Effects of Long-Term Fertilization on Carbon Management Index of Krasnozem in South China

In order to understand the effect of various fertilization measures on soil carbon and carbon stock management index, the long-term fertilization experiment area established for 19 years in Heshengqiao Town, Hubei Province was studied. The effects and differences of no fertilization(CK), application of organic fertilizer(T1), NPK fertilizer(T2)and NPK fertilizer combined with straw(T3)on soil organic carbon and carbon management indexes were studied. The results show that:(1)long-term fertilization can significantly reduce soil bulk density, significantly increase capillary porosity, capillary water holding capacity, saturated water content and pH(p<0.05);(2)long-term fertilization significantly increased the contents of soil organic carbon(SOC), labile organic carbon(LOC)and total carbon(TC)in the three soil layers, as well as the contents of water soluble organic carbon(WSOC), hot water soluble carbon(HWSC)and particulate organic carbon(POC); the contents of SOC, LOC, TC and POC in the 0—15 cm soil layer treated by T3 increased by 78%, 62%, 113% and 241% compared with CK, and the difference was significant(p<0.05); compared with CK, WSOC and HWSC in 0—15 cm soil layer under T1 treatment increased by 21.38 mg/kg and 22.07 mg/kg, respectively, and the difference was significant(p<0.05);(3)the sensitivity index showed that POC(33.33%～251.52%), WSOC(5.60%～193.89%)and HWSC(16.32%～147.14%)in the three soil layers were generally higher than SOC(29%～59%), and POC, WSOC and HWSC were more suitable indicators to determine the impact of field management measures on soil organic carbon than SOC; there was a significant(p<0.05)and extremely significant(p<0.01)positive correlation between carbon management index(CMI)and SOC and LOC, and CMI could reflect the change of soil organic carbon;(4)meanwhile, according to the CMI value, T3(CMI=176.16)>T1(CMI=157.18)>T2(CMI=134.93), combined with the improvement of soil properties and organic carbon by each fertilization treatment, the best field fertilization method in this study was T3.