Soil organic carbon active fractions as early indicators for total carbon change under straw incorporation

Changes in total organic C ( C T ), water-soluble organic C ( C WS ), microbial biomass C ( C MB ), C mineralization, particulate organic C ( C P ), labile organic C ( C L ), C management index (CMI), and C storage in surface Hapli-Ustic Cambisol (0–20 cm) under straw incorporation after both 2- and 10-year durations were investigated in a maize ( Zea mays L.) field experiment in northeast China, in order to examine the effectiveness of these active C fractions and CMI as early indicators for total C change. The treatments included straw removal (0%S), 50% of straw incorporation (50%S), and 100% of straw incorporation (100%S). Under the straw incorporation, C T concentration and C storage did not significantly change under 2-year duration, while were significantly increased under 10-year duration. However, C MB , total C mineralization ( C TM ), C P , and C L , and CMI were significantly increased under the straw incorporation even after only 2-year duration, and the responses were more significant after 10-year duration. There were positive correlations between all these C indicators with each other. Our findings demonstrate that the measured active C fractions (except for C WS ) and CMI can provide an early indication of change in total soil organic C induced by straw incorporation.