Soil phytoremediation reveals alteration in soil microbial metabolic activities along time gradient of cover crop mulching.

The vitality and diversity of soil microbial metabolism are the core of soil function expression, cover crop is an environmentally friendly agricultural production practice; however, shifts in soil microbial metabolic activities along time gradient of cover crop remain unclear. Here, we used metagenomic and biological techniques to investigate soil microbial potential function and carbon (C) source utilization capacity in the time series of white clover (WC, Trifolium repens L.) for 6, 10, and 15 years in a typical semiarid apple orchard. Conventional tillage (CT) was taken as the control. This study demonstrated that living mulch 6 years of WC had little effect on soil microbial functions. However, after 10 and 15 years of crop cover, an enrichment of genes related to amino acid metabolism, carbon cycle, and nitrogen metabolism was observed in soil microorganisms. Furthermore, average well color development (AWCD) was increased in 10 and 15 years of cover crop, soil microbiome exhibited a stronger preference for carbohydrates, amino acids, and polymers as C sources. The results mainly provided insight into the variation character of microbial metabolic function under increasing duration of cover crop.