Abstract: Huang-Huai-Hai plain is the most important region for grain production with winter wheat-summer corn rotation in one year as its dominating cropping system in China. Soil organic matter (SOM) dynamics and management in intensive agricultural soils is significant for sustainable crop production. Based on the 10-20-years data of 7 independent long-term soil fertility and fertilizer efficiency experiments total in 76 treatments, SOM dynamics in the plough layer were simulated by the modified CQESTR model. The results shows: the SOM mineralization rate (MR) in the plough layer increases with the magnitudes of annual organic inputs, indicating improvement in SOM quality, the inter-annual mean value of which ranges from 2.16% to 5.95% in the 76 treatments; at the respective sites the inter-annual mean MR of minimum is 54.2% that of maximum. Both quantity and quality of SOM will rise upon the increment of inorganic manure and/or organic manure applied. The inter-annual mean carbon dioxide flux (FCO2) mineralized from organic compounds in the plough layer ranges from 337.1 g CO2·m-2·a-1 of minimum to 2 144.3.7 g CO2·m-2·a-1 of maximum, on the average the mean FCO2 of minimum is 31.9% that of maximum at the respective sites. Statistical analysis shows that MR enhances 0.22 percent point and FCO2 enhances 96.5 g CO2·m-2·a-1 when annual crop yield increases 1 t·ha-1; the annual apparent soil respiration efflux (EFCO2) from whole soil profile reflects not merely the intensity of soil organism and plant metabolism, but the SOM MR in the plough layer with regression coefficient r2 of 0.31 on 1235 pairs of data between MR and EFCO2

Key words: Soil organic matter, Mineralization rate, Organic input, Modeling, CQESTR model