Effect of Different Types of Phosphate Fertilizer on Phosphorus Absorption and Desorption in Acidic Red Soil of Southwest China

The effects of different types of phosphate fertilization on the phosphorus (P) adsorption-desorption in low-P red soil remain unclear. A field plot location test was carried out, and fifteen red soil samples were collected at depths of 0–20 cm from five phosphate fertilizers (CK—no-phosphate, SSP—single superphosphate, CMP—calcium magnesium phosphate, MAP—monoammonium phosphate, and DAP—diammonium phosphate) after the maize was harvested to evaluate the soil physicochemical properties, P adsorption, and desorption characteristics. The structural equation model (SEM) and adjacent tree method (ABT) were used to quantitatively analyze the relative contribution of P adsorption and desorption. The yield, P accumulation, and the P use efficiency of maize were the highest under SSP and CMP treatments. The P adsorption amount was CK > DAP > MAP > CMP > SSP, and the P desorption amount was DAP > MAP > CMP > SSP > CK. Compared with the CK treatment, P adsorption of other P treatments reduced by an average of 21.4%, while P desorption increased by 154.8%. The effect of different types of phosphate fertilizers on soil P adsorption was mainly through regulation of soil organic matter (SOM) and Olsen P, and the effect on soil P desorption was mainly through regulation of SOM and CaCO3. Al2O3 had the greatest effect on P adsorption with a relative contribution rate of 31.52%, and SOM had the greatest effect on P desorption with a relative contribution rate of 53.04%. SSP and CMP treatments had an optimal matching with acidic red soil, which can promote P adsorption, effectively slow down P loss, improve P utilization, and increase crop yield.