Corn Residue Management and Soil Organic Matter1

Abstract Organic matter in a soil results from the balance between rate of loss from decomposition of the soil organic matter and rate of gain from formation of organic matter during decomposition of crop residues and roots returned to the soil. Interest in using corn plant residues as a source of energy production raises the question of how much residue removal would reduce soil organic matter and soil productivity. Effect of residue management was studied in field experiments with corn ( Zea mays L) on a Raub silt loam (Aquic Arqiudoll) near Lafayette, Ind. One experiment had continuous corn growth for 11 years with residues removed, residues returned, and double residues returned. It also had a continuous fallow treatment. A second experiment had differing levels of residues returned because of N levels used on 12‐year, continuous corn. Soil samples taken from the plow layer during and at the conclusion of the experiments were analyzed for organic carbon. Losses of organic matter from plots fallowed continuously for 6 years indicated a decomposition rate of 2.4% per year. Corn stalk residue removal for 10 years was compared with residue return. About 11% of the C in the residues was synthesized into new organic matter. In a fertility experiment, where level of residues varied with treatment, the change in soil organic matter after 12 years indicated 8% of the C in residues was transformed into C in organic matter. Corn roots also appeared to contribute at least 18% of their C to formation of new organic matter. These results are in agreement with an experiment in Iowa and can be used to estimate the effect of residue management practices on soil organic matter level of similar soils.