A Balanced Reduction In Mineral Fertilizers Benefits P Reserve And Inorganic P-Solubilizing Bacterial Communities Under Residue Input

Given the contribution of crop residue to soil phosphorus (P) pools, reducing mineral fertilizers should be a worthy management goal in agro-ecosystems for the rational use of scarce P resources. However, little data on whether and how P availability and P-solubilizing bacterial communities change under this condition are accessible. Here, in addition to conventional NPK fertilizers (NPK) and maize straw mulching (NPKS), residue mulching combined with a 20% reduction in only mineral P (NPmKS) or simultaneous NPK (mNPKS) was used on fields with successive years of mineral fertilizers in Northeast China. After two growing seasons, maize yield and total P were consistent across treatments. Nonetheless, compared to NPK, easily labile inorganic P and stable organic P significantly increased in NPKS, which suggests that the risk of P loss and P reserve for long-term transformation increased with residue input. The content of the two P forms recovered separately in mNPKS and NPmKS, which indicates that a balanced reduction in mineral fertilizers may be better for maintaining the P supply. High-throughput sequencing of the pqqC gene, which encodes pyrroloquinoline quinone related to P solubilization, suggested significant contrasts between the inorganic P-solubilizing bacterial communities of NPK and other treatments, nearly 70% of which could be explained by P fractions. In particular, moderately labile inorganic P played a bridging role between P fractions and P-solubilizing bacterial species. Moreover, the correlation between P fractions and P-solubilizing bacteria was enhanced when pH increased, i. e. , in mNPKS, which further confirmed the advantages of a balanced reduction in mineral fertilizers in P-solubilizing bacteria.