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Soil and Water Quality: An Agenda for Agriculture Contents EXECUTIVE SUMMARY   1     Basic Concepts   1     The Agenda   4     Implementing the Agenda   8     Influencing Producers' Decisions   13 PART ONE     1.   SOIL AND WATER QUALITY: NEW PROBLEMS, NEW SOLUTIONS   21     Soil and Water Quality Problems   21     Search for Solutions   30     Time to Move Ahead   34 2.   OPPORTUNITIES TO IMPROVE SOIL AND WATER QUALITY   35     Conserving and Enhancing Soil Quality   38     Increasing Input Use Efficiencies   55     Increasing Resistance to Erosion and Runoff   95     Creating Field and Landscape Buffer Zones   103 3.   A SYSTEMS APPROACH TO SOIL AND WATER QUALITY MANAGEMENT   107     Linkages Among Objectives   107     Linkages Among Programs   108

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Soil and Water Quality: An Agenda for Agriculture     Advantages of the Farming Systems Approach   110     Farming System as Unit of Analysis and Management   113     Targeting Problem Areas and Farms   127     Implementing a Systems Approach   137 4.   POLICIES TO PROTECT SOIL AND WATER QUALITY   145     Environmental and Agricultural Policy   146     Factors Affecting Producers' Decisions   160     Continuum of Policies   162 PART TWO     INTRODUCTION:   SOIL, WATER, AND FARMING SYSTEMS   187 5.   MONITORING AND MANAGING SOIL QUALITY   189     Defining Soil Quality   190     Importance of Soil Quality   191     Importance of Monitoring Changes in Soil Quality   204     Extent of Degradation of U.S. Soils   218 6.   NITROGEN IN THE SOIL-CROP SYSTEM   237     The Nitrogen Cycle   237     Nitrogen Mass Balance   240     Opportunities to Reduce Nitrogen Losses   266 7.   PHOSPHORUS IN THE SOIL-CROP SYSTEM   283     The Problem of Phosphorus Delivery to Surface Waters   283     Sources of Phosphorus   284     Phosphorus in the Soil-Crop System   289     Transport Processes   299     Possible Management Methods for Phosphorus Loss Reduction   302 8.   FATE AND TRANSPORT OF PESTICIDES   313     Fate and Transport Processes   314     Reduction of Pesticide Pollution   329     Assessments of the Knowledge Base   333     Proper Use of Pesticides   334 9.   FATE AND TRANSPORT OF SEDIMENTS   337     Effects of Erosion and Sedimentation   337     Sedimentation Processes   338

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Soil and Water Quality: An Agenda for Agriculture     Sediment Estimation and Prediction Technologies   342     Treatment Technology   351 10.   SALTS AND TRACE ELEMENTS   361     Overview of Salinity and Drainage Problems   363     Sources and Effects of Salinity   369     Sources and Effects of Trace Elements   377     Alternative Management Options   387 11.   MANURE AND NUTRIENT MANAGEMENT   399     Resource Utilization or Waste Disposal   399     Improving Manure Management   403 12.   A LANDSCAPE APPROACH TO AGRICULTURAL NONPOINT SOURCE POLLUTION   417     Nonpoint Source Pollutant Attenuation Mechanisms   418     Process-Place Interactions   425     Implementing a Landscape Approach   426 APPENDIX   429 REFERENCES   449 GLOSSARY   489 ABOUT THE AUTHORS   495 INDEX   499

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Soil and Water Quality: An Agenda for Agriculture Tables and Figures TABLES 1-1   U.S. Department of Agriculture and U.S. Environmental Protection Agency Soil and Water Quality Programs   23 1-2   Cropland and Pastureland Soils Affected by Saline or Sodic Conditions   26 1-3   New Initiatives in the 1990 Food, Agriculture, Conservation and Trade Act   28 2-1   Regional and National Estimates of Nitrogen Inputs, Outputs, and Balance on Croplands   61 2-2   Nitrogen Budgets for Four Farms (A, B, C, and D) in Southeastern Minnesota   62 2-3   Crops Receiving Fertilizer Nitrogen Before, During, and After Seeding   67 2-4   Regional and National Estimates of Phosphorus Inputs, Outputs, and Balances on Croplands   72 2-5   Percentage of Soil Tests Reporting High to Very High Levels of Soil Phosphorus   74 2-6   Proportion of Cropland Soils Tested for Nutrient Levels, Major Field Crops, 1989   76 2-7   Use of Integrated Pest Management for 12 Major Crops in the United States, 1986   85 2-8   Highly Erodible, Not Highly Erodible, and Nondesignated Lands on which Conservation or Conventional Tillage Systems Are Used for Various Crops, 1990   100

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Soil and Water Quality: An Agenda for Agriculture 3-1   Application of Farming System Approach at Different Geographic Scales   114 3-2   Ranking of Information Sources by Surveyed Farmers   126 3-3   Expenditures for Soil and Water Quality Programs as a Percentage of Expenditures on Pesticides, Synthetic Fertilizers, and Commodity Programs   143 4-1   Constraints to Adopting New Technologies and Program Responses to Nonadoption   147 5-1   Reference and Measured Values of Minimum Data Set for a Hypothetical Typic Hapludoll from North-Central United States   202 5-2   Indicators of Change in Soil Quality and Their Relationship to Components of Soil Quality   208 5-3   Some Pedotransfer Functions   212 5-4   Organic Carbon Additions Necessary to Maintain Soil Organic Carbon at Present Levels at Several Locations   225 5-5   Amounts of Organic Carbon Needed Annually in Residue to Maintain Soil Organic Carbon on Lands with Different Slopes and Erosion Levels   226 5-6   Extent of Salinity and Associated Problems by Land Use in California   231 5-7   Salinity and Drainage Problems by Major Irrigated Areas   232 6-1   Nitrogen (N) Inputs, Outputs, and Balances in the United States under the Low, Medium, and High Scenarios   241 6-2   Nitrogen Accumulation and Nitrogen Replacement Value Estimated for Alfalfa and Soybeans   243 6-3   State and National Nitrogen Inputs and Outputs (metric tons)   244 6-4   State and National Nitrogen Contributions to Total Inputs and Outputs   250 6-5   Nitrogen and Phosphorus Fertilizer Use: Top Ten States   256 6-6   Estimated Nitrogen Balance for Crop Production in the United States, 1977   262 6-7   Potential Reductions in Nitrogen Fertilizer Applied to Corn   268 7-1   Phosphorus Inputs and Outputs in the United States, 1987   291 7-2   State and National Phosphorus Inputs and Outputs (metric tons)   294 7-3   State and National Phosphorus Inputs and Outputs as Percentage of Total Mass of Phosphorus Inputs   296 7-4   Soils Testing Very Low to Medium or High to Very High for Soil-P (percent)   305 8-1   Partition Coefficients and Half-Lives of Pesticides Used in Florida   318

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Soil and Water Quality: An Agenda for Agriculture 9-1   Conservation Tillage Systems in the United States   353 9-2   Surface Soil Cover, Soil erosion, and Runoff from Different Wheat Tillage Systems   354 9-3   Runoff and Soil Loss from Watersheds under Conventionally and Conservation Tilled Systems   354 9-4   Cropland Area under Various Forms of Conservation Tillage, 1985   355 10-1   Concentration of Trace Elements Commonly Observed in Forage Crops   385 10-2   Recommended Maximum Concentration of 15 Trace Elements in Irrigation Waters for Long-Term Protection of Plants and Animals   386 10-3   Total Removal by Crops of Cadmium and Zinc from Sludge-Treated Greenfield Sandy Loam Soils, 1976–1981   389 11-1   Manure and Its Associated Nutrient Content   401 11-2   Economic Value of Nitrogen, Phosphorus, and Potassium in Manures   401 11-3   Quantity of Livestock or Poultry Manure Needed to Supply 100 kg of Nitrogen over the Cropping Year with Repeated Applications of Manure   405 A-1   Factors Used to Estimate Total Nitrogen and Phosphorus Voided in Manures   435 A-2   Nitrogen Voided in Recoverable Manures   436 A-3   Phosphorus Voided in Recoverable Manures   437 A-4   Estimates of Nitrogen Fixation by Legumes   438 A-5   Estimated Rates of Nitrogen Accumulation and Nitrogen Replacement Value for Alfalfa and Soybeans in Low-, Medium-, and High-Fixation Scenarios   440 A-6   Factors Used to Estimate Nitrogen and Phosphorus in Crop Residues   442 A-7   Nitrogen and Phosphorus Content of Harvested Crops   443 A-8   Inputs and Outputs of Nitrogen and Phosphorus on Croplands in the United States, 1987   445 FIGURES 1-1   Percentage of land eroding by sheet and rill erosion at greater than the soil loss tolerance level   25 1-2   Farm production regions used in this report   27 1-3   Sources and types of nonpoint source pollution in affected U.S. rivers and lakes   29 1-4   Interactions of factors that influence producer's decisions   31

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Soil and Water Quality: An Agenda for Agriculture 2-1   Changes in soil quality affect water quality   46 2-2   Nutrient cycle and pathways in agroecosystems   56 2-3   Pesticide pathways in agroecosystems   56 2-4   Irrigation pathways of water in agroecosystems   57 2-5   Economic return from insurance nitrogen (N) and deficit N applications   92 2-6   Distribution of erosion events over 38 years on a field in Missouri   102 3-1   Proportion of national nitrogen and phosphorus inputs and balances contributed by each farm production region   111 3-2   Conceptual diagram of three-dimensional targeting   129 3-3   Use of a geographic information system to target and direct soil and water quality programs   136 3-4   Conservation expenditures by the U.S. Department of Agriculture (USDA) and related state and local programs, 1983 to 1990   140 4-1   History of land set-aside programs in the United States as cropland area reductions by type of program (1933–1991) and net farm income (1945–1990)   173 4-2   States with water quality laws that affect agriculture   178 5-1   Processes of soil degradation   218 5-2   Interactions of factors that cause soil degradation   219 5-3   U.S. pH soil test summary as percentage of soils testing 6.0 or less in 1989   235 6-1   The nitrogen cycle   238 6-2   Amount of fertilizer-N and manure-N applied in relation to annual average nitrate concentration in groundwater in Big Spring Basin, Iowa   265 6-3   Yield response of corn to nitrogen applied to three soils   276 6-4   Yield response of corn to fertilizer for three crop rotations   277 6-5   Nitrogen recovery related to fertilization rate   278 7-1   The phosphorus cycle   290 7-2   Relationship between broadcast phosphorus (PB) and extractable soil phosphorus (Ps)   298 7-3   Economic returns on investments of annual applications of phosphorus (P) fertilizers   306 7-4   Decrease of soil-P over time, measured as Mehlich 1-extractable phosphorus, on Portsmouth soil during the residual phase   308 8-1   Interactions and loss pathways of organic chemicals (OCs) in soils   315 8-2   Pesticide transport and transformation in the soil-plant environment and the vadose zone   316 8-3   Mass balance of a hypothetical aerial foliar-spray application of an insecticide   324

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Soil and Water Quality: An Agenda for Agriculture 9-1   Crop residue levels on planted acreage by region in 1992   356 10-1   Typical salt accumulation patterns in surface soils for various methods of water application   373 10-2   Detrimental effects of salinity on plant growth   374 10-3   Relative salt tolerance of agricultural crops   376 10-4   Possible abiotic and biotic processes affecting the reactivities and mobilities of trace elements   379 10-5   Total selenium concentrations in the top 30.5 cm (12 inches) of soil (A) and in shallow groundwater from 1984 to 1989 (B) in the San Joaquin Valley   382 10-6   Heavy metal contents in Greenfield sandy loam treated with composted sludge from 1976 to 1981   384 10-7   Concentrations of selenium in tissues of various edible crops   388 11-1   Schematic of livestock-crop system showing gap in traditional manure recycling system because of use of relatively inexpensive fertilizers   403 11-2   Ratio of amount of manure produced to amount of cropland available for manure application   408 11-3   Average amount of manure nitrogen produced by animals per unit area in relation to animal spacing   409 12-1   Conceptual diagram of a landscape showing potential for grass vegetative filter strips and riparian buffer zones to intercept nonpoint source pollutants transported by surface water runoff and groundwater flow   419 12-2   Conceptual diagram comparing (A) cropland enrolled by field in the Conservation Reserve Program (CRP) with (B) the same area of land set aside in riparian buffer zones   428

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Soil and Water Quality: An Agenda for Agriculture SOIL AND WATER QUALITY An Agenda for Agriculture

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