ARS | Publication request: Simulating Soil Organic Carbon Dynamics in Long-term Agricultural Experiments Using CQESTR

Submitted to: Biological Systems Simulation Group Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 22, 2010
Publication Date: April 13, 2010
Citation: Gollany, H.T., Rickman, R.W., Liang, Y., Albrecht, S.L., Douglas Jr, C.L. 2010. Simulating Soil Organic Carbon Dynamics in Long-term Agricultural Experiments Using CQESTR. 40th Annual Biological Systems Simulation Conference: conference proceeding: 10-11

Technical Abstract: Soil carbon (C) models are useful for examining the complex interactions between climate, crop, and soil management practices and their influences on long-term changes in soil organic carbon (SOC). The CQESTR model was developed to evaluate the effect of agricultural management practices on short- and long-term SOC dynamics. The CQESTR model is a process-based soil C balance model that computes the rate of biological decomposition of crop residue or organic amendments as they convert to SOC. The model operates on a daily time-step and performs long-term (100-yr) simulations. The C pools are depicted as a continuum. The organic material decomposition is a three phase process. After each residue placement in the soil, decomposition occurs in two phases. Phase I, is a rapid phase covering the first 1000 cumulative degree-days (CDD or thermal time), approximating the oxidation of readily metabolizable substrate. Phase II, is a slow decomposition phase, representing oxidization of more recalcitrant materials. Crop residues and organic amendments are categorized by their placement in the soil and their identities are maintained during the two phase decomposition. Each organic residue addition is tracked separately according to its placement within distinct soil horizons. After 15,000 CDD when Phase II is complete, the composted residue is transferred to the stable SOM pool (Phase III). The CQESTR model can be used for field scale evaluation of SOC changes from various agricultural management practices including residue removal for biofuel. [GRACEnet]