氧化还原条件下红壤磷吸附与解吸特性及需磷量探讨

研究了5个酸性红壤由氧化条件转为还原条件的P吸附和解吸特性,以及确定供试红壤作为水田或旱地相应的施P量。结果表明:5个土样P吸附量随P液浓度的增加而增加,土壤对P的吸附曲线均可用Langmuir方程拟合,氧化条件下P最大吸附量变化范围为794.22～956.75mg/kg,还原条件下P最大吸附量变化范围为867.31～1195.62mg/kg。P解吸量随P吸附量的增加而增加,P解吸率的结果表明,淹水不同程度地降低土壤P解吸量。以Langmuir方程计算土壤溶液中P浓度在0.2mg/kg时的土壤需P量作为施P量的依据,淹水后土壤标准需P量增加。

Study on adsorption and desorption characteristics of soils and phosphorus requirement under oxidized and reduced conditions

Phosphate requirement of paddy or upland were investigated by adsorption/desorption experiment under oxidized and reduced conditions in five red soils. Results showed that P adsorption capacity increased with the increase of added P concentration. Phosphate adsorption curves of soils fitted well with Langmuir equation. The range of the maximum capacities of P adsorption (Qm) ranged from 794.22 to 956.75 mg/kg under oxidized condition and from 867.31 to 1 195.62 mg/kg under reduced condition. The capacity of desorption P increased with the increase of the capacity of P adsorption, P desorption rate of soils was lower under reduced condition than that under oxidized condition. Phosphorus requirement was calculated from the Langumir equation on the basis of P concentration in soil solution at 0.2 mg/kg. Phosphorus requirement of soils increased after water logging.