Stronger effects of maize rhizosphere than phosphorus fertilization on phosphatase activity and phosphorus-mineralizing-related bacteria in acidic soils

The bacterial phoC and phoD genes encode acid (ACP) and alkaline phosphatase (ALP), respectively, which mineralize organic phosphorus (P) to inorganic P. The relative importance of P fertilization and the plant rhizosphere on soil phosphatase activities and associated bacterial communities in acidic soils are poorly understood; additionally, the different responses of the phoC- and phoD-harboring bacterial communities remains undetermined. Here, we grow maize in an acidic soil (pH 4.40) supplemented with 0 (P0), 8.74 (Low phosphorus, LP) and 87.36 (High phosphorus, HP) mg P kg(-1), and determined phosphatase activities and associated bacterial abundance and community composition in bulk and rhizosphere soils. The results showed that relative to bulk soils, rhizosphere showed higher ACP and ALP activities and phoC and phoD gene abundance, but this effect strength was reduced under HP treatment, except for phoC gene abundance. The rhizosphere effect increased alpha-diversity of phoC-harboring bacteria under P fertilization but reduced phoD-harboring bacterial alpha-diversity under P0 and LP treatments. The rhizosphere significantly influenced phoC- and phoD-harboring bacterial community compositions, with stronger effect on phoD-harboring bacteria; while P fertilization only affected phoD-harboring bacteria. Immigrated and extinct species play important roles in reshaping phoC- and phoD-harboring bacterial communities, respectively, in response to the rhizosphere effect. Overall, compared with P fertilization, the maize rhizosphere more strongly influenced soil phosphatase activities, phoC- and phoD-harboring bacterial communities in acidic soils, with phoD-harboring bacteria responding more strongly to the rhizosphere effect and P fertilization. Notably, the strength of the rhizosphere effect heavily relied on P fertilization level.