Impacts of 9 years of a new conservational agricultural management on soil organic carbon fractions

• Soil management regimes had no significant effects on soil organic C.
• The new conservation management markedly increased labile organic C fractions.
• KMnO4–C was the most sensitive fraction to different agricultural managements.

Labile soil organic carbon pools are widely regarded as valuable indicators of changes in soil C sequestration pools and dynamics induced by different soil management practices. The objective of this study was to evaluate how a new conservational agricultural management (NCAM), which has been proved to be an effective pattern to increase corn yield, affects soil organic C (SOC) and labile SOC pools after a 9-year experiment in Northeast China. Narrow-wide row (1.70 m wide row and 0.30 m narrow row, corn is sowed in the narrow row with two lines), no-till, residue retention, change of ridge direction, and fallow are adopted for NCAM. Soil under conventional agricultural management (CAM) was also studied to be as a comparison. Soil samples were taken from 0–20 to 20–40 cm depths. The results showed that no significant difference was found for SOC between the two managements for both depths, indicating that SOC is a too gross measurement. Soil labile organic C fractions: microbial biomass C, hot-water extractable organic C and permanganate oxidizable C (KMnO4–C) contents were significantly higher under NCAM compared to CAM for both depths, reflecting the build-up of labile C pools under NCAM. In addition, of the three C fractions, KMnO4–C was the most sensitive indicator of changes in SOC induced by different agricultural management regimes. Our results implied that the application of NCAM is important to soil C sequestration and improving soil quality.