淹水对酸性红壤磷吸附解吸特性的影响——以江西省旱地红壤和水稻土为例

The effect of flooding on the phosphorus sorption and phosphorus desorption properties of upland red soil and paddy soil from Jiangxi province

采用室内培养法研究了淹水对2种酸性红壤(旱地红壤、水稻土)磷吸附解吸特性及草酸可提取态P的影响。淹水培养实验中,2种土壤分别淹水0(对照),1、2、3、4、8周,淹水培养结束后进行P吸附解吸实验,解吸实验结束后测定土样中草酸可提取态P。结果表明:与氧化状态相比,淹水后旱地红壤P吸附量减少,水稻土淹水1、2、3周P吸附量高于氧化状态,继续淹水4和8周后P吸附量减少。淹水前后旱地红壤P吸附量均大于水稻土。用简单Langmuir方程拟合P等温吸附曲线,除淹水4周外,P最大缓冲容量(MBC)随淹水时间延长而降低。结合能常数(K)淹水前后的变化规律性差。2种土壤P解吸量随加入P量增加而增加。氧化、还原状态下,2种土壤酸性草酸铵可提取P均远远大于CaCl2解吸P,虽然水稻土吸附P量低于旱地红壤,但P解吸量无论是CaCl2解吸P还是酸性草酸铵可提取P均大于旱地红壤,主要原因在于水稻土全P及速效P含量大于旱地红壤。淹水后草酸可提取态P增加,吸附P的释放和被新近形成的铁氧化物再吸附是淹水后草酸可提取态P增加的主要原因。

The purpose of this study was to determine the effect of flooding on phosphorus adsorption-desorption characteristics and on oxalate extractable phosphorus of two soils.In a laboratory incubation study,two soils were flooded for a period of 0（control）,1,2,3,4,8 weeks.After the incubation period,P adsorption and desorption experiment were carried out.Sorption isotherms were described by the classical Langmuir equation.At the end of desorption experiment,Pox was determined.The results form the adsorption experiment showed that upland red soil adsorbed less P under reduced than oxidized conditions.Soil reduction also caused an increase in P-sorption.There was a large increase in the phosphate sorption capacity after 1 week flooding in paddy soil.Less P-sorption increased under reduced condition in paddy soil after 2,3 week flooding and then decreased.With prolonged waterlogging,an apparent decrease in maximum buffer capacity was observed for two soils;however,4 week flooding was an exception.Flooding caused an inconsistent variation in bonding energy of two soils. Desorption of adsorbed P under reduction was greater in acid ammonium oxalate solution than in CaCl2 solution.Desorbed P increased with level of applied P and desorption patterns of adsorbed P were similar to adsorption patterns but values of P in solution were lower at desorption in CaCl2 solution.Paddy soil adsorbed less P and desorbed more P than upland red soil because total P and Olsen-P of paddy soil were larger than that of upland red soil. The amount of oxalate extractable P（Pox） increased after flooding.Releasing of adsorbed P and reabsorbed by newly formed iron oxide was the main reason of Pox increasing after flooding.