Changes in soil organic carbon fractions and microbial community under rice straw return in Northeast China

The return of straw to soil can help closing the nutrient cycle in agricultural ecosystems and is an effective means of improving the physical and chemical properties of soil. The objective of this research was to evaluate the effect of rice straw return on soil organic carbon (SOC) fractions and microbial community with a 10-year plot experiment in Northeast China. The study involved four treatments: no rice straw return (S0), a low amount of rice straw return (S1), a high amount of rice straw return (S2), and abandoned farmland (AL). The results indicated that the labile organic carbon (LOC), particulate organic carbon (POC), dissolved organic carbon (DOC), and microbial biomass carbon (MBC) in the S1, S2, and AL treatments were significantly higher than those in the S0 treatment. Rice straw return increased soil microbial richness but did not affect the soil microbial diversity. Proteobacteria, Bacteroidetes, Firmicutes, Acidobacteria, and Verrucomicrobia were the dominant phyla in all treatments based on their relative abundances. Redundancy analysis indicated that MBC and DOC had relatively large influences on the microbial community. •Rice straw return increased concentrations of active soil organic carbon fractions.•Rice straw return enhanced the relative abundances of microbes involved in the carbon cycle.•Microbial community composition was closely related to the active soil organic carbon contents.