The effects of Long-term Fertilization on the Labile Organic Carbon and Carbon Management Index in Black Soil

The effects of fertilization on black soil labile organic carbon and carbon management index(CMI) were studied through a long-term fertilization experiment.Through the 15-year long-term experiment,the results showed that soil organic carbon,active organic carbon and CMI had undergone significant changes.Compared with the original soil,in the NPKOM and NP2K,NPK treatments,soil organic carbon content was significantly increased and there was no significant difference among others treatments.Except for NPKOM treatment,the others treatments had a declining trend of the CMI in the soil.The results of different labile organic carbons showed general trend of high-labile organic carbonmiddle-labile organic carboninert labile organic carbon.The organic carbon content in different treatments arranged as NPK NOMNPKNP≈NP2KNK≈N2PKPKCK.The regression equation analysis showed that high-labile organic carbon changes could explain changes of cation exchange capacity in 89.5%,exchangeable-Ca content in 78%,and exchangeable-Mg content in the 70.6%.The correlation analysis showed that crop yields,CMI and high-labile organic carbon content had highly significant correlations.