Effects of residue management and fertilizer application mode on soil organic carbon pools in an oasis cotton region.

Abstract

To reveal the regulation mechanisms of agricultural management practices on soil organic carbon (SOC) pools and provide scientific basis for improving soil productivity and formulating agricultural fixed carbon and reducing discharge measures, we monitored the changes of SOC pools and organic carbon fractions in an oasis cotton field under different residue management and fertilizer application modes. A split-plot experimental design was used with differing residue management including residue incorporation (S) and residue removing (NS) in the main plots and differing fertilizer application modes including no fertilizer (CK), NPK fertilizer (NPK), organic manure (OM) and NPK fertilizer plus organic manure (NPK+OM) in the subplot. The results showed that fertilization and residue incorporation significantly increased SOC pool, soil organic carbon (CT), labile carbon (CL), microbial biomass carbon (CMB), water-soluble organic carbon (CWS), hot-water-soluble organic carbon (CHWS), accumulative amount of soil organic carbon mineralization (CTM) and carbon management index (CMI). The SOC pool was increased by 20.6% by residue incorporation compared to residue removing. SOC pools were increased by 7.8%, 29.5% and 37.7% in NPK, OM and NPK+OM treatments compared to CK, respectively. The contents of CT, CL, CMB, CWS and CHWS under different fertilization treatments were shown as NPK+OM>OM>NPK>CK. CTM was increased by 5.9% by residue incorporation compared to residue removing and CTM was increased by 32.7%, 59.5% and 97.3% in NPK, OM and NPK+OM treatments compared to CK, respectively. There was a significant correlation between CMI and CT, CMB, CL, CWS, CHWS, CTM, C pool and C sequestration. Therefore, we concluded that CMI is an important index for evaluating the effect of agricultural management practices on soil quality. In order to construct high-standard oasis farmland in arid region and develop cotton production, we should consider adopting reasonable agricultural management practices (i.e. combining residue incorporation with NPK fertilizer plus organic manure), which could increase the content of SOC, organic carbon fractions and soil fertility, promote soil carbon sequestration, and help the efficient use of agricultural resources and sustainable deve-lopment.