Planting Chinese milk vetch with phosphate-solubilizing bacteria inoculation enhances phosphorus turnover by altering the structure of the phoD-harboring bacteria community

This study aimed to reveal how planting Chinese milk vetch (CMV) as green manure in combination with phosphate-solubilizing bacteria-based biofertilizer can enhance phosphorus (P) utilization in CMV-rice crop rotations. The pot experiment included two factors: the presence of Acinetobacter calcoaceticus (ACC) inoculation, and the variety of CMV (six varieties), resulting in 12 treatments. The experiment lasted for 190 d and soil and plants were analyzed thereafter. ACC inoculation increased the average shoot dry weight by 37.1 % and P uptake by 73.9 % of CMV, and increased the average content of soil labile P by 9.2 %; decreased the average content of moderately labile P by 6.9 % and stable P by 5.4 %, compared to control. ACC inoculation increased the average concentrations of acetic acid, gluconic acid, oxalic acid, citric acid, acid phosphatase and alkaline phosphatase. Structural equation model showed that organic acid and phosphatase correlated with soil labile and moderately labile P pools. The average abundance and diversity of the alkaline phosphatase gene (phoD) and the proportion of dominant species in the mineralization of organic P (Streptomycetaceae) increased under ACC inoculation. Thus, planting CMV with ACC inoculation increased the average concentrations of organic acid and alkaline phosphatase, activating insoluble inorganic P and organic P. However, their combination enhanced the average abundance and altered the structure of the phoD-harboring bacteria community, which in turn promoted organic P mineralization. Planting Chinese milk vetch with Acinetobacter calcoaceticus inoculation can effectively utilize P in paddy soil, which can enhance P availability for subsequent rice crops.