Selected Trends in
American Agriculture:
A Future Perspective
The MITRE Corporation
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Selected Trends in
American Agriculture:
A Future Perspective
William G. Conner
Richard K. Travis
Philip N.Trudeau
November 1980
MTR-80W228
Sponsor: Environmental Protection Agency
Contract No.: EPA 68-01-5064
The MITRE Corporation
Metrek Division
1820 Dolley Madison Boulevard
McLean, Virginia 22102
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ABSTRACT
The potential environmental and economic effects of four
agricultural trends are investigated and areas of long-range research
concern are identified. The trends—conversion of agricultural land,
use of reduced tillage technologies, improvements in irrigation
efficiency and the introduction of integrated pest management—
promise to have significant impacts, especially on soil erosion,
energy consumption and the quality and quantity of water.
111
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PREFACE AND ACKNOWLEDGMENTS
This is one of several documents on environmental trends and
future problems produced to support the Environmental Protection
Agency's Office of Strategic Assessment and Special Studies (OSASS)
in preparing its annual Environmental Outlook report. That report
assists the Agency in its long-range research and development role.
Last year's Environmental Outlook 1980 was an ambitious project,
covering a broad spectrum of issues. This year, studies like this
one focus on selected issues, dealing with them in greater depth.
This approach was conceived by Dr. Irvin L. (Jack) White, formerly
with the Environmental Protection Agency (EPA), and project guidance
was provided by John W. Reuss, OSASS director.
MITRE staff members who played central roles in the development
of this study included: Brian Price, program manager; Beth Borko,
project manager; Vivian Aubuchon, editor; and Carol Kuhlman,
production support.
Valuable guidance was provided by Dr. Stephen Lubore and Ernest
P- Krajeski, both of MITRE, as well as Charles Oakley and Donald Cook
of EPA.
IV
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TABLE OF CONTENTS
Page
LIST OF FIGURES vii
LIST OF TABLES ix
EXECUTIVE SUMMARY xi
1.0 INTRODUCTION 1
1.1 Background 1
1.2 Purpose 2
1.3 Approach 3
2.0 AGRICULTURAL LAND CONVERSION 5
2.1 Conversion of Agricultural Land 5
2.2 Implications of Agricultural Land Conversion 16
3.0 REDUCED TILLAGE 29
3.1 An Emerging Trend 30
3.2 Implications of Reduced Tillage 33
4.0 IMPROVED IRRIGATION EFFICIENCY 45
4.1 Water Use Trends 45
4.2 Implications of Irrigation Efficiency Improvements 55
5.0 INTEGRATED PEST MANAGEMENT 67
5.1 Trends in Pest Control 68
5.2 Implications of Integrated Pest Management 76
6.0 CONCLUSIONS: IMPLICATIONS OF CHANGING 87
AGRICULTURAL PRACTICES
6.1 Soil Erosion 87
6.2 Water Quality and Supply 90
6.3 Energy Consumption 92
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TABLE OF CONTENTS (Concluded)
7.0 UNRESOLVED QUESTIONS
7.1 Land Conversion
7.2 Reduced Tillage
7.3 Irrigation Efficiency Improvements
7.4 Integrated Pest Management
REFERENCES 103
VI
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LIST OF FIGURES
Figure Number Page
1 Land Use Conversion, 1967 to 1975 8
2 Amount and Percentage of Rural Land 10
Converted to Urban Development and Water
Projects, 1967-1975
3 Past and Projected Cropland Acreage in 12
the U.S., 1960-2030
4 Major Limitations of Land with High and 15
Medium Potential for Conversion to Crop-
land, by Farm Production Region
5 Relationships Between General Land Use and 18
Total Phosphorus and Total Nitrogen Concen-
trations in Streams
6 Trends in World Population 25
7 Past and Future Projections of No-Till and 31
Minimum Tillage on Cropland
8 Representative Irrigation Water Budget for 46
the U.S. and Caribbean
9 Percentage of Total Harvested Cropland 48
Irrigated, 1974
10 Past and Projected Irrigated Acres on 50
U.S. Farms
11 Percentage of Water Consumption and With- 52
drawal, By User, 1975 and 2000
12 Trends in Surface Water and Groundwater 53
Use for Irrigation, 1950-1975
13 Areas in Which Groundwater Withdrawal 57
Exceeds Natural Recharge
14 Monthly Streamflow Depletion Levels in the 59
U.S.
vii
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LIST OF FIGURES (Concluded)
Figure Number Page
15 Idealized Representation of Integrated Pest 71
Management
16 U.S. Use of Synthetic Organic Pesticides, 77
1964-1990
17 Use of Economic Threshold Population Density 82
to Initiate Pest Control
viii
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LIST OF TABLES
Table Number Page
1 Trends in the Use of Non-Federal Land in the 6
U.S. and the Carribean
2 Potential Convertibility of Non-Federal 14
Lands to Agricultural Lands from Other Land
Uses
3 Comparison of Average Peak Pollutant 17
Concentrations in Stormwater Runoff from
Areas With Different Land Uses
4 Representative Erosion Rates With Various 19
Land Uses
5 Index of World Food Security 26
6 Regional Use of Reduced Tillage Methods 30
in 1977
7 Crops Using No-till and Minimum Tillage 32
1977
8 Weighted Average Soil Loss for 14 35
Cornbelt Regions Under Five Different
Tillage Systems
9 Water, Soil, and Herbicide Leaving 37
Conventional and No-Till Corn Fields
10 Regional Agricultural Energy Consumption, 42
by Fuel Type, 1976
11 Estimated Maximum Possible Energy Savings 44
per Year in Several Agricultural Areas
12 Net Increases in Value of Output, Wages 62
and Farm Income and Employment
Attributable to Federal Irrigation Projects
13 Estimated Costs and Effectiveness of 63
Irrigation Efficiency Improvement Measures
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LIST OF TABLES (Concluded)
Table Number Page
14 Cost-Benefit Evaluation of Irrigation 65
Improvement Options in the Snake River
Basin
15 Percentage of Total Herbicide, Insecticide 73
and Fungicide Applied to Specific U.S.
Crops, 1976
16 Number of Pesticide Related Occupational 79
Illness Cases, California, 1973
17 Average Yield Values and Insecticide Costs 84
per Acre for Users and Nonusers of Inde-
pendent Pest Control Advisers' Programs,
San Joaquin Valley Cotton
18 Projected Future Implications of Trends in 88
Agriculture
19 Potential Energy Savings from Agricultural 93
Trends
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EXECUTIVE SUMMARY
To remain profitable, agriculture is adapting to the higher costs
of scarce resources, and to domestic and foreign demands for larger,
more desirable yields. Four recently observed changes in agricul-
tural practices are expected to continue in the future: conversion of
agricultural land to other uses, use of reduced tillage technologies,
improvements in irrigation efficiency and the introduction of
integrated pest management (IPM). Concomitantly, the environmental
effects of farming practices are also expected to change. These
trends and their environmental implications are investigated in this
report.
Conversion of Agricultural Land
Presently, American agricultural land is being lost to urbaniza-
tion and water impoundments or wetlands at the rate of 3 million
acres per year. At the same time, another 1 million acres are lost
each year to cropland isolation through leap-frog urbanization.
Between 1967 and 1977, 25 million acres of cropland were converted to
other uses, compared with a 10 million-acre loss in the previous
decade. Shifts from cropland to other uses would appear to be
reversible, but they are practically irreversible when the conversion
is made to urban use or water impoundments, and only 50 percent
reversible when the shift is to pasture or range.
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Enough cropland is presently available to feed the U.S. into the
first part of the next century and probably beyond if the conversion
of cropland to other uses is halted. Our ability to meet foreign
demand for our food products, however, remains in question. Three
factors will determine whether the U.S. has sufficient farmland:
U.S. population growth, foreign demand and our ability to increase
agricultural productivity. Increased yield will depend on the
success of yield enhancers such as improved plant breeding, inte-
grated pest management, increased irrigated acreage, genetic
engineering and intensive aquaculture.
Approximately 110 to 125 million acres of noncropland are
presently thought to have the potential for conversion to cropland.
Conversion would depend on crop prices, physical characteristics of
the land and expected conversion costs. Foreign demands, yield
enhancers and conversion trends of present cropland to urban and
water impounded land will determine how much of this potentially
convertible land will be used.
Future research efforts related to land conversion could be
directed toward answering several questions raised in this study,
including:
o Leap-frog development—What is the potential for using the
resultant small tracts of land for specialty crops? What
crops would be best for each region of the country? What tax
incentives or land use regulations would have to be insti-
tuted to save these 10- to 40-acre plots near urban centers
from development? How effective have previous programs for
the preservation of farmland near cities been? If they have
failed, why have they failed?
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o Noncropland with the potential for conversion to cropland—
What would be the most likely changes in the use of this land
during the next 30 years? What actions can be taken to
insure that it will retain the attributes which make it
potential cropland? What programs have previously been at-
tempted? What portions of the programs have been successful?
o Cropland conversion—Why are only half of the conversions to
pasture or rangeland reversible? Are there any factors which
would increase this reversibility? Have Federal lands been
adequately inventoried concerning their cropland potential?
If answers can be found for such questions, then land conversion
could be slowed and the associated adverse environmental effects
could be reduced.
In addition, future cropland needs could be more accurately pre-
dicted with a cropland production computer model. Through projec-
tions for a range of scenarios, the effects of potential conversions
and future needs could be better estimated.
Reduced Tillage
With reduced tillage, chemical herbicides are used to control
weeds and there is little or no cultivation. In 1977, 67 million
acres of U.S. cropland were actually under cultivation by reduced
tillage methods, and that may increase to 240 to 280 million acres by
the year 2010.
In no-till farming, one machine can apply herbicide, fertilize,
open the ground to plant a seed and close it upon passing. Crop res-
idues left in the fields at the end of the growing season serve as a
mulch to prevent erosion, add organic matter to the soil, maintain
higher soil water content, aid in weed control, lower soil surface
xiii
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temperature and, at the same time, provide a habitat and/or food for
wildlife. Erosion is sharply reduced, not only because of the crop
residues, but also because fields are not opened up by tillage.
The ecological impacts of reduced tillage could be more fully
investigated to determine their adverse or beneficial effects.
Information on expected increases in the use of herbicides and
insecticides could be correlated with data on the adsorption and
breakdown of these chemicals, as well as with known decreases in soil
erosion and water runoff.
This would require coalescing information from many sources such
as the data manufacturers must compile to register herbicides and
insecticides to answer several questions, including: Which of the
commonly used herbicides and insecticides are adsorbed on soil
particles, adsorbed on the surface of plants or absorbed into plant
tissues? What are their in-the-field decomposition rates? When crop
residues are left in the fields, what is the rate of release and/or
breakdown of the pesticides?
Other questions could also be addressed. Since several herbi-
cides might be used simultaneously, what synergistic impacts can be
expected between various herbicides or between herbicides and pesti-
cides? If animal populations are expected to increase in reduced
tillage areas, what is the potential for pesticide or herbicide
bioconcentration or transfer into neighboring terrestrial environ-
ments?
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Irrigation Efficiency Improvement
Between 1975 and 1977, 45 to 56 million acres of U.S. cropland
were irrigated and this land provided 25 percent of cash crop value.
Irrigation, which most notably increases yields (11 percent in the
East and 38 percent in the West), also makes more land arable, in-
creases crop variety in a region and insulates farmers from drought.
Irrigation systems are often inefficient. Only about 41 percent
of water diverted for irrigation during 1975 (180 million acre-feet)
was consumed by crops; the remainder was lost through evaporation and
other routes or returned to the source. Higher efficiency can be ob-
tained with existing technology. This technology will not be
adopted, however, unless it proves to be cost effective.
Florida, Louisiana and the western states are the primary areas
of intensive irrigation. In the future, expansion of irrigated acre-
age is expected in the central and southeastern U.S., but not in the
West, for two reasons: the western states have already appropriated
most of their water resources for various uses, and western water
resources will face increasing competition from energy and energy-
related industries.
Other trends in water use will include multiple use and treat-
ment of water resources, such as treated municipal sewage for farm
use, and an expanded use of groundwater resources rather than surface
water resources. By the year 2000, agriculture is expected to be
responsible for 70 percent of the nation's water consumption.
xv
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Again, research might focus on answering several questions,
including:
o What are the long-term, acceptable limits on stream depletion
due to irrigation and other withdrawals?
o What impacts on aquatic life could result at these stream de-
pletion limits?
o What are acceptable limits on groundwater withdrawal in dif-
ferent regions?
o By state, what surface and groundwater supplies are avail-
able for irrigation and what other demands on these supplies
are anticipated?
o What is the physical and legal potential for interbasin water
transfers and what impacts would result from such transfers?
o What shifts in crops or irrigated acreage would be necessary
to bring each state's surface and groundwater irrigation
problems within acceptable limits?
Integrated Pest Management
Integrated pest management (IPM) is a continuous system to
manage pest populations over time by the selection and simultaneous
application of various chemical, biological and cultural control tech-
niques. The control measures have economic, ecological and sociolog-
ical bases. Since 1940, one-third of the dollar value of agricul-
tural production has been lost to pest destruction. IPM seeks to
manage these pest populations below the level at which they cause ec-
onomic injury.
By the simultaneous use of multiple tactics and in-the-field
sampling and monitoring, pest populations are continuously con-
trolled. Multiple tactics include chemical pesticides (with a trend
xvi
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toward more efficient, pest-specific, biodegradable, non-accumulating
pesticides), biological methods (improved plant breeding; discovery,
importation and/or use of natural enemies and disease causing organ-
isms; sterilization of insects; pheromones; and insect growth
hormones), and cultural methods (crop rotation, crop residue removal,
trap cropping and timing of planting and harvesting). Continuous,
in-the-field sampling and monitoring of pest, plant and pest enemy
populations and development stages allow farmers and pest advisers to
make decisions on which of the multiple control tactics to use and
when to use them.
Presently, and increasingly in the future, computer models will
be constructed for individual components of agricultural systems. As
more knowledge is gained in the individual areas of IPM, portions of
the data collection will be automated. Ultimately, when the individ-
ual components are better known, agroecosystem computer simulations
could be developed to make quick, accurate and up-to-date predictions
on plant growth and pest populations so that decisions can be made
before any economic damage is done to the crop.
In addition to computer modeling, IPM research endeavors should
also concentrate on personnel training. Special training programs
might have to be developed if it appears that there will not be suf-
ficient trained personnel for future, sophisticated IPM techniques in
sampling, monitoring, data analysis and modeling.
xvii
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Conclusions
Examination of the selected agricultural trends reveals three
major areas of environmental quality they may affect: soil erosion,
water quality and supply, and energy consumption.
Collectively, the trends could lead to decreased soil erosion.
With reduced tillage farming, crop residues left on land decrease
erosion by 50 to 95 percent, or more. Improved irrigation techniques
can also reduce erosion because a larger portion of the water with-
drawn for crops would actually be consumed on the farm—not returned
to the source, burdened with suspended sediments, pesticide residues
and salts. These two factors are expected to outweigh episodic
increases in soil erosion that would accompany three phenomena: the
conversion of new cropland from other land uses, shifts of present
cropland to urban uses and the traditional agricultural technique,
also associated with IPM, of eliminating crop residues to destroy
pest habitats.
No definitive statement can be made concerning the overall
effect of these agricultural trends on future water supplies. Irri-
gation efficiency improvements would conserve water, although expan-
sion of irrigated acreage could require more water. The magnitude of
efficiency improvements and of acreage increases will ultimately
determine whether water supplies increase or decrease. Areas in the
West are already beyond critical stream depletion levels and ground-
water overdrafts are becoming more common. Moreover, competition for
xviii
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these supplies from the energy industry and manufacturers may cause a
shift of new irrigated acreage to the central and southeastern
states, or a change to the production of higher value, more inten-
sively managed, cash crops on western irrigated acreage. Finally,
the conversion of agricultural land to water impounded land will tend
to augment supplies.
Together, the trends are also expected to benefit water quality.
Reduced tillage will lead to the use of more herbicides and pesti-
cides, but, with substantially lower soil erosion, a smaller quantity
of the soil bound chemicals and suspended sediments will be carried
to streams and reservoirs. The conversion of cropland to urban uses
will cause a shift in nonpoint source pollutants and an increase in
episodic erosion associated with construction and with clearing new
cropland. Conversion of agricultural land to water impounded land
generally has a favorable impact on the quality and quantity of
water, as well as on flood protection. Improvements in irrigation
efficiency will reduce the concentrating effect on dissolved solids
and the amount of pesticides and suspended sediments transported back
to surface waters. Integrated pest management is expected to result
in reduced pesticide use, also benefitting water quality.
Modest energy savings could be an incidental benefit from the
selected trends. Estimates indicate that reduced tillage, improved
irrigation efficiency and integrated pest management could reduce
energy used in conventional tillage by 7 percent; in irrigation, by
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20 percent; and, in pesticide practices, by 4 percent. Consequently,
total agricultural fuel use could be reduced by 5 percent, since re-
duced tillage would require less frequent use of equipment; improved
irrigation would cut the amount of water transported to serve a given
need; and IPM would lower the amount of pesticide produced, trans-
ported and applied.
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1.0 INTRODUCTION
1.1 Background
This report examines the environmental implications of four
«
major trends affecting farming, and identifies important questions
for long-range research by the Environmental Protection Agency's
Office of Research and Development. For generations, the American
farmer has been led to believe that soil could be endlessly renewed
by chemical fertilizers, insects could be killed with pesticides and
a desert turned into an oasis by pumping seemingly limitless quanti-
ties of water from surface streams and underground reservoirs.
Today's farmer is faced with new realizations. Chemical ferti-
lizers return specific nutrients to soil, but they cannot repair ero-
sion or damage to soil structure. Moreover, with rising crude oil
prices, the cost of transporting and applying these chemicals is
soaring, along with the purchase price of the petroleum-based ferti-
lizers themselves.
Pesticide price increases are also keeping pace with the rising
price of oil and the farmer is discovering that these chemicals are
ineffective against new, resistant insect strains. At the same time,
the farmer and government are confronting the fact that water sup-
plies are not limitless. In some parts of the West, water is already
in critically short supply and industrial competition for this
resource is intensifying.
Like the American automobile buyer, the farmer is being forced
to change some fundamental assumptions. With rising gasoline prices,
1
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Americans turned to more fuel-efficient cars. Similarly, economic
factors are pushing the farmer toward new practices, including
improved irrigation efficiency, reduced tillage and integrated pest
management. These three trends are investigated here, along with a
fourth trend, the conversion of agricultural land to other uses.
Each of these trends has implications for areas of concern to the
Environmental Protection Agency^ including water quality, en-
vironmental health and ecosystems maintenance.
1.2 Purpose
The intent here is to explore both beneficial and adverse im-
pacts of agricultural trends on the environment, economy and energy
that could be of concern to the Federal Government. The introduction
of new farming techniques can be expected to have substantial effects
on the environment, in part, because of the sheer magnitude of agri-
culture itself. When defined as the sum of crop, pasture, range and
forest land,* agricultural acreage encompasses more than 1.3
j.
Agricultural land, as defined by the National Agricultural Lands
Study (1980c), is land currently used or having the potential to be
used to produce agricultural commodities such as food, feed, fiber,
forage, oilseed, ornamental plants, wood products and, potentially,
biomass energy. These lands have a favorable combination of soil
quality, growing season, moisture supply, size and accessibility for
producing agricultural commodities. By their definition (National
Agricultural Lands Study 1980c), crop, range, pasture and forest
land would all be considered agricultural land. Additionally, not
all the land normally listed under cropland during any year is actu-
ally under cultivation; a portion of it lies fallow. Therefore,
while many sources have been used and a variety of terms and data
groupings encountered, in this report, agricultural land refers to
crop, range, pasture and forest land and cropland refers to all
agricultural lands not used for range, pasture and forest land.
Cultivated cropland is designated as such.
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billion acres, or about 85 percent of non-Federal land (National
Agricultural Lands Study 1980d). Cropland conversion is an example
of a finite resource becoming less plentiful and more costly. Crop
production in the U.S. may ultimately be limited by the amount of
available, farmable (or convertible) land, and by our ability to
increase per acre productivity.
All four trends could have future environmental ramifications.
For example, lakes and streams would be affected by changes in soil
erosion that would alter the types and quantities of chemicals and
soil particles in stormwater runoff. In turn, this would affect the
quality of water, along with the welfare of aquatic life.
Increased emphasis on long-range planning is appropriate to
identify additional agricultural trends and devise solutions to
potential problems before resources are unduly taxed and before the
environmental impacts are beyond management. Only a continuing
program of long-range forecasting and analysis can insure that the
Environmental Protection Agency can meet its wide-ranging responsi-
bilities. Such analysis can help the Agency to prepare legislation
and regulations that will lead to the most efficient use of our
resources and, concurrently, the least degradation of our environ-
ment.
1.3 Approach
The trends selected here for study are just a few of many that
are changing the face of American agriculture. Others include:
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moves toward larger farms and mechanization; cultivating crops for
biomass energy; and improvements in feedlot waste disposal, range
management and silviculture. The four trends discussed in this
report were selected because they could change the fundamental nature
of farming in the U.S. and because of the extent of their potential
effects on the environment, society and the economy.
Available data indicate that the four selected trends are
building momentum in the U.S. However, new practices are not likely
to be adopted by farmers unless they promise increased profits. Just
as the car buyer clung for years to inefficient luxury cars, the
farmer is reluctant to abandon beliefs and assumptions that have
governed farming for generations. Thus, the degree to which these
trends will actually assert themselves in U.S. farming depends on a
complex mix of cost-effectiveness, and social and technical
questions.
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2.0 AGRICULTURAL LAND CONVERSION
2.1 Conversion of Agricultural Land
A finite resource, agricultural land is being lost in the U.S.
as it is converted to urban development and open water. Since
only a limited amount of land is available to replace converted
cropland, land use decisions being made today are likely to be
recognized as important early in the 21st century, depending upon the
pressure placed on our agricultural system by foreign demands.
2.1.1 Current Land Usage
Land use patterns in the U.S. have been changing in recent
decades. As shown in Table 1, between 1958 and 1977, the acreage
devoted to urban development increased by 39 million acres or nearly
77 percent, while areas of open water increased by about 2 million
acres. During the same period, 49 million acres of agricultural land
(crop, pasture, range and forest land) were converted to other uses.
Approximately 35 million acres of this was cropland, and 25 million
acres of it were converted between 1967 and 1977, for a conversion
rate almost 2.5 times greater than in the previous decade. Similar-
ly, 86 million acres of forest land were lost from 1967 to 1977,
after a moderate increase of 10 million acres between 1958 and 1967.
Non-Federal pasture and rangeland have actually increased since 1958,
but the amount of combined Federal and non-Federal land used for
Open water refers to water impoundment/improvement projects and
conversion of altered land back to its original state
as wetlands.
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TABLE 1
TRENDS IN THE USE OF NONFEDERAL LAND IN THE
U.S. AND THE CARIBBEAN
Millions of
Land Use*
Cropland
Pasture /Range land
Forest Land
Urban Land
Areas of Open
Water
Other
Total
1958
448
486
453
51
7
67
1,512
1967
438
483
463
61
7
57
1,509
Acres
1977
413
548
377
90
9
76
1,513
Change from
Millions
of Acres
-35
+62
-76
+39
+2
+9
1958 to 1977
Percentage
-7.8
+12.8
-16.8
+76.5
+28.6
+13.4
Some inconsistencies caused by changes in land use definitions between
inventories.
Note: Data differences between this table and Figure 1 are a result of different
time periods and subset data manipulations in the source document for Figure
1 (Dideriksen et al. 1977).
Source: Adapted from U.S. Department of Agriculture 1980a.
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pasture and range has declined by 20 percent since the turn of the
century (U.S. Department of Agriculture 1980a).
Figure 1 depicts land use shifts between 1967 and 1975, when
cropland was reduced by approximately 30 million acres. (Data
differences between Figure 1 and Table 1 are a result of different
time periods in the two sources and subset data manipulations in
Dideriksen et al. 1977.) Five million acres of this lost cropland
were converted to urban uses and open water. Concerning the cropland
conversions, Dideriksen et al. (1977) concluded:
o Although some rural land was converted into water inundated
lands, this particular type of conversion was largely from
marginal cropland or previous wetlands and had little effect
on good quality cropland (a similar statement cannot be made
for the rural to urban conversion); and
o Although there had been a substantial loss of cropland during
the period under study, the percentage of cropland in the
best classes had increased slightly.
Most of the cropland lost between 1967 and 1975 was converted to
pastureland. Logically, the cropland to pastureland conversion would
appear to be reversible and readily carried out by farmers in re-
sponse to market conditions, but this does not seem to be the case.
Although the time frame was short, one study of land conversion
between 1967 and 1975 showed that good quality cropland converted to
pasture and range has only a 50 percent likelihood for return to
cropland use, mainly because of the economics of conversion, erosion
and tract size (Hidlebaugh 1980). The conversion of cropland to
urban use is rarely reversed. Between 1967 and 1975, the net loss of
forest land was approximately 70 million acres, with most of this
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oo
0)
•c
1)
>
o
O
-o
c.
ffl
Forest
Land Converted To:
Pasture, idle,3 Urban,b
Cropland Range Rural Res. Water
Forest
Cropland
Pasture,
Range
Idle,3
Rural
Residence
Urbanb
Water
—
8
14
4
0
11
—
32
6
0
62
52
—
13
0
15
13
14
—
0
7
5
5
7
aldle Land, Rural Residence, Etc.
bUrban Buildup, Open Water
Numbers Represent Millions of Acres
Note: Data differences between the above matrix and diagram
arise from data inconsistencies in the source.
Source: Adapted from Dideriksen etal., 1977.
13
cldle Land, Rural
Residence, Etc.
1967-57°
1975-70
S Urban buildup,
Open Water
(1967to1975
Total Conversion
ToUrban-24)
1967 Acreage
1975 Acreage
Note: This diagram is a pictorial representation of land conversion, showing shifts both to
and from the various categories
FIGURE 1
LAND USE CONVERSION
1967-1975
(Millions of Acres)
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converted to pasture and rangeland. Conversion of pasture, range, or
cropland back to forest would require between 25 and 100 years of
regrowth, depending on the region, tree species and intended wood
product.
Figure 1 also shows that, between 1967 and 1975, 24 million
acres were converted to urban uses and open water from forest,
cropland, pasture, range and idle land. Regionally, as shown in
Figure 2, the Southeast lost the largest amount of agricultural land
to urban development and water projects between 1967 and 1975—5.9
million acres—or about 5.3 percent of all rural land in the region
in 1967. The Southern Plains, Appalachian and Corn Belt regions each
had between 2.5 and 2.7 million acres converted, while the remaining
regions experienced conversions of between 0.9 and 1.4 million acres.
Currently, agricultural land is being converted to urban and
water uses at a rate of about 3 million acres per year (National Agri-
cultural Lands Study 1980a). Typically, one-third of this acreage is
prime farmland, as defined by the U.S. Department of Agriculture,
before conversion. For each acre converted, it is estimated that
another acre is effectively lost due to isolation from other
farmland—a result of so-called leap-frog or buckshot development
(Dideriksen and Sampson 1976). Isolated plots of cropland are often
too small to cultivate profitably, or surrounding development may
render farming impractical or unacceptable. The problems resulting
from leap-frog development include higher property values and taxes;
inaccessibility to large tracts of farmable land; and community
-------
Alaska, Hawaii
Puerto Rico, Virgin
Islands 0.3 (3.6%)
Total 21.5 (1.5%)
'Data differences between the total listed in this figure (21.5 million acres) and the summation of
the conversions into urban and water improved lands in Figure 7 (24 million acres) are a result of
data differences presented in the original sources.
Note: Expressed in mil/ion acres lost and (percent of rural land lost to urban and water projects).
Source: Adapted from data in Dlderiksenetal. 1977
FIGURE2
AMOUNT AND PERCENTAGE OF RURAL LAND CONVERTED TO
URBAN DEVELOPMENT AND WATER PROJECTS
1967-1975
(Millions of Acres)
-------
objections to the sites, sounds and odors associated with farming
practices. If fanners are given tax protection, one possible future
use for these isolated plots could be the development of spe-
cialty crop markets with high cash value.
2.1.2 Projected Cropland Needs
It is not clear whether the recent trend of cropland conversion,
illustrated in Figure 3, will continue. Projections range from a
substantial decline in cropland acreage to a modest increase. The
amount of land lost due to urban buildup and other factors will
depend on economic conditions, population growth, population shifts,
demand for agricultural products (domestic and foreign) and effec-
tiveness of land preservation measures.
If crop yields continue to increase, then total agricultural
production could be maintained while cropping fewer acres. Increases
in crop yield may be sustained or increased if future sophisticated
integrated pest management (IPM) methods cut crop losses by control-
ling destructive pests and if other methods, such as plant breeding,
genetic engineering, tissue culture and intensive aquaculture, are
successful. Some agricultural experts say, however, that past suc-
cesses in yield enhancement will not continue beyond the immediate
future and yields will begin to level off, rather than show continued
growth. In the near future—at least until the year 2000—it appears
that sufficient land will be available to meet the demand for agri-
cultural products (U.S. Department of Agriculture 1980a). Neverthe-
less, in the long term, the production of adequate quantities of
11
-------
<
'o
450
440
420
410
380
370
360
1960
1970
1980
1990
Years
2000
2010
2020
2030
Source: "U.S. Department of Agriculture 1980a.
' "Results from Application of Berry and Plant 1978 loss factors from the 1977
resource base of U.S. Department of Agriculture 1980a. Estimated range.
^Projection from U.S. Department of Agriculture 1980a.
a Projection from Olderiksen etal. 1979.
FIGURES
PAST AND PROJECTED
CROPLAND ACREAGE IN THE U.S.
1960-2030
12
-------
agricultural products will depend on the availability of new crop-
land.
2.1.3 Potential for New Cropland
Athough cropland is being lost to urbanization and other uses,
some land is currently being converted from forest, range, pasture
and idle land to new cropland. Two recent studies (Dideriksen et al.
1977, National Agricultural Lands Study 1980d) on the conversion
potential of noncropland acreage have demonstrated that 110 to 125
million acres have high and medium potential for conversion. Table 2
illustrates, on a regional basis, the amount of acreage in other land
uses which have this potential. Whether the acreage is actually
converted to cropland will depend on previous commodity prices,
expected conversion costs and physical characteristics such as soil,
slope and climate. Adding the figures in Table 2 reveals that 124.6
million acres (11.3 percent) out of 1.1 billion acres of non-Federal,
noncropland have a high or medium conversion potential (National
Agricultural Lands Study 1980d).
Dideriksen et al. (1977) found that approximately two-thirds of
this acreage had a high and one-third a medium conversion potential.
Figure 4 graphically demonstrates the limitations on such conversions
for both medium and high potential land.
In general, medium conversion potential land would require sub-
stantial investment prior to cropping for erosion control, draining
or clearing. Concerning the high potential land, approximately 35 to
13
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TABLE 2
POTENTIAL CONVERTIBILITY OF NONFEDERAL LANDS TO AGRICULTURAL LANDS FROM OTHER LAND USES
•a
(Millions of Acres )
Acreage in Other Uses That is Convertible to Cropland'5
Region
Northeast
Appalachian
Southeast
Lake States
Corn Belt
Delta States
Northern Plains
Southern Plains
Mountain
Pacificd
Total
Cropland
16.9
20.8
17.5
44.1
89.9
21.2
94.6
42.2
42.2
23.5
412.9
Pastureland
1.9
6.9
7.1
3.2
10.9
5.1
4.7
7.6
2.4
1.8
51.6
Range land
0.0
0.0
0.6
0.0
0.0
0.0
12.5
11.5
11.4
2.8
38.8
Forest
2.2
7.2
8.0
4.2
2.6
4.7
0.2
0.8
0.2
0.8
30.9
Other0
0.5
0.2
0.1
0.7
0.8
0.1
0.4
0.2
0.1
0.2
3.3
aNumbers rounded to nearest 100,000 acres.
t>High or medium potential for conversion according to the previous years commodity prices, physical character-
istics such as soil and climate, and expected conversion costs.
°Land reserved for wildlife, windbreaks and associated farming activities such as feedlots and nurseries.
"Includes Alaska and Hawaii.
Source: Adapted from National Agricultural Lands Study 1980d.
-------
.0
0.21
Alaska, Puerto Rico, T0.02
Virgin Islands ancfHawaii L °-03
No Limitations
Erosion
Wetness
Soil
Climate
Northern Plains
0.51
1.0
0.25
0.97
Southern Plains
15
Source: Adapted from Dideriksen et al. 1977
Millions of Acres
FIGURE4
MAJOR LIMITATIONS OF LAND WITH HIGH AND MEDIUM
POTENTIAL FOR CONVERSION TO CROPLAND
BY FARM PRODUCTION REGION
15
-------
40 million acres could be converted simply by initiating tillage. A
similar amount would require a minor investment to initiate soil
conservation practices prior to tillage (Dideriksen et al. 1977).
The remaining 88.7 percent of the non-Federal, noncropland (975
million acres) has a low potential for conversion to cropland
(National Agricultural Lands Study 1980d). Dideriksen et al. (1977)
have outlined many of the problems discouraging this kind of conver-
sion: small tracts, isolated tracts, small ownership units, held for
urban use, committed to noncropland uses, short growing season, lack-
ing dependable water supply, high density forest, substantial envir-
onmental impact, high erosion control costs, drainage outlet
problems, seepage, seasonal high water table, wetlands, common flood-
ing, high erosion hazard, thick overburden, low fertility, stones or
rock outcrops and accumulated salts.
2.2 Implications of Agricultural Land Conversion
2.2.1 Environmental Implications
Urbanization, the main cause of agricultural land conversion,
raises a number of environmental concerns. These concerns lie in the
areas of water quality, soil erosion, flood control and wildlife
displacement. When urbanization takes over agricultural land, it not
only affects the area where construction occurs, but also influences
the use of surrounding land.
Table 3 indicates that stormwater runoff from urbanized areas is
characterized by chemical oxygen demands two to eight times higher
16
-------
TABLE 3
COMPARISON OF AVERAGE PEAK POLLUTANT CONCENTRATIONS
IN STOR11WATER RUNOFF FROM AREAS WITH DIFFERENT LAND USES
(Milligrams per Liter)
Land Activity Chemical Oxygen Suspended
Use Level Demand Solids
Rural
Residential
Commercial
Central
Business
District
Lowa
Highb
Lowc
Highd
Low6
Highf
HighS
41
58
166
194
87
320
336
289
416
664
1,199
575
1,082
528
Total
Phosphorus
1.40
0.76
0.84
1.03
0.83
1.08
0.66
Lead
<0.1
<0.1
0.6
2.1
0.2
1.7
0.9
Predominantly forested and agricultural without major roads or
significant development.
^Predominantly forested and agricultural, but containing some major
development such as roadways and airports
"^Predominantly low density residential with little or no commercial
activity and few major thoroughfares.
"Predominantly residential, but with a heavier concentration of
commercial or institutional areas and considerable vehicular
traffic.
Predominantly light industrial or commercial areas where major
vehicular activity occurs during the rush hour periods in the
morning and afternoon.
fPredominantly light industrial, institutional or commercial areas
where vehicular traffic is likely to be heavy throughout the day.
^Eighty percent of the area impervious.
Source: Adapted from Rimer et al. 1978.
than in rural areas, suspended solids two to four times higher and
lead concentrations up to 20 times higher. These and other pollu-
tants may be harmful to aquatic organisms in surface waters and,
17
-------
Forestb
Mostly Forest0
Mixed
Mostly Urban0
Mostly Agriculture0
Agriculture0
MEAN TOTAL PHOSPHORUS CONCENTRATIONS
VS
LAND USE
0.014
135
0.05 0.10
Milligrams per Liter
MEAN TOTAL NITROGEN CONCENTRATIONS
VS
LAND USE
0.15
Forestb
Mostly Forest0
Mixed
Mostly Urban0
Mostly Agriculture0
Agriculture0
0.850
0.885
1.282
1.286
1.812
^•4.170
J L
1.0
"Data on 473 subdrainage areas in eastern U.S.
(Forest, 53; subdrainage areas, mostly forest, 170; Mixed, 52;
mostly urban, 11; mostly agriculture, 96; agriculture, 91)
bOther types negligible
cOther types present
Source: Adapted from Omernik 1976.
2.0
Milligrams per Liter
3.0
4.0
FIGURE 5
RELATIONSHIPS BETWEEN GENERAL LAND USE
AND TOTAL PHOSPHORUS AND TOTAL NITROGEN
CONCENTRATIONS IN STREAMS
18
-------
without treatment, they could make surface or groundwater unsuitable
for human and industrial use. In contrast, streams in cropland areas
typically have total phosphorus and total nitrogen concentrations 50
to 200 percent higher than streams in urbanized areas (Figure 5),
resulting primarily from the increased use of fertilizers in
agriculture. The runoff of plant nutrients into streams and lakes
contributes to accelerated eutrophication.
Cropland under conventional tillage can erode at a substantial
rate, but Table 4 indicates that construction areas often erode at
rates ten times greater during the construction period. Concentra-
tions of suspended solids in runoff from residential areas are
frequently two to four times greater than in rural areas. Erosion
TABLE 4
REPRESENTATIVE EROSION RATES WITH VARIOUS LAND USES
Land Use
Forest
Grassland
Abandoned Surface Mines
Cropland
Harvested Forest
Active Surface Mines
Construction
Tons per
Square Mile
per Year
24
240
2,400
4,800
12,000
48,000
48,000
Relative To
Forest = 1
1
10
100
200
500
2,000
2,000
Source: Adapted from U.S. Environmental Protection Agency 1978b.
19
-------
and transportation of suspended solids can cause siltation of streams
and lakes and degrade surface water quality, often with adverse
consequences for aquatic organisms, including: 1) change in water
temperature, 2) change in pH, 3) increases in dissolved chemicals
such as sodium, calcium, potassium and magnesium, A) increases in
both biological and chemical oxygen demand, 5) decreases in light
penetration and photosynthesis, 6) reduction of dissolved oxygen in
the water and associated metabolic activity in organisms, 7) inter-
ference with feeding behavior of filter feeders, 8) reduction of
habitat diversity and desirability through siltation, 9) settling of
phytoplankton from the water column due to surface adsorption onto
sedimentary particles, and 10) removal of spawning areas (U.S.
Environmental Protection Agency 1976). In addition, the terrestrial
environments from which soil is eroded experience a loss of topsoil,
removal of soil nutrients and loss of soil fertility.
Land conversion could have both negative and positive effects on
flood control. Converting cropland to urbanized land generally
increases flood potential; while conversion to water impounded or
wetlands decreases the flood hazard. In wetlands, flood protection
is by detention storage and in man-made water impoundments, flood
water management is by controlled storage. Conversion to a wetland
has the added benefits of improving water quality (through nutrient
and suspended solid filtering), providing additional habitats for
wildlife and enhancing groundwater recharge (U.S. Water Resources
Council 1979, Horwitz 1978).
20
-------
Cropland urbanization would cause a shift in wildlife species, a
decrease in wildlife population densities, and a decrease in wildlife
diversity. Rural species (pheasant, quail, dove, deer, rabbit, etc.)
would be replaced by species characteristic of developed areas (rock
dove, starling, house sparrow, squirrel, etc.). The exact nature of
the wildlife shift would depend on the region and the level of devel-
opment involved. If there is a large increase in water impoundments
and wetlands due to the conversion of marginal cropland sites
(Dideriksen et al. 1977), then wildlife diversity, density and
community structure could all be expected to increase and improve.
Finally, a shift to farming marginal land, which commonly has
high slopes or infertile soil, would have the negative environmental
consequences associated with higher erosion rates and heavier fer-
tilizer use. Such a shift could result from development of a full
scale biomass program or replacement of good quality agricultural
land lost to urbanization.
2.2.2 Social Implications
The current population migration to rural areas is altering com-
munities and creating new lifestyles. Changes occur in land use, the
type of farming done and the nonfarm population's perception of
acceptable activities. The original community becomes a blend of
rural and urban attitudes and lifestyles.
Normal farming operations may be constrained by a population
influx. New neighbors may object to noisy machinery, slow moving
21
-------
tractors on highways and the application of aerial pesticides and
herbicides. As the nonfarm population increases, the farmer's rela-
tive political and economic power in the community decreases (Berry
and Plant 1978).
2.2.3 Economic Implications
Conversion of cropland has affected local economies. Farms have
been faced with increasing costs for land, labor and pest control.
As a result of increasing land values near urban areas and because of
productivity limits, new cropland is being sought. As previously
uncropped land is converted to cropland uses, the reserve of poten-
tial cropland is depleted. The reserve depletion and increasing pop-
ulation pose concerns related to future world and U.S. food supplies.
The tendency for property values to rise near urban areas
encourages the urbanization of still more land in what is called the
"impermanence syndrome." Development potential increases as urbani-
zation expands. Cropland is often priced out of the farm market by
increasing taxes. New public services such as domestic water mains,
sewage lines and trash collection place an additional tax burden on
small farmers. Urbanization also brings other public and private
facilities and services, including shopping centers, processing and
manufacturing plants, parking areas, utilities, storage and distribu-
tion facilities, schools, playgrounds, hospitals, clinics and service
centers, all resulting in generally higher living and farming costs
(Vlasin 1975). If uncertain about the future of farming in the area,
22
-------
farmers are reluctant to make any long term Investments. This, in
turn, adversely affects local support industries and creates a
decline in the local farm economy, possibly increasing farm area
unemployment.
Another factor affecting farmland use is the rising cost of
fertilizers, pesticides and irrigation. As these costs rise, there
may be a tendency to maintain total production by allowing productiv-
ity per acre to decrease, but bringing more acreage into cultivation
(U.S. Congress 1979a). This trend accelerates reduction of the
finite cropland reserve. Demand for agricultural products is likely
to be met in the foreseeable future, but achieving this goal while
depleting a valuable finite resource could have long-term, adverse
implications.
In some areas of the country, there has been a trend toward
preserving farm land with stricter zoning regulations and better tax
incentives. Impressive results have been realized in specific loca-
tions, but often the zoning changes and tax incentives are too little
and too late. In other areas, conservationists are advocating, or
even planning for residential development on marginal or unfarmable
land. In addition, other potentially important programs include the
purchase of development rights, the transfer of development rights or
agricultural districting (Council on Environmental Quality 1979).
Conversion of agricultural land in the U.S. also has implica-
tions when viewed in the context of global food shortages and rapidly
23
-------
increasing agricultural exports. Whether these exports continue to
rise because of humanitarian, political or economic reasons, they are
a central factor in the consideration of cropland expansion in this
country (U.S. Congress 1979a).
U.S. agriculture responds to world food markets and world market
prices. If foreign demand increases at an accelerating rate, without
U.S. legislative action, American market prices will be driven up by
foreign demand. This would provide an economic benefit to the
American farmer, but an increase in inflationary pressures upon the
public.
The magnitude of the potential problem becomes apparent when
world population increases are compared to world food reserves.
Rapid advances in medicine (Swaminathan 1979) and increases in the
food supply through mechanization, pesticides, plant breeding, etc.,
have resulted in an unprecedented growth in world population as shown
in Figure 6. Examination of projected world population growth
highlights the difficulties in helping to supply enough food to the
growing world population.
The situation seems even more critical when this population
growth is compared to an index of world food security in Table 5
(Brown 1975). Reserve grain stocks in exporting countries and idle
cropland in the U.S. equaled 105 days of world food consumption in
1961. Reserves began to drop abruptly in 1972 and continued to a low
of 33 days in 1974. Preliminary estimates of carry-over stocks indi-
cated an even lower level of 31 days in 1976.
24
-------
to
c
.0
m
c
c
g
05
Q.
O
Q.
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0
-
.
-
-
.
.
1 1
8000BC 7000BC 6000BC1 ' 1000BC
Source: Adapted from Swaminathan 1979; Oram 1980
2015
1980
1000AD
2000AD
Year
FIGURES
TRENDS IN WORLD POPULATION
25
-------
TABLE 5
INDEX OF WORLD FOOD SECURITY
Year
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976b
Reserve
Grain3
Stocks
(Millions of
Tons)
179.7
194.0
164.2
168.7
162.0
166.4
126.8
158.7
175.3
207.2
185.2
143.3
163.1
119.0
122.4
110.2
Grain
Equivalent
of Idle
U.S.
Cropland
(Millions of
Tons)
75.0
89.3
77.2
77.2
78.3
86.0
56.2
67.2
80.5
78.3
45.2
86.0
26.5
0.0
0.0
0.0
Total
Reserves
(Millions of
Tons)
254.6
283.3
241.4
245.8
240.3
252.4
183.0
226.0
255.7
285.5
230.4
229.3
189.6
119.0
122.4
110.2
Reserves as
Days of
Annual Grain
Consumption
105
105
95
87
91
84
59
71
85
89
71
69
55
33
35
31
aBased on carry-over stocks of grain at the beginning of the crop
year in individual countries for year shown. The U.S. Department of
Agriculture has recently expanded the coverage of reserve stocks to
include importing as well as exporting countries, so the reserve
levels are slightly higher than those published earlier.
bPreliminary estimates by U.S. Department of Agriculture.
Source: Adapted from Brown 1975.
26
-------
The decline in grain reserves along with three other factors—
the disappearance of idled U.S. cropland, dependence on the U.S. and
Canada for food surpluses and the Soviet decision to become a net
grain importer in 1972—indicate current or impending instability in
the world food economy (Brown 1975).
The productivity increases in our agricultural system are prob-
ably not without limits. Application of fertilizer, pesticides,
irrigation and other measures to increase yields is practical only as
long as marginal cost is below the economic return. New and improved
technologies such as improved plant breeding and tissue culture tech-
niques, genetic engineering (e.g., nitrogen fixing, nodulated corn
plants; Fox 1980), widespread use of integrated pest management and
intensive aquaculture might allow a continued increase in per acre
and total productivity, or they might not. Therefore, it may be
necessary to have a large potential cropland reserve. Development or
conversion of potential cropland now may preclude the future use of
the land and cause significant expansion into marginal farm lands.
Such a shift could be accompanied by decreasing crop yields,
increasing fertilizer use and erosion.
The magnitude of the economic and environmental impacts of
rapidly increasing exports is not completely clear, but it is appar-
ent that more land will be required if recent export trends continue
and crop yields cannot be substantially increased by new technology.
Viewed in the context of rapidly increasing farm exports, whether for
27
-------
humanitarian reasons or to alleviate the balance of payment problem,
the conversion of farmland in the U.S. could have significant impacts
early in the next century.
Some conservationists contend that, in the near future, we could
be as concerned over the loss of farmland as we now are over the oil
shortage (National Agricultural Lands Study undated). More optimis-
tic observers claim that the potential cropland base is adequate for
future food and fiber needs, if existing high quality cropland is
retained, while high and medium potential reserves are not committed
to irreversible uses (Dideriksen et al. 1977). No quantitative
studies adequately support either contention, but recent literature
has clearly indicated that the U.S. is losing far more cropland to
urbanization and retaining correspondingly less in reserve than
anyone had previously expected (American Land Forum 1979).
28
-------
3.0 REDUCED TILLAGE
Reduced tillage involves the substitution of chemical herbicides
for physical control of weeds, an essential requirement to maintain
high crop yields. Until recently, with conventional tillage, the
moldboard plow or some other cultivator has been used to break
ground, prepare the seed bed and control weeds. However, convention-
al tillage leaves cropland exposed to soil erosion by water and wind.
Tens of tons of soil can be eroded from an acre of cropland in a
single year. Loss of topsoil reduces yield and ultimately renders
cropland unfarmable as occurred in portions of the U.S. during the
1930s. Reduced tillage alleviates erosion problems associated with
plowing (Hall and Hartwig 1979, Skidmore 1977 and Onstad and Otterby
1979), but may lead to environmental problems caused by herbicide
use.
Reduced tillage was originally proposed in the early 1900s to
lower production costs by eliminating repeated tillage. In the fol-
lowing decades, various no-till systems were put into limited use to
reduce erosion and runoff. It was not until the late 1940s, however,
that selective herbicides became available for use in conjunction
with reduced tillage farming. Since that time, weed control has
become less troublesome to no-till farmers and the use of reduced
tillage more widespread. The crop most frequently grown with reduced
tillage is corn and the areas using this technology to the greatest
extent are the Corn Belt and Lake States regions.
29
-------
3.1 An Emerging Trend
Reduced tillage has been implemented by American farmers to the
extent that by 2010, if the present trend continues, 50 percent of
U.S. cropland may be farmed using no-till or minimum tillage methods
(U.S. Environmental Protection Agency 1978b). The number of acres
under no-till and minimum tillage more than doubled between 1972 and
1977, as shown in Figure 7. By the year 2010, it has been predicted
that 40 to 80 million acres of American cropland will be farmed using
no-till and another 200 million acres using minimum tillage methods
(U.S. Environmental Protection Agency 1978b). On a regional basis,
Table 6 reveals that the Corn Belt and Lake States had the greatest
amount of farmland under no-till (3.9 million acres) and minimum
tillage (22 million acres) in 1977.
TABLE 6
REGIONAL USE OF REDUCED TILLAGE METHODS IN 1977
(Thousands of Acres)
Region
Minimum
No-Tillage Tillage
No— And Minimum
Tillage
Conventional (Percentage of
Tillage Regional Total)
Northeastern
Southeastern
Corn Belt/
Lake States
Great Plains
Western
Overall
823
2,324
3,939
723
160
7,969
1,632
6,753
22,087
18,474
9,877
58,823
5,530
31,137
73,736
85,609
23,352
219,364
30.7
22.6
26.0
18.3
30.1
23.3
Source: Adapted from U.S. Environmental Protection Agency 1978b,
exhibit C-9.
30
-------
200
190
180
170
160
150
c 140
O 130
•5 12°
-------
Corn, the most widely grown crop using minimum tillage,
accounted for about 31 percent of all acreage planted under reduced
tillage in 1977, as shown in Table 7. Collectively, corn, soybeans,
grain sorghum, and small grains accounted for 98 percent of all
reduced tillage acreage in 1977. Cotton, peanuts, wheat, tobacco and
some vegetables have also been successfully produced with reduced
tillage (Triplett and Van Doren 1977).
TABLE 7
CROPS USING NO-TILL AND MINIMUM TILLAGE
1977
Crop
Corn
Soybeans*
Grain Sorghum
Small Grains
Other
Thousands
of Acres
20,976
15,354
4,664
24,477
1,321
Percentage of Reduced
Tillage Acres
31.4
23.0
7.0
36.6
2.0
Double cropped soybean acres counted twice.
Source: Adapted from U.S. Environmental Protection Agency 1978b,
exhibits C-9 and C-10.
Deterrents to a wider use of no-till include the need to invest
in new equipment and the underutilization of other, previously pur-
chased equipment. Another is the farmer's fear of being scorned by
his peers for leaving "trash" on his fields (Kelley 1977). Leaving
32
-------
crop residue on the field until the next planting conflicts with the
long held belief of some farmers that a clean, well-tilled field is
synonymous with good farming.
In a reduced tillage operation, the seeds of a new crop are
planted in unturned soil still covered with the residue of previous
crops. The residue serves as a mulch, maintains a higher soil water
content, aids in soil erosion control, provides a habitat for insect
pests, rodents and wildlife and maintains a lower surface soil
temperature (Phillips et al. 1980). In a single operation, a
planting machine employed in no-till cropping can apply herbicide,
fertilize, open the ground to plant a seed, and press the seed into
place (Baldridge and Ranney 1977). Under some conditions, subsequent
herbicide application or tillage may be required to ensure a good
yield.
There is no universally accepted terminology assigned to various
kinds of reduced tillage. Chisel plow, till-plant, plow-plant, slot-
plant, no-till, and stubble-mulch are all used to refer to different
reduced tillage methods. A simple spray-plant-harvest system would
be called no-till or zero-tillage. Any modification of spray-plant-
harvest which involves tillage or cultivation would be called low-
till, reduced tillage or minimum tillage.
3.2 Implications of Reduced Tillage
3.2.1 Environmental Implications
The most obvious environmental implications of minimum tillage
relate to improved erosion control, increased herbicide use and
33
-------
increased pest management requirements. One of the less obvious
implications relates to the use of cropland by wildlife.
Control of cropland erosion is one of the most important bene-
fits of reduced tillage. Minimum tillage programs can lower annual
soil erosion from 5, 10 or 20 tons per acre under conventional til-
lage to less than 1 ton per acre (Kelley 1977). Soil erosion reduc-
tions from no-till are commonly 50 to 95 percent (U.S. Environmental
Protection Agency 1978b). Phillips et al. (1980) cite four investi-
gations of various slopes which all demonstrated soil erosion reduc-
tions from conventional to no-till methods of at least 98 percent.
One severe storm study demonstrated a 99.9 percent reduction. Simi-
larly, working with corn, Harrold and Edwards (1971, as cited in U.S.
Congress 1979a) found a sevenfold decrease in erosion between conven-
tionally clean-tilled sloping rows (45,000 Ibs per acre) and conven-
tionally clean-tilled contoured rows (6,430 Ibs per acre). They
found an additional one-hundredfold decrease in no-till contoured
rows (63 Ibs per acre).
Lindstrom et al. (1979), using the known conditions for 14 major
land resource regions in the Corn Belt, predicted similar results,
listed in Table 8. Their projection utilizes two variables—tillage
and amount of residue left in the field. Conventional tillage soil
erosion estimates were 10.5 tons per acre per year, while reduced
tillage soil erosion estimates ranged from 4.1 to 7.0 tons per acre
per year, depending on whether a high or low amount of crop residue
34
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TABLE 8
WEIGHTED AVERAGE SOIL LOSS3 FOR 14 CORNBELT REGIONS
UNDER FIVE DIFFERENT TILLAGE SYSTEMS
(Tons per Acre per Year)
UJ
Ui
Conservation Tillage
MLRAb
Number
102
103
104
105
106
107
108
109
110
111
112
113
114
115
Weighted
Average
Conventional
Tillagec
6.3
4.3
6.0
10.6
12.7
19.9
12.3
15.4
7.3
6.4
7.8
13.1
11.3
14.0
10.5
Chisel Plow
With Residues'1
5.1
3.5
4.9
7.8
10.3
15.1
8.8
9.5
4.9
4.3
5.3
7.9
7.1
8.6
7.0
Chisel Plow
With Residues6
3.1
2.0
2.9
4.8
5.3
8.6
5.1
5.8
2.8
2.8
2.8
4.6
4.2
5.3
4.1
No-Tillage
With Residues*1
4.1
2.8
3.2
5.8
8.6
11.4
6.8
7.4
4.2
3.5
4.3
5.8
5.2
6.3
5.4
With Residues6
2.5
1.8
2.4
3.7
4.5
7.1
3.9
4.3
1.9
1.8
2.0
2.9
2.9
3.5
3.1
aPredicted from the Universal Soil Loss Equations for the conditions in each region.
"Major Land Resource Area Number.
cNormal spring plowing sequence plus fall moldboard plow and residue removal.
^1,500 Ibs of residue per acre.
e3,500 Ibs of residue per acre.
Source: Adapted from Lindstrom et al. 1979.
-------
was left in the field. No-tillage estimates were between 3.1 and 5.4
tons per acre per year, depending on the residue left, for a 50 to 70
percent decrease from those expected with conventional methods.
Reduced tillage has also been shown to be effective in controlling
wind erosion (Fenster and Wicks 1977, Skidmore 1977).
Besides maintaining more fertile soils and higher yields, ero-
sion control is also important in maintaining the quality of nearby
surface waters. As previously mentioned, if delivered to surface
waters, suspended sediments and agricultural chemicals can cause
adverse impacts, including changed water temperatures, increased
oxygen demand and decreased light penetration (U.S. Environmental
Protection Agency 1976). Substances such as insecticides, herbicides
and phosphorous can become associated with soil particles in agricul-
tural fields. Eroded particles can then act as vehicles to transport
these chemicals off the farm and into nearby surface waters.
A comparison of conventional and no-till soybean crops reported
by Kelley (1977) showed an 85 percent reduction in total phosphorus
lost from cropland under no-till. In the no-till case, dissolved
phosphorus carried in runoff increased by 1.5 pounds per acre, but
the amount of phosphorus bound to eroded sediment particles was
reduced by 14.7 pounds per acre, accounting for the large overall
reduction. Table 9 summarizes the results of a similar study,
reported by Hall and Hartwig (1979), concerning an herbicide. These
researchers found a substantial reduction in cyanazine leaving
36
-------
no-till fields, even though more cyanazine was applied under the
no-till system. Apparently, the herbicide had been adsorbed onto
soil particles and less of it left the cornfields because plant
residues decreased the erosion rate and the amount of stormwater
runoff. But, depending on its decomposition rate and affinity for
soil particles, the herbicide could be leached below the till zone by
water (Miller et al. 1978) and potentially into groundwater supplies.
TABLE 9
WATER, SOIL AND HERBICIDE LEAVING
CONVENTIONAL AND NO-TILL CORN FIELDS
Tillage
Conventional
Plowed
No-Till
Cornstalk
Residue
No-Till
Crown Vetch
Total Cyanazine
Applied
(Lbs per Acre)
4.0
6.0
6.0
Amounts
Water
(Inches)
3.83
0.38
0.13
Leaving
Soil
(Tons per
Acre)
14.37
0.37
0.03
Cropland
Cyanazine
(Lbs per
Acre)
0.21
0.03
0.01
Source: Adapted from Hall and Hartwig 1979.
Reduced tillage requires heavier doses of a wider variety of
herbicides for weed control. The increased use of herbicides
presents the possibility of increased environmental impacts,
37
-------
particularly to aquatic organisms in nearby surface waters. Success-
ful no-till farming may require 6 to 11 different herbicides (Kelley
1977), commonly including paraquat, atrazine, alachlor, and cyanazine
(Dean 1979). In general, herbicide use is expected to increase by 15
percent with no-till farming and a lesser percent as a result of
minimum tillage farming (U.S. Environmental Protection Agency 1978b).
The severity of herbicide impacts on the aquatic environment will be
determined by the stability and persistence of the chemicals, the
sensitivity of exposed organisms to herbicide toxicity, their mode of
action, their synergistic effects with other pollutants and the
degree to which herbicides are actually transported from the fields.
Generally, herbicides and fungicides are thought not to persist as
long or to bioconcentrate as much in aquatic environments as
organochlorine insecticides (e.g. DDT, ODD) (Livingston 1977).
Leaving crop residues on agricultural fields has been found to
worsen crop pest problems as crop residues provide a suitable habitat
for disease organisms, rodents and insects. For example, reduced
tillage methods in cornfields seem to favor the black cutworm, army
worm, seed corn maggot and seed corn beetle (Kelley 1977). Root
diseases, fungi and bacterial blights have also been associated with
no-till practices (Fenster and Wicks 1977). In spite of pest
problems associated with reduced tillage, it is generally thought
that profitable yields can be maintained by watchful crop management.
38
-------
Insecticide use is expected to increase by 11 percent and 9
percent as a result of no-till and minimum tillage, respectively
(U.S. Environmental Protection Agency 1978b). Increased environ-
mental hazards are associated with certain pesticides in aquatic and
terrestrial environments, including the accumulation of pesticides in
eggs of aquatic organisms, death of embryos, alterations in develop-
ment and growth and changes in feeding and reproductive behavior
which affect survival. These impacts have been reasonably well
documented for some species under certain conditions, but additional
research is needed on effects at the community and ecosystem level
(Livingston 1977). Due to the expected decrease in erosion and
transport of pesticides into aquatic environments from reduced
tillage systems, the projected impact for aquatic systems would be
less, even with increased pesticide use, but it would ultimately
depend on the specific pesticide and the amount entering the aquatic
system.
Residues maintained on the soil surface with no tillage or limi-
ted tillage serve as a habitat and food source for game animals and
birds. In many areas of intensive conventional cropping, populations
of game birds have been severely reduced. However, field mice,
pocket gophers, ground squirrels, and game birds tend to increase
where crop residues are left on the soil surface during the use of
minimum tillage (Fenster and Wicks 1977). The potential for
39
-------
increased pesticide-induced deaths and bioaccumulation of certain
pesticides in food chains would be expected to increase with increas-
ing wildlife use of the agricultural fields.
3.2.2 Yield Implications^
Yields from reduced tillage systems will depend on a variety of
factors related to soil types, crops, and general conditions
(Resources for the Future 1979). In areas where plants are subject
to moisture stress in summer, reduced tillage yields are often higher
than those with conventional tillage. The opposite is true on poorly
drained soils, however, where reduced tillage results in a decline in
yield (Phillips et al. 1980). Reduced tillage should have a signifi-
cant advantage where soils are thin and protection from erosion is
crucial.
Although the yield of a single reduced tillage crop may vary
depending on several factors, a distinct advantage is gained through
the potential for double cropping. Eliminating tillage field prepa-
ration makes it possible to plant more quickly, perhaps the same day.
Double cropping typically involves planting soybeans after wheat or
barley. No-till advantages, such as reduced labor costs, moisture
conservation, soil erosion reduction, maintenance of soil structure
and quick planting procedures are more significant when two or three
crops per year are considered (Phillips et al. 1980) and yields from
the same land double or triple.
Projections indicate a considerable expansion of no-till and
reduced tillage practices in the future. The rate of implementation
40
-------
and geographic distribution of these practices will be determined to
a large extent by how they affect crop yields.
3.2.3 Farm Labor Implications
There is general agreement that less labor is needed for reduced
tillage because the number of passes over the field is reduced enough
to offset any increased labor associated with greater applications of
chemicals for weed and insect control (Resources for the Future
1979). Estimates of the labor required for alternative tillage
systems vary. Labor productivity with no-till has been estimated to
increase as much as threefold over conventional tillage (Triplett and
Van Doren 1977). This is supported by a survey that reported labor
requirements of 2.0 to 2.4 times less for reduced tillage than for
conventional tillage of corn, cotton, sorghum, and soybeans
(Resources for the Future 1979). Another estimate claims that, with
minimum tillage, farmers spend 20 percent less time preparing their
fields for planting (U.S. Congress 1979a).
3.2.4 Energy Use Implications
The energy shortage suggests a need for energy conservation in
farming. Rising energy costs will force adjustments in farming
methods and will ultimately increase prices of food and other farm
products. This is true because a major part of the energy used in
agriculture is derived from petroleum products, as shown in Table 10.
Approximately one-half to two-thirds of total energy used in agri-
culture comes from gasoline or diesel products (U.S. Department of
41
-------
Agriculture 1980b) and almost half the energy consumed by agriculture
is used in only three agricultural regions—the Corn Belt, Northern
Plains and Southern Plains. All three are extremely vulnerable to
petroleum shortages and cost increases, although the vulnerability of
the Southern Plains and Mountain regions is somewhat alleviated by
their partial reliance on natural gas.
TABLE 10
REGIONAL AGRICULTURAL ENERGY CONSUMPTION
BY FUEL TYPE
1976
(Percentage)
Diesel
Fuel Liquid Regional
and Petro- Percentage
Fuel leum Natural Elec- of U.S.
Region Gasoline Oil Gas Gas Coal tricity Total
Northeast
Lake States
Corn Belt
Northern Plains
Appalachian
Southeast
Delta States
Southern Plains
Mountain
Pacific
United States
54.0
58.0
50.1
30.3
33.7
26.5
26.4
22.0
23.8
23.2
35.3
29.0
26.4
29.8
41.7
39.1
56.3
51.6
20.6
23.5
36.5
33.7
7.0
8.7
15.8
10.5
22.5
12.5
15.8
9.2
3.3
2.9
10.9
0.5
*
A
14.0
0.2
0.6
3.0
43.6
31.4
2.7
11.6
A
*
*
*
0.5
0.2
0.0
0.0
*
*
*
9.0
6.7
4.2
3.5
4.4
3.8
3.2
4.7
17.9
34.7
8.4
4.4
9.6
19.7
15.5
6.6
7.2
5.2
13.8
9.4
8.6
100.0
* Insignificant.
Source: Adapted from U.S. Department of Agriculture 1980b
Estimates of potential energy savings from reduced tillage
technologies vary considerably depending on the type of tillage
42
-------
practiced, type of crop, region, soil characteristics, equipment size
and the size and slope of the fields. Although there is considerable
variation among estimates of energy savings from reduced tillage, it
is generally agreed that reduced tillage requires less energy prior
to harvest than conventional tillage because of fewer passes over the
field. Most studies report a savings of two to three gallons of fuel
per acre from the total elimination of plowing and other tillage
practices (Triplett 1977). Table 11 shows that employing reduced
tillage on 40 percent of the 413 million acres of cropland in the
U.S. would save 413 million gallons of diesel fuel annually or about
58 trillion Btu's per year (U.S. Department of Agriculture 1980b).
This would equal a savings of about 15 percent of the diesel fuel
used in agriculture in 1978, or a savings of about 7 percent of the
total energy consumed for agricultural production in 1978.
Similarly. Phillips et al. (1980), in a detailed energy compari-
son of conventional and no-till corn production, indicate that a 7
percent energy savings could be realized. They also estimate that
no-till corn and soybean systems alone could save 50 trillion Btu's
annually by the year 2000. A third estimate predicts an annual
savings of 850 million gallons of fuel by the year 2000 from minimum
tillage (U.S. Congress 1979a). In addition to energy savings through
reduced use of tillage machinery, the U.S. Department of Agriculture
(1980b) estimates that 113 trillion Btu's could be saved each year by
reducing soil erosion, as shown in Table 11. A portion of this
savings would be attributable to the use of reduced tillage.
43
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TABLE 11
ESTIMATED MAXIMUM POSSIBLE ENERGY SAVINGS PER YEAR
IN SEVERAL AGRICULTURAL AREAS
(Trillion Btu's)
Maximum Possible
Area Savings
Conservation Tillage 58
Fertilizer Use 51
Soil Erosion 113
Prime Farmland 78
Agricultural Water Management 73
Total 373
Source: Adapted from U.S. Department of Agriculture 1980b.
Estimates of fuel-cost savings from reduced tillage clearly
offset any increased energy requirement related to heavier applica-
tion of herbicides and insecticides (Resources for the Future 1979).
It is unclear, however, whether these savings are significant enough
to encourage a substantial increase in reduced tillage practices.
But its other advantages, coupled with rising fuel costs, should make
reduced tillage more attractive.
44
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4.0 IMPROVED IRRIGATION EFFICIENCY
Agricultural water use is a major component of the national
water budget and it is essential to continued agricultural produc-
tion. Therefore, efficient water use in agriculture is of environ-
mental and economic importance.
4.1 Water Use Trends
4.1.1 Present Usage
Between 1975 and 1977, 45 million (Interagency Task Force on
Irrigation Efficiencies 1979) to 56 million acres (National Agricul-
tural Lands Study 1980d) of U.S. cropland were irrigated. Irrigated
lands provide about 25 percent (by dollar value) of total crop pro-
duction in the U.S. (Interagency Task Force on Irrigation Efficien-
cies 1979). The importance of irrigation to agriculture is clear. In
addition to simply increasing yields, irrigation makes more land
available for cropping, augments the variety of crops that can be
grown in a given area and insulates farmers from the uncertainties of
rainfall.
An irrigation water budget for the U.S. and the Caribbean in
Figure 8 illustrates average U.S. irrigation efficiency by listing
diverted and lost waters. In this budget, representing a year with
normal water supplies and the 1975 level of demand, nearly 180 mil-
lion acre-feet of water would be diverted for irrigation use from
rivers, reservoirs, and groundwater sources. Of the total water
An acre-foot is the volume required to cover one acre with water
to a depth of one foot.
45
-------
Crop
Consumption3
73.5
(41%)
Farm
Deliveries
138.9
(78%)
Gross
Diversions
177.8d
(100%)
Net Depletion
96.8
(54%)
Deep Percolation
and Surface Runoff
65.4
(37%)
Operational Spills
and Seepage
38.9
(22%)
Irrecoverable
Lossesb
23.3
(13%)
(59%
Total
Unused Water
104.3
Return Flow
81.0
(46%)
Water Source Supply
Note: Year with normal water supplies and 1975 level of irrigation development
'Includes 45.5 million acres of irrigated cropland In 1975.
bEvaporation, deep percolation to ground water, phreatophyte consumption
c Percent of gross diversions
^Millions of acre feet
Source: Adapted from Interagency Task Force on Irrigation Efficiencies 1979
FIGURES
REPRESENTATIVE IRRIGATION WATER BUDGET FOR
THE U.S. AND CARIBBEAN
(Millions of Acre-Feet)
46
-------
diverted, only about 41 percent would actually be consumed by crops.
Some 46 percent would ultimately be returned to water supply sources
via deep percolation, surface runoff and intentional return flows.
About 13 percent of the total diverted water would be lost to noncrop
fates such as evaporation, irrecoverable groundwater losses and
phreatophyte consumption.
This national water budget points out the potential for
improving irrigation efficiency which exists both in delivery systems
to the farm, and in on-farm application systems. The average
efficiency for conveyance of diverted water to the farm is now 78
percent. The average efficiency of on-farm irrigation systems (ratio
of water used by crops to water delivered to the farm) is only about
53 percent (Interagency Task Force on Irrigation Efficiencies 1979).
Irrigated agriculture is a regional phenomenon. Substantial
proportions of cropland are irrigated in Florida, Louisiana, and most
western states, notably those in the Southwest, as illustrated in
Figure 9. In the western states, the most commonly irrigated crops
are hay and alfalfa mixtures, cotton, corn, and sorghum (Interagency
Task Force on Irrigation Efficiencies 1979). In some areas, fruits,
assorted vegetables and potatoes are commonly grown as high value,
irrigated crops. On the average, about 90 percent of all irrigation
water comes from surface sources and 10 percent from groundwater;
*A phreatophyte is a deep-rooted plant which taps groundwater
sources instead of normal capillary soil mositure.
47
-------
-C-
CO
Alaska 5.8%
Hawaii 94.0%
Source: Adapted from U.S. Department of Agriculture 1978.
9.8%
FIGURES
PERCENTAGE OF TOTAL HARVESTED CROPLAND IRRIGATED
1974
-------
however, this varies greatly by region (U.S. Department of
Agriculture 1980b). Natural flooding and surface furrows are the
primary means of water application, accounting for 75 percent of the
irrigated acreage in the country. A lesser amount of sprinkler
irrigation and a relatively small amount of drip irrigation are also
used.
In humid areas, such as the midwestern and eastern states, much
less land is irrigated. The principal crops irrigated there are corn
and small grains, vegetables, orchard fruits and berries (Inter-
agency Task Force on Irrigation Efficiency 1979). Groundwater con-
tributes most of the irrigation water (66 percent), followed by
streams (24 percent) and reservoirs (10 percent). The dominant forms
of application are sprinkler (52 percent) and surface furrows (47
percent), with a minimal amount of drip or trickle application (1
percent) (Interagency Task Force on Irrigation Efficiencies 1979).
4.1.2 Future Water Consumption
Figure 10* illustrates the steady increase in irrigated acre-
age that has taken place since 1939. It is expected that irrigation
will continue to expand, primarily in the central and southeastern
U.S. where water supplies are adequate, rather than in the West where
many water sources are already overused (Skogerboe et al. 1979).
Note that a previously mentioned estimate of 56 million acres of
irrigated cropland (National Agricultural Lands Study 1980d) is
already approaching the upper projection for irrigated land in the
year 2000 shown in Table 10 (U.S. Department of Agriculture 1980b).
49
-------
60
tn
£ 50
o
-------
Figure 11 shows agricultural water consumption continuing to increase
between now and the end of the century, when it will remain the
major component of the national water budget (U.S. Department of
Agriculture 1980b). Withdrawal* will also increase, but not as
sharply, due to more efficient irrigation.
As the overall amount of water consumed for irrigation has in-
creased, groundwater consumption has increased faster than surface
water consumption, as illustrated in Figure 12 (U.S. Congress 1979a,
Skogerboe et al. 1979). This trend is expected to continue and it
correlates with the expectation of expanded irrigation in the central
and southeastern U.S., where the use of groundwater frequently
predominates over surface water.
With tighter water supplies, an increase is projected in multi-
ple use and treatment of existing water (Skogerboe et al. 1979). In
irrigated agriculture, this would mean an expanded use of treated
municipal sewage, industrial waste effluents, and heated waste waters
from power generating facilities. If carefully controlled, these
practices will increase the efficiency of water use, while solving
other environmental problems. They do, however, emphasize the need
for better management of the quality as well as quantity of irriga-
tion water withdrawals and return flows to sufficiently meet future
water needs.
Withdrawal refers to the removal of water from sources such as
reservoirs rivers and the ground.
51
-------
Withdrawal
400
Consumption1
140
130
120
110
ra 100
Q
£ 90
S" 80
.0 70
3 60
g 50
I 40
30
20
10
1956
1975
Year
82.8%
1975
2000
70.4%
7.0%
2000
Year
'Consumption (evapotranspiration plus products) = withdrawal (surface and grountfwaferl—return (surface water!
Domestic and Commercial | [Manufacturing and Minerals
t.Vx'5sJ Agriculture BH Public Lands and Other
I Steam Electric Generation
Source, Adapted from U.S. Water Resources Council as cited in U.S Department of Agriculture I980b
FIGURE 11
PERCENTAGE OF WATER CONSUMPTION AND WITHDRAWAL BY USER
1975 AND 2000
52
-------
180
160
« 14°
Q
Q.
g 100
5
3 80
1 60
m
40
20
Q
-
-
-
_
-
I
1
1950
0 Surface Water
Frl Ground water
I
I
ll
1
I
1955 1960 1965
Year
I
!T
1970
-
—
—
^
1975
- 600
- 500
- 400
- 300
- 200
- 100
to
Q
Q.
o
id
O
c
o
Source: Adapted from Skogerboe et al. 1979.
FIGURE 12
TRENDS IN SURFACE WATER AND GROUNDWATER USE FOR IRRIGATION
1950-1975
53
-------
Originally, the only objectives of irrigation in the U.S. were
to enhance yield and to allow farming of land that could not other-
wise be cropped. Today there are additional considerations related
to the environment, energy and economy which have to be evaluated.
Moreover, agricultural water use is expected to face increasing
competition from industrial and municipal users and, in western
regions, increasing requirements for water to process and transport
coal (U.S. Congress 1979a) and process oil shale. Increased water
demands may lead to public policies favoring more careful water
development and management, and possibly mandating increases in
irrigation efficiency (Skogerboe et al. 1979).
4.1.3 Irrigation Improvement Technologies
The overall efficiency of agricultural water use could be
increased by 20 to 50 percent through widespread implementation of
currently available technology (U.S. Congress 1979a). Irrigation
efficiency may be enhanced in two areas: off-farm conveyance and
on-farm water application. Although the normal range of conveyance
efficiency is 40 to 85 percent in unimproved systems, higher effi-
ciencies are attainable. Available technological improvements for
conveyance systems include lining canals for piping water to the
Includes conveyance efficiency and application efficiency. Con-
veyance efficiency is the ratio of water reaching the farm to water
withdrawn from the source; application efficiency is the ratio of
water used by a crop to water delivered to the farm.
More detailed discussions of available technologies are available
elsewhere (Interagency Task Force on Irrigation Efficiencies 1979,
Skogerboe et al. 1979 and U.S. Department of Agriculture 1980c).
54
-------
farm, consolidating and realigning existing systems, installing water
flow monitoring and flow regulating structures, automating regulating
structures, properly maintaining and designing systems and scheduling
deliveries (Interagency Task Force on Irrigation Efficiencies 1979).
Many of the same principles and procedures may be applied to
increase on-farm irrigation efficiency. In addition, proper water
application is critical to on-farm efficiency. Sprinklers are
generally more efficient than surface furrows and drip or trickle
application can be efficient in the right situations. Control of
the rate, amount and timing of irrigation is also important. Tail-
water reduction, treatment, and reuse can also increase on-farm
efficiency.
Cost is the main factor preventing widespread adoption of effi-
ciency improvement devices. As competition for water—and its cost—
increases, this economic barrier will be overcome in many cases.
Regulatory requirements for irrigation efficiency could significantly
speed up the process.
4.2 Implications of Irrigation Efficiency Improvements
4.2.1 Environmental Implications
Increasing irrigation efficiency could result in a number of
environmental benefits relating to water quality and quantity. In
general, using water for irrigation has a negative effect on its
*Tailwater is that portion of water withdrawn from a source, trans-
ported and returned to a source without being used for irrigation.
55
-------
quality. Irrigation concentrates existing, dissolved constituents
(primarily salts) in the water through evaporation. Irrigation
waters also carry pesticides, nutrients, suspended sediments and
dissolved solids back to surface water supplies in the return flows
and possibly into groundwater supplies by percolation.
Treatment of tailwaters before recycling or returning them to
the source would have a beneficial effect on water quality; however,
continued research is needed on proper treatment of tailwaters and
disposal of isolated tailwater contaminants. At the present time, it
may not be cost effective. In any case, an increase in irrigation
efficiency allows withdrawal of less water for irrigation, with a
smaller amount of water consequently degraded and returned to the
source.
Improved irrigation efficiency might also reduce such negative
environmental effects as land subsidence due to groundwater overdraft
(the sinking of land when groundwater is extracted faster than it can
be recharged) (Skogerboe et al. 1979). An additional benefit might
include increased groundwater availability for other withdrawal
purposes. Figure 13 shows those regions where groundwater withdrawal
currently exceeds natural recharge. In this figure, the most
critical areas are those where less than 30 percent of the
groundwater withdrawal is being recharged. Withdrawals from these
areas will be impractical within 30 years and there are already
problems at some locations (U.S. Department of Agriculture 1980b).
56
-------
Most Critical
Critical
Significant
Source: Adapted from U.S. Department of Agriculture 1980b.
FIGURE 13
AREAS IN WHICH GROUNDWATER WITHDRAWAL EXCEEDS
NATURAL RECHARGE
57
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The potential for improving irrigation efficiency is substantial in
the water-short areas of Texas, New Mexico, Arizona, and Nevada,
which comprise more than 20 percent of all irrigated acreage in the
U.S.
Figure 14 illustrates another problem: stream flow depletion,
which is especially common in the Southwest. Better irrigation effi-
ciency could help alleviate low flow problems. If the surface water
saved from improved agricultural consumption practices were not
withdrawn for other purposes, benefits would accrue to fisheries,
wildlife, recreational resources and groundwater recharge. Figure 14
also shows regional variations in streamflow depletion. Depletion
ratios below 40 percent indicate generally healthy instream flow
conditions; ratios of 40 to 70 percent are less than optimal; ratios
of 70 to 90 percent indicate undesirable flow conditions generally
incapable of sustaining harvestable fish populations; and ratios of
90 percent or more reflect even more serious depletion of stream flow
(Interagency Task Force on Irrigation Efficiencies 1979).
As increased pressure is placed on existing surface and ground-
water irrigation supplies, there may be an increased tendency for
interbasin water transfers. An environmental consequence of this
might be the transfer or exchange of previously unintroduced aquatic
species between basins. This could cause a shift in natural popula-
tions of aquatic organisms and a change in aquatic community
structure, possibly affecting endangered or threatened species by
development of new predator-prey relationships.
58
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Ln
VO
Hawaii 4/0/0
Puerto Rico
and
Virgin Islands 12/11/6
/Vole: Numerical entries (e.g., 1211018) indicate the number of months per year when streamf/ow depletion is greater than 40 percent, 70 percent, and 90 percent of
that in an average year.
Source: Adapted from Second National Water Assessment as cited in Interagency Task Force on Irrigation Efficiencies 1979
FIGURE 14
MONTHLY STREAM FLOW DEPLETION LEVELS IN THE U.S.
-------
A major problem associated with irrigation, especially in the
West, is the buildup of dissolved solids (salts) in agricultural
soils (Skogerboe et al. 1979). Salts frequently become concentrated
in irrigation water by evaporation before reaching the field. Once
applied, additional evaporation in the fields and transpiration by
plants can cause further salt concentration and buildup in soils.
Finally, high concentrations of salts in return flows increase the
salinity concentration in the receiving water body. The effects of
salt buildup include decreased yield, forced shifts to salt tolerant
crops and, in severe cases, loss of farm profitability. Salt buildup
presents a potential hazard to production on 50 percent of all irri-
gated acres in the West (U.S. Environmental Protection Agency 1978b),
and may accelerate the development of desalination plants so that
poorer quality water sources could be used and existing sources would
deliver less salt to irrigated lands (Skogerboe et al. 1979).
4.2.2 Yield and Cost Implications
Irrigation has allowed the development of large amounts of land
for productive cropping which would otherwise have been unusable.
Similarly, a national comparison of yields from irrigated and non-
irrigated fields indicates that, on the average, one would expect 11
percent higher yields from irrigated land in the East, and 38 percent
higher yields from irrigated land in the West (U.S. Environmental
Protection Agency 1978b). In the long term, however, irrigation can
reduce productivity and local yields if salt accumulation in soils
reaches detrimental levels.
60
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Irrigation may enhance productivity by reducing the risk of crop
failure, while allowing the production of specialty crops or more
profitable products. It is estimated that 90 percent of all citrus
production; 75 percent of all potatoes, fresh and processed vegeta-
bles; and nearly 100 percent of all almonds, sugar cane and rice in
the U.S. are produced with irrigation.
The national economic implications of federal irrigation proj-
ects have been examined by Milliken et al. (as cited in Interagency
Task Force on Irrigation Efficiencies 1979). According to the
results of that study, shown in Table 12, the net increase in output
value associated in 1975 with irrigated lands under Bureau of Recla-
mation irrigation projects was nearly $5 billion. While crop produc-
tion accounted for nearly $2.8 billion of the net increase, other
farm-related sectors of the economy also experienced growth, as
indicated by the nearly $2 billion increase for food processing. Al-
though not shown in this table, the fertilizer, pesticide and machin-
ery industries would also have realized financial benefits (Inter-
agency Task Force on Irrigation Efficiencies 1979). In addition, a
labor equivalent of 342,000 man-years was generated as a result of
these irrigation projects.
A study of 61 areas in 15 western states has shown that 3.1
million acre-feet per year out of a total of 11.9 million acre-feet
of water per year could be saved by improving irrigation efficiency
(U.S. Department of the Interior 1978). One-half of the total
possible improvement in irrigation efficiency would result from
61
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TABLE 12
NET INCREASES IN OUTPUT, WAGES AND FARM INCOME, AND
EMPLOYMENT ATTRIBUTABLE TO FEDERAL IRRIGATION PROJECTS
Type of Output
Net Increase
in Value
of Output
(Millions
of Dollars)
Total Wages and
Net Farm Income
(Millions
of Dollars)
Employment
in Man-Years
(Thousands)
Net Crop Production
Livestock
Food Processors
Total
$2,786.9
$ 145.8
$1,958.0
$4,890.7
$1,643.7
$ 36.5
$1,078.0
$2,758.2
215.3
5.7
121.6
342.6
Note: Bureau of Reclamation irrigation projects in 1975.
Source: Adapted fromMilliken et al., as cited in Interagency Task
Force on Irrigation Efficiencies 1979.
reduced seepage in off-farm delivery systems and on-farm distribution
mechanisms, as indicated in Table 13. Conserving water by seepage
reduction costs an estimated $20 to $50 per acre-foot for off-farm
conveyance and $10 to $60 per acre-foot for on-farm distribution.
The study also shows that the most costly way to conserve water would
be changing the application method from furrow to sprinkler or drip,
and the least costly method would be through irrigation scheduling
and improved water distribution management. Moreover, it is expected
that, in the future, groundwater costs will increase faster than
surface water costs due to groundwater depletion and the energy
dependence of groundwater extraction (Resources for the Future 1979).
62
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TABLE 13
ESTIMATED COSTS AND EFFECTIVENESS OF
IRRIGATION EFFICIENCY IMPROVEMENT MEASURES
Improvement Measure
Contribution To
Total Possible
Efficiency Improvement
(Percentage)
Cost*0f Water
Conservation
(Dollars
per Acre-Foot)
Off-Farm Conveyance
Improved Water
Management
Seepage Reduction
(Canal Lining and Pipe)
Automation And Improved
Control Measures
Recycle Return Flow
Other
10
37
7
11
1
2
20
1
Not
- 10
- 50
- 5
10
available
Recycle Return Flow
Other
Total
On-Farm Distribution
and Application
Irrigation Scheduling
Seepage Reduction
(Ditch Lining And Pipe)
Leveling And Reorienting
Fields
Changing Application
Method
Recycling of Irrigation Runoff
Total
11
1
66
6
13
4
8
_3
34
10
Not available
4-30
10 - 60
5-80
60 - 90
10 - 15
*Costs are based on total annual capital, operation, maintenance
and replacement costs.
Source: Adapted from U.S. Department of the Interior 1978.
63
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Cost-benefit analysis of irrigation improvement efforts is best
carried out in site-specific studies. One such study has been con-
ducted in the upper Snake River Basin and is summarized by the Inter-
agency Task Force on Irrigation Efficiencies (1979). The study
evaluated delivery and on-farm distribution alternatives for an irri-
gation project in Bingham County, Idaho, where the major crops are
alfalfa, grains and potatoes. In the study area, the Snake River
supplies water to farms through a series of canals. The majority of
on-farm systems employ unlined ditches and border or surface furrow
application. Table 14 shows the range of alternatives evaluated,
projected overall efficiency, yield enhancement, improvement cost and
net annual benefit expected.
The study shows that substantial improvement in water use
efficiency could be achieved with existing technology. Further, effi-
ciency enhancement would be cost effective in some cases. The max-
imum increase in primary net economic benefits ($34.35 per acre com-
pared to current conditions) would be expected with improved gravity
systems and unlined distribution systems (alternative 5 in Table 14).
Maximizing efficiency at 62 percent by using sprinkler application
and installing ditch linings would result in a net economic loss to
the farmer of $17.32 per acre, compared to current conditions. The
results of this type of cost-benefit analysis are sensitive to future
changes in product value, water cost, crop distribution and energy
cost. It is anticipated that, in the future, irrigation efficiency
64
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TABLE 14
COST-BENEFIT EVALUATION OF IRRIGATION IMPROVEMENT OPTIONS IN THE UPPER SNAKE RIVER BASIN
Characteristics 1
Future
Without
Change
Project Efficiency (Percentage) 21.4
On~Farm Application System
Unimproved Gravity (% of Area) 100
Improved Gravity (% of Area) 0
Sprinklers 0
Distribution System Type (All Reaches) Unllned
Benefits and Costs 1
Annual Primary Benefits
Net Returns To Management,
Overhead, Land, and Water ($ per Acre) 138.97
Annual Project Costs
Application System Costs ($ per Acre) 14.76
Distribution System Costs ($ per Acre) 9.60
Total Project Costs ($ per Acre) 24.36
Annual Primary Net Benefits
Net Returns To Management, Overhead,
Land, And Water ($ per Acre) 114.61
Change In Primary Net Benefits ($ per Acre) 0
Alternative Application and Distribution Systems
23456 7
Progressive
Change
30 35 40 45 51 21.4/40*
56 36 18 0 0 18
44 64 82 100 0 82
0 0 0 0 100 0
Hnlined Unlined Unlined Unlined Unlined Unlined
Alternative Application and Distribution Systems
234567
163.33 174.40 184.37 194.34 200.10 167.55
23.80 28.28 33.36 37.74 75.44 26.56
8.89 8.33 7.84 7.64 7.40 8.67
32.69 36.61 41.20 45.38 82.84 35.23
130.64 137.79 143.17 148.96 117.26 132.32
16.03 23.18 28.56 34.35 2.65 17.71
8
51
6
94
0
Lined
8
191.02
36.23
28.48
64.71
126.31
11.70
9
62
0
0
100
Lined
9
200 . 10
75.44
27.37
102.81
97.29
- 17.32
*Gradual shift in efficiency from 21.4 to 40 percent.
Note: This shows projected average annual benefits and costs over 50 years.
Source: U.S. Department of Agriculture et al., as cited in Interagency Task Force on Irrigation Efficiencies 1979.
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enhancement will become increasingly desirable, based on both
economic and environmental considerations.
4.2.3 Energy Implications
Irrigation requires energy to lift, transport, distribute and
apply water to crops. Extraction of groundwater generally requires
more energy than the use of surface water. In 1977, irrigation con-
sumed about 260 trillion Btu's of energy, or 11 percent of the total
energy used on farms (U.S. Department of Agriculture 1980b). Any
reduction in water usage or increase in irrigation efficiency would
result in a direct energy savings, with substantial cost benefits.
Indirectly, any reduction in the use of fertilizer or other agricul-
tural chemicals that is allowed as a result of more efficient irri-
gation would also reduce energy use. It has been estimated that
improving irrigation efficiency could save approximately 53 trillion
Btu's annually, or 20 percent of the energy currently required for
irrigation (U.S. Department of Agriculture 1980b).
Competition for water from fuel processing and energy generating
industries may make it too expensive to grow crops such as cereal,
forage or fiber crops in the West, causing a shift of these crops to
the South and Midwest and increasing the production of more cost
effective specialty crops on the original acreage (Skogerboe et al.
1979). Actual shifts will depend on the extent of western develop-
ment, increases in irrigation efficiency and the number of new water
projects begun.
66
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5.0 INTEGRATED PEST MANAGEMENT
Based on specific economic, ecological and sociological para-
meters, integrated pest management (IPM) is the process of monitor-
ing, selecting and applying various biological, physical and chemical
pest controls practices (Good 1977, Bottrell 1979). The goal of IPM
is not to eradicate crop pests, but to keep pest populations below
the threshold where they begin to cause economic injury. The empha-
sis is on diagnosis, timing and selective application of specific
pest control methods.
Control of agricultural pests is required to maximize yields.
Pimental (as cited in Brown 1978) estimated agricultural production
losses in 1970 from various pests at $11.1 billion dollars (insects,
$5.5 billion; nematodes, $0.4 billion; weeds $2.5 billion; and
disease, $2.7 billion). The Council on Environmental Quality (1978)
estimates that, since 1940, roughly one-third of the dollar value of
all agricultural production has been lost to pests.
The advent of organic pesticides in the 1940s initially provided
effective control of insect pests. These broad spectrum pesticides
were effective, readily available and commonly used in heavy applica-
tions for the prevention of pest problems. The widespread and heavy
use of insecticides, however, caused the following problems:
o Evolution of resistant pest strains which were immune to the
application of certain pesticides rendered them ineffective.
67
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o Poisoning of normal predators by ingestion of pesticide-laden
pests reduced the effectiveness of natural population con-
trols.
o General environmental contamination by persistent chemicals
caused danger to nontarget species, including health hazards
to man.
Due to these problems, the early success of organic pesticides was
temporary. Their desirability waned as a portion of their effec-
tiveness was lost on resistant pest strains and as the environmental
hazards of pesticide use became known.
Within the last decade, it has become apparent that pest control
can be carried out using integrated pest management in a way which
would reduce negative environmental effects and health hazards while
maintaining yield levels and profit margins.
5.1 Trends in Pest Control
5.1.1 Use of Integrated Pest Management
IPM development is progressing at different rates for different
crops and crop situations. Huffaker and Croft (1976) recognize
several phases of IPM development and implementation ranging from the
use of multiple tactics, to computer simulation of farm ecosystem
response, to alternative pest control strategies.
A forerunner of IPM development was the single tactic phase of
pest control, characterized by calendar date spray programs (Huffaker
and Croft 1976). Calendar date spraying is the application of
pesticides according to a predetermined schedule without diagnosing a
problem or determining a need for pesticide use. Due to the
68
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potential wastefulness and occasional ineffectiveness of this
practice, as well as potential environmental problems with heavy
pesticide applications, better methods were sought.
As envisioned by Huffaker and Croft (1976), the first stage of
IPM is the multiple tactics phase and it has to intermesh completely
with the second stage, the biological monitoring phase, if integrated
pest management is to work successfully. The multiple tactics phase
embraces the development and utilization of alternative pest control
techniques. Besides the necessary control of pests with active chem-
ical compounds, much research and effort has been initiated to find
new, and improve old methods of biological (natural enemies, sterili-
zation of insects, plant breeding), cultural (crop rotation, crop
residue removal, timing of planting and harvesting, trap cropping)
and alternative biological-chemical controls (pheromones, chemical
plant and insect growth regulators) (U.S. Environmental Protection
Agency 1980, Bottrell 1979).
The second phase has been the development of more refined
sampling and biological monitoring programs which include monitoring:
exact plant growth stages and susceptibilities to pests; pests, their
development stages and population levels; environmental conditions,
including climatic conditions and soil parameters; natural pest
enemies, their growth stages and population levels; and the
effectiveness of previous control measures (Huffaker and Croft 1976,
Mathys 1977 and Bottrell 1979). In essence, a detailed life-cycle
69
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knowledge of the crop, the pest, and the pest's natural enemies, in
conjunction with controlling environmental parameters, are essential
for a well developed biological monitoring program. Scouting and
sampling for these factors allows pest control advisers and managers
to diagnose pest problems early and select a chemical, biological or
cultural remedy before the crop suffers economic injury.
Beyond the biological monitoring phase, Huffaker and Croft
(1976) identify stages progressing from modeling to a systems man-
agement phase. In the modeling phase, individual components of the
crop/pest/pest-enemy system are studied to the extent that control-
ling elements and critical parameters can be mathematically modelled
to predict a large number of cause-effect interactions. Then, model
data and predictions have to be validated and tested for their
accuracy and sensitivity. Ultimately, the individually modelled
components can be assembled in a complete agroecosystem computer
simulation to predict farm ecosystem responses. Such a simulation
would consider, among other parameters, weather and climate, planting
date, tillage method, soil type, crop variety, growth rate, fertili-
zation, irrigation, pests, natural pest enemies and man initiated
pest control measures (Mathys 1977). Figure 15 provides a schematic
presentation of such a system. The system would integrate up-to-date
field information from scouts and monitoring systems with previously
gained information on pests, their populations and crop injury levels
70
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Animal Pest
Complex Model
Agent/Grower
Co-operative
Source: Adapted from Ruesink as cited In Mathys 1977.
FIGURE 15
IDEALIZED REPRESENTATION OF INTEGRATED
PEST MANAGEMENT
71
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so that predictions about crop production could be made and pest
control measures initiated.
The key to managing pest populations is to implement a dynamic
management system over time and continuously manage pest populations
below the economic threshold level. The economic threshold is deter-
mined by the time required for a control mechanism to work, the cost
of control, crop market value and a number of other factors. For
some crops, such as garden vegetables, the economic threshold may be
modified by visual or aesthetic damage which could render the crop
unsalable (Willey 1978). As more research is conducted on the man-
agement of farm ecosystems and pest populations, more widespread and
effective use of IPM can be expected (U.S. Environmental Protection
Agency 1978b).
5.1.2 Techniques of IPM
In IPM implementation, pest populations may be controlled by
chemical, biological or cultural control techniques. Since the
introduction of synthetic organic pesticides during World War II, the
use of chemical herbicides, nematicides, insecticides and fungicides
has become a necessity in maintaining high yield levels, and will
continue to be an integral part of IPM pest control. As shown in
Table 15, specific pesticides are more heavily used on specific
crops. In 1976, more than 50 percent of herbicides were used on corn
and more than 60 percent of insecticides were used on corn and
cotton. Most fungicides were applied to fruits, vegetables and
72
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Table 15
PERCENTAGE OF TOTAL HERBICIDE, INSECTICIDE AND FUNGICIDE
APPLIED TO SPECIFIC U.S. CROPS
1976
Herbicide
Crop (Percentage)
Corn
Cotton
Wheat
Sorghum
Rice
Oats, Rye, Barley
Soybeans
Tobacco
Peanuts
Alfalf a/Hay/Forage
Pasture/Rangeland
Fruits, Potatoes, Sugar
Beets and Other
Vegetables
Other3
52.5
4.6
5.6
4.0
2.2
1.4
20.6
0.3
0.8
0.4
2.4
5.2
b
Insecticide
(Percentage)
19.8
39.6
4.4
2.8
0.3
1.1
4.9
2.0
1.5
3.9
0.1
19.6
b
Fungicide
(Percentage)
a
a
2.0
a
a
a
0.4
0.3
15.8
a
a
81.3
0.2
aUnder fungicide use, "other" includes corn, cotton, sorghum,
rice, other grain, alfalfa, hay, pasture and rangeland.
bNot applicable.
Source: Adapted from Eichers et al. 1978.
ground crops such as potatoes, sugar beets and peanuts. Due to this
concentrated use of chemical pesticides on cotton, corn and a few
ground crops, improved pest management on these crops alone could
substantially reduce the amount of pesticides used in the U.S. While
the use of pesticides is expected to continue under IPM techniques,
73
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they would only be judiciously applied when other techniques were not
sufficient and quick control of large populations became necessary
(U.S. Environmental Protection Agency 1980). In addition, emphasis
is now being placed on developing pesticides which are more effi-
cient, pest-specific, more biodegradable and which do not accumulate
in soil, water, or organisms (U.S. Environmental Protection Agency
1978b). Several active areas of testing include the use of micro-
encapsulated and systemic pesticides, surfactant herbicides and new
biodegradable insecticides (U.S. Environmental Protection Agency
1978b).
Biological or biological-chemical control of pest populations is
a significant part of integrated pest management. Plant breeding for
insect and disease resistance is now a major pest management tech-
nique for many crops. It has been estimated that more than 75 per-
cent of U.S. cropland is now planted with crop varieties that resist
one or more plant disease organisms (Bottrell 1979). This is a con-
tinual process; as disease organisms generally adapt and overcome
resistances, new and broader based plant resistances are always
required. Other types of biological control include (U.S.
Environmental Protection Agency 1980):
o Natural enemies—using local or imported natural parasites,
insect enemies (ladybugs, green lacewings, Trichogramma
wasps) disease-causing viruses, protozoa, fungi or
bacteria.
o Sterile males—flooding a breeding population of pests with
an abundance of sterile males reduces the reproductive
efficiency of the population.
74
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o Pheromones—mimics of the sex attractant chemical of some
species can interfere with effective reproduction by masking
naturally produced pheromones or by assisting in mechanical
trapping.
o Juvenile hormones—natural, synthetic or mimics of insect
juvenile hormones disrupt normal development and/or produce
non-reproducing insects.
Among the available biological pest controls, selective crop
breeding for pest resistance has been the most widely used and it
will probably continue to be very important in the future. Juvenile
hormones and pheromones are the most promising of the new biological
methods. With further development, it is expected that the use of
juvenile hormones and pheromones will be minor to moderate in 1985
and moderate to major by 2010 (U.S. Environmental Protection Agency
1978b). The advent of juvenile hormones may not greatly decrease
overall use of pesticides because such controls are generally pest
species-specific, and other pests may still require simultaneous
control. The use of predators, parasites and sterile males is
effective in special cases, but these techniques are not expected to
be of major significance on a national scale by 2010 (U.S. Environ-
mental Protection Agency 1978b).
The use of cultural controls is also an important part of the
IPM strategy. Most of these controls have been used for years, but
are more successful when part of a total management system. Several
of the methods are: crop rotation to prevent large pest population
buildups, removing crop residues which form suitable pest habitats,
timing planting and harvesting to avoid peak pest populations and
75
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planting trap or expendable crops with the desired crops such as rows
of alfalfa with cotton. Only through close sampling and monitoring
of pest populations and the combined use of chemical, biological and
cultural pest controls in the right situations can IPM work success-
fully.
5.2 Implications of Integrated Pest Management
5.2.1 Environmental Implications
The environmental implications of future pest management pro-
grams will be primarily related to the types and amounts of pesti-
cides used in the future. The use of insecticides has decreased in
specific IPM experiments or programs and some researchers feel that,
as a result of IPM, future pesticide use could decrease by 30 percent
(Good 1977, U.S. Congress 1979b). However, industry estimates call
for continued moderate increases in domestic pesticide use, as shown
in Figure 16 (McCurdy 1980). Historical increases in insecticide use
probably resulted from increasing crop production or the rapid spread
of resistant strains of insect pests. Herbicide and fungicide
production has remained relatively constant since the early 1960s but
is expected to show moderate increases. Industry projections do not
show usage of pesticides per unit of production which would be a
better indicator of the effectiveness of various application
techniques or of pest control programs such as IPM.
Substantial reductions in pesticide use can be expected with the
implementation of IPM on cotton alone, according to the results of a
76
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W
-------
Federal program focusing on IPM control for insects and mites attack-
ing cotton, citrus, and various other crops, sponsored jointly by the
U.S. Environmental Protection Agency, the National Science Foundation
and the U.S. Department of Agriculture from 1972 through 1979 (U.S.
Environmental Protection Agency 1980). At that time, cotton accoun-
ted for more than 45 percent of all insecticide use in the U.S.
(Huffaker and Croft 1976). The program showed that insecticide use
on cotton may be reduced 35 to 50 percent while increasing or main-
taining yield and increasing the grower's profit level (Huffaker and
Croft 1976, Bottrell 1979).
In 1974, apple growers in New York, Michigan and Washington
reduced insecticide use by 43 to 57 percent; while fungicide use
increased at some locations and decreased at others (Bottrell 1979).
Parallel developments may be expected in the future on various vege-
table crops (Huffaker and Croft 1976). A reduction in the reliance
on chemical herbicides for weed control, however, appears less
likely. The use of chemical herbicides is a key element in reduced
tillage technologies which are likely to gain wider acceptance in the
future. Development of IPM schemes leading to less reliance on
chemical herbicides could only occur through major expansion of
research on weed biology and efforts to search for alternative
control measures (U.S. Environmental Protection Agency 1978b).
Based on the information presented above and an assumed increas-
ing importance of IPM, it appears reasonable to expect the use of
insecticides and fungicides to be substantially reduced by 2010, at
78
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least on a per production unit basis. Health benefits in the general
population are expected to remain small through the year 2010 (U.S.
Environmental Protection Agency 1978b). However, there are segments
of the population that could be immediately affected by reductions in
pesticide use as a result of IPM programs. These are the people
directly exposed to pesticides through the manufacture, transporta-
tion and application of these chemicals, as well as those that come
in contact with pesticide-laden plants at harvest time. An example
of the extent of the problem is shown in Table 16. In one year, in
one state, 1,474 occupational illnesses were reported among applica-
tion workers alone. Any reduction in occupational illnesses through
the use of integrated pest management would be beneficial to at least
these segments of the population.
TABLE 16
NUMBER OF PESTICIDE RELATED
OCCUPATIONAL ILLNESS CASES
CALIFORNIA
1973
Occupation
Ground
Applicators
Mixex Loader
Field Worker
Nursery
Greenhouse
Other
Occupations
(11)
Total
Systemic
187
121
45
18
294
665
Skin
103
19
94
71
165
452
Eye/Skin
13
3
0
1
16
33
Eye
121
22
18
22
141
324
Totals
424
165
157
122
606
1,474
Source: Adapted from Smith and Calvert 1976.
79
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Two other potential environmental concerns could be associated
with IPM techniques:
o Imported natural predators, parasites or disease causing
organisms such as viruses, protozoa, fungi and bacteria
should be carefully screened to insure maximum compatability
with North American ecosystems. Otherwise, devastating
consequences similar to those of Dutch Elm disease or the
Chestnut Blight, both caused by fungi, could occur.
o The cultural control of removing crop residues which are
suitable pest habitats is in direct opposition to the
environmental concern of leaving the residues for erosion
protection in reduced tillage technologies.
5.2.2 Economic Implications
Success or failure of any integrated pest management program
ultimately depends on economics. In other words, IPM must be
economically justifiable if it is to be accepted by the farm com-
munity. IPM's ultimate goal is to produce an optimum, high quality
yield at minimum cost, taking into consideration ecological and
sociological constraints as well as long term preservation of the
environment (Smith and Calvert 1976). An established concept aimed
at achieving this goal involves the measurement of economic threshold
and economic injury levels. In basic terms they can be defined as
(Apple 1977):
o Economic threshold—the pest population density at which
appropriate control measures should be selected and imposed
to avoid reaching the economic injury level.
o Economic injury level—the lowest pest population density
that will cause economic damage. The relationship between
economic threshold and economic injury level is shown in
Figure 17. Threshold injury levels are lower than economic
injury levels to allow sufficient time to initiate control
procedures, preventing economic damage.
80
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Values of economic thresholds and injury levels can vary accord-
ing to several factors, including the market value of the commodity,
the cost of alternative control measures and the pest tolerance of
specific crops (Tillman and Baum 1979). As shown in Figure 17, the
levels of economic injury and economic threshold vary over time as
tolerance levels change, as crops mature and as market values
fluctuate (Mathys 1977). For example, if market values increase
while control costs remain constant, economic injury levels will
decrease. In this case, the grower can afford to spend more to
maintain a lower pest population level and the increased yield will
justify the cost (Tillman and Baum 1979). Conversely, if market
values remain constant and control costs increase, the economic
injury level will increase. The grower cannot afford to prevent all
economic damage because the yield received at that given level of
pest management would no longer justify higher control costs. Con-
sequently, due to continuous change throughout the growing season,
the economic threshold may have to be adjusted (Tillman and Baum
1979).
Although the economic reasoning used to justify the adoption of
an IPM program is relatively straightforward, substantial problems
are associated with determining the threshold for optimum timing of
application (Baum and Tillman 1978). Establishing economic thres-
holds and economic injury levels is a complex process involving
knowledge of pest biology and ecology, yield loss assessment and
81
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Economic Injury Level (EIL)
Population Density
Economic Threshold (ET)
Population Density
Pest Population Density
Time
Note: ET population density is used to initiate control of a pest before its numbers exceed the EIL.
The EIL and ET values are shown to change with time reflecting a change in tolerance of the crop at different growth stages.
3Contro! initiated
Source: Adapted from Ti/lman and Baum 1979
FIGURE 17
USE OF ECONOMIC THRESHOLD POPULATION DENSITY
TO INITIATE PEST CONTROL
82
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economics (Tillman and Baum 1979). But without threshold values,
crop protection remains guesswork (Mathys 1977).
5.2.3 Economic Results
While the concepts of economic threshold and economic injury
level discussed in the preceding section are basic to the successful
formulation of IPM programs, the real measure of economic success or
failure is the change in profits as a result of IPM. Since market
values of crops are relatively unaffected by IPM, the key element in
increased profits is the reduction of control costs, particularly in
view of the rapid rise in the cost of pesticide application (Bottrell
1979). But any reduction in pesticide expenditures must be balanced
against increased costs related to IPM practices. For example, the
farmer would pay for scouting and the use of consultants. There are
indications that the costs of these services will be outweighed by
savings realized from reduced control costs. A five-year study in
California showed that average expenditures for materials and
application were significantly reduced by integrated pest management
(Hall 1978).
Another study compared yield values and costs for users and non-
users of independent adviser firms. The results, listed in Table 17,
indicate that average yields for cotton and citrus were greater and
average insecticide costs lower for both crops over tvro seasons.
While the data from these limited studies cannot be considered con-
clusive due to the high standard deviations, they do indicate a
potential advantage of IPM.
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TABLE 17
AVERAGE YIELD VALUES AND INSECTICIDE COSTS PER ACRE FOR
USERS AND NONUSERS OF INDEPENDENT PEST CONTROL ADVISERS' PROGRAMS
SAN JOAQUIN VALLEY COTTON
Yield Value Insecticide Costs
(Dollars) (Dollars)
Standard Standard
Category and Year Mean Deviation Mean Deviation
Users, 1970
Nonusers, 1970
Users, 1971
Nonusers, 1971
271.25
255.00
281.93
221.65
35.38
22.71
20.51.
72.93
6.13
9.34
4.21
11.97
4.61
5.51
4.72
7.38
AVERAGE YIELD VALUES AND INSECTICIDE COSTS PER ACRE FOR
USERS AND NONUSERS OF INDEPENDENT PEST CONTROL ADVISERS' PROGRAMS
SAN JOAQUIN VALLEY CITRUS
Yield Value Insecticide Costs
(Dollars) (Dollars)
Standard Standard
Category and Year Mean Deviation Mean Deviation
Users, 1970
Nonusers, 1970
Users, 1971
Nonusers, 1971
527.17
509.47
506.65
496.23
237.22
187.36
274.81
118.79
24.58
45.64
17.99
42.97
13.89
19.42
15.14
16.76
Source: Adapted from Willey 1978.
84
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Cotton and alfalfa have been selected here to illustrate IPM
applications. It is important to emphasize that these studies are
crop- and site-specific and only indicate the future potential that
might be realized from IPM programs. For example, following the use
of an IPM program in the Brazos River area of Texas, insecticide use
on cotton declined from 12 to 6.4 pounds per acre while lint yield
increased from 229 to 345 pounds. Fifty percent of this increase in
yield was attributed to pest control (Huffaker and Croft 1976). In
the Trinity River region, insecticide use was reduced from 10.8 to
5.6 pounds per acre and yields increased by 80 pounds per acre.
Finally, an analysis of the statewide Texas Extension IPM cotton
program demonstrated an increase in farmer profits of $20 and $24 per
acre in 1974 and 1975, respectively, while pesticide use was reduced
and yields maintained (U.S. Congress 1979a). .
In a similar vein, alfalfa, is another crop that has proven
amenable to integrated pest management. While it generally does not
require large amounts of pesticides, it has significant implications
for IPM since insects initially found in alfalfa often affect
associated crops (Huffaker and Croft 1976). In California, where a
general integrated control program was developed in the late 1950s,
costs and losses attributed to the spotted alfalfa aphid dropped from
approximately $9.7 million to about $1.7 million only one year after
the program was begun (U.S. Congress 1979a). Later, resistant
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alfalfa varieties nearly eliminated the insect as a pest from
California alfalfa. Similar results for several other states are
discussed in U.S. Congress (1979a).
5.2.4 Employment Implications
There are also employment advantages to be realized from IPM
programs. Integrated pest management advisory services involve sub-
stitution of labor for capital, in contrast to the past trend toward
capital intensification in agriculture (Willey 1978). State coopera-
tive extension services provide training to growers, scouts, and
private organizations that offer advisory services to the farmer.
5.2.5 Energy Use Implications
It has been estimated that 1 billion gallons of fuel are requir-
ed to produce, transport and apply pesticides in the U.S. each year
(Bottrell 1979). Although this amount accounts for only 0.2 percent
of total U.S. energy consumption and about 5 percent of that used in
agriculture, continuing energy shortages are expected to affect the
future availability and cost of pesticides. Any reduction in energy
use through reductions in pesticide application will, therefore, save
the farmer money by lowering operating costs. IPM requires energy
expenditures for the continuous monitoring of pest populations and
these would probably offset a portion of the energy savings from
reduced pesticide use.
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6.0 CONCLUSIONS: IMPLICATIONS OF CHANGING AGRICULTURAL PRACTICES
Examination of the selected agricultural trends reveals several
areas of environmental quality that may be affected. In Table 18 the
effects likely to result from the agricultural trends discussed here
are identified. Land conversion is listed simply as urbanization,
but the implications of using marginal lands due to land conversion
pressure are listed separately. Table 18 entries indicate whether
each trend is likely to have a beneficial effect, no apparent effect
or an adverse effect on specific aspects of the environment. For
example, it is expected that increased use of reduced tillage will
have a beneficial effect by lowering concentrations of suspended
sediments in surface waters. In some cases, either beneficial or
adverse effects could occur, depending on specific conditions. For
instance, urbanization would eliminate erosion and suspended sedi-
ments related to tillage, but would involve episodic heavy erosion
during construction. Table 18 provides a means for comparing the
implications of the selected agricultural trends and for evaluating
the effects that might result from more than one trend. From an
examination, one can conclude that three areas have a high potential
for being affected: soil erosion, water quality and supply, and
energy consumption.
6.1 Soil Erosion
Control of erosion is essential to maintaining long-term agri-
cultural productivity and minimizing the adverse effects associa-
ted with suspended soils and adsorbed pesticides which can enter
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TABLE 18
PROJECTED FUTURE IMPLICATIONS OF TRENDS IN AGRICULTURE
oo
oo
LAND
CO to ffi hj
M F V tO
r1 M < H
a; 3 M
so H 3 H
o ^ w a
co i-s ra
M >
§f FO
co pq
a
TREND M
tO
Land Conversion
(Urbanization)
Land Conversion
(Use of Marginal Lands)
Reduced Tillage
Technology
Irrigation Efficiency
Improvement
Integrated Pest
Management
+/- 0 - +
-00-
+ 00-
+ -00
000 +
SURFACE WATER
M ti 2 M >• PJ O
> CO 1-3 CO t-1 CO f*
•C "Td to to H H g
K § 5S < H M
M W i-3 M --G D >
H o co a w §
f CO O »
CO M X M CO
8 3 W £
M g M Jfl
§ M ^<
H to
- +/- + +/- 0 +
0 - - - 0 - 0
0 + + + 0 - +
0 40 0 + + +
0 00 00 + 0
GROUNDWATER
s; ^ to < EC
| 5 is g E
jd H M C <
in M as He ^<
M O H H
H O ^ > H
O >
M CO CO
co C
a r«
+ +00
0 000 0
0 0 0 0
0 0 + + 0
0+00 0
AIR
*ti tO H H
> C2 50 O
£5 to g x
H *B M M
MM HO
S§ S"
f1 M HO
> O CO PO
H
M
to
-
0
+ 0
0 0
0 +
SOCIAL AKD ECONOMIC
CONSIDERATIONS
M n TJ MJ r4 f
« O td M t- Pi
p] CO O PI 08 <
W H D tr1 O M
O G D ?o tr1
>< n
H O
OM ^
O O
2: z ^
CO >
g
H
O
z
0 - +/-
- - - 4-
+ +/- +/- -
+ +/- + +/-
+ +/- +/- +
+ Beneficial Effect
0 No Apparent Effect, or Very Small Effect
- Adverse Effect
+/- Effect Could be Beneficial, Neutral, Or Adverse, Depending on Conditions
(See Section Discussion)
-------
surface waters. All four trends are expected to affect soil erosion
to some extent, but reduced tillage would have the greatest impact.
Reduced tillage and no-tillage farming techniques have decreased
erosion by 50 to 95 percent, and frequently by even more. Conse-
quently, the amount of suspended soil and adsorbed pesticides
expected to reach surface waters should decrease even though a 15
percent increase in herbicide use for no-till and a 9 percent
increase for minimum till operations is expected. At the same time,
more insecticides might be applied since the plant residues left in
the field provide a suitable pest habitat. Nevertheless, with
decreased soil erosion, the impact from suspended soil sediments and
adsorbed pesticides should decrease if the use of reduced tillage
technologies increases.
Comparatively, the remaining trends are expected to have a less
important impact on soil erosion. The conversion of agricultural
land to other uses could have three effects on soil erosion:
(1) Residential land often has suspended sediments two times
that of rural land and the short-term episodic erosion
rates from residential and urban construction areas can be
ten times that expected from cropland.
(2) If more cropland is lost and new cropland is needed, many
of the lands with medium potential could require clearing
or drainage and temporarily high erosion rates could be
expected.
(3) Due to cropland losses, if new cropland is sought in
marginal lands, more erosion could be expected due to the
use of less desirable land, often with higher slopes or
grades.
89
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In a less direct manner, irrigation techniques can affect soil
erosion. An increase in irrigation efficiency would mean less water
withdrawal, transport and return to satisfy a given requirement. If
less water returns, less suspended soil will be carried back to sur-
face waters as a result. Additional erosion reducers such as drip
irrigation or settling ponds for return waters would also help, but
they may not be cost effective at the present time. And finally, an
integrated pest management (IPM) cultural control of removing poten-
tial pest habitat plant residues would increase erosion.
Overall, it appears that the anticipated soil erosion reduction
associated with reduced tillage technologies, coupled with the reduc-
tions expected from improved irrigation methods, should override the
effects of urbanization of agricultural land, marginal land
development and IPM cultural techniques.
6.2 Water Quality and Supply
Water supply will be most affected by irrigation practices and,
to a minor extent, by the reduced tillage and land loss trends.
Anticipated improvement in irrigation efficiency would conserve
water, but an expansion of irrigated acreage would require more
water. The expected increases are in the central and southeastern
portions of the country where more water exists, which should
alleviate some problems. However, in the West, stream flow depletion
levels are already at or beyond critical levels and groundwater
overdrafts will make water withdrawals impractical within the near
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future. This area needs relief and, instead, it will face increas-
ingly stiff competition for available water. Thus, it appears that a
smaller increase in irrigated lands and a further reduction of sup-
plies will occur in the West. Due to the increasing pressure on
western water supplies there could be a tendency for more interbasin
water transfers which could shift species to new geographic ranges,
altering aquatic community structure and potentially adding pressure
to endangered or threatened species.
Another trend that will affect water quality is the conversion
of cropland to urban use and water impoundments. First, there would
be a shift in.nonpoint source pollutants, from those which
characteristically run off croplands (nitrogen, phosphorus, and
pesticides), to those more typical of development areas (oil, grease,
fecal coliforms and lead). Second, the conversion of cropland to
water impoundments or to wetlands will increase the quality and
supply of water and the availability of it for wildlife uses. And
third, if the shift of cropland to other uses causes the conversion
of marginal lands into cropland, then temporary decreases in water
quality can be expected during land clearing. Continued
deterioration of water quality would result from higher soil erosion
and nutrient runoff rates associated with steep and/or infertile
lands.
Irrigation can affect water quality by returning suspended
solids and pesticides to a receiving water body. Another major water
91
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quality problem associated with irrigation is the increased buildup
of salts in return flows, soils and groundwater. Improving
irrigation efficiency will mitigate this problem by reducing the
concentrating effect on dissolved solids. In addition, efficiency
improvement will mean less water entering and leaving the field as
well as a reduction in pesticides and suspended sediments entering
surface waters.
The trend toward reduced tillage would probably have a bene-
ficial effect. Since erosion from reduced tillage lands is expected
to be less, the amount of suspended sediments and adsorbed pesticides
is expected to decrease. The use of herbicides and pesticides may
increase, but, with less erosion, a smaller quantity of these chemi-
cals and suspended sediments would be carried to surface waters.
Integrated pest management is expected to result in reduced
pesticide use, benefitting water quality. Collectively, the four
agricultural trends would probably have a beneficial impact by
reducing suspended sediments and pesticides entering surface water,
thereby increasing the quality and availability of aquatic habitats.
6.3 Energy Consumption
Energy conservation is not the primary goal of any major
agricultural trend considered here, but it would be a secondary
benefit of reduced tillage, improved irrigation efficiency and
integrated pest management. Farms currently consume 2,320 trillion
Btu's or about 2.9 percent of all energy consumed in the U.S. (80,000
92
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trillion Btu's). The majority of energy used in farming is in the
form of gasoline and diesel fuel. Potential energy savings in
trillion Btu's are shown in Table 19.
TABLE 19
POTENTIAL ENERGY SAVINGS FROM AGRICULTURAL TRENDS
(Trillion Btu's)
Agricultural Trend Savings
Conservation Tillage 58
Improved Irrigation 53
Reduced Pesticide Use 5
TOTAL 116
aBased on the following assumptions: a savings of 4 percent of the
1 billion gallons of fossil fuel required to produce, transport and
apply pesticides in the U.S. each year; 5.5 x 10& Btu's per barrel
of fossil fuel.
Source: Adapted from U.S. Department of Agriculture 1980b, Bottrell
1979.
Based on these figures, the total energy savings on farms would be 5
percent and, in the U.S., 0.15 percent. Fuel savings from reduced
tillage would result from fewer passes by equipment over fields.
Irrigation efficiency improvement would result in energy savings due
to a decrease in the amount of water withdrawn, transported and
applied. Similarly, integrated pest management could save energy by
lowering the amount of pesticide produced, transported and applied.
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7.0 UNRESOLVED QUESTIONS
Over the long term, several important questions concerning
demand and supply of agricultural products have to be answered. Put
in an ecological framework, many relate to two broad questions:
o What is the carrying capacity of American agriculture?
o What are the environmental boundaries and resource con-
straints which would limit this capacity?
Concerning the first question, how productive can modern farming
practices be on existing, potential and marginal agricultural lands
without any environmental or resource constraints? Then, given
acceptable limits to environmental degradation and resource deple-
tion, how productive can modern agricultural practices be on these
same lands? Will productivity estimates meet anticipated demands?
If not, what higher levels of resource depletion or environmental
degradation would have to be accepted to attain the needed level of
production? Or, in contrast, should the U.S., in conjunction with
other nations or international agencies, mount a sustained effort to
help other areas of the world increase their agricultural productiv-
ity, possibly alleviating future pressures on North American agricul-
tural systems?
American agriculture is energy, fertilizer, water and pesti-
cide dependent. Due to these dependencies, it is one of the most
productive systems in the world. However, additional demands are
being placed on these resources by other sectors of the American
economy. Energy resources, especially natural gas and petroleum
95
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derivatives, are becoming scarce. Pesticides are petrochemically
based and production of the nitrogen portion of fertilizers is energy
intensive. Water for irrigation is already over-taxed in some
regions. Water resources will be subject to increased demands for
processing, transportation (e.g., coal slurry) and conversion of coal
and shale into fuels. Supplies of mineral fertilizer inputs, such as
potassium and phosphorous, are limited. As supplies run low, costs
may be driven up beyond the farmer's ability to pay. So that other
segments of the economy will be assured of having sufficient raw
materials, what limits should be set on the use of these resources to
increase or maintain agricultural production? Similarly, soil
erosion, pesticide use, water quality and water supply affect the
quality and availability of both terrestrial and aquatic habitats.
What limits on environmental degradation will the U.S. be willing to
accept concerning these habitats?
To place the limits of agricultural carrying capacity in
perspective, we have to know what the demand will be for future agri-
cultural land and products. The demand will depend on U.S. popula-
tion growth, immigration levels and foreign demand. The first two
can be reasonably well estimated; the last will depend on political,
humanitarian and economic factors. Will legislative constraints have
to be placed on foreign demands to insure our quality of life? For
example, should foreign grain sales be limited to prevent a potential
decline in meat production that could push beef prices beyond the
reach of the average American household?
96
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Whether the U.S. will be capable of meeting total agricultural
demands will also depend on whether productivity can be increased or
maintained and whether the resources needed for this level of produc-
tivity will be available. Increasing per acre agricultural produc-
tion will be a function of the success of new or improved techniques
such as plant breeding, integrated pest management (IPM), heavy
fertilizer applications, genetic engineering, and intensive aquacul-
ture. The success of these techniques, however, depends on the
availability and cost of key agricultural inputs such as prime farm-
lands, fertilizers, pesticides, water and energy. In turn, energy
supplies will largely determine the availability and cost of
fertilizers, pesticides and water. Therefore, many of the demands
and the abilities to meet these demands are completely interwoven.
The theoretical carrying capacity of American agriculture is
much higher than the carrying capacity which could be expected in an
era of costly, scarce resources, when the U.S. is trying to maintain
acceptable levels of environmental degradation. Studying the limits
of resources and the acceptable levels of environmental degradation
would assist in determining the future carrying capacity of American
agriculture.
7.1 Land Conversion
Taking a narrower focus, questions concerning the individual
agricultural trends also should be answered since they will have an
effect on the supply of agricultural products. Some of these kinds
97
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of questions have been partially or completely addressed, but the
combined results of numerous studies will be needed for intricate
trade-off analyses and to make decisions concerning the trends.
Several questions should be answered about the small or isolated
tracts of land that are products of leap-frog urbanization. What is
the potential for these tracts to be used for specialty crops? What
crops would be best for each region of the country? Would reduced
transportation costs and increased accessibility to urban markets
increase a farmer's profits? What tax incentives or land use regula-
tions would have to be instituted to save these 10- to 40-acre plots
near urban centers from development? How effective have previous
programs for the preservation of farmland near cities been? If they
have failed, why have they failed?
To facilitate future planning, several characteristics of land
that can be converted to cropland should be better understood. What
would be the most likely changes, if any, in the use of this land
that could occur during the next 30 years? Besides previously
attempted programs, what actions can be taken to preserve the 110 to
125 million acres of potential cropland? What incentives can be used
to force more development in areas which have a low conversion poten-
tial? What programs have previously been attempted and what portions
of the programs have been successful? What costs (e.g., taxes) would
result from forcing this type of development? Comparatively, would
it be less costly to force this type of development or to put large
sums of capital into yield enhancement?
98
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Another area that should be examined in detail concerns the
potential for using Federal lands to grow crops. Dideriksen et al.
(1977) and the National Agricultural Lands Study (1980d) investigated
the potential for converting various kinds of privately owned land to
cropland. Since the Federal government owns 750 million acres of
land, what is its potential to be used as cropland? Although many
Federal lands are used for grazing and timber-cutting, have they been
adequately inventoried for their crop-growing potential?
Finally, concerning the conversion of agricultural land to other
uses, why are only half of the conversions to pasture or rangeland
reversible? Are there any factors which could be altered to increase
this reversibility?
To more accurately predict future cropland needs, an agricul-
tural production computer model could be developed. It could take
into account at least the following: present cropland; crops and
production by region; land conversion rates; present yield enhancers,
their costs, their effectiveness and the regions in which they could
be used; future yield enhancers presently in the development stages
and estimates of their potential yield increases; present and future
demands from the U.S. population and foreign sources; and the poten-
tial for various legislative actions to control some factors such as
costs or demand. Through projections and scenarios, the effects of
the conversion of present cropland and the potential need for future
cropland could be better estimated.
99
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7.2 Reduced Tillage
In reduced tillage technologies, decreased erosion is antici-
pated and a decrease in transport of pesticides to surface water is
expected, even though herbicide and possibly pesticide use would
increase. Herbicide use and ecological impacts could be more fully
investigated to determine the adverse or beneficial effects of the
trend. This would require coalescing information from a variety of
sources, including the data required from manufacturers registering
pesticides with the Environmental Protection Agency, to answer
several questions. Which of the commonly used herbicides and insec-
ticides are adsorbed on soil particles? What are their in-the-field
decomposition rates? Which herbicides are adsorbed on the surface of
plants or absorbed into plant tissues? When crop residues are left
in the fields, what is the rate of release and/or breakdown of these
herbicides from the surface of the plant or from the plant tissues?
Other questions could also be addressed. Since six or more
herbicides might be simultaneously used in reduced tillage technolo-
gies, what synergistic impacts could be expected on terrestrial or
aquatic organisms at the levels which might be encountered in runoff?
If increases in herbicide and pesticide use were correlated with
decreases in soil erosion and water runoff as well as the amount of
pesticides adsorbed to soil surfaces over time, then the concentra-
tion of pollutants expected to reach surface water and their ecologi-
cal impact could be more accurately predicted.
100
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Several biological or ecological impacts from siltation and pes-
ticides should be examined in more detail. The impacts of siltation
and pesticides on individual species populations have been analyzed.
In addition, several bioaccumulation and biomagnification studies
have been carried out. However, for a holistic approach, research
should be conducted on plant-animal community systems considering,
for example, energy or nutrient flows.
In reduced tillage technologies, the number and diversity of
animals in fields are expected to increase due to the increase in
crop residues left there. What economic damage to the crop would be
expected from these animals? What environmental costs (e.g. , rodenti-
cide treatments) or economic costs would be caused by their increased
numbers? Due to increased herbicide and possibly insecticide use,
what would be the impacts on these animals? Is there a potential for
bioaccumulation and biomagnification in this terrestrial ecosystem?
Is there a potential for transfer of these pollutants into neighbor-
ing environments due to predation on farm field animals?
To what extent will reduced tillage technologies be integrated
with IPM strategies? For which crops and which regions of the coun-
try would this integration be most effective?
7.3 Irrigation Efficiency Improvements
To better plan for long-term irrigation needs, several questions
should be addressed in addition to those which have previously been
examined. What are the long-term, acceptable limits on the amount of
101
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stream depletion due to irrigation? How would stream depletion
affect aquatic and terrestrial life? What are acceptable limits on
groundwater withdrawal in different regions to insure sufficient
recharge and avoid ground subsidence? By subregion, what surface and
groundwater supplies are available for irrigation? What other de-
mands are anticipated for these water supplies? What is the poten-
tial for interbasin transfers? Answers to these questions would help
to determine the shifts in crops or irrigated acreage which would be
necessary to bring surface and groundwater irrigation use within
acceptable limits.
7.4 Integrated Pest Management
IPM research endeavors should be concentrated in the areas of
computer modeling and personnel training. Modeling of individual
components (pest populations, pest growth and development, crop
growth) for important crops, such as corn, cotton and soybeans,
should continue. Subsequently, for one region, an agroecosystem
simulation for one crop should be developed. After fine tuning and
validation, other crops and other regions should be addressed.
Will there be sufficient trained personnel for future
sophisticated IPM techniques in sampling, monitoring, data analysis
and modeling? If adequate staffing to meet future needs will not be
available, special training programs might have to be developed.
102
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Apple, J.L. 1977. Integrated Pest Management, Philosophy and Princi-
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Baldridge, D. and Ranney, J. 1977. The Till-Plant System of Farming
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Baum, K.H., and Tillman, R.W. 1978. The Economics Behind Integrated
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Berry, D., and Plant, T. 1978. Retaining Agricultural Activities
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1979. Environmental Quality—1913, 041-011-00047-5.
Washington, D.C.: U.S. Government Printing Office.
Dean, J.E. 1979. No-Till Pays Off. Soil Conservation 45(1):220.
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Integrated Pest Management. Proceedings of the Soil and Crop
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Dideriksen, R.I., and Sampson, R.N. 1976. Important Farmlands: A
National View. Journal of Soil and Water Conservation 31:195-
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Dideriksen, R.I., Hidelbaugh, A., and Schmude, K.O. 1977. Potential
Cropland Study. Statistical Bulletin Number 578. Soil Conserva-
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the Future pp. 13-29. Ankeny, Iowa: Soil Conservation Society
of America.
Doster, D.H., and Phillips, A.J. Costs, Inputs, and Returns: Humid
and Subhumid Areas. Conservation Tillage, pp. 163-168. Ankeny,
Iowa: Soil Conservation Society of America.
Egr, E.J. 1978. Erosion: It's Not Just a Farm Problem. Soil Con-
servation 44(1):16.
Eichers, T.R., Andrilenas, P.A., and Anderson, T.W. 1978. Farmer's
Use of Pesticides in 1976, no. 418. U.S. Department of Agricul-
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110
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