Decomposition and Interactions among Wheat Residue Components

Abstract Developing effective management strategies that protect soil against erosion necessitates an understanding of residue decomposition. Predicting decomposition of crop residues requires knowledge of their chemical and physical composition. Wheat ( Triticum aestivum L.) residue decomposition is influenced by the amount of residue, ratio of residue components, and chemical composition of component mixes. This study describes winter wheat residue components and chemical composition, and assesses the effect of mixing residue components on the rate of decomposition. Winter wheat residue levels were measured on 20 field sites having grain yields ranging from 1 to 6 Mg ha −1 . Residue was positively correlated with grain yield for the 1984 and 1985 crop years ( r 2 = 0.99***, 0.94***, respectively [significant at P = 0.001]). Residue‐to‐grain ratios averaged 1.47 for 1984 and 1.17 for 1985. Ratios of stem (ST), leaf sheath (LS), chaff (CH), and leaf blades (L) averaged 37:30:20:13. Total C and N, soluble C, and nonstructural carbohydrate (NSC) concentrations were not correlated with residue or grain yield. Stem and LS components had greater lignin and NSC contents than L and CH components. Rates of C mineralization for components were: L > LS > CH = ST. When components were mixed at the ratio of 32:30:28:10 ST/LS/CH/L, cumulative CO 2 evolution was 1.25 times greater than that predicted by summing cumulative CO 2 evolved from individual components. Comparison of single‐ and multiple‐term exponential decay models showed that a single‐term model adequately described decomposition of wheat residues.