Simulation of Soil Carbon Dioxide Flux During Plant Residue Decomposition

Abstract

Based on information obtained from recent studies, we modified the CENTURY model to improve simulation of short‐term soil respiration, especially in soils with surface‐applied crop residues. This involved adding N availability as a factor controlling the decomposition rate. Translocation by filamentous fungi was assumed to be the mechanism supplying mineral N to residues decomposing on the soil surface. When available N is nonlimiting, the N availability factor is 1, otherwise decomposition rates of all pools of soil surface and belowground organic matter are reduced proportionately until N supply meets demand. The modified model was evaluated using CO 2 flux data from a laboratory experiment which included different wheat ( Triticum aestivum L.) straw types (fresh and weathered straw), straw placements (incorporated and surface‐applied) and soil water regimes (continuously moist and alternating moist‐dry conditions). In general, CENTURY successfully simulated daily CO 2 fluxes in these treatments, except for an underestimation in the first day after watering and an overestimation immediately after rewetting dry soil in the moist‐dry water regime. For treatments with surface‐applied straw, CENTURY overestimated soil respiration, while the modified version gave substantially better simulations. The correlation between measured and simulated total (in 77 d) respiration was improved by model modification. CENTURY underestimated the soil mineral N remaining in the soil at the end of the experiment. The modified model gave improved mineral N simulations for the surface straw treatments.