Effects of Phosphorus Input on Rhizosphere Soil Respiration Rate and Microbial Community in Corn and Soybean

Phosphorus inputs play a critical role in modulating microbial dynamics in crop rhizosphere soils, yet their specific effects remain underexplored. This study investigated the impacts of P addition on soil respiration rates, enzyme activities, and microbial communities in maize and soybean rhizosphere soils under a 20-year corn-soybean rotation system. Results demonstrated that P inputs significantly elevated rhizosphere soil respiration rates. In maize, LP treatment yielded the highest initial rate (3.2 times CK on day 0) and maximum rate (1.45 times CK), peaking early (days 0–4). In soybean, HP treatment produced the peak rate, occurring on day 4. Glucosidase activity increased under P treatments, with HP in maize showing values up to 1.5–2 times CK before day 8, and HP in soybean peaking at 1.2 times CK on day 8. Acid and neutral phosphatase activities generally declined initially, reflecting feedback inhibition, while alkaline phosphatase rose early. Microbial community structure shifted markedly. Key taxa like Reyranella and Luteimonas increased with P concentration, while Gp1 decreased. Correlation analysis indicated strong associations; e.g., Proteobacteria positively correlated with acid phosphatase and negatively with neutral phosphatase. These findings underscore the crop-specific responses of rhizosphere microbiomes to P inputs, informing targeted fertilization strategies for enhanced nutrient efficiency and sustainable agriculture.