Highly weathered acidic soils tend to have high phosphorus adsorption rates. Studying the differential phosphorus adsorption and desorption characteristics of these soils is of great significance to improve phosphorus utilization efficiency and reduce soil phosphorus loss in agricultural management. Erosive weathered granite soil (TL-Tillage layer, LL-Laterite layer, and SL-Sand layer) in Anji County, Zhejiang Province were selected for batch experiments and phosphorus fractionation test. The soil properties that are generally considered to have a greater impact on phosphorus adsorption and desorption are also studied. Derived from the Langmuir adsorption isotherm, the maximum absorption capacity (Qmax) of phosphorus in TL soil was greater than that in LL and SL soil. With a pH of 4.3-5.0, the three soils have the most phosphorus adsorption. The desorption ratio (Dr) in the SL soil is larger than the LL and TL soil. Six key soil property indicators can fit Qmax and Dr values well. Al-P is the main fraction in the phosphorus adsorption-desorption process. The particle size classification (PSC) method can be used to accurately calculate soil-specific surface area. The results of the soil phosphorus adsorption-desorption test can be used as an explanation of the results of artificial rainfall tests. Our results reveal the differential adsorption-desorption mechanism of eroded weathered granite soil, and provide a reference for selecting soil indicators for soil adsorption-desorption studies in different regions.
Keywords: Clay; Isothermal model; Phosphorus fractionation method; Specific surface area; Weathered granite soil.