ESTIMATING CROP RESIDUE DECOMPOSITION COEFFICIENTS USING SUBSTRATE-INDUCED RESPIRATION

Modeling of crop residue decomposition for nutrient cycling and effect iveness of residues to control soil erosion requires information on cr op-specific decomposition coefficients (k). Respiration of decomposing residues reflects the activity of the microbial community and should give an indication of the residue decomposition rate. A method for est imating k using substrate-induced respiration (SIR) of plant residues was evaluated. Basal respiration, total SIR, fungal SIR and bacterial SIR were measured for five crop residues monthly for 1 y. In general, total SIR and basal respiration declined for the more decomposable res idues, but were somewhat constant for the more resistant residues. Mas s loss was used to determine k for a single exponential decay function . Prediction of k from SIR using an equation proposed by Neely et al. (1991) (Soil Biology & Biochemistry 23, 947-954) was unsatisfactory fo r the five crops. A new equation (k = -6.07 x 10(-4) + 6.23 x 10(-6) x SIR) was determined using the data of Neely et al. (1991) and data fr om the current study. Prediction of k using the 60-day SIR measurement was significantly improved with the new equation. Predicting k from S IR could greatly reduce the labor and time involved in evaluating deco mposition differences between residues and locations. Published by Els evier Science Ltd.