Abstract: Organic carbon dynamics in intensive agricultural soils is significant for sustainable crop production. Based on the short-, mid-term buried organic material experiments in China's Huang-Huai-Hai Plain, the CQESTR model is modified with the division of 4 decomposition stages according to the relation between biomass decomposition and cumulative degree days and the biomass type factors in different stages are determined. Through the validation of soil organic matter (OM) by 7 independent long-term soil fertility and fertilizer efficiency experiments in China's Huang-Huai-Hai Plain, the modified CQESTR model can be used to predict the mineralization of residue, added organic amendment and native soil OM based on cropping and management practices, thus predicting the effect of tillage and crop rotation on organic carbon decomposition and storage in agricultural soils. The modified model provides estimates with a 95% confidence interval of 1.91 g·kg-1 OM and regression coefficient r2 of 0.91 on 1 151 pairs of fitted and observed soil OM from 7 independent fertility experiments in the plough layer. The modified model performs better than the original one.

Key words: Huang-Huai-Hai Plain, CQESTR model, Organic carbon, Modeling, Agricultural soil, Intensive cropping