Effects of fertilization on soil active organic carbon and carbon sequestrationof forage in Karst region

The objective of this experiment is to study the effects of fertilization on different fractions of soil active organic carbon and carbon sequestration of forage in Karst region. There were nine treatments, CK (no fertilization), N1(N 150 mg/kg soil), N2(N 250 mg/kg soil), N1P1(P2O5 100 mg/kg soil), N2P2(P2O5 150 mg/kg soil), N1P1K1(K2O 70 mg/kg soil), N1P1K2(K2O 105 mg/kg soil), N2P2K1 and N2P2K2 in the experiment. Compared to the control (no fertilization), the contents of organic carbon (SOC), microbial biomass carbon (MBC) and readily oxidizable carbon(ROC) in soils, daily mineralization (DMC) and accumulated mineralization (AMC) of organic carbon in soils, and carbon sequestration by forage under the fertilizer treatments are increased. The N1P1K1 has the highest contents of SOC and ROC in soils, the N1P1 has the highest content of MBC, the N2P2K1 has the highest content of the dissolved carbon, and the N2P2K2 has the highest carbon sequestration by forage and the highest contents of DMC and AMC. Generally, more soil active organic carbon is accumulated in the treatments of low NPK, while more carbon is fixed by forage plant in the treatments of high NPK.