SOIL ORGANIC MATTER—THE NEXT 75 YEARS

Abstract

Part I of this paper presents an account of what we know at this time about SOM (soil organic matter). It deals with the distribution and functions in soils of SOM, descriptions of methods of extraction and fractionation, and chemistry of the major components. These include carbohydrates, nitrogenous compounds, organic P and S compounds, and last but not least, humic substances. The latter are discussed in greater detail in terms of analytical characteristics, chemical structure, free radical content, colloid-chemical characteristics, physiological effects, uses, and interactions with metals, clay minerals, and organics (especially pesticides). The second part of this paper focuses on the laboratory of the future and the agenda for the next 75 years. There will be major changes in laboratory procedures from wet chemical to sophisticated instrumental methods, using solid-state samples. Gaps in our knowledge of major SOM components and their interactions with metals, clays, and organics will be filled. Because SOM serves as soil conditioner, nutrient source, substrate for microbial activity, preserver of the environment, and major determinant for sustaining or increasing agricultural productivity, SOM chemists are bound to play an important role in the soil science of the future.