Predicting Soil Organic Carbon Dynamics of Integrated Crop-Livestock System in Brazil Using the CQESTR Model

Land degradation and reduction in productivity have resulted in losses of soil organic carbon (SOC) in agricultural areas in Brazil. Our objectives were to 1) evaluate the predictive performance of CQESTR model for a tropical savannah; and 2) examine the effect of integrated management systems, including Integrated Crop-Livestock System (ICLS) scenarios on SOC stocks. Two long-term paddocks, under similar edaphic and climate conditions were used in this study. In Paddock 4 (P4) the rotation was corn (Zea mays L.) and 3.5/4.5 years pasture (Urochloa ruziziensis), while rotations in Paddock 5 (P5) included 2.5 years of soybean (Glycine max L.), dryland rice (Oryza sativa L.), and corn followed by 2.5/3.5 years pasture (U. brizantha). Measured and CQESTR simulated values were significantly (0.0001) correlated (r = 0.94) with a mean square deviation (MSD) of 7.55, indicating that the model captured spatial-temporal dynamics of SOC. Predicted SOC increased by 18.0 and 12.04 Mg ha(-1) at the rate of 0.90 and 0.60 Mg ha(-1) year(-1) under current ICLS management for P4 and P5, respectively, by 2039. ICLS increased soil C sequestration compared to simple grain cropping systems under both NT and CT due to high biomass input into the production system.