Deep phosphorus application changed bacterial structure and functional genes, improved phosphorus availability but decreased organic carbon content in soil
Deep fertilisation is considered an effective strategy for optimising fertilisation because deep phosphorus application promotes root growth and enhances soil phosphorus availability. However, information on potential mechanisms for enhancing phosphorus availability and the response of soil bacterial communities and functional genes to deep phosphorus application remains limited. This study used metagenomics to comprehensively investigate how soil bacterial communities and phosphorus cycling genes changed at three different depths of phosphorus application (8, 16, and 24 cm) and how these changes influenced soil phosphorus fractions. The results showed that deep phosphorus application complicated bacterial and phosphorus cycling gene networks, increased the relative abundance of gcd and phoD genes within the 16-24 cm soil layer, and enhanced inorganic phosphorus dissolution and organic phosphorus mineralisation. Total, available, and microbial biomass phosphorus in fertilised soil layers increased by deepening phosphorus application. However, the abundance of carbon degradation-related genes and soil organic carbon content decreased. This study provides important theoretical information for the optimisation and improvement of deep phosphorus fertilisation.