Crop residue management and fertilization effects on soil organic matter and associated biological properties.

Abstract

Returning crop residue may result in nutrient reduction in soil in the first few years. A two-year field experiment was conducted to assess whether this negative effect is alleviated by improved crop residue management (CRM). Nine treatments (3 CRM and 3N fertilizer rates) were used. The CRM treatments were (1) R0: 100% of the N using mineral fertilizer with no crop residues return; (2) R: crop residue plus mineral fertilizer as for the R0; and (3) Rc: crop residue plus 83% of the N using mineral and 17% manure fertilizer. Each CRM received N fertilizer rates at 270, 360, and 450kgNha(-1) year(-1). At the end of the experiment, soil NO3-N was reduced by 33% from the R relative to the R0 treatment, while the Rc treatment resulted in a 21 to 44% increase in occluded particulate organic C and N, and 80°C extracted dissolved organic N, 19 to 32% increase in microbial biomass C and protease activity, and higher monounsaturated phospholipid fatty acid (PLFA):saturated PLFA ratio from stimulating growth of indigenous bacteria when compared with the R treatment. Principal component analysis showed that the Biolog and PLFA profiles in the three CRM treatments were different from each other. Overall, these properties were not influenced by the used N fertilizer rates. Our results indicated that application of 17% of the total N using manure in a field with crop residues return was effective for improving potential plant N availability and labile soil organic matter, primarily due to a shift in the dominant microorganisms.