vvEPA
United States
Environmental Protection
Agency
Robert S. Kerr EPA-600/2-78-046
Environmental Research Laboratory March 1978
Ada OK 74820
Research and Development
Environmental Impact
Resulting from
Unconfined Animal Production
Environmental Protection
Technology Series
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U S Environmental
Protection Agency, have been grouped into nine series These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields
The nine series are
1 Environmental Health Effects Reseatch
2 Environmental Protection Technology
3 Ecological Research
4 Environmental Monitoring
5 Socioeconomic Environmental Studies
6 Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8 ' Special" Reports
9 Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series This series describes research oerforrred to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmenta1 degradation from point and non-point sources of pollution This work
provides the new or improved technology required for the control and treatment
of pollution sources to rner't environmental quahtv standards
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161
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EPA-600/2-78-046
February 1978
ENVIRONMENTAL IMPACT RESULTING FROM
UNCONFLNED-ANIMAL PRODUCTION
by
Jackie W. D. Robbins
Department of Agricultural Engineering
Louisiana Tech University
Ruston, Louisiana 71272
Grant No. R804497
Project Officer
S. C. Yin
Source Management Branch
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
''•" Agency
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DISCLAIMER
This report has been reviewed by the Robert S. Kerr Environmental
Research Laboratory, U.S. Environmental Protection Agency, and approved
for publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency, nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
ii
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FOREWORD
The Environmental Protection Agency was established to coordinate
administration of the major Federal programs designed to protect the
quality of our environment.
An important part of the Agency's endeavors to fulfill its mission
involves the search for information about environmental problems, management
techniques and new technologies through which optimum use of the nation's
land and water resources can be assured. The primary and ultimate goal of
these efforts is to protect the nation from the scourge of existing and
potential pollution from all sources.
EPA's Office of Research and Development conducts this search through
a nationwide network of research facilities.
As one of these facilities, the Robert S. Kerr Environmental Research
Laboratory is responsible for the management of programs to: (a) investi-
gate the nature, transport, fate and management of pollutants jn groundwater;
(b) develop and demonstrate methods for treating wastewaters with soil and
other natural systems; (c) develop and demonstrate pollution control tech-
nologies for irrigation return flows; (d) develop and demonstrate pollution
control technologies for animal production wastes; (e) develop and demon-
strate technologies to prevent, control or abate pollution from the petroleum
refining and petrochemical industries; and (f) develop and demonstrate tech-
nologies to manage pollution resulting from combinations of industrial
wastewaters or industrial/municipal wastewaters.
This report is a contribution to the Agency's overall effort in ful-
filling its mission to improve and protect the nation's environment for the
benefit of the American public.
f
1
William C. Galegar, Director
Robert S. Kerr Environmental
Research Laboratory
iii
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ABSTRACT
This report outlines and evaluates current knowledge related to environ-
mental problems resulting from unconfined animal production. Animal species
directly addressed are cattle, sheep, and to a limited extent, hogs. Informa-
tion for the report came from literature and current research reviews plus
direct inputs from a group of 17 specialists in the subject field.
Unconfined animal production utilizes about 40% of U.S. land area, con-
sists of hundreds of thousands of individual units, receives almost 50% of all
livestock wastes, and is compatible with a high quality environment. Associ-
ated environmental problems are limited to those that affect surface water
quality. These nonpoint source problems are not directly related to number of
animals involved; they are intimately dependent on hydrogeological and manage-
ment factors and are best described as results of the erosion/sediment phe-
nomenon.
Unconfined animal production can cause changes in vegetative cover and
soil physical properties that may result in increased rainfall runoff and
pollutant transport to contiguous surface waters. The most common stream
water quality change is elevated counts of indicator bacteria. Increased
levels of inorganic (eroded mineral soil) and organic sediments with associ-
ated plant nutrients and oxygen demands may also result from certain high
impact or problem areas where inadequate management and/or poor site con-
ditions exist. These areas are usually only a small portion of the total
production area and are readily identified by observation. The pollutant
levels from the remainder of the production area are seldom discernible from
background levels and, on an areal basis, are of the same magnitude as yields
to land from rainwater and yields from relatively undisturbed lands. If other
changes occur (such as to affect groundwater or air quality), they are either
at such low levels as to be of no environmental consequence, or they are so
site specific that they are not characteristic of unconfined animal production.
Prediction of increases in pollutant yields to receiving waters due to
unconfined animal production is not possible with present state of the art
technology. In principle, control is realized by locating high impact,
problem areas according to hydrological dictates and by following good manage-
ment practices. One major challenge is to demonstrate cost-effective routes
toward achievement of various levels of control.
This report was submitted in fulfillment of Grant No. R804497 by the
Louisiana Tech University Department of Agricultural Engineering, under the
sponsorship of the U.S. Environmental Protection Agency. This report covers
a period from May, 1976, to October, 1977, and work was completed as of
October, 1977.
iv
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CONTENTS
Foreword ill
Abstract . iv
Acknowledgements vi
I. Findings and Conclusions 1
II. Recommendations 3
III. Introduction 6
Scope 6
Context 7
IV. Characteristics of Unconfined Animal Production 9
Impact on Soil and Vegetation 10
Animal Behavior 12
Beef Systems 14
Dairy Systems 16
Sheep Systems 17
Swine Systems 17
V. Water Quality Effects from Unconfined Animal Production. . 19
Background Levels of Pollutants .... 19
Prediction of Pollutant Yield 20
Sediment 22
Case Studies 24
VI. References 31
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ACKNOWLEDGEMENTS
Early in the life of the project, a group of specialists/scientists was
formed to conduct the study. Their cooperation in both identifying informa-
tion and giving guidance to the project was of major importance to the
development of this document. Sincere appreciation is hereby expressed for
the major roles performed by:
James V. Albritton, Louisiana Tech University
Richard W. Guest, Cornell University
Frank J. Humenik, North Carolina State University
C. R.eid McLellan, Louisiana Tech University
Stewart W. Melvin, Iowa State University
J. Ronald Miner, Oregon State University
Jeff Powell, Oklahoma State University
John M. Sweeten, Jr., Texas A&M University
Joe R. Wilson, Louisiana Tech University
S. C. Yin, EPA, Ada, Oklahoma
Appreciation is also expressed for the information and guidance provided
by:
James B. Allen, Deceased, Mississippi State University
Clyde L. Earth, Clemson University
James K. Koelliker, Oregon State University
Eugene W. Rochester, Auburn University
J. Ike Sewell, University of Tennessee
Ralph E. Smith, University of Georgia
Ted L, Willrich, Oregon State University
Special appreciation goes to Wayne Mulig for a thorough job of assembling
pertinent literature and to Candy Daniels for patient secretarial assistance
throughout the project.
vi
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SECTION I
FINDINGS AND CONCLUSIONS
Generally, unconfined animal production is both environmentally sound and
compatible with a high quality environment. Documented cases of pollution
resulting from production of livestock on pasture and rangeland are limited,
indeed. Furthermore, all the available data indicate that neither the number
nor the seriousness of environmental problems resulting from unconfined animal
production is directly related to the number of animals involved or to the
amount and characteristics of animal wastes generated. Rather, these nonpoint
source problems are intimately dependent on hydrogeological and management
factors, and are best described as results of the erosion/sediment phonemenon.
Unconfined animal production can cause changes in vegetative cover and
soil physical properties that may result in increased rainfall runoff and
pollutant transport to contiguous surface waters. The most common stream
water quality change, and often the only change that can be definitively
discerned, is elevated counts of indicator bacteria. Increased levels (con-
centrations) of inorganic (eroded mineral soil) and organic sediments with
associated plant nutrients and oxygen demands may also result from certain
high impact or problem areas — where inadequate management and/or poor site
conditions exist. These areas are usually only a small portion of the total
production area and are readily identified by observation. The pollutant
levels from the remainder of the production area are seldom discernible from
background levels and, on an areal basis, are of the same magnitude as yields
to land from rainwater and yields from relatively undisturbed lands. There
is some evidence that pollutant yields (amounts rather than concentrations)
increase in direct proportion to rainfall runoff from these non-problem areas.
Seemingly, this is more generally the case when the stocking rate is rela-
tively large. If other changes occur (such as to affect groundwater or air
quality), they are either at such low levels as to be of no environmental con-
sequence or they are so site specific that they are not characteristic of
unconfined animal production.
Prediction of increases in pollutant yields to receiving waters due to
unconfined animal production is not possible with present state of the art
technology. As measured in receiving streams, these increases are not only
usually small in value but extremely erratic in occurrence as well. As a
first approximation, factors that govern erosion/sediment yields also are the
factors that govern pollutant yields from unconfined livestock systems.
While organic materials entering surface waters from these systems may
exert oxygen demands in water quality tests, the organics are usually rela-
tively unavailable to organisms indigenous to the receiving waters and, thus,
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may not materially affect oxygen kinetics in receiving streams. Increased
yields of chemical constituents such as nitrogen and phosphorus are generally
so small that they are confounded in streams with background levels. The
actual significance or meaning of elevated bacterial counts in this case is
not clear. Bacterial indicators are reputed to be the most sensitive index
of water quality impacts resulting from unconfined livestock. These organisms
are properly used to designate the bacteriological safety of potable water.
Their presence in water is accepted by public health authorities as an indi-
cation of fecal pollution. Whenever water is polluted with fecal waste, it
poses a potential health hazard if used untreated for drinking or body contact
recreational purposes. There is a dearth of documented cases of health
problems correlated with bacterial indicators counts in water related to
unconfined animal production systems, but this may be due solely to the lack
of intensive and systematic research in this area.
While certain specific questions such as desired level of control and
best methods to achieve water quality goals remain unresolved, the basic con-
cepts, methods, processes, and procedures needed to reduce pollutant yields
from unconfined animal production systems are available in principle. Since
the pollutants are nonpoint in origin, control methodology is effected through
changes in the production management system; i.e., by incorporating practices
involved in controlled grazing, regulated animal congregation patterns, sus-
tained forage production (establishment and protection of desired species),
intensive erosion control, and proper land use.
Pasture and rangeland management practices leading to optimal forage
production on a long-term sustaining basis, such as that resulting from main-
taining correct stocking rates and forage production practices with erosion
control, are also those practices which minimize environmental impacts.
Still, less pollutants would reach streams if the operating philosophy of such
production systems were broadened to include control or elimination of any
problem areas. On the other hand, when exploitive production (poorly managed)
is followed, unnecessary detrimental effects on surface water quality are
likely to occur. These systems may require major modification/adaptation to
meet environmental goals as well as to achieve other objectives which govern
pasture and rangeland use.
One major challenge is to demonstrate cost-effective routes toward
achievement of various levels of pollution control for unconfined animal
production systems. Whether resources should be used to reduce pollutant
yields from a given production system really requires an on-site evaluation
of whether the pollutants have a real adverse effect on the quality of the
receiving water and whether the yields can be significantly and definitively
reduced. Certainly, control will be difficult and costly if control is de-
fined as the ability to establish and enforce effluent standards. In cases
where pollutants from livestock activity are not discernible from background
levels, little or no change may be noted in stream quality even when signifi-
cant efforts and resources are expended on control. However, if control is
approached using well-planned management practices that include pollution
control as an integral part rather than a laissez faire approach, the impact
of unconfined animals will be well within acceptable limits and in keeping
with the national water quality goals.
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SECTION II
RECOMMENDATIONS
1. Exploitive range and pasture management practices such as overgrazing
are to be discouraged due to the associated potential of increased rainfall
runoff inputs to contiguous surface waters. Mechanisms should be developed so
that intensive, well planned management practices that are supportive of long-
term, sustained forage yields will be adopted. While no regulatory action
seems justified to further reduce the environmental impact resulting from such
well managed systems, the operating philosophy of these systems should be
broadened to include pollution control for any high impact problem areas.
2. Multidisciplinary and multiagency review teams should be used to
evaluate specific environmental problems resulting from unconfined animal
production and to recommend changes in management practices to correct the
problems. Their recommendations should be applied in concert with established
regulatory procedures.
3. Regulatory programs should account for local (site specific) condi-
tions. Regulated changes in management practices should be restricted to
those documented to have measurable water quality benefits for receiving
waters. Due to the low level of pollution associated with unconfined animal
production, regulatory programs that would in general discourage or restrict
livestock production on pasture and rangeland should be avoided.
4. When developing or modifying management practices for unconfined
animal production systems to include environmental protection, logic and field
observation suggest that consideration should be given to the following con-
cepts :
a) Install and maintain an effective and complete program of soil
erosion control.
b) Follow stocking rates and controlled utilization of forages
(e.g., rotation, deferred, and seasonal grazing) that reduce
erosion and waste accumulation. Reduce stocking rates in problem
areas and at critical times or seasons. Stocking rates and graz-
ing programs should be tailored to the soil vegetation, topogra-
phy, hydrogeology, and microclimate of the particular site.
c) Avoid animal stocking rates and other practices that create hold-
ing areas rather than grazing areas. Promote necessary animal
congregation in areas that are hydrologically remote from streams
and other major drainage channels. Periodically move bedground,
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shelter, salting, feeding, and/or watering areas to control waste
accumulation, soil compaction, and erodible paths and areas.
d) Maintain to the extent ecologically feasible, highly productive
forage and dense ground cover on the land to decreases volume and
rate of runoff, to entrap and hold animal wastes, to utilize
fertilizer nutrients, and to prevent erosion. Increase herbaceous
cover in proximity of stream banks, downslope from animal congre-
gational areas, and on other critical areas.
e) Where the number of animals per unit area or the characteristics
of the site present pollution problems, appropriate drastic man-
agement alternatives/practices may include:
(1) Restrict animal access to critical areas. Use fencing to
prevent livestock from entering highly erodible areas and
critical stream or pond reaches and to prevent animals from
wading in water. Provide summer shade (trees or artificial
shelters) and insecticides to lessen the need for animals to
enter water for relief from heat and insects. Block erodible
paths with physical barriers and revegetate eroded paths.
Move drinking facilities outside critical areas.
(2) Increase rate of fecal degradation and incorporation. Modify
feed formulation and/or texture. Use tillage to break up,
manipulate, and incorporate wastes in particular problem
areas.
(3) Use land forming and diversions to modify drainage patterns.
Total stream fencing and other drastic controls will usually be
both unnecessary and impractical except for a few problem areas
within an operation.
5. In view of the many desirable characteristics of unconfined animal
production compared with alternate livestock production techniques, adequate
research, management, and educational resources should be allocated to:
a) Assess the importance and significance of increased levels of
pollutants (indicator bacteria, plant nutrients, and oxygen
demands) in surface waters (streams and impoundments), with con-
sideration given to fate of the pollutants and uses of the waters.
b) Increase operational understanding, improve design, and demon-
strate effective management practices of control concepts (through
study of pilot/demonstration sites).
c) Demonstrate water quality benefits of control practices.
d) Demonstrate cost-effective routes for achieving various levels of
environmental protection.
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e) Ultimately develop models of the environmental impact resulting
from unconfined animal production that can be used to help in the
design of best management practices for each sub-part of the
total system.
f) Develop technology and establish educational and assistance
programs that encourage producers to adopt management practices
that include environmental protection.
6. Several areas do not need additional research:
a) Studies of environmental problems associated with unconfined
animal species other than cattle and sheep seem unjustified since
there are such small numbers of these species in unconfined
systems and it should be possible to design adequate controls for
such systems by extrapolation from cattle and sheep systems.
b) Studies of pollution problems other than those associated with
increased levels of sediments, nutrients, and bacteria in surface
waters seem inappropriate. Studies of air and groundwater
pollution, for example, could only be expected to yield incon-
clusive or negative results. Other potential hazards such as
those associated with using insecticides and herbicides are not
unique to unconfined animal production systems and, thus, should
be covered in more general studies.
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SECTION III
INTRODUCTION
SCOPE
This report outlines and evaluates current knowledge related to environ-
mental effects of unconfined animal production. The difference between con-
fined and unconfined animal production is that wastes generated in confined
systems are subject to handling/diverting for conventional control or treat-
ment while those in unconfined systems cannot be handled and, thus, must be
controlled through the management scheme. Correspondingly, the contrast
between confined and unconfined animal production systems is very similar to
the differentiation between point and nonpoint sources of pollution where a
nonpoint source is one whose specific point of generation and exact point of
entry into the environment cannot be defined. All grazing systems—where
livestock have free access to pasture, range, woodland, or cropland and
utilize the associated forage/residue as a major feed source—are unconfined
systems.
Animal species directly addressed in this report are cattle (both dairy
on pasture and beef on pasture and range) and sheep (on pasture and range).
Some consideration is given to goats, hogs, poultry, and horses. Commercial
or farm production of these latter species in the U.S. either utilizes con-
fined systems almost exclusively or, as in the case of goats, unconfined pop-
ulations are relatively small and information specific to the environmental
impacts they produce is unavailable.
Specific tasks set for this report included:
1. Characterize unconfined animal production/management systems.
2. Identify the associated environmental problems.
3. Evaluate the magnitude and seriousness of the problems.
4. Assemble and prepare recommendations for reduction or control of the
pollution problems cited.
5. Identify gaps in present knowledge and suggest: areas needing addi-
tional evaluation, control, and research.
Environmental concerns investigated in preparing the report included:
1. Surface water quality as affected by both runoff from grazing areas
6
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and direct contact with animals (including pesticide problems).
2. Impact on soil and vegetation.
3. Accelerated erosion - streambank as well as general wind and water
erosion.
4. Groundwater quality.
5. Air quality - odors and dust.
The report does not address each of these concerns directly. It deals only
with those found to be problems.
The basic approach used to gather information for this report was to
evaluate existing literature, collaborate with specialists in the field, and
review ongoing research relating to nonpoint source pollution. Major efforts
were made to find information that would fill in gaps in the information
assembled early in the study and to make sure that the information gathered
was not misinterpreted or extended beyond its limits of applicability. To
help assure that this was the case, specialists in the subject field reviewed
drafts of the report and made suggestions for improvements and additions.
Their assistance in both identifying information and helping interpret it was
of major importance in the conduct of the study.
An original intent was to present the information in this report by
geographical/climatic regions. However, analysis of various regional compi-
lations of information did not reveal unique results for the regions as first
envisioned. Thus, the effort to organize the report along regional boundaries
was abandoned.
CONTEXT
Unconfined animal production systems have characteristics similar to
other nonpoint, potential pollution sources which historically have been con-
sidered as natural and generally uncontrollable. Sources of this type have
included precipitation, drainage from urban areas, runoff from forests and
grasslands, return irrigation flows, leachate from decaying vegetation, and
wastes from wild animals. Generally, these nonpoint sources have been assumed
to be small compared to such point sources as municipal and industrial waste
discharges. More information on the characteristics and magnitude of the
nonpoint sources has led to questions about the validity of this assumption.
At least one-third of the pollutants entering United States waters have been
estimated to come from nonpoint sources.
The emphasis of our national water pollution control policy is now on the
amount of wastes that can be kept out of surface waters rather than on the
amount of wastes that can be assimilated by the waters. A major goal of
Public Law 92-500 is that the discharge of pollutants into navigable waters
be eliminated by 1985. The law also sets as the national goal that wherever
obtainable, an interim goal of water quality which provides for the protection
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and propagation of fish, shellfish, and wildlife and provides for recreation
in and on the water be achieved by July 1, 1983. Thus, it is imperative that
potential pollution sources be evaluated so that appropriate remedial measures
and control technology may be formulated and applied as needed. This document
is an analysis of the technical information on the environmental impact
resulting from unconfined animal production systems.
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SECTION IV
CHARACTERISTICS OF UNCONFINED ANIMAL PRODUCTION
While approximately 50% of all livestock wastes in the United States are
estimated to be produced in confinement, about 75% of cattle, 85% of sheep,
and 10% of hogs are in unconfined systems at any given time. Table 1 con-
tains approximate numbers of animals being maintained in various production
systems. Although specialization, labor reduction, and improved efficiency
have caused a trend toward confined production systems, unconfined production
is expected to continue to predominate, particularly in the beef and sheep
industries.
TABLE 1. DISTRIBUTION OF LIVESTOCK
Type Animal
No. of
Production
Units*
No. of
AnimalsV
No.
Confined^
No. Un-
Conf ined
Percent
Unconfined
Thousands
Cattle and Calves
Beef Cattle
Dairy Cattle
Sheep and Lambs
Goats and Kids
Hogs and Pigs
r\
Horses and Ponies
490
220
50
10
260
—
123 000
101 500
21 000
12 700
1 300
55 000
8 000
30 000
20 000
10 000
2 000
200
50 000
—
93 000
81 500
11 000
10 700
1 100
5 000
—
76
80
52
84
85
9
—
* From 1971 USDA census.
From 1977 USDA inventory figures.
Based on USDA estimates of livestock on feed and the assumption that 6% of
all breeding beef cattle are confined and that 50% of all dairy cows and
replacement heifers are confined.
Q
From registration of various breeds and Extension Service estimates.
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About 40% (360 x 106 ha) of the land area of the United States is used
for grazing livestock. Forages account for the production of more than 50%
of the nation's milk, nearly 80% of the total feed for beef cattle, and 90%
of the total feed for sheep. Less than 5% of swine feed comes from forages.
While some forages are harvested and brought to confined livestock, the vast
majority are grazed. Ensminger (1970) gives tables of stocking rates to in-
sure sustained yield of forage for a wide variety of conditions, including
soil and forage types. Table 2 gives ranges in suggested stocking rates for
each of the ten generally recognized grazing regions. The procedures for
determining the correct stocking rate for a given site are generally well
understood and require input data regarding both site and management factors.
TABLE 2. RANGE OF STOCKING RATES BY GRAZING REGION (AFTER ENSMINGER 1970)
Region
Animal units/ha
Permanent Pasture Temporary Pasture
Northeastern
East Central
Southeastern (and Deep)
Southeastern)
Northern Great Plains
Southern Great Plains
(Irrigated)
Northern Intermountain
(Irrigated Only)
Southern Intermountain
(Irrigated Only)
Northern Pacific Slope
Southern Pacific Slope
(Irrigated Only)
1.5 to 3.0
2.0 to 3.0
2.0 to 6.0
0.5 to 3.0
0.1 to 1.0
(2.0 to 10.0)
2.0 to 4.0
2.0 to 7.0
1.0 to 5.0
2.0 to 3.0
2.0 to 4.0
2.0 to 5.0
2.0 to 6.0
1.5 to 4.0
0.5 to 2.0
(1.0 to 4.0)
1.0 to 5.0
0.5 to 7.0
0.5 to 5.0
2.0 to 5.0
Smaller value represents stocking rates for continuous grazing; higher value
represents rotational grazing. One animal unit equals 1 mature horse or cow,
2 yearling horses or cattle, 4 nursing calves, 2.5 mature swine, 5 hogs
raised to 100 kg, 7 mature sheep, or 14 lambs.
IMPACT ON SOIL AND VEGETATION
As grazing animals traverse ranges and pastures, the stresses applied to
the soil beneath their hooves often exceed the strength of the soil. The high
10
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stresses result in chipping of dry soils, compaction of moist soils, and de-
formation of wet soils. Resistance to compaction or deformation is deter-
mined by the soil's texture, structure, porosity, and moisture content. Maxi-
mum compaction is most predominate at a moisture content between wilting point
and field capacity. Soils with high porosity and wide particle size range are
more susceptible to compaction than are other soils under the same pressure
and moisture content (Heady 1975).
The effect of soil compaction is to alter pore volume and structure.
These alterations increase the soil bulk density and decrease infiltration
capacity, permeability to water, water storage capacity, aeration, root pene-
tration, and forage production. Trampling by grazing animals may cause poorer
water infiltration, as indicated by numerous studies. For example, Trimble
and Weitzman (1951) measured average infiltration rates of 52 and 11 cm/h on
ungrazed and grazed pastures, respectively. In a New Mexico study of grazing
intensity-infiltration relationships, infiltration rates were determined to
be 10.5, 5.5, and 2.1 cm/h on undergrazed, overgrazed, and depleted ranges,
respectively (Flory 1936).
Reductions in infiltration rates on pastures and ranges due to grazing
correlate with increases in runoff. A decrease in infiltration and increase
in runoff on grazed lands may lead to more arid conditions than normal. For
example, Hanson et al. (1970) found that the reduction in available moisture
on heavily grazed South Dakota ranges averaged 2 cm a year, or about 8% of the
annual precipitation available for plant production. A decrease in moisture
available for forage production is usually accompanied by an increase in soil
erosion.
Selective defoliation by grazing animals decreases the preferred forage
species and allows the proliferation of less desirable species. Close
grazing of desired plant species during critical stages of growth such as
before seed maturation hinders their competitive capacity. Reduction of the
leaf area of forages by close grazing reduces their photosynthetic abilities
and may affect plant succession (Stoddart et al. 1975). Heady (1975)
attributes the most prevalent cause of rangeland retrogression to overgrazing
and other faulty management of livestock operations.
Pastured woodlands and shelterbelts serve dual purposes and can have
amplified stresses imposed by grazing animals. If grazing is poorly managed,
direct damage to trees from browsing and trampling by livestock is compounded
with soil compaction, reduced infiltration rates, and denudation of mulch and
vegetation. Young trees within reach of browsing animals often suffer from
defoliation and removal of shoots and buds. Older established trees may be
damaged by horning, rubbing, or similar activities, resulting in broken limbs
or ruptured bark through which pathogens may enter.
The severity of the impact of grazing animals upon tree establishment
and growth depends upon the kind of animal and its forage preferences, inten-
sity of grazing, type of trees, age of the stand, and availability of
alternative forage sources. For example, under proper management, tree losses
due to browsing damages on ponderosa pine forests may be as little as 4 per-
cent from sheep and less than 1 percent from cattle. Between tree types,
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deciduous trees usually are more susceptible to browsing than are conifers;
hardwood forests under open-range conditions can be grazed with minimal tree
damage if properly managed (Stoddard et al. 1975).
ANIMAL BEHAVIOR
Behavior patterns and preferences of livestock species tend to result in
certain areas showing intense environmental stresses. These problem areas
are usually only a small fraction of the total unconfined production site and
are caused by uncontrolled animal behavior that leads to selective and over-
grazing (of sites as well as plant species) and to animal congregation and
waste elimination in or near water sources or other critical areas. The
general behavior patterns of livestock follow ancestral instincts but may be
influenced by management practices.
Ingestion Preferences
Anatomical differences of digestive systems and mouth parts affect the
ingestive behavior of animals. Cattle have no upper incisors. They xjrap
their tongue around forage and cut it off with their lower teeth by jerking
forward. Thus, cattle do not graze as closely as other animals but may up-
root plants. They primarily graze grasses but will readily consume forbs and,
to a lesser extent, browse from woody plants. In order of preference, cattle
will consume grasses, forbs, and browse (depending on species composition),
with the volume of grasses generally exceeding the combined total of the
latter two. Within the grasses, cattle will select certain species if more
than one is available. Thus, controlled grazing may be necessary to maintain
desired species composition and ground cover.
Shrubs produce forage favored by sheep and goats that cattle and horses
usually reject. Sheep and goats also feed on grasses, provided the forage is
tender. Due to the cleft upper lip structure of the mouth parts, sheep and
goats can graze plants close to the ground. Uncontrolled grazing by these
species may result in denudation of the area.
Horses possess full sets of teeth and are very forage selective. Al-
though monogastric animals, horses have a highly specialized area of the
colon (the cecum) in which microorganisms break down forages. Horse pastures
show definite areas of short, heavily grazed grasses and tall, mature un-
grazed portions. While swine have full sets of teeth, their monogastric
(simple stomach) nature limits their ability to utilize forages. As a result,
swine are not generally provided grazing. Even though poultry have no teeth,
they can graze. But, unlike other farm animals, they are not capable of
digesting forages; thus, poultry are raised in confinement.
Site Preferences
Areas that will be most heavily utilized for grazing by the various
livestock species are dependent upon topography, water distribution, vegeta-
tion, prevailing winds, and the kind of livestock. Cattle prefer accessible
areas such as valley bottoms, saddles between drainages, areas around salt
sources, and level mesas. They lightly graze areas away from water and areas
12
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with steep slopes if more preferred grazing grounds are available. Con-
versely, unherded sheep and goats tend to overutilize slopes and ridge tops.
These areas serve as their preferred bedding, as well as grazing, grounds.
Elimination Behavior
When animals are confined in lots, essentially all rainfall and runoff
come in direct contact with manure-covered surfaces. But in unconfined
systems where animal density is less, the vast majority of runoff may show no
fecal contamination. On the other hand, small portions of the total runoff,
particularly that from animal congregation and waste elimination areas, may
contain pollutant levels similar to runoff from manure-covered surfaces.
Sweeten and Reddell (1976) reviewed the literature related to excreta loading
rate, distribution, and "fouling" of vegetation. By assuming completely uni-
form spreading of manure by grazing cattle, thereby giving the highest esti-
mate of areal coverage over a given time period, they calculated the percent
of coverage for various grazing densities, as given in Table 3. From their
study, the researchers reasoned that sustained high stocking rates on pastures
tend to be self-limiting because of so-called "dung-fouling" of vegetation and
that "dung-fouling" is a more natural and permanent constraint to limiting
waste buildup on true grazing areas than any water pollution control regula-
tion. However, even when physical features (such as pasture size and shape,
water, trees, and fences) have no effect on animal eliminative behavior,
excreta are not uniformly distributed throughout the production site.
Petersen et al. (1956) observed that when dairy cows were not attracted by
physical features, the distribution of excreta was approximated by a negative
binomial distribution (i.e., non-uniform). Beyond this, physical features do
attract unconfined animals and, thus, eliminative patterns of livestock tend
to result in areas of both high and low density waste deposition.
Swine and horses tend to deposit fecal wastes in the same general areas
time after time. Swine usually void their excreta in places away from
sleeping areas, but may eliminate wastes near watering places. Cattle, sheep,
and goats eliminate wastes without preference to location and generally do not
exhibit any inclination to avoid contact with depositions, except cattle do
show an oral or grazing-related avoidance.
TABLE 3. PASTURE AREA COVERED BY MANURE AS A FUNCTION OF
STOCKING RATE (SWEETEN AND REDDELL 1976)
Waste
Material
Feces
Urine
Feces and Urine
Area Covered,
m2hd *day ~l
1.1
2.8
3.9
Area
Covered, %/yr
Stocking Rate, m'Vkg liveweight
0.2
430
1080
1500
2
43
108
150
20
4
11
15
200
0.4
1.1
1.5
2000
0.04
0.11
0.15
Assumes cattle weigh 450 kg/hd and uniform distribution of waste material.
Values exceeding 100% indicate overlap of waste deposits.
13
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As ruminants (pregastric fermentation of roughages), cattle on pasture or
range generally graze about 8 hours and then retire to shade or shelter to
ruminate approximately 8 hours. During the period of rumination and inactiv-
ity, cattle tend to congregate in and around watering areas, shade, or
shelter. These areas are subject to waste accumulation and tend to become
compacted and denuded as cattle repeatedly congregate in the same location.
A similar situation exists with sheep and goats. In particular, sheep on
pasture with shelters tend to eliminate larger amounts of wastes in the
shelter areas.
BEEF SYSTEMS
Unconfined beef cattle production systems are divided into three unique
categories — cow-calf system, stocker system, and grass finishing system.
Cow-Calf System
The cow-calf system is the propagating unit of the beef chain. In this
system, mature cows weighing 350-500 kg are maintained on pasture for the
express purpose of producing a calf and raising that calf to a weight of
approximately 250 kg at 8-10 months of age. About 70 million animals (42
million cows and replacement heifers, 26 million calves, and 2 million bulls)
are in cow-calf systems. As noted by Dixon et al. (1977), the average number
of animals per cow-calf operation varies with region:
Corn Belt and Southeast 50
Northern Plains 150
Intermountain, Southwest, and
High Plains 350
Animals in cow-calf systems roam unconfined throughout the year and graze
for virtually all of their feed during the forage growing season. Main forage
growing seasons vary from 4 months in northern-most states to 8-10 months in
the southern states. In addition, winter forages are often used in the South-
eastern and Pacific Slope regions, making year-round grazing and unconfined
production a reality. In most rangeland areas, cattle are maintained during
non-growing seasons on dormant vegetation and fed small amounts of supplemen-
tal concentrates. Hay is fed when snow or ice prevents grazing. In other
regions, surplus forages are harvested during peak growing seasons and fed to
the cattle during non-growing seasons.
In areas of heavy winter rains or wet snows and in areas of intense cold
and high winds, winter lots with open sheds may be provided for the cattle.
Some winter lots include small paved areas and larger adjacent areas. The
cattle are turned into the larger areas for exercise when the ground is frozen
or dry. In regions where the winters are relatively dry, open rolling land
with trees for shelter is commonly used. A more confined area may be used in
other management systems, and particularly so for cows with new-born calves.
14
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Important characteristics of cow-calf systems from an environmental
standpoint are:
a) Within a system that follows stocking rates and management practices
that maximize long-term sustained forage production, only certain
problem areas are likely to contribute increased pollutant loads and
to warrant control beyond the good soil and water conservation
practices that are characteristic of such systems. These problem
areas are alluded to below and are readily recognized by observation.
b) During non-grazing periods of the day, cattle tend to congregate
(around shaded watering areas or other places of shelter), and the
areas of congregation tend to be constant.
c) Cattle tend to follow the same paths to and from grazing areas,
water, and shelter. Ingress and egress points to ponds and streams
are usually particularly heavily traveled.
d) Cattle are often grouped into smaller areas during winter (and
droughts).
Stocker System
The stocker systems take the product of cow-calf system and provide a
growing phase for calves between weaning and the time they are ready to go to
a finishing system or be returned to the breeding herd. Major emphasis is
placed on obtaining economical gains on forage. Of the 1977 beef inventory,
approximately 17.5 million cattle (6.5 million replacement beef females plus
11 million steers and heifers not on feed) were in stocker systems.
Primary grazing regions of stocker management systems are the South-
eastern and Pacific Slope regions which make maximum utilization of winter
grazing capabilities as well as lush summer growth. In addition, small grain
areas of the Southern Great Plains region (particularly Texas, Kansas, and
Oklahoma) utilize stocker calves for grazing grain fields during winter
months.
Cattle remain in stocker systems for periods of four to six months,
Some systems utilize both summer and winter pastures for year-round stocker
production. Stockers may be obtained in the fall and wintered on hay and
other coarse roughages and grazed on spring and summer grasses. They may
otherwise be obtained in late winter or spring, for spring and summer grazing
only.
From an environmental standpoint, stocker systems are similar to cow-calf
systems. Additional features to consider include:
a) While more animals are maintained per unit area, they are smaller in
size. Liveweight per unit area is at first lower and subsequently
similar to cow-calf systems.
15
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b) Most stocker programs make use of temporary pastures. Excessive
rain or snc^' jnd ice may make grazing impractical, creating need for
stockers 10 bo maintained in smaller areas and provided supplemental
feed. Otherwise, the temporary nature of these programs is such
that poie-mj.il problem areas are not used throughout the year and
have opportunity to recover, thereby lessening the potential envi-
roninenrul Lnp^ct .
Grass Finishing iVsj _eta
Interest In grass i Ur! suing programs has periodically increased as a
result of increased prices and competition for feed grains. A clear estima-
tion of numbers ol ,-mima.Ls in this program is not available. It. represents
only a small fraction of animals on feed, however. In this program calves
grown on a stocker system to a weight of 300-350 kg are finished to market
weight (400-45G kg/ and giade on good quality forages. One alternative is
the "grain-on-grass" pic-gran: where calves graze 120-150 days at a recommended
grazing stocking rai.e (e.g., 8-10 hd/ha) and then are fed a limited ration of
grain for an addition^ 60-90 days of grazing. During this "grain phase",
stocking rates nuv ""- increased to those common to open feedlots (e.g., 12-15
hd/ha). In another alternative, cattle are maintained from a weight of 350
kg to market weight ot 500 kg, receiving no grain but obtaining all feed from
grazing. For short periods of time these finishing systems may also involve
stocking rates approaching feedlot levels.
Adequate fertilization, pasture rotation under controlled conditions,
and forage harvesting practices are characteristics of this system. Grass
finishing systems are located primarily in the Southeastern and, to a limited
extent, in the Pacific Slope regions where year-round grazing is possible.
DAIRY SYSTEMS
Dairy cattJe systems range from completely unconfined to totally confined
with semi-confined in between. The semi-confined dairy system involves main-
tenance of 20 to 25 mature (450 to 550 kg) females per ha (open feedlot
densities). Green forage is cut daily and brought to the herd. In intensive
dairying areas of the Northeastern, Northern Intermountain, Southern Pacific
Slope and Southeastern regions, total confined and semi-confined systems
represent 60 to 70% of all dairy systems, with equal representation by both
systems.
Portions of all. dcJ.ries, including unconfined systems, have areas that
should be managed ss confined systems. For example, loafing areas and parlor
holding areas, whether surfaced and flushed or not, should generally be
managed as point sources (wastes and/or runoff collected for control).
Likewise, most dairiosj including many confined systems, have areas that are
characteristic of uiron Fined production. Dairy replacement calves for all
systems are most often a part of the total dairy system and these animals are
generally rnaint iineul on pasture.
16
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Environmental impact considerations of dairy systems are the same as for
cow-calf management systems, with the following additions:
a) Unavoidable high impact (problem) areas such as the approach paths
to milking barns and loafing areas are common.
b) In the pasture or paddock area of semi-confined systems, where
stocking rates equal those of open feedlots, only a small portion of
total wastes generated by the animals may be deposited on the
pasture; a major portion may be collected in the milking area and
managed as point source wastes. Nevertheless, the pasture area may
still be so heavily impacted that it requires controls appropriate
to open feedlots (collection of runoff, etc.).
SHEEP SYSTEMS
Sheep are unique in that they can attain top meat grade (prime) on
forages alone. Consequently, the majority of lamb production occurs in
unconfined management systems. The unique systems of sheep production are
range systems, farm flock systems, and lamb feeding systems. Environmental
problems associated with these systems are similar to those for beef systems.
Range systems are designed to maximize utilization of available rangeland
forage. This system is found primarily in the Great Plains and Intermountain
regions. Range management systems are nomadic in that large herds move over
vast areas following seasonal availability of forages. These herds move up
mountainsides in summer as higher elevation forages become available and
return in the fall to lower elevations where protection from winter weather
can be effected. On summer ranges, ewes and their spring-born lambs are
maintained together. Lambs are weaned in late summer or early fall, with
heavier lambs being sent directly to slaughter and lighter lambs sent to con-
fined or pasture finishing systems.
Farm flock systems predominate in the eastern U.S. This system differs
from the range system in that improved pastures of legumes and/or grasses meet
most of the nutrient requirements of the flock. As a result, farm flocks are
usually maintained in small areas at high stocking rates. Rotational grazing
is common.
In lamb feeding systems, 30 kg lambs are grazed at rates of 10-25 hd/ha,
depending on the intensity of management of livestock and improved forages.
In the Southeastern regions, grass-legume mixtures may provide the nutrients
for production of 45-55 kg slaughter lambs at 4 to 6 months of age.
SWINE SYSTEMS
Swine management systems are generally classified according to the number
of litters produced per year. Due to the monogastric nature of the swine
digestive system, forages are not essential, although they may be advantageous
if utilized properly. Swine production tends to center around grain production
17
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areas with approximately 80% of all hogs produced in the North Central states
and Great Plains regions. The Southeastern regions account for 14% of total
production. The remainder is divided evenly among other regions.
A frequently used management procedure is a 2-litter system in which each
breeding female weans two 7-8 pig litters in 12 months. Althoug;h swine man-
agement systems involve total confinement to a large degree, many sow opera-
tions include pasture (rotated drylots) or drylots (permanently denuded areas)
with stocking rates as low as 1000 kg/ha. Rates of 6000 kg/ha (30 to 36 sows
weighing 200 kg or less, or 20 to 24 sows with 7-8 pig litters per ha) are
more common. Hogging off grain fields, once very popular, is still practiced
to a limited extent, but usually only for a short duration. Also, a very few
feeder pigs are finished by feeding on pasture. Due to the efficiency of con-
finement feeding, most such unconfined finishing operations are temporary.
Environmental problems common to swine systems are similar to those for
dairy systems. Additional features to consider include:
a) Hogs on pasture and drylots often have access to streams. Such
access must be controlled if the environmental impact is to be
minimized.
b) Even when pastures are rotated, much of the area may be heavily
impacted and soon denuded. The entire pasture area is generally
a problem area and requires control appropriate to confined systems/
point sources.
c) Swine tend to uproot forages if not controlled and are attracted to
streams and waterways for wallowing areas.
18
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SECTION V
WATER QUALITY EFFECTS FROM UNCONFINED ANIMAL PRODUCTION
Excellent reviews of agricultural nonpoint sources of pollution, in-
cluding consideration of unconfined animal production, have been prepared by
Loehr (1974), Dixon et al. (1977), Sweeten and Reddell (1976), Dornbush et al.
(1974), and USEPA (1973). Numerous other studies have reported information
that is very helpful in assessing the character and extent of the effect of
unconfined animal production on water quality. However, a word of caution is
in order on the use of the reported information. Some otherwise potentially
useful data are so confounded with regard to cause and effect (e.g., uncer-
tainties imposed by incomplete descriptions of the systems) that their use
must be guarded. Other information is of a speculative, general nature,
often based on less than definitive data. Still other information concerns
site specific problems and, thus, cannot be considered characteristic of un-
confined animal production in general. And, as Loehr (1974) found, some is of
limited usefulness because of its form: concentration of pollutant in water
rather than yield of pollutant per unit of watershed area. With due regard
then, the available information has been reviewed, screened, and, when
appropriate, used to formulate the following discussion of the nature and
extent of the problems.
BACKGROUND LEVELS OF POLLUTANTS
In assessing the environmental impact of unconfined animal production,
the concept of "background (natural) levels" of pollutants is important.
Known background levels of a particular pollutant for a particular site can
serve as a point of reference for determining what environmental quality level
might reasonably be acceptable and achievable in water quality management.
From a study of 12 agricultural watersheds, Robbins et al. (1971) found
that distinguishing between pollutants from farm animal production units and
natural pollutants in receiving streams is difficult or impossible. They con-
cluded that control of pollutants from unconfined animal production units may
be to no avail unless other pollutant sources that naturally occur in the
watershed are controlled as well. They stressed that additional information
and research on the types and yields of natural pollutants are needed to for-
mulate meaningful water quality management programs.
Loehr (1974) summarized reported data concerning oxygen demands, nitrogen,
and phosphorus transported in drainage from various land-uses and the amount
of pollutants deposited on land by precipitation. Nitrogen and phosphorus
yields from various sources are given in Table 4. These values vividly reveal
19
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that background levels of pollutants can be appreciable. Note that precipi-
tation can deposit as much as 10 kg ha'^yr'1 total nitrogen and 0.06 kg
ha"1yr~1 total phosphorus. Also note the yields of nitrogen and phosphorus
from undisturbed forestland can be as much as 13 and 0.9 kg, ha ~lyr ~l , re-
spectively. Realistically, Loehr described undisturbed forestland and range-
land as natural situations and reasoned that the runoff from these lands
contains only background levels of pollutants. Concentrations and yields of
pollutants from these two nonpoint sources are of the same type and magnitude
as those of precipitation.
TABLE 4. AREAL YIELD OF NITROGEN AND PHOSPHORUS (LOEHR 1974)
Source
Precipitation
Forested Land
Rang eland
Cropland Runoff
Urban Land Drainage
Cropland Receiving Manure
Feedlot Runoff
Total N,
kg ha^yr"1
5.6- 10
3- 13
0.65*
0.1- 13
7- 9
4- 13
100-1600
Total P,
kg ha " yr ~l
0.05-0.06
0.03-0.9
0.76
0.06-2.9
1.1 -5.6
0.8 -2.9
10 -620
* value for NOyN
As suggested by Dixon et al. (1977), water quality data reported by Doty
and Hookano (1974) from a study of three pristine watersheds in northern Utah
are suitable for background or benchmark information. The watersheds had been
protected from fire, domestic livestock, and timber cutting for 45 years.
Table 5 gives ranges of some water quality characteristics reported. Compar-
ison of such data as these with similar data from unconfined animal production
sites allows a first evaluation of the importance of the production practice
on water quality. In such comparisons, it is important to note that for most
indices the order of magnitude of differences are to be considered significant
rather than small differences in the values themselves.
PREDICTION OF POLLUTANT YIELD
An ultimate goal in pollution control technology is to have some form of
model/method that will estimate pollutant losses from pollution sources. No
such model exists for unconfined animal production systems. Once models of
other nonpoint sources are developed, they will no doubt be modified to serve
the need. Discussion of models for nonpoint sources is given by Donigian and
Crawford (1976) and True (1976). Also, Sweeten and Reddell (1976) presented
20
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concepts based on information from McElroy et al. (19/6) for estimating yield
of nutrients and organic matter from nonpoint sources.
TABLE 5. WATER QUALITY FROM PRISTINE WATERSHEDS (DOTY AND HOOKANO 1974)
Parameter
PH
Phosphorus, ppm
Nitrate, ppm
Suspended Sediment, ppm
Total Coliform, cts/100 ml
Fecal Coliform, cts/100 ml
Fecal Streptococcus, cts/100 ml
Range cf
All Values
5
0
0
0
1
0
0
.50- 8. 00
- 0 , 6 3
.07- 0.70
.10-247.80
-570
-183
-500
Range of
Watershed Averages
6.98-7.13
0.06-0.07
0.3A-0.37
5.55-9.86
42 -72
2 -13
Jl -60
Guidance for—and a view of the difficulties involved in--developing
models for predicting pollutant yields from unconfjned anir.nl production units
may be surmised from work by Robbins et al. (1971). The two-year study was
designed to determine the pollutant loads in runoff from farm animal produc-
tion areas and to evaluate factors governing the timing, amount, and concen-
tration of pollutant discharges. Generalized findings related to the present
discussion follow:
1. Concentrations of pollutants in land runofi increase with runoff
intensity and are proportional to flowrate. But, the value of the proportion-
ality varies throughout the runoff event and even more so between events.
Thus, determination of pollutant yield requires niensureirpnt cf both pollutant
concentration and flowrate throughout the entire runoff ^vent.
2. High correlations exist between most pollution indices other than
bacteriological indicators, both for a given runoff even!: and between events.
Relationships between such indices as chemical oxygen demand and phosphorus
levels generally hold constant enough for modeling pmposes. This suggests
that with the measurement of one key index such as phosphorus content, the
concentration of other pollutants in the stream can be estimated. However,
bacteriological indicator organisms are poorly correlated with other pollutant
indices except for a given runoff event and at a given sampling site. Bacte-
riological counts are highly dependent on temperature (bnrrerial activity in-
creases with temperature) and may exhibit either a die-.uf or an aftergrowth
with time (or flow distance). While correlations between various bacteriolog-
ical indicator organisms are often high, they are also ^natic and change with
both season (temperature) and time (flow distance). Thus, estimations of
either the level of bacteriological activity or the r-itiop between indicator
21
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organisms are not reliable; these values must be determined by measurement.
3. Pollutant yields are not related to number of animals involved and,
therefore, they are not related to either the amount or the characteristics of
animal wastes involved. Rather, yields are intimately related to hydro-
geological and management factors. The process is less of an animal waste
problem than a soil and water conservation problem. Mainly, it is an erosion/
sediment transport phenomenon. For example, the researchers found a yield of
five times as much phosphorus per animal from a site with a high rate of
erosion as from a site with less erosion, when no differentiation of pollutant
source was made (all phosphorus reaching the streams was attributed to animal
activity). Models must be built around a sound accounting of these watershed
and management factors, including the changes watersheds undergo with time.
4. The increases in pollutant concentration in receiving waters caused
by an unconfined animal production system, particularly when pollutants from
problem areas are controlled, are generally so small compared to and so com-
pletely confounded with background or other pollutants, that the contribution
from the system is impossible to definitively establish. At a given time
during a runoff event, pollutant inputs may be only from natural or other
non-livestock related sources in the watershed, while at other times inputs
from unconfined animal activities may also be included. In most cases, it is
not possible to differentiate between sources.
Again, the movement of pollutants from unconfined animal production units
to receiving waters is governed by numerous, complex, and variable hydro-
geological and management factors which are yet to be codified. In lieu of a
model that will estimate pollutant yields, an understanding of the erosion/
sediment process plus a review of pollution studies (research results) related
to unconfined animal production should be helpful in assessing the environ-
mental impact resulting from these systems. Since the erosion/sediment
process is so fundamental to pollutant yields resulting from unconfined animal
production activities, one is encouraged to review the subject in detail.
SEDIMENT
Sediment is both a pollutant and a carrier of pollutants from unconfined
animal production systems. As a first approximation, factors that govern
erosion and sediment yields are the same factors that control pollutant yields
from unconfined animal production systems. Robbins et al. (1971) pointed to
the need for good soil and water conservation practices to minimize the move-
ment of pollutants from animal production units into streams. Excellent,
detailed, and thorough reviews and discussions of erosion, erosion models, and
sediment yields as related to agricultural nonpoint sources have been prepared
by USEPA (1973), Stewart et al. (1975), and Sweeten and Reddell (1976).
Sediment yield to streams and lakes exceeds 2 t ha"1yr"1 on the average
for the total U.S. land area. On-site erosion is estimated to be twice this
value, or more than 4 t ha^yr"1 for a U.S. total yield of 3.6 x 109 t/yr.
According to Froehlich (1976), the smallest levels of sediment loss are from
22
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certain undisturbed forestlands in the Rocky Mountains where sediment reaching
certain high elevation streams may range up to 0.36 t ha^yr"1. Other
examples of background sediment yields are 0.59, 0.90, and 1.10 t ha"1yr~1
from three neighboring watersheds in western Oregon. Well stocked southern
pine forests may yield 0.7-1.1 t ha Vr *• In southwestern forests with low
precipitation, yet high intensity storms, sediment yields may be 1.1-1.4 t
ha ~lyr ~1-
Background sediment yields may be compared with yields from cropland.
Cropland has been credited with responsibility for 50% or 0.9 x 109 t/yr of
the 1.8 x 109 t/yr total sediment delivered to U.S. streams and lakes. As
noted by Sweeten and Reddell (1976), 70% of the nation's cropland yields more
than 6.7 t ha^yr"4. Representative values for on-site erosion from several
sources as reported by USEPA (1973) are given in Table 6. Here, grassland
includes pasture and rangeland. While the erosion rate from grassland is 10
times that from forestland, it is considerably less than the average rate for
all land of 4 t ha"1yr"1 and it represents the average background or natural
rate for grassland ecosystems.
TABLE 6. REPRESENTATIVE RATES OF ON-SITE EROSION FROM VARIOUS LAND USES
(USEPA 1973)
Land Use
Forest
Grassland
Cropland
Harvested Forest
Construction
Rate
t ha^yr"1
0.085
0.85
17
42
170
Relative Rate,
Forest = 1
1
10
200
500
2000
Total,
t/yr
16.8
185
2840
187
100
Relative Total
Forest = 1
1
11
168
11
6
Sediment yields are very erratic (Froehlich, 1976). The largest annual
sediment loads for a given stream are often 20 times greater than the smallest
sediment load and can generally be correlated with those years of greatest
runoff. Large differences in sediment yield can exist on adjacent streams
discharging at the same rate. And, even in the same stream, suspended sedi-
ment concentration can vary 10-fold at a given discharge rate, depending on
many factors.
Most sediment from a watershed may come from a relatively few small
areas needing corrective attention. Stewart et al. (1975) listed conditions
indicative of high sediment yield potential that can usually be identified by
observation. Overgrazing, and resultant loss of groundcover can greatly in-
crease the erodibility of pasture and rangeland.
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CASE STUDIES
Important results have been obtained from studies concerning the pollu-
tion potential of unconfined animal production operations. Early work by
Meiman and Kunkle (1967) revealed that bacteriological indicators provided a
more sensitive evaluation of grazing than did suspended sediment or turbidity.
Of three indicator groups—fecal coliform (FC), total coliform (TC) , and fecal
streptococci (FS)—FC and TC were the most sensitive in detecting the grazing
impact, with FC being the best. Ratios of FC/FS ranged from less than 1 to
4.5 on natural areas and less than 1 to 44 on impacted areas. Bacteriological
concentrations in the stream were related to overland flow, stream discharge,
and season of the year. Maximum concentrations were obtained during periods
of lower storm runoff flows and warmer water temperatures.
Additional work by the researchers (Kunkle and Meiman 1968 and Kunkle
1970) essentially verified the fact that increased levels of bacteriological
indicator organisms occur in streams draining grazing operations. The
researchers studied sites where animals did and did not have direct access to
streams and found no detectable differences from a bacteriological contami-
nation standpoint. Also, their work underscores the fact that predicting the
level of bacteriological indicator counts resulting from unconfined animals
is inaccurate and difficult, if not impossible. As indicated above, their
conclusions could not be more specific than to relate that hydrological and
watershed characteristics are of great importance in bacteriological yields,
and greater counts are common to warmer weather.
Smeins (1976) studied the effect of various rangeland livestock grazing
management programs on the quantity and quality of surface runoff. He tenta-
tively concluded that nitrogen and phosphorus yields from pastures are
greater from a "heavy continuous grazing system" than from a "four-pasture
deferred rotation grazing system". This conclusion was made on the basis of
increased runoff caused by overgrazing and drastically reduced—to less than
half—infiltration rates under the continuous grazing program, rather than to
discernible differences in runoff quality. The concentrations of pollutants
in runoff were low. Nutrient losses appeared to be related to sediment loss
rather than to animal waste contributions. Generally, less sediment loss
occurred on the better vegetated watersheds. The findings emphasize that
grazing management systems influence water quality through erosion/sediment
control, that pollutant yields are directly proportional to runoff amounts,
and that grazing may decrease infiltration rates and, thereby, increase runoff
and pollutant yields.
Schreiber and Renard (1976) studied the chemical quality of runoff from
grazed and ungrazed rangelands. Nitrate, phosphorus, sodium, and potassium
concentrations were found to be higher in runoff from the grazed watershed;
but lower concentrations of calcium, carbonates, and magnesium and lower pH
and electrical conductivity values were exhibited. The researchers noted that
the concentrations of the pollutants in runoff were low (near background
levels). Although comparison between the grazed and ungrazed watersheds indi-
cated these slight differences in runoff water quality, the researchers also
noted that the differences may have been caused by differences in soil and
vegetation (hydrogeological) characteristics.
24
-------
Colthrap and Darling (1975) studied three mountain streams to determine
the impacts of grazing cattle and sheep on rangeland watersheds. Results of
chemical and physical analyses were inconclusive. Turbidity, pH, nitrate,
and phosphate values were generally not affected by grazing. Statistically,
stream temperature was a more frequent indicator of grazing than these
variables, indicating that grazing had no definitive impact on the physical
and chemical parameters. The bacteriological results of the study did, how-
ever, indicate that grazing cattle and sheep significantly increased the total
coliform, fecal coliform, and fecal streptococci counts in streams draining
grazed areas. Examples of results are presented in Table 7 and reveal that
the increased bacterial activity resulting from grazing was not large enough
to remove the values beyond the range of background or natural levels that
might otherwise be anticipated for such an ecosystem void of livestock.
Counts reached relative maximums during snowmelt runoff, absolute maximum
levels during grazing periods, and minimums in winter months.
TABLE 7. BACTERIOLOGICAL QUALITY BY LAND USE (COLTHARP AND DARLING 1975)
Watershed
Land Use
Grazed
Grazed
Ungrazed
Bacteriological Quality,
Total Coliform Fecal Coliform
24
103
18
88
38
4
cts/100 ml
Fecal Streptococci
325
101
27
These bacteriological findings agree with a Laycock and Conrad (1967)
study in Colorado which investigated rangeland adjacent to a stream. They
also substantiate a USDA (1976) study in Idaho which showed that bacteriologi-
cal counts increase in streams when cattle are introduced to graze, remain
high until the cattle are removed, and, according to the researchers, are
flushed into streams for as long as three weeks after cattle are removed.
Milne (1976) evaluated the impact of a livestock wintering operation on
a mountain stream. Within a 3.6 km stream segment, 1200 sheep, 350 cows, 50
heifers and 85 hogs were held in partial confinement (corrals and pastures)
with access to the stream. Also, a 200-head cattle feedlot lay alongside the
stream. From the four-year stream monitoring program, he concluded that the
livestock wintering operation had negligible effect on chemical properties of
the stream. For example, the concentration of nutrients in the creek passing
by the wintering operation increased from 0.007 to 0.019 ppm nitrate nitrogen
and from 0.007 to 0.027 ppm orthophosphorus.
Bacteriological counts were significantly increased at the location of
greatest livestock activity when compared to counts taken upstream. The
average total coliform and fecal streptococci counts per 100 ml of stream
water before entering the wintering area were 7.08 and 17.62, respectively.
Just downstream from the wintering area, the respective average counts were
1431.27 and 996.92 per 100 ml. However, these high bacterial densities were
25
-------
shortlived, with marked reduction within 5 km downstream. Bacteriological
analyses were deemed more suitable (more sensitive) than chemical analyses for
evaluating livestock nonpoint inputs.
A study conducted by Greathouse et al. (1971) near Lake City, Michigan
found no difference in nitrogen and phosphorus concentration as a result of
wintering and pasturing cattle along rivers and streams. Similarly Campbell
et al. (1977) found no significant water quality impacts from production of
beef cows and calves on Florida flatwood soils and at stocking rates greater
than those for regular pasture systems.
After reviewing the information relevant to nonpoint pollution from
cattle wintering sites, Dixon et al. (1977) concluded that cow-calf opera-
tions involving a rangeland operation with confined wintering (to pasture
stocking densities) most probably will contribute little to the nutrient and
chemical load of a stream. The operation very likely could contribute to
microorganism contamination of the stream, however. The researchers also
reasoned that consideration of microorganisms as a pollutant from range-type
wintering operations might be overemphasized because they may be the only
discernible pollutants from the operation. They concluded that the concen-
tration and quality of pollutants from cattle wintering areas are not known.
Dornbush et al. (1974) evaluated runoff quality from seven agricultural
land-use areas, including a 6.3 ha summer pasture. The study yielded values
of the bacteriological quality of runoff water, pesticides carried in runoff,
and physical and chemical characteristics of land surface drainage. Bacterio-
logical indicator organisms in runoff exceeded drinking water supply criteria
50 percent of the time for fields with heavy ground cover (including the
pasture) and from 50 to 100 percent for fields with minimum cover (including
cropland). It is significant that no bacteriological effect directly attrib-
utable to pastured animals was discernible. The researchers realistically
concluded that the runoff was probably not a potential health hazard.
Also, the level of pesticides present in runoff seemed quite low and the
majority of concentrations were below analytical limits. Values of the yield
of other pollutants are given in Table 8 and indicate that pastureland con-
tributes less than cultivated fields but more than permanent grasslands. The
researchers noted that even these low pollutant yields may have important
implications regarding lake eutrophication.
Sewell and Alphin (1972) studied problem areas associated with unconfined
animal production systems. They took grab samples at 24 test sites involving
cropland, ungrazed woodland, barnyards, and heavily-grazed pastures. Results
from four test sites which exemplify water quality resulting from suspected
problem sites and unimpacted sites are given in Table 9. Average BOD values
were found to be least in runoff samples from ungrazed woodlands and
normally-grazed pasturelands and greatest from heavily-grazed areas within
pastures, animal resting areas, and heavily-used farm ponds. Also, BOD
values tended to be greater in farm ponds than in flowing streams. Nitrate-
nitrogen averages in surface runoff from two (problem) sites on a heavily-
grazed dairy pasture system exceeded those from all other sites, including
those of an aerobic lagoon and drainage from cultivated lands. The mean
26
-------
orthophosphate, total coliform, and fecal coliform levels from the problem
areas in the dairy pasture were exceeded only by those of aerobic lagoon
waters. Based on data from all the test sites, the researchers concluded that
while bacterial counts and chemical concentrations of surface receiving waters
depend upon land use activities and is increased by livestock operations, the
most important factors affecting the measured levels of these parameters are
the location of the sampling points with reference to the source, the dilution
of the pollutants, and the time during the runoff cycle at which samples are
taken. Their work vividly illustrates that problem areas within unconfined
systems may result in substantial input of pollutants to contiguous surface
waters.
TABLE 8. POLLUTANT YIELD BY LAND USE (DORNBUSH ET AL. 1974)
Pollutant
Total Residue
Suspended Solids
Total Phosphorus
Nitrate-Nitrogen
Total Kjeldahl Nitrogen
Chemical Oxygen Demand
Cultivated
334
286
0.30
0.37
0.91
48
Yield, kg ha'1 yr -i
Pasture
58.2
11.8
0.25
0.40
1.12
28
Grassland
32.4
4
0.1
0.24
0.73
13
TABLE 9. WATER QUALITY BY LAND USE (SEWELL AND ALPHIN 1972)
BODc
DO
Land Use
N03-N
P04-P
Total Coliform,
cts/100 ml
Ungrazed
Woodland 2.5 8.6 0.05 0.05 1500
Heavily-Grazed
Pasture 13.8 6.1 4.5 7.1 330000
Farm Pond in
Pasture 10.0 7.9 0.20 0.05 600
Farm Pond in
Woodland 3.J. 7.6 0.12 0.02 1500
As indicated by the work of Sewell and Alphin (1972) and as pointed out
by Dornbush et al. (1974), small increases in pollutant yields may have
27
-------
important implications when the receiving waters are impounded. In a study of
farm pond water quality, Dickey and Mitchell (1975) found BOD values of pond
water in livestock watersheds exceeding 20 ppm while the average BOD value of
pond water for grassed watersheds free of animals was 0.77 ppm. The average
level of phosphate in pond water where animals had direct access was 5.82 ppm,
or 32.3 times the average value for grassland watersheds. Pond water on the
pastureland reached a maximum nitrate nitrogen level of 22.0 ppm.
A more intensive study of pond water quality by Willrich (1961) gave
evidence that generally indicates that grazing of grassed watersheds does not
materially affect the nitrate concentration in pond water. Heavily-grazed
watersheds, as contrasted to watersheds which were predominantly cultivated or
in meadow, did not cause a higher nitrate nitrogen level in the pond water in
his study. He also reported similar results from other studies.
Janzen et al. (1974) sampled streams above, adjacent to, and below 22
dairies. While the study tested waste handling techniques (lagooning, dry
disposal, and liquid manure spreading) rather than solely the effect of uncon-
fined production, the results exemplify the environmental impacts to be ex-
pected from unconfined dairies when the contributions from problem areas are
included. Fecal coliform counts exceeded 1000 cts/100 ml for 90% of all
stream samples, including samples from all but three sites above the animal
production units. Statistically, 42% of the farms studied contributed in
varying amounts to a reduction in stream water quality on the basis of bac-
teriological activity (26%), dissolved oxygen (14%), pH (19%), and/or oxygen
demand (9%). Overall, increased nitrate nitrogen (from about 2.3 to about
3.8 ppm) and phosphate (from about 2.4 to about 3.7 ppm) levels existed
between upstream and adjacent sampling sites. Average concentrations of both
of these indices were about 2.9 ppm at sampling points 50 to 600 m below the
dairies.
Of the 12 animal agricultural watersheds examined by Robbins et al.
(1971), two exemplified solely unconfined production units: a beef pasture
(site Z) and a hog drylot (site K). They also studied a watershed (site E)
that received hog wastes by spreading in addition to that from sows on drylot.
A watershed (site F) free of domestic animal wastes was used to determine back-
ground levels of pollutants. Results from study of these land runoff sites are
summarized in Table 10. For comparison, the Table includes results from three
watersheds (sites D, H, and J) that included direct waste discharges to streams.
The pollution loads in the land runoff streams followed a general increase
with time from winter to summer. Bacteriological counts were very responsive
to temperature. During runoff events, average bacteriological quality of all
streams, including the stream draining control site F, far exceeded any known
maximum allowable for body contact. Nutrient contents in streams were always,
including periods of base flow, well in excess of that needed for algal growth.
Phosphorus entering the streams was mainly orthophosphate and, thus, was imme-
diately available to plants. Wastes that reached the streams were relatively
well oxidized.
Considering the level of pollutants measured in the stream draining con-
trol site F, much of the pollutants observed in the other land runoff streams
could be attributed to natural sources. For example, a comparison of nitrogen
28
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yields per unit watershed area from the sites (F vs. E, K and Z) suggests that
no increase occurred due to animal activity. (The researchers attributed the
increase nitrogen yield from site E to the hog wastes spread in the watershed,
increasing the nitrate nitrogen content of the groundwater and base flow in
the stream, rather than to the sow drylot operation.)
The results from the beef pasture (site Z) suggests that grazing cattle
can be maintained without materially affecting stream quality. The pasture
area in this case was free of observable problem areas except possibly a small
area where the cattle entered the stream for watering purposes. And, the in-
creased levels of pollutants from sites E and K over those from control site
F exemplify contributions to be expected from problem sites (swine drylots in
these cases). These results suggest the need to concentrate control efforts
on any problem areas within the total production system.
The results in Table 10 for sites D, H, and J show the effects of dumping
fresh wastes directly into streams and are to be compared in orders of magni-
tude with pollutant yields from land runoff sources. The calculated amounts
of pollutants (natural plus swine or dairy) carried by the streams draining
these sites compared to the estimated amounts of animal waste pollutants pro-
duced in the watersheds were 375, 875 and 1340 percent of FC; 56, 6 and 23
percent of BOD5; 67, 10 and 10 percent of N; and 49, 23 and 30 percent of P
for sites D, H and J, respectively. Again, the phosphorus carried by the
stream draining site D amounted to 49% of the estimated phosphorus excreted
by the hogs at site D. The exceptionally high values of FC carried by the
streams with direct waste inputs suggest that an aftergrowth of bacteria
occurred in the short 500 m reaches of the streams between the discharge and
sampling points. The aftergrowth was limited to warmer weather, and most FC
bacteria died off before reaching the sampling points during the winter
period.
While these direct discharge operations involved only small numbers of
animals and were only a portion of production systems that included largely
unconfined animals, their pollutant contributions were several orders of
magnitude greater than those from the land runoff areas. These results
vividly emphasize the need to consider any such operations separately as point
sources rather than including them as part of otherwise nonpoint systems.
30
-------
SECTION VI
REFERENCES
Campbell, K. L., D. A. Graetz and R. A. Nordstedt. 1977. Environmental
impact of beef cattle on flatwoods soils. Paper No. 77-4048. American
Society of Agricultural Engineers, St. Joseph, Michigan.
Colthrap, G. B. and L. A. Darling. 1975. Livestock grazing—a nonpoint source
of water pollution in rural areas. In; Water Pollution Control in Low
Density Areas. University Press of New England, Hanover, New Hampshire.
Dickey, E. C. and J. K. Mitchell. 1975. Pond water quality in a claypan soil.
Transactions of the ASAE 18(1):106-110.
Dixon, J. E., G. R. Stephenson, A. J. Lingg and D. D. Hinman. 1977. Nonpoint
pollution control for wintering range cattle. Paper No. 77-4049.
American Society of Agricultural Engineers, St. Joseph, Michigan.
Donigian, A. S. and N. H. Crawford. 1976. Modeling nonpoint pollution from
the land surface. EPA-600/2-76-083. Superintendent of Documents, U.S.
Government Printing Office.
Dornbush, J. N., J. R. Andersen and L. L. Harms. 1974. Quantification of
pollutants in agricultural runoff. EPA-660/2-74-005. Superintendent of
Documents, U.S. Government Printing Office.
Doty, R. D. and E. Hookano, Jr. 1974. Water quality of three small water-
sheds in northern Utah. USDA Forest Service Research Note INT-186.
Intermountain Forest and Range Experiment Station, Ogden, Utah.
Ensminger, M. E. 1970. The stockman's handbook, 4th edition. The Interstate
Printers and Publishers, Inc., Danville, Illinois.
Flory, E. L. 1936. Comparison of the environment and some physiological
responses of prairie vegetation and cultivated range. Ecology 17:67-103.
Froehlich, H. A. 1976. Inorganic pollution from forests and rangelands.
Publication No. SEMIN-WR-021-76. Water Resources Research Institute,
Oregon State University.
Greathouse, T. R., W. T. Magee, N. R. Kevern and R. C. Ball. 1971. Effect of
wintering and pasturing cattle along rivers and streams on water quality
and bank erosion. Report 141. Pp. 41-43. Michigan Agricultural Experi-
ment Station, Michigan State University.
31
-------
Hanson, C. L, , H. G. Heinemann, A. R. Kuhlman and J. W. Neuberger. 1970.
Grazing effects on runoff and vegetation on western South Dakota range-
Land. J. Range Management 23:418-420.
Heady, H. F. 1975. Rangeland management. McGraw-Hill Book Company, New York.
Janzen, J. J., A. B. Bodine and L. J. Luszcz. 1974. A survey of effects of
animal wastes on stream pollution from selected dairy farms. J. Dairy
Science 57(2):260-263.
Kunkle, S. H. 1970. Concentrations and cycles of bacterial indicators in
farm surface runoff. In; Relationship of Agriculture to Soil and
Water Pollution. Conference on Agricultural Wastes Management, Cornell
University.
Kunkle, S. H. and J. R. Meiman. 1968. Sampling bacteria in a mountain stream.
Hydrology Paper No. 28. Colorado State University.
Laycock, W. A. and P. W. Conrad. 1967. Effect of grazing on soil compaction
as measured by bulk density on a high elevation cattle range. J. Range
Management 20:136-140.
Loehr, R. C. 1974. Characteristics and comparative magnitude of non-point
sources. J. Water Pollution Control Federation 46(8):1849-1872.
McElroy, A. D., S. Y. Chiu, J. W. Nebgen, A. Aleti and F. W. Bennett. 1976.
Loading functions for assessment of nonpoint sources. EPA-600/2-76-150.
Superintendent of Documents, U.S. Government Printing Office.
Meiman, J. R. and S. H. Kunkle. 1967. Land treatment and water quality con-
trol. J. Soil and Water Conservation 22:67-70.
Milne, C. M. 1976. Effect of a livestock wintering operation on a western
mountain stream. Transactions of the ASAE 19(4):749-752.
Petersen, R. G. , H. L. Lucas and W. W. Woodhouse, Jr. 1956. The distribution
of excreta by freely grazing cattle and its effect on pasture fertility:
I. excretal distribution; II. effect of returned excreta on the residual
concentration of some fertilizer elements. Agronomy Journal 48(10) :440-
448.
Robbins, J. W. D., D. H. Howells and G. J. Kriz. 1971. Role of animal wastes
in agricultural land runoff. EPA-13020DGX. Superintendent of Documents,
U.S. Government Printing Office.
Schreiber, H. A. and K. G. Renard. 1976. Water quality in runoff from range-
land in southeastern Arizona. Unpublished Report. Soil, Water, and Air
Sciences Program. United States Department of Agriculture.
Sewell, J. I. and J. M. Alphin. 1972. Effect of agricultural land use on the
quality of surface runoff. Progress Report 82. Tennessee Farm and Home
Science, University of Tennessee.
32
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Smeins, F. E. 1976. Influence of vegetation management on yield and quality
of surface runoff. Annual Report No. C-6310. Texas Water Resources
Institute, Texas A&M University.
Stewart, B. A. (ed.) et al. 1975. Control of water pollution from cropland:
volume I. EPA-600/2-75-026a or ARS-H-5-1. Superintendent of Documents,
U.S. Government Printing Office.
Stoddart, L. A., A. D. Smith and T. W. Box. 1975. Range management, 3rd
edition. McGraw-Hill Book Company, New York.
Sweeten, J. M. and D. L. Reddell. 1976. Nonpoint sources: state-of-the-art
overview. Paper No. 76-2563. American Society of Agricultural
Engineers, St. Joseph, Michigan.
Trimble, G. R., Jr. and S. Weitzman. 1951. Effect of soil and cover condi-
tions on soil-water relationships. Station Paper No. 39. U.S. Forest
Service, Northeastern Forest Experiment Station.
True, H. A. 1976. Planning models for nonpoint runoff assessment. EPA-600/9-
76-016. Superintendent of Documents, U.S. Government Printing Office.
USDA. 1976. ARS-BLM cooperative studies, Reynolds Creek Watershed. Interim
Report No. 6. USDA, ARS Northwest Watershed Research Center, Boise,
Idaho.
USEPA. 1973. Methods for identifying and evaluating the nature and extent of
nonpoint sources of pollutants. EPA-430/9-73-014. Superintendent of
Documents, U.S. Government Printing Office.
Willrich, T. L. 1961. Properties and treatment of pond water supplies.
Ph.D. Thesis. Iowa State University, Ames.
33
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-78-046
_I
4. TITLE AND SUBTITLE
ENVIRONMENTAL IMPACT RESULTING FROM UNCONFINED
ANIMAL PRODUCTION
5. REPORT DATE
March 1978 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Jackie W. D. Robbins
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Louisiana Tech University
Ruston, Louisiana 71272
3. RECIPIENT'S ACCESSION NO.
10. PROGRAM ELEMENT NO.
1HB617
11. CONTRACT/GRANT NO.
R-804497
12. SPONSORING AGENCY NAME AND ADDRESS
Robert S. Kerr Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Ada, Oklahoma 74820
13. TYPE OF REPORT AND PERIOD COVERED
Final (5/10/76-9/30/77)
14. SPONSORING AGENCY CODE
EPA/600/15
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report outlines and evaluates current knowledge related to environmental
effects of unconfined animal production. Animal species directly addressed include
cattle, sheep, and hogs. All available date indicate that pollutant yields from
pasture and rangeland operations are not directly related to the number of animals
or amount of wastes involved. Rather, these nonpoint source problems are intimately
related to hydrogeological and management factors and are best described as the
results of the erosion/sediment phenomenon.
Unconfined livestock production can cause changes in vegetative cover and soil
physical properties that may result in increased rainfall runoff and pollutant trans-
port to surface waters. The most common stream water quality result is elevated
counts of indicator bacteria. Increased levels of inorganic and organic sediments
with associated plant nutrients and oxygen demands may result from problem areas.
These areas are usually only a small portion of the total production system and are
readily identified by observation. Generally the pollutant levels from the remainder
of the production site are not discernible from background levels. If other changes,
such as those affecting groundwater quality, occur, they are of no environmental
consequence.
A major challenge remaining is to demonstrate cost-effective routes toward
achievement of various levels of pollution control from unconfined animal production.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Animal Husbandry
Livestock
Range grasses
Pasture
Water Pollution
Agricultural Wastes
Nonpoint pollution
source
Unconfined animal
production
Water pollution sources
Agricultural land
Animal Wastes
43 0
68 D
98 B
13. DISTRIBUTION STATEMEN1
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
40
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
34
*US GOYBSIIBITIHimmCOITICE-1978— 720-335/6087
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U.S. Environmental Protection Agency
Region 5, Library (PI..-12J)
77 West Jackson £-.• ' , ..;L;I
Chicago, 1L 60604-.. ^ j
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