Organic matter decomposition and retention in arid soils

Abstract

Abstract Humus may account for 1 to 2% or less of the surface horizon in arid soils; however, it is still a very important fraction with many beneficial properties. Decomposition of fresh organic residues is discussed in terms of the fate of their constituent carbons. Before residues can be considered part of the true soil humus, they undergo profound transformations and no longer resemble the original material. Important factors influencing the degradation and stabilization of organic residues in soil are examined, along with information on the characterization of soil humic acids and polysaccharides that has accumulated through the use of various degradative and spectral procedures. A brief overview of some current hypotheses on the formation of humic acids and soil polysaccharides is presented along with possible mechanisms for their increased resistance to biodegradation. Concluding remarks include some suggestions on soil management practices that will help increase the humus content of soils.