Effect of Short-Term Organic Matter Returns on Soil Organic Carbon Fractions, Phosphorus Fractions and Microbial Community in Cold Region of China

Abstract

To investigate the effect of different organic matter returns on soil organic carbon (SOC) fractions, phosphorus (P) fractions and microbial communities, a pot experiment was conducted in a cold region of China for three years. There were six treatments in this study, including no rice straw return (S0), rice straw return (SR), decomposed rice straw return (DS), rice-straw-burned return (BS), rice root return (RR) and decomposed cattle manure return (DM). The results indicated that the organic matter returns had no significant effect on the rice yield after three years. The SR, DS and DM treatments significantly increased the content of the soil’s total organic carbon (TOC), light fraction organic carbon (LFOC), particulate organic carbon (POC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC). The BS treatment decreased the soil MBC content. The SR, DS, BS and DM treatments significantly increased the content of the soil’s total P, NaHCO3-P, NaOH-P and residual-P. The proportion of nonlabile P (HCl-P and residual-P) was reduced by the organic matter returns. The SOC fractions were positively correlated to the soil P fractions (except HCl-P). The organic matter returns did not affect the microbial diversity but did change the microbial community composition. The dominant phyla included Proteobacteria, Firmicutes, Chloroflexi, and Bacteroidetes. Compared with the S0 treatment, the organic matter returns increased the relative abundance of Actinobacteria, Anaerolineae and Alphaproteobacteria and decreased the relative abundance of Bacteroidetes, Clostridia and Bacteroidia. The contents of MBC, DOC and NaOH-P were the main factors affecting the microbial community composition, and the soil’s P fractions had a larger influence on the microbial community than the SOC fractions. These results indicated that the incorporation of rice straw, decomposed rice straw and decomposed cattle manure might be an effective practice for maintaining soil fertility in the cold region of China.