Soil organic matter changes resulting from tillage and biomass production

Because soil is a limited resource, agricultural production is dependent on improving soil quality. Improved soil quality also has an impact on water use, as high quality soil more effectively collects and stores water, reducing the need for irrigation. Intensive use of soil throughout history has led to depletion in soil quality, leading in turn to reduced yields because of the consequent reduced organic matter. Recognizing the lessons of history, scientists at research stations such as Rothamstead in England; Pendleton, Oregon; Champaign, Illinois; and Columbia, Missouri, began long-term studies on the effects of crop rotation, crop fertilization, manure additions, and residue management on the productivity and organic matter of cropped soils. In general, it was found that soil cultivation caused a decline in organic carbon content (which constitutes about half of the organic matter), or at best stabilized organic matter, even with heavy manure treatment, as long as conventional tillage continued. In the 1960s and 197Os, many investigators noted that tillage made soils more erodible, and that crop residues left on the surface were highly effective in reducing erosion. The introduction of more and …