Increasing soil clay content increases soil phosphorus availability and improves the growth, physiology, and phosphorus uptake of rice under alternative wetting and mild drying irrigation

Rice is threatened by ineffective inputs of water and fertilizers. Therefore, we detected the effect of soil clay content on plant physiological traits and their relationships to phosphorus (P) utilization -efficiency of rice under different irrigation options. Thus, our experiment was conducted in a two-factor randomized complete block design. The first factor was irrigation method, including three choices: alternate wetting/critical drying (AWCD) (50% drying), alternate wetting/sharp drying (AWSD) (30% drying), and alternative wetting/minor drying (AWMD), (10% drying). The second factor was soil clay amount, with three levels at 65, 50, and 30%, corresponding to SHC, SMC, and SLC. The root's growth and activity were lower in AWCD × SLC than in AWMD × SHC. While the former treatment decreased the P content in soil, the latter increased their availability. The glutamine synthetase (492.5 µmol g^-1h^-1) was lower in AWCD × SLC than in AWMD × SHC at 1006.1 µmol g^-1h^-1, leading to the increase of oxidative cell damage. The optimal P nutrition improved plant growth under AWMD × SHC. The AWCD × SLC led to the minimum agronomic efficiency of P (PAE, 13.67 g/g) and the apparent recovery efficiency of P (PARE, 1.55%). However, the maximum values of PAE (44.05 g/g) and PARE (21.45%) were detected in AWMD × SHC. This study suggests that increasing soil clay content encourages the growth, yield, and P uptake of rice under alternate wetting/minor drying irrigation. The study has excellent application potential, providing technical support for precision water and P fertilizer management of rice.