Influence of Rate of Plant Residue Addition in Accelerating the Decomposition of Soil Organic Matter

Abstract

AbstractThe addition of corn and soybean residues to soils increased the rate of decomposition of the native soil organic matter. The residues were comparable to green manure crops and the data provide an explanation for the failure of green manures to be helpful in building or maintaining the organic matter content of soils.Plant materials containing radioactive carbon were added to soils at the rates of 2.5, 10 and 50 tons per acre. The use of the isotopes permitted a partition of the evolved CO2 into that coming from the plant residue and that coming from the soil organic matter.The high rates of residue addition resulted in greater losses of native soil organic matter than did the low rate. Corn and soybeans were similar in their influence on the decomposition of soil carbon.The rate of plant residue addition had a marked influence upon the rate of residue decomposition. At the rate of 2.5 and 10 tons per acre the decomposition of residue was considerably more rapid than when added to soil at the rate of 50 tons per acre. Residues apart from soil decomposed at about the same rate as when added to soil at the rate of 50 tons per acre.