ABSTRACT
Farmers have long recognized the organic matter content of a soil as a key attribute of soil fertility. The development of agriculture in temperate regions has exhibited patterns of exploitative soil use followed by the introduction of regenerative practices as soil resources fell to unacceptable levels. In the simplest terms, the level of soil organic carbon (C) in a soil will be governed by the difference between inputs of organic matter and outputs through mineralization, erosion, and leaching. The controls on decomposition processes are, in most respects, more complex and less easily manipulated by management than are inputs of organic matter. Climate and soil differences constrain management options and thereby determine which practices are most important in affecting soil C. Plant residues are the major source of C inputs in all terrestrial ecosystems. The history of agriculture is replete with examples of the depletion of organic matter and the subsequent loss of soil fertility through poor management.
