and total phosphorus that are
transported by runoff may exceed 90 percent in silt loam soils. Dissolved
substances, such as nitrates, may be removed from discharge to downstream
areas because of the increased infiltration. Where geologic condition permit, the
practice will lead to increased loadings of dissolved substances toward ground
water. Water temperatures of surface runoff, released through underground
outlets, may increase slightly because of longer exposure to warming during its
impoundment.
Water Table Control (641): Water table control through proper use of subsur-
face drains, water control structures, and water conveyance facilities for the
efficient removal of drainage water and distribution of irrigation water.
The water table control practice reduces runoff, therefore downstream sediment
and sediment-attached substances yields will be reduced. When drainage is
increased, the dissolved substances in the soil water will be discharged to
receiving water and the quality of water reduced. Maintaining a high water
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table, especially during the nongrowing season, will allow denitrification to
occur and reduce the nitrate content of surface and ground water by as much as
75 percent. The use of this practice for salinity control can increase the dis-
solved substance loading of downstream waters while decreasing the salinity of
the soil. Installation of this practice may create temporary erosion and sediment
yield hazards but the completed practice will lower erosion and sedimentation
levels. The effect of the water table control of this practice on downstream
wildlife communities may vary with the purpose and management of the water in
the system.
Waterspreading (640): Diverting or collecting runoff from natural channels,
gullies, or streams with a system of dams, dikes, ditches, or other means, and
spreading it over relatively flat areas.
Water Well (642): A well constructed or improved to provide water for irriga-
tion, livestock, wildlife, or recreation.
The location of the well must consider the natural water quality and the hazards
of its use in potentially contaminating the environment. Hazards exist during
well development and its operation and maintenance. Care must be taken to
prevent contamination of the aquifer from back flushing, accident, or flow down
the annular spacing between the well casing and the bore hole.
Water-Measuring Device: An irrigation water meter, flume, weir, or other
water-measuring device installed in a pipeline or ditch.
The measuring device must be installed between the point of diversion and water
distribution system used on the field. The device should provide a means to
measure the rate of flow. Total water volume used may then be calculated using
rate of flow and time, or read directly, if a totalizing meter is used.
The purpose is to provide the irrigator the rate of flow and/or application of
water, and the total amount of water applied to the field with each irrigation.
Wetland Wildlife Habitat Management (644): Creating, maintaining, or
enhancing wetland habitat for desired wildlife species.
Wetland Restoration (657): A rehabilitation of a drained or degraded wetland
where the soils, hydrology, vegetative community, and biological habitat are
returned to the natural condition to the extent practicable.
Wildlife Upland Habitat Management (645): Creating, maintaining, or
enhancing upland habitat for desired wildlife species.
Windbreak/Shelterbelt Establishment (380): Linear plantings of single or
multiple rows of trees or shrubs established next to farmstead, feedlots, and rural
residences as a barrier to wind.
Windbreak/Shelterbelt Renovation (650): Restoration or preservation of an
existing windbreak, including widening, replanting, or replacing trees.
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Chapter 10: Appendix
Appendix B: The NRCS Field Office Technical
Guide (FOTG)
The NRCS Field Office Technical Guide (FOTG)
The Natural Resources Conservation Service (NRCS) Field Office Technical
Guide (FOTG) (www.nrcs.usda.gov/technical/efotg/) is a compilation of resource
information about soil, water, air, plant, animal, and socio-economic resources in
each local field office area. It also contains other conservation planning aides,
including standards and specifications for conservation practices that are appli-
cable in the local area.
The driving concept behind the FOTG is that effective conservation must
recognize the inherent variability of natural resources across the land. Each
FOTG represents a continuing commitment of NRCS to provide its field office
professionals with science and technologies that are tuned to resources they will
encounter in their work. Because there are many factors to be considered
through the NRCS conservation planning process, regardless of program or
purpose, the FOTG provides the place to go for those considerations.
The FOTG is a key part of the materials needed to carry out NRCS' technical
assistance. The National Planning Procedures Handbook, NRCS' technical
handbooks and manuals, and the FOTG provide the basic framework for doing
high quality conservation planning assistance.
FOTG is a work continually in progress. Because our professional needs change,
our conservation programs change, our information technologies change, and
our knowledge of resources grows, we know that the FOTG is dynamic.
The FOTG and Conservation Planning:
Conservation planning and the FOTG go hand in hand. Conservation planning is
the vehicle we use to deliver technical information then allows clients to sustain
the productive use of the natural resources they manage. At the same time, feed-
back from conservation planning, application, and evaluation efforts helps expand
the quantity and improve the quality of the technical material found in the FOTG.
Conservation planning is the cornerstone of the technical work NRCS does with
clients, groups, and conservation partners. It is an integrated, systematic way of
utilizing technical information and knowledge to help people address resource
problems and opportunities.
National Conservation Practice Standards Subcommittee:
The National Conservation Practice Standards Subcommittee (NCPSS) is a
function of the National Technical Guide Committee. It exists to coordinate
development and review of national level practice standards; and, it publishes
those national standards in the NRCS National Handbook of Conservation
Practices. NCPSS does not make selection of practice standards for inclusion in
the FOTG. State Conservationists, through their state-level technical guide
committees, direct which national practices are selected for inclusion in FOTGs
in their respective states. Those state-level selections are made with needs of
each field office in mind.
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Chapter 10: Appendix
Selection of national practices for inclusion does not end the process. In most, if
not all cases, national practice standards are too general for application through
NRCS assistance. There are technical processes, procedures from handbooks
and manuals, and other details to be added. State laws and local ordinances may
impose performance criteria that must be addressed, too. NRCS state-level and
other technical specialists (including NRCS field personnel) may be called upon
to adapt the national practice standard and to develop the practice specifications.
Since 1996, state practices that are used with highly erodible land or in wetland
programs are required to have public review prior to their placement in the
FOTG. This is a requirement of the 1996 Farm Bill. This process is undergoing
review along with other parts of NRCS' FOTG policy in order to make it more
responsive to field needs.
After all these activities and reviews, the practice standard (and its specifica-
tions) are ready for inclusion in the field office FOTG. It is a process that
ensures that the technical guidance each standard and specification provides is
pertinent to field office conditions.
FOTG Contents:
Section I: General Resource References
Section I lists references and other information for use in understanding natural
resources of the field office service area or in making decisions about resource
use and management systems. The actual references listed are to be filed, to the
extent possible, in the same location as the FOTG. Computer-based tools used in
resource analysis and modeling will be listed in Section I. References kept in
other locations will be cross-referenced. Examples include texts and publications
dealing with databases found in Section II (below) as well as other resource
issues.
Section II: Natural Resources Information
Section II contains natural resource data, databases, and procedures for interpre-
tation. These may include Ecological Site Descriptions and Forage Suitability
Group Descriptions. This section will have a statement indicating exactly what
is used as the "official" copy of the Soil Survey. In some cases separate state-
ments may be needed for maps, tables, and data.
Section III: Resource Management Systems and Quality Criteria
Resource Management Systems (RMS) will address all identified resource
concerns at or above the level of sustainability, taking into account human-
cultural, economic and social concerns relative to the Soil, Water,
Air, Plant, and Animal natural resources. Quality Criteria for treatment required
to achieve a RMS will be established by NRCS and filed in this section of the
FOTG. Criteria shall be stated in either qualitative or quantitative terms for each
resource consideration. Where national criteria have not been established, the
State Conservationist will establish criteria. Where State and/or local regulations
establish more restrictive criteria, these must be used in developing the RMSs.
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Chapter 10: Appendix
Section IV: Practice Standards, Specifications and Supplements
Section IV of the FOTG contains conservation practice standards applicable in
that field office. Practice standards contain minimum quality criteria for each
practice while the specifications describe requirements necessary to install the
practice. Supplements add new information as it becomes available. It may also
include specifications guide sheets developed for use with the standards.
Section V: Conservation Effects
Conservation effects provide indicators of the impacts conservation practices
and systems have on the natural and cultural resources. They are based primarily
on empirical data and field experience with practices and systems of practices.
The effects are listed for each individual practice. States may provide hardcopy
effects or refer the user to the Conservation Effects data. The effects of systems
can be estimated by evaluating the combined effects of practices included in a
specific system. When properly planned and applied, systems of conservation
practices are generally complimentary and accumulative. When conservation
practices are installed, the effects on all natural resources are considered.
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