Long-term moderate fertilization increases the complexity of soil microbial community and promotes regulation of phosphorus cycling genes to improve the availability of phosphorus in acid soil

Microbial community and functional genes associated with phosphorus (P) cycling are intrinsic to soil P transformation. Yet, how the P fertilization rates affect the interactions of the microbial community and functional genes of P profiles is urgently needed to improve fertilizer P utilization efficiency. To address this, we conducted a long-term field experiment on purple acid soil in southwestern China using five mineral P fertilization rates. We analyzed the amplicon and metagenomic sequencing data to investigate the impact of P application rates on the bacterial and fungal communities as well as P cycling genes. Our results indicate that the community structure of both microbes and functional genes was significantly affected by P fertilization. Compared to other P levels, P application at 33 kg P ha-1 significantly increased the average degree and cohesion in the bacteria-fungi network, while the interactions between P cycling genes and microbes were also complex. Meanwhile, P application up to 16 kg P ha-1 increased the abundance of dominant functional genes (gcd and phoD), which were negatively correlated with Po and Pi. Nocardioides, Candidatus Solibacter, and Gaiella were the dominant taxon that induced the P cycling. The partial least squares path model (PLS-PM) revealed that SOM and pH were the main factors influencing AP by affecting the diversity and cohesion of the bacteria-fungi community, as well as gene abundance of P cycling genes under long-term gradient P fertilization. Overall, these results highlight the potential of moderate P fertilization to promote the stability of the microbiology and P transformation in acid soil.