Testing the modified Rothamsted Carbon Model for paddy soils against the results from long-term experiments in southern China

We compared predictions of the modified Rothamsted Carbon Model (RothC) for paddy soils (RothC-26.3_p), with decomposition rate constants set at 0.2 and 0.6 times the values in the original RothC-26.3 for submerged and drained periods, respectively, with the results of five long-term field studies in southern China. These field studies included two paddy-upland rotation sites (Chongqing and Wuchang) and three double rice cropping sites (Wangcheng, Nanchang, and Jinxian). Several treatments (no fertilizer, inorganic fertilizer, and inorganic fertilizer with organic amendments such as straw, green manure, and farmyard manure) were tested at each site. RothC-26.3_p satisfactorily simulated the observed changes in soil organic carbon (SOC) at all paddy-upland rotation sites and in all plots without organic matter application at the double rice cropping sites, but overestimated SOC in plots with organic matter application at double rice cropping sites. We conclude that RothC-26.3_p is suitable for use in China with paddy-upland rotation management and with the regime based on relatively low carbon input at double rice cropping sites. However, for systems with large carbon inputs, RothC needs further modification.