Phosphorus adsorption and desorption characteristics of different textural fluvo-aquic soils under long-term fertilization

PurposePhosphorus (P) fertilizer has been widely applied to improve crop yields in the North China Plain; however, most of applied P fertilizer is disabled due to the strong sorption/fixing processes in the soil. This study evaluates the change characteristics of soil properties on different textural soils and their relationships with the P adsorption and desorption under long-term fertilization to do a favor to make strategies for improving the P availability of the soil.Materials and methodsFive textural fluvo-aquic soils including gritty sand, silt sand, sandy loam, medium loam, and light clay were investigated in a 27-year (1990-2017) long-term fertilization experiment at Zhengzhou (Henan province) of China. Soil samples were collected in 1990, 1999, and 2017 at 0-20cm to measure soil properties (i.e., soil mechanical composition) and P adsorption and desorption characteristics.Results and discussionThe clay and silt contents decreased and sand content increased in the light clay soil with the cultivation years, the opposite situation for the gritty sand and silt sand soils. The contents of total P, Olsen-P, and organic matter (SOM) in the five textural soils were increased over time. There were stronger P absorption capacity and weaker desorption ability for the light clay soil relative to others, which was reflected in the largest P maximum buffer capacity (MBC) and the lowest value; however, the P adsorption capacity tended to decrease over time for the light clay soil. Clay and silt fractions were positively correlated with MBC, while negatively correlated with (P<0.01); similar disciplines were found in the contents of SOM, total iron (Fe), and free Fe oxides (FeDCB).ConclusionsThe mechanical composition of five textural fluvo-aquic soils changed to some extent under the long-term cultivation, thereby improved P absorption and desorption capacity. The clay and silt fractions as well as SOM and FeDCB contents were the major factors for the P adsorption, but sand content was the major factor for the P desorption.