Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 18, 2005
Publication Date: November 18, 2005
Citation: Olk, D.C. 2005. Chemical stabilization of soil nitrogen by phenolic lignin residues in anaerobic agro-ecosystems. 6th Meeting of the Brazilian Substances Society [abstract]. p. P 36-38.
Several agricultural systems are associated with repeated cropping under wet or submerged soil conditions. Independent reports from these systems indicate yield declines or yield gaps, which may be due to reduced crop uptake of N mineralized from soil organic matter (SOM). These trends are most evident in continuous lowland rice systems in the Philippines, but similar trends are evident in a continuous rice rotation in Arkansas and in no-till cropping systems in regions with cool, wet climatic conditions in spring. Soil analyses from some of these systems have found an accumulation of phenolic lignin residues in SOM. Phenolic compounds covalently bind nitrogenous compounds into recalcitrant forms in laboratory conditions, and occurrence of this chemical immobilization under field conditions would be consistent with field observations of reduced soil N supply. Through recent advances in nuclear magnetic resonance spectroscopy, agronomically significant quantities of lignin residue-bound nitrogen (N) were found in a triple-cropped rice soil in the Philippines. In rice fields of Arkansas and the Philippines, more anaerobic soil conditions were associated with (i) inhibitions during the growing season of both soil N mineralization and soil phenol degradation, and (ii) decreased crop uptake of soil N. A major research challenge is to elucidate in the anaerobic agro-ecosystems the magnitude and cycling dynamics of lignin residue-bound N relative to the seasonal pattern of crop N uptake. Anaerobic decomposition of crop residues may be the key feature of anaerobic cropping systems that promotes the accumulation of phenolic lignin residues and covalent binding of soil N. Potential mitigation options include improved timing of applied N fertilizer and aerobic decomposition of crop residues.