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
                                 xx

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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.
                                 xi

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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?
                                 xiv

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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
                                 xix

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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
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        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)

-------
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

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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

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                              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

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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

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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

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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

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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

-------
                               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

-------
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

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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

-------
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

-------
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

-------
     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

-------
                              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

-------
     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.

-------
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

-------
     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

-------
             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

-------
 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

-------
                              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

-------
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

-------
     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.
                                  83

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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
                                  85

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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.
                                 86

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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




                                  87

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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
                                  90

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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.

                                 93

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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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Casper, H.R.  1979.   Soil Taxonomy as a Guide  to Economic Feasibility
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Dideriksen, R.I., and Sampson, R.N.  1976.  Important Farmlands:   A
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Dideriksen, R.I., Hidelbaugh, A., and Schmude, K.O.  1977.  Potential
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Doster, D.H., and Phillips, A.J.  Costs, Inputs, and Returns:  Humid
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Egr, E.J.  1978.  Erosion:  It's Not Just a Farm Problem.  Soil Con-
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Eichers, T.R., Andrilenas, P.A., and Anderson, T.W.  1978.  Farmer's
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Fenster, C.R., and Wicks, G.A.  1977.  Minimum Tillage Follows System
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Fletcher, W.W.  1979.  Changing Role of the Federal Government in
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Gass, R.  1977.  Drip Irrigation in Land Reclamation  and  Landscaping.
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Good, J.M.  1977.  Integrated Pest Management—A Look to  the  Future,
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Hall, D.C.  1978.  Profitability and Risk of Integrated Pest  Manage-
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Hall, J.K., and Hartwig, N.L.  1979.  No-Till Planting Effective in
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Harker, J.M., Michaelson, E.L. , and Meyer, N.L.  1977. Erosion Con-
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Hazeltine, W.E.  1978.  Integrated Pest Management:   Real and Politi-
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Hidlebaugh, A.  1980.  Resource inventory and monitoring  specialist.
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Hillel, D.  1978.  A Method of Promoting Penetration  of Water into
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Horwitz, E.  1978.  Our Nation's Wetlands.  Interagency Task Force
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Huffaker, C.B., and Croft, B.A.  1976.  Integrated Pest Management  in
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Huffaker, C.B., and Croft, B.A.  1978.  Integrated Pest Management in
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Interagency Task Force on Irrigation Efficiencies.  1979.   Irrigation
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Kelley, H.W.  1977.  Conservation Tillage:   Hazards Ahead?  Soil Con-
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Lee, L.K.  1978.  A Perspective on Cropland Availability.   Agricul-
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Lindstrom, M.J., Gupta, S.C.,  Onstad,  C.A., Larson, W.E.,  and Holt,
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Livingston, R.J.  1977.  Review of Current  Literature Concerning the
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Mathys, G.  1977.  The Strategy and Tactics of  Integrated  Pest Man-
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Miller, J.H., Keeley, P.E.,  Thullen, R.J.,  and  Cater, C.H.  1978.
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                                106

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                        REFERENCES (Continued)


	.  1980d.  Agricultural Lands Data Sheet.  Interim Report No. 2.
     Washington, B.C.:  National Agricultural Lands Study Group.

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Olson, B.R.  1977.  Peculiarities of Drip Irrigation System Design.
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Omernik, J.M.   1976.  The Influence of Land Use of Stream Nutrient
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Onstad, C.A., and Otterby, M.A.  1979.  Crop residue effects on
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Oram, F.  1980.  World Population Society staff.  Washington, D.C.
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                                   107

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Skidmore, E.L.  1977-  Tillage Research Needed to Reduce Wind Erosion.
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Skogerboe, G.V.,  Walker, W.R. , and Evans,  R.G.  1979.  Environmental
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                                  108

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                        REFERENCES  (Continued)
	.   1975.  The Pesticide Review  1974.  U.S. Department of Agricul-
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	•   1980a.   Review  Draft Program Report and Environmental Impact
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                                   109

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                        REFERENCES  (Concluded)
         1978b.  Environmental Implications  of Trends  in Agriculture
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     26(6):46-51.
                                  110

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