Effects of organic residue chemistry on soil biogeochemistry: Implications for organic matter management in agroecosystems

While there is significant evidence that the addition of organic residues to soils can improve overall soil fertility, it is unclear as to what organic residues will have the most beneficial impact. The use of residue chemistry as an index for assessing organic resource quality is highly reported and has been linked to organic matter decomposition and nutrient release patterns. However, less is reported on the direct linkages between organic residue chemistry and soil biogeochemistry and how the impact varies between sole and mixed organic residues. In this research, we investigated the residue chemistries of Tithonia diversifolia, Vicia faba and Zea mays (either applied alone or in combination) and how they affected and related to soil microbial activities and biochemical properties. The results revealed significant differences in chemical composition among the species and affirmed that organic materials impact differently on soil microbial and biochemical properties based on their chemistry. Carbon, polyphenol, C: P and lignin: N ratios had the greatest impact on soil microbial activities and biochemical properties. The levels of biological activities were comparable in sole and mixed amendments but N mineralization and availability increased significantly in V. faba and T. diversifolia amendments. The results also demonstrated that basal respiration, microbial biomass carbon and the activities of β-glucosidase and β-glucosaminidase are sensitive indicators of nitrogen availability and organic C levels in soils. © 2012 Nova Science Publishers, Inc.