Rice-fish coculture without phosphorus addition improves phosphorus availability in paddy soil by regulating phosphorus fraction partitioning and alkaline phosphomonoesterase-encoding bacterial community

Rice-fish coculture (RFC) has gained extensive concern for its contribution to food security and resource conservation, but whether it can promote soil phosphorus (P) availability as well as affect microbial-mediated P turnover remains elusive. Herein, we conducted a microcosm experiment to assess the impact of RFC combined with and without inorganic P (0 and 50 mg P kg-1 as KH2PO4) addition on P fractions, P availability, and phoD-harboring bacterial community composition. Results revealed that RFC significantly improved the P availability and phosphatase activity without P addition, while the available P (AP), pH and soil microbial biomass P (MBP) are primary mediators for regulating soil P fractions. Moreover, the phoD-harboring bacterial abundance is linked to the phosphatase activity, which is primarily regulated through the contents of AP, total carbon (C) and total P, ratios of total C to total nitrogen and total nitrogen to total P. We also found that these keystone taxa of phoD-harboring bacteria contributed to phosphatase production as well as organic P mineralization, thereby improving the P availability. Our findings suggest that RFC combined without P addition is benefical to promote the expression of phoD-harboring bacterial functions to improve the capacity of P mineralization. Overall, our study provides insights into the response of the phoD-harboring bacterial functions for P turnover to rice-fish coculture combined without versus with P addition, which is also necessary for the potential utilization of P resources in agricultural soil and the contribution of phosphatase activity to P acquisition in agriculture ecosystem.