Submitted to: International Humic Substances Society Conference
Publication Type: Abstract Only
Publication Acceptance Date: May 26, 2004
Publication Date: July 30, 2004
Citation: Olk, D.C. 2004. In: L. Martin-Meto, D. Milori, and W. da Silva. Humic Substances and Soil Water Environment EMBRAPA Instrumentacao Agropecuaria. Does Anaerobic Decomposition of Crop Residues Alter Soil Organic Matter Quality and Nutrient Cycling? International Humic Substances Society Conference. p. 615-617. Technical Abstract: Inhibited cycling of soil nitrogen but also of copper, zinc, and certain other micronutrients has been reported for several agrosystems in which decomposition of plant residues is anaerobic. This includes natural wetlands, fields of irrigated lowland rice, paddy taro, and to a lesser degree no-tilled maize in temperate regions and low-lying, wet areas in fields planted to upland crops. These specific nutrients share the tendency for chemical stabilization by organic ligands under laboratory conditions. Hence the question arises whether anaerobic decomposition of plant materials under field conditions promotes chemical stabilization of specific soil nutrients by decomposing plant materials or newly formed organic matter. Here will be summarized evidence for nutrient deficiencies associated with anaerobic decomposition in tropical continuous rice (Philippines), subtropical rice-wheat rotation (Japan), temperate continuous rice (Arkansas, U.S.), and temperate no-till maize (U.S. Midwest). One mechanistic explanation is that lignin molecules of incorporated plant residues decompose slowly enough under anaerobic conditions so that they chemically bind organic nitrogen (N) or these inorganic cations. Release of such bound nutrients into plant-available forms will be inhibited as long as the soil remains flooded and aerobic microbial degradation of the lignin molecules is precluded.