Long-term fertilization differentially increased the CAZyme encoding genes responsible for soil organic matter decomposition under winter wheat on the Loess Plateau of China

Long-term fertilization greatly affects soil organic matter (SOM) decomposition in cropping systems, but less information was related to carbohydrate active enzyme (CAZyme) encoding genes in decomposing the components that derived from plant and microbial biomass. Using high-throughput metagenomic sequencing, the responses of CAZyme encoding genes to 35-yr fertilization were assessed in a winter wheat field on the Loess Plateau of China. Four treatments were included as chemical nitrogen fertilizer (N), manure (M), chemical nitrogen plus manure (NM), and control with no fertilization (CK). The results showed that the abundances of genes encoding auxiliary activities and glycosyl transferases were greater in N, and those encoding carbohydrate esterases and glycoside hydrolases were higher in NM than in other treatments. The abundance of genes encoding glycosyl hydrolases was lower in M than in other treatments. Compared to CK, long-term fertilization increased the abundances of CAZyme encoding genes in decomposing the SOM that derived from plant and bacteria biomass, but did not affect those in decomposing fungi-derived component. The Actinobacteria and Proteobacteria were the main phyla contributing to plant- and microbe-derived SOM decomposition. Mantel test indicated that the abundance of CAZyme encoding genes for plant-derived SOM decomposition was mainly affected by the content of microbial biomass nitrogen, while that for bacteria-derived SOM decomposition was associated with soil carbon and nitrogen fractions. Overall, long-term fertilization improved the CAZyme encoding genes in decomposing SOM especially derived from plant and bacteria biomass. These findings help to better understand the decomposition potential of SOM in cropping systems.