Influence of corn stalk and corn stalk biochar application on the strategy of phosphorus sorption and release in brown earth

Abstract The characteristics of soil phosphorus (P) fixation and release have a critical impact on the availability of P and the risk of environmental loss. Investigation of the effects of corn stalk and corn stalk biochar on the P adsorption–desorption characteristics of brown earth can provide a theoretical basis for the rational return of crop stalk to the field and improving the availability of soil P. The Langmuir adsorption isotherm equation provided a better fit than the Freundlich equation for the curve of soil P adsorption and equilibrium solution P concentration. Biochar application increased the maximum adsorption capacity (MAC) and maximum buffer capacity (MBC) of the soil for P by 8.5% and 17.2%, respectively. Corn stalk and its biochar reduced the P adsorption saturation (DPS) by 41.8% and 31.9%, respectively, but increased the amount of readily desorbable P (RDP) by 39.7% and 154.4%, respectively. The application of corn stalk and its biochar improved the soil P desorption rate at substrate P concentrations of less than 5 mg L −1 , whereas significant reductions in the soil P desorption rate were observed between 5 mg L −1 and 30 mg L −1 , and no significant effects were observed at P concentrations over 40 mg L −1 . In addition, the total P and Olsen‐P contents of the soil were significantly associated with the P adsorption–desorption process ( p < .05). Therefore, corn stalk and corn stalk biochar can enhance the capacity of soil for P adsorption, with a stronger effect observed for biochar than for corn stalk, and the rate of P desorption from treated soil is dependent on P concentration in the soil solution.