Effects of temperature and crop residues on the mineralization of organic carbon in purple paddy soil

This study aimed toward better understanding of characteristics of the mineralization of organic carbon in purple paddy soil affected by temperature, which is one of the important determinants of organic carbon accumulation and decomposition in paddy fields. Soil samples from the Long-term Experimental Farm of Southwest University, Chongqing, China (30°26'N, 106°26'E, alt. 230m) were incubated for 62 days under 2 temperature treatments, 28℃ and 40℃, and mixed with 3 crop residues, Faba bean (Vicia faba) residue, rice (Oryza sativa) residue and Maize (Zea mays) residue, respectively. The results indicate that accumulative mineralized amount of CO2-C are C 66.79 mg/g and C 86.99 mg/g at 28℃and 40℃, respectively. The accumulative mineralized amounts of CO2-C at 40℃ are significantly higher than those at 28℃ (p0.01). The mineralization rate of the crop residues could be quantitatively described by the first-order kinetics equation. The decomposition rate constants (k) of the crop residues are in the order of Faba bean residue maize residue rice residue at the 28℃ treatment, and rice residue maize residue Faba bean residue at the 40℃ treatment. In summary, the carbon dynamics is affected by significant differences in temperature and in chemical composition of crop residues.