Mulching decreased the abundance of microbial functional genes in phosphorus cycling under maize

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Microorganisms regulate soil phosphorus (P) cycling in cropping systems. However, the response of microbial functional genes involved in soil P cycling to mulching practices is largely unknown. We used a metagenomic sequencing approach to analyze microbial functional genes related to soil P cycling in a spring maize field that was mulched with crop straw (SM) and plastic film (FM) for ten years and without mulching (CK). Thirty-nine P cycling functional genes were identified. These genes were involved in organic P-mineralization and inorganic P-solubilization, P-uptake and transport, and P-starvation response regulation. Relative abundances of functional genes coding for P-mineralization and solubilization significantly decreased by 8.8 % and 13.9 % in SM and FM (P < 0.05) than in CK, respectively. FM also decreased the total relative abundance of functional genes involved in P-uptake and transport by 13.2 % (P < 0.05) compared to CK. However, mulching practices did not affect the relative abundance of functional genes related to P-starvation response regulation. Random forest analysis suggested eleven key functional genes coding for soil P cycling as determinants of available P in which the gcd gene encoding PQQGDH was dominant. The Proteobacteria and Actinobacteria were two dominant phyla for which P cycling genes were taxonomically attributed. The Mantel test indicated that soil C:P ratio, pH, and available P were closely associated with the relative abundances of functional genes responsible for soil P cycling. Overall, this study demonstrated a decrease in the relative abundance of soil P cycling genes with mulching practices in agroecosystems, irrespective of the mulch type. The mechanism may differ depending on the mulch type.