Differentiating bacterial community responses to long-term phosphorus fertilization in wheat bulk and rhizosphere soils on the Loess Plateau

Mineral phosphorus (P) fertilizers are frequently applied to fields to support high crop yields, but long-term P input changes soil chemical and biological fertility. In the present study, based on a long-term P experiment (with three P levels (0 (P0), 50 (P50), and 100 (P100) kg P 2 O 5 ha −1  yr −1 )), we evaluated the effects of P input on the bacterial community in wheat bulk (BS) and rhizosphere (RS) soils. Compared to the control (P0), the P50 and P100 treatments significantly ( P  < 0.05) increased soil available P (AP) in the BS and RS, but they did not affect the numbers of observed species or diversity, and these indices were significantly lower in the RS than in the BS. Additionally, P fertilization changed the bacterial community compositions in both RS and BS, with minor changes in the RS but major changes in the BS; the bacterial community in the RS was different from that in the BS, with weaker network complexity but closer relationships among the bacterial taxa. An average of 2.95% of all the analyzed genes were involved in P metabolism, with a higher abundance in RS than in BS samples; however, no differences among the three treatments were observed in the BS or RS samples. In conclusion, long-term P fertilization had little impact on bacterial community diversity but changed the community compositions in wheat BS and RS; the changes in the bacterial community and functional profiles in the rhizosphere soil were mainly mediated by roots, which could help supply more available P to the plants.