Study on the dynamics of phosphorus adsorption and the risk of release in black soils by conservation tillage

In this experiment, the adsorption characteristics and release risk of phosphorus from three types of soils-namely no-tillage with straw off the field (CK), no-tillage with straw crushed and mulched (FS), and no-tillage with straw high-stubble mulched (GH), were investigated using a batch experimental method. The data showed that the adsorption of phosphorus was divided into three stages and reached equilibrium at 480 min. Compared with CK, FS and GH treatments reduced phosphorus adsorption by 14.68% and 24.63%, respectively. The highest adsorption occurred at pH 7, and the adsorption of phosphorus by the soil gradually decreased with increasing nitrogen concentration. Correlation analysis of soil physicochemical properties and adsorption characteristics showed that the maximum adsorption of phosphorus (Qmax) was significantly negatively correlated with the available nitrogen (AN) and positively correlated with the pH value. The environmental risk index (ERI) followed the order to GH > FS > CK, with physicochemical interactions contributing 87.13% to phosphorus adsorption. Comprehensive analysis concluded that straw return decreased the soil's phosphorus adsorption capacity, enhanced phosphorus availability, but increased the risk of phosphorus release. Appropriately increasing soil pH and reducing nitrogen fertilizer application can enhance phosphorus adsorption.