Estimating crop residue decomposition coefficients using substrate-induced respiration

Modeling of crop residue decomposition for nutrient cycling and effectiveness of residues to control soil erosion requires information on crop-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 estimating 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 residues, but were somewhat constant for the more resistant residues. Mass 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 for the five crops. A new equation (k = − 6.07 × 10−4 + 6.23 × 10−6 × SIR) was determined using the data of Neely et al. (1991) and data from the current study. Prediction of k using the 60-day SIR measurement was significantly improved with the new equation. Predicting k from SIR could greatly reduce the labor and time involved in evaluating decomposition differences between residues and locations.