Soil organic matter has long been known for its central role in many functions in the soil. They range from controlling nutrient availability to modifying the global carbon budget. In recent and more varieties of organic materials, including municipal sewage sludge, industrial organic wastes, as well as crop residues and animal manures, are returned to the soil organic matter is not always clearly understood. Efforts in optimizing crop production, minimizing environmental pollution, and enhancing soil quality all require a better understanding of the nature of soil organic matter for its proper management. In spite of its importance, there has been a lack of concerted effort in developing appropriate analytical methods for proper characterization and quantification of soil organic matter. As nutrient management and pesticide application recommendations become more precise, demand for more accurate determination of soil organic matter also is increasing. This publication is a timely response to this increasing demand. It provides a state-of-the-art review on the current methods and calls attention to the need for developing specific and improved tests for characterizing soil organic matter undoubtedly, soil organic matter will continue to provide a challenging field for future research.
H.H. Cheng, President
Soil Science Society of America
Interest in soil organic matter has increased substantially during the last few decades. This has been brought about by a deeper appreciation for organic matter's central role in so many soil processes and properties that are critical for crop growth and environmental quality. The relatively recent activity focused on a better understanding of soil quality has also played a role in the enhanced appreciation for the importance of organic matter.
One area that has not received sufficient attention has been the current and proposed soil organic matter tests and their interpretations. Organic matter tests are presently used by some states to modify soil fertility recommendations. In addition, the labels on a number of herbicides call for modifying application rates based on soil organic matter level. Following a discussion at the 1993 business meeting of the Soil Testing and Plant Analysis Committee (S877), it was decided to request that Divisions S-4 and S-8 jointly sponsor a symposium on the practical issues of soil organic matter testing and test interpretation at the annual meeting to be held in Seattle, WA, in 1994. The two divisions agreed to cosponsor the symposium, which was organized by Fred Magdoff, Chair of S877.
The written versions of talks presented at the symposium are presented in this publication. The first chapter by M.A. Tabatabai covers the procedures of currently used soil organic matter tests. The second chapter by Fred Magdoff discusses potential problems associated with test interpretations. The third chapter by E.E. Schulte and B.G. Hopkins evaluates the weight loss on ignition procedure. The fourth chapter by K.D. Frank and F.W. Roeth presents information on how organic matter is currently used to modify recommendations for lime, fertilizers, and herbicides. The fifth chapter by L. J. Sikora, C. Cambardella, V. Yakovchenko, and J.W. Doran evaluate various proposed tests for assessing changes in soil quality. The sixth chapter by C.L. Henry and R.D. Harrison compares tests proposed for evaluating compost maturity.
These chapters summarize the state of the art and practice of testing for soil organic matter, test interpretation, and using results to modify recommendations for field practices. They should also stimulate researchers and extension specialists to continue to seek improvements in soil organic matter testing-recommendation systems.
Cynthia A. Cambardella
Soil Scientist, USDA-ARS-MWA, National Soil Tilth Laboratory, 2150 Pammel Drive, Ames, IA 50011-4420
John W. Doran
Soil Scientist, USDA-ARS, 116 Keim Hall, University of Nebraska, Lincoln, NE 68583
K. D. Frank
Extension Agronomist, Department of Agronomy, University of Nebraska, Lincoln, NE 68583-0916
Robert B. Harrison
College of Forest Resources, 234 Bloedel Hall, University of Washington, Seattle, WA 98195-2100
Charles L. Henry
College of Forest Resources, 218 Bloedel Hall, University of Washington, Seattle, WA 98195-2100
Bryan G. Hopkins
Laboratory Director, Servi-Tech Laboratories, P.O. Box 169, Hastings, NE 68902
Professor of Soil Science, Department of Plant and Soil Science, Hills Building, University of Vermont, Burlington, VT 05405
F. W. Roeth
Professor of Agronomy, Department of Agronomy, South Central Research and Extension Center, Box 66, Clay Center, NE 68933
E. E. Schulte
Professor of Soil Science (Emeritus), University of Wisconsin-Madison, 518 S. Owen Drive, Madison, WI 53711
Lawrence J. Sikora
Microbiologist, USDA-ARS, Soil Microbial Systems Laboratory, Building 318, BARC-East, Beltsville, MD 20705
M. A. Tabatabai
Professor of Soil Chemistry, Department of Agronomy, Iowa State University, Ames, IA 50011-1010
Soil Scientist, USDA-ARS, Soil Microbial Systems Laboratory, Building 318, BARC-East, Beltsville, MD 20705