Effect of Biochar of Different Sources on Adsorption and Desorption of Phosphorus in Soil
Effects of biochars derived from rice straw,wheat straw,maize straw and peanut shell on the adsorption and desorption behaviors of phosphorus in soil were studied in this experiment.The results showed that effects of biochars on adsorption of phosphorus depended on phosphorus concentration in soil solution.Compared with the control,theeffect of biochars on adsorption of phosphorus was small when phosphorus concentration was lower than 90 mg L-1.However,adsorption of phosphorus was inhibited by biochars derived from wheat straw and peanut shell and was promoted by biochars derived from rice straw and maize straw,when phosphorus concentration was high in soil solution.Addition of biochars to soil decreased adsorption amount of phosphorus under the condition of equilibrium and adsorption amount followed the order:wheat straw biochar ＞ maize straw biochar ＞ peanut shell biochar ＞ rice straw biochar.The four kinds of biochar promoted desorption of phosphorus from soil.Desorption amount of soil phosphorus with maize straw biochar added was 1.76 times higher than that of control.Adsorption isotherm of phosphorus could be well described by Langmuir equation and Freundlich equation (P ＜ 0.01).Adsorption kinetics of phosphorus could be well described by pseudo-first-order kinetics and pseudo-second order kinetics equation (P＜ 0.01).
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