The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences.

The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Robert M. White is president of the National Academy of Engineering.

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The list of environmental problems on the agricultural agenda has grown in the past 15 years. The long-standing concerns about soil erosion and sedimentation have been supplemented with new concerns about soil compaction, salinization, and loss of soil organic matter. The transfer of nitrates, phosphorus, pesticides, and salts from farming systems to surface water and groundwater has also become more important.

Efforts to address the larger complex of environmental problems has been hampered by concerns about trade-offs. For example, best-management practices designed to reduce soil loss are now scrutinized for their role in increasing the leaching of nitrates and pesticides to groundwater. Other trade-offs arise between efforts to improve agriculture's environmental performance and efforts to reduce costs of production and maintain U.S. agriculture's share of world markets.

In 1989 the Board on Agriculture of the National Research Council was asked to convene a committee to assess the science, technical tools, and policies needed to protect soil and water quality while providing for the production of food and fiber from U.S. croplands. More specifically, the committee was asked to

• investigate the threats to soil resources and recommend criteria to guide soil management;

• analyze fate and transport of agricultural chemicals to identify changes in farming systems required to improve water quality;

• identify remedial approaches that minimize trade-offs between

improving soil or water quality, surface water or groundwater quality, or between different pollutants; and

• recommend policy and program options to improve long-term conservation of soil and water quality.

The committee focused primarily on water quality, rather than water quantity, problems and on croplands rather than on forestlands or rangelands. The committee presents its work in two parts. Part One contains Chapters 1 through 4 and presents the committee's synthesis of the technical, economic and policy issues relating to soil and water quality. In Part Two, Chapters 5 through 12 describe in greater detail the scientific and technical knowledge on which the chapters in Part One are based.

During its deliberative process, the committee first analyzed the physical, chemical, and biological processes that determine farming systems' impact on soil and water quality. The committee analyzed the effects of farming practices on soil, the role of soil in mediating the effect of farming systems on water quality, as well as the processes leading to the loss of nitrogen, phosphorus, pesticides, sediment, salts, and trace elements from farming systems. The committee studied the special problems posed by managing animal wastes and examined the important influence of the landscape in shaping the effects of farming systems on soil and water quality. The results of these analyses are presented in Chapters 5 through 12 of this report. The Appendix describes the methods used by the committee to estimate national, regional, and state nutrient budgets.

Chapter 1 reviews the status of soil and water quality and discusses how and why emphasis has changed over the years from simply soil erosion and sedimentation to include soil degradation and water pollution. The presence of nutrients, pesticides, salts, and trace elements in crops, soil, and drinking water has created new problems that require new solutions. The search for solutions includes recognizing the importance of state and local policies as well as the needs and characteristics of the agricultural sector in efforts to improve soil and water quality.

Based on the understanding gained by analyzing the processes that govern the interaction of farming systems and the environment, the committee identified promising opportunities for managing those processes in ways that protect soil and water quality and are profitable for the producer. The committee's analysis identified four major objectives for the management of soil and water resources:

• conserve and enhance soil quality as a fundamental first step to environmental improvement;

• increase nutrient, pesticide, and irrigation use efficiencies in farming systems;

• increase the resistance of farming systems to erosion and runoff; and

• make greater use of field and landscape buffer zones.

These objectives and the technologies available to implement them in agricultural production are presented in Chapter 2.

The task then became to develop strategies to implement those objectives and to identify the changes in concepts, technologies, and policies that might be needed. The farming system concept was central to the development of this report, and the need for a farming system approach at the farm enterprise, regional, and national levels underlies all of the recommendations that the committee developed. The advantages of using a farming systems approach to direct and target soil and water quality programs are presented in Chapter 3.

Ultimately, to achieve long-term improvements in soil and water quality, the behaviors of some producers must be changed. A constant challenge in preparing this report was the attempt to link the social and economic factors that determine producer behavior with the physical, chemical, and biological factors that determine the effects of that behavior on soil and water quality. The committee used the understanding gained from studying these links to recommend a combination of policy and program reforms that will be needed to achieve long-term improvements in soil and water quality. The policy and program reforms recommended by the committee are discussed in Chapter 4.

The debate over national policy to protect soil and water quality has intensified during the course of the committee's deliberation. The 1990 Food, Agriculture, Conservation and Trade Act and the 1990 Coastal Zone Act Reauthorization Amendments created new programs and new authorities that can be used to implement many of the committee's recommendations. Reauthorization of the Clean Water Act and the prospect of a new farm bill in 1995 provide more opportunities to move ahead with an agenda to protect soil and water quality.

A great deal of progress could be made—even in the absence of new legislation—by integrating the multitude of federal, state, and local programs that are already addressing pieces of the soil and water quality problem. The opportunities to make current programs more effective are great and, in many cases, the authorities needed are already provided by legislation. It is the committee's hope that this report will help provide a framework to facilitate the integration of existing and new programs.

SANDRA S. BATIE, Chair

Committee on Long-Range Soil and Water Conservation Policy

A report of this magnitude represents the combined efforts of many individuals from a variety of backgrounds. The committee thanks all those who contributed their ideas and experiences in technical and policy areas. During the course of its deliberations, the committee sought advice and special assistance. Among those who gave generously of their time were Raymond R. Allmaras, University of Minnesota; Ramon Aragues, Agricultural Research Service, Zaragosa, Spain; Peter E. Avers, U.S. Department of Agriculture, Forest Service at Washington, D.C.; Russell R. Bruce, U.S. Department of Agriculture, Agricultural Research Service at Watkinsville, Georgia; H. H. Cheng, University of Minnesota; C. V. Cole, U.S. Department of Agriculture, Agricultural Research Service at Colorado State University; Cornelia Butler Flora, Virginia Polytechnic Institute and State University; George R. Foster, U.S. Department of Agriculture, Agricultural Research Service at Oxford, Mississippi; Robert Grossman, U.S. Department of Agriculture, Soil Conservation Service at Lincoln, Nebraska; Benjamin F. Hajek, Auburn University; Roger Hanson, North Carolina State University; Fawzi Karajeh, University of California at Davis; Jean A. Molina, University of Minnesota; Gary B. Muckel, U.S. Department of Agriculture, Soil Conservation Service at Lincoln, Nebraska; Mathias J. Romkens, U.S. Department of Agriculture, Agricultural Research Service at Oxford, Mississippi; C. Ford Runge, University of Minnesota; David L. Schertz, U.S. Department of Agriculture, Soil Conservation Service at Washington, D.C.; Steven J. Taff, University of Minnesota; and Ward B. Voorhees, U.S.

Department of Agriculture, Agricultural Research Service at Morris, Minnesota.

The committee is particularly grateful to Christopher D. Koss, President of the J. N. ''Ding" Darling Foundation, Key Biscayne, Florida, for his generous assistance in providing the four Ding Darling cartoons that help illustrate this report.

The committee also acknowledges the special efforts of Amy Gorena, who served as a senior project assistant during the early stages of the study; Michael Hayes, who provided editorial expertise during development of the manuscript; and Rolla Chuang, who assisted as a student intern sponsored by the Midwest Universities Consortium for International Activities, Inc.