Abstract: We investigated rhizosphere phosphorus (P) dynamics of four green manure crops in lateritic red soil and calcareous soil, aiming to provide a scientific basis for maximizing the biological potential of green manure crops to mobilize soil P. A pot experiment was conducted to explore the effects of planting Raphanus sativus (LB), Vicia angustifolia (ZHS), Desmodium intortum (SMH), and Stylosanthes guianensis (ZHC) on the rhizosphere soil pH, acid phosphatase activity and phosphorus fractions in lateritic red soil and calcareous soil. In both soil types, Raphanus sativus had significantly higher biomass, P concentration, and P-use efficiency than the other crops. Except for Stylosanthes guianensis, planting green manure crops moderately increased soil pH and acid phosphatase activity in both soils. In lateritic red soil, the four green manure crops significantly depleted total inorganic P, labile inorganic P, moderately labile inorganic P, stable inorganic P, and residual P. In contrast, planting green manure crops (except Desmodium intortum) significantly depleted total organic P in the calcareous soil. Results of random forest analysis indicated that stable inorganic P, labile inorganic P, moderately labile inorganic P, and labile organic P were the most important predictors of plant P uptake in lateritic red soil, while soil moderately labile inorganic P, stable organic P, stable inorganic P, and acid phosphatase activity showed significant impacts on plant P uptake in calcareous soil. In lateritic red soil, different green manure crops tended to utilize various forms of inorganic P, while in calcareous soil, acid phosphatase-mediated turnover of soil organic P played an important role in plant P uptake. Taken together, Raphanus sativus and Vicia angustifolia showed significant P mobilizing potential in both soils and can serve as suitable crop species for improving the quality of typical degraded soils in South China.

Key words: green manure crop, soil phosphorus fraction, lateritic red soil, calcareous soil, phosphorus use efficiency