Rhizosphere microbial carbon utilization stimulates soil phosphorus fraction transformation in response to maize (Zea mays L.) and soybean (Glycine max.) interspecific interactions

This study aimed to investigate the mechanism of rhizosphere soil microbial carbon (C) source utilization affects phosphorus (P) fraction transformation under root interactions.

Intercropping pot experiments with maize and soybean were performed. Three root separation methods combined with 50 P mg kg⁻¹ and 150 P mg kg⁻¹ supply levels were used. The effects of root interactions on crop P uptake, rhizosphere soil available P content, the Hedley-P fraction and rhizosphere microbial C source utilization intensity were studied, and the relationships between soil P fractions and microbial C source utilization were explored.

Compared with separation barrier (SB) treatment, no barrier (NB) treatment increased P uptake of maize and soybean, increased the available P content in maize rhizosphere soil, while reduced the proportion of the moderate P fraction in soybean rhizosphere, increased the utilization ratio of microbial active C sources in soybean rhizosphere, but the effect of P levels on these changes differed between plots. Root interactions also increased the positive symbiosis ratio between microbial C metabolism and P fractions in maize rhizosphere. Structural equation modeling (SEM) analysis revealed that microbial C source utilization has the negative influence on non-labile organic P (Po) or moderate Po, ultimately promoted soil P availability.

Maize and soybean root interactions can change microbial C source utilization, thereby promoting the transformation of non-labile Po or moderate Po fraction to available P and subsequently increasing shoot biomass and P uptake. Moreover, the effect mentioned above is closely related to the P supply level.