Phosphorus fertilization affects soybean rhizosphere phosphorus dynamics and the bacterial community in karst soils

Background Despite the high phosphorus (P)-mobilizing capacity of legumes, little is known about the dynamics of the P fractions and bacterial communities in the rhizosphere of legumes in karst soils. Methods A field experiment was established to investigate P uptake, rhizosphere P fractions and bacterial community structure of soybean (Glycine max(L.) Merr.) in response to P fertilization (0 and 90 kg P ha(-1)) in karst soils. Results Significant rhizosphere acidification was observed during soybean cultivation. Phosphorus fertilization further decreased soil pH, HCl-P(i)and residual P, but increased NaHCO3-P(i)in the rhizosphere of soybean variety YC03-3, which was associated with the simultaneous increase in P uptake and biomass. In addition, the bacterial community composition was significantly altered by P fertilization through its effects on soil pH and Ca.BacillalesandPseudomonadaleswere the primary taxa influencing P dynamics, especially in soils without P input. Nevertheless, P fertilization decreased the relative abundance ofBacillalesandPseudomonadales, probably due to the enhanced rhizosphere acidification and improved P status. Conclusions In karst soils, recalcitrant P can be depleted directly or transformed into more labile fractions by soybean rhizosphere acidification, even when P fertilizer is applied. As a consequence, P fertilization suppressed the growth of bacteria (BacillalesandPseudomonadales) that contribute to P mobilization due to the reduced demands on these taxa to release P. Our findings highlight the importance of P fertilization in chemical P mobilization, which may consequently influence biological P turnover in the soybean rhizosphere.

Automated summary

Little is known about the dynamics of P fractions and bacterial communities in the rhizosphere of legumes in karst soils. In this study, a field experiment was conducted to investigate P uptake, rhizosphere P fractions and bacterial community structure of soybean in response to P fertilization. Results showed that rhizosphere acidification during soybean cultivation led to changes in P fractions and bacterial community composition. Phosphorus fertilization further affected soil pH and different P fractions, leading to alterations in bacterial community composition, especially in soils without P input.