Coupled Effects of Soil Properties and Phosphatase Activity on Phosphorus Dynamics Under Different Land Uses and Fertilization Regimes in Red Soils

ABSTRACT The availability of soil phosphorus (AP) is profoundly affected by multi‐factors, such as soil properties, fertilization, and land‐use. Those multi‐factor coupling interactions are widely spread and particularly important in field ecosystems in the subtropical and tropical regions. However, there is still a large knowledge gap in those comprehensive effects, especially the long‐term effect. To explore the coupling interactions of fertilization, land use, and soil properties in AP, several treatments of long‐term experiments (> 30 years) in red soil were carried out, including two types of land use (upland and paddy soil), five fertilizations, and differential soil properties. The addition of manure increased the total phosphorus (∆TP), the change of available phosphorus (∆AP), and phosphorus activation coefficients (PAC) of both upland and paddy soils. The P application increased ∆TP and PAC of paddy soil while made no difference in PAC of upland soil. The random forest modeling showed that P balance, organic carbon, pH, iron‐aluminum oxides, and acid phosphatase activity (ACP) were the critical factors in regulating the variation of PAC. Moreover, pH and amorphous iron‐aluminum oxides were the most important for upland and paddy soil, respectively. The partial least squares path model indicated that P balance and organic carbon directly affected PAC and indirectly affected PAC by regulating the iron‐aluminum oxides and ACP. In addition, the pH indirectly increases PAC by influencing iron‐aluminum oxides and ACP. Therefore, the long‐term input of P is key for an increase of AP and TP in red soil areas, especially the combination of chemical P and manure. Furthermore, the rise of soil PAC in upland was higher than that in paddy soil under the same fertilizations. Overall, this study provides a framework for understanding the mechanism and driving factors of P dynamics in agricultural ecosystems with red soils.