我国23个土壤磷素淋失风险评估Ⅱ.淋失临界值与土壤理化性质和磷吸附特性的关系

从13个省（市）采取23个耕地表层土壤,通过室内模拟试验测定其磷素淋失临界值和pH、有机质、＜0.01mm、＜0.002mm、交换性钙镁、活性铁铝、磷等温吸附特性等,以建立土壤磷素淋失临界值与土壤基本理化性质和磷吸附特性之间的关系.结果表明：土壤pH＜6.0时,随土壤pH提高临界值增加,土壤pH与临界值之间呈显著的指数关系;而当土壤pH＞6.0时,随土壤pH提高临界值减小,在pH6.5左右土壤磷素淋失临界值最高.土壤磷素淋失临界值与土壤有机质、活性铁（铝）、交换性钙之间存在显著的相关,而与交换性镁、CEC、＜0.01mm、＜0.002mm、K、Qm的相关性受土壤酸碱度影响.可以通过测定土壤有机质或活性铁的含量,来计算土壤磷素淋失临界值,评价土壤磷素淋失的风险.供试的23个土壤,除了采自湖北潜江的20号水稻土存在比较大的磷素淋失风险,其余土壤发生磷素淋失的风险很小.

The evaluation of phosphorus leaching risk of 23 Chinese soils Ⅱ.The relationships between soil properties, P adsorption characteristics and the leaching criterion

23 soils were collected from the croplands of 13 Chinese provinces.Their P leaching criterions were determined by laboratory experiments.Soil parameters including pH,organic matter,cation exchange capacity(CEC),<0.01mm,(<0.002mm,) exchangeable Ca and Mg,active Al and Fe,and P adsorption isotherm were measured at same time.The purpose of this work was to establish the relationships between the soil properties and the P leaching criterions obtained from the relationships between Olsen-P and CaCl-2-P.The results showed that the P leaching criterions increased exponentially with soil pH<6.0,but decreased with soil pH>6.0.The highest value was found at about soil pH6.5.There were close relationships between soil P leaching criterions and soil organic matter, active Fe(Al),exchangeable Ca.In general,exchangeable Mg,CEC,<0.01mm,<0.002mm,K and Q-m were not significantly related with P leaching criterions.However,the relationships were high in(pH<6.0) soils.It is concluded that soil P leaching criterions can be estimated from either soil organic matter or active Fe(Al) contents.Accordingly,the tested 23 soils,except the paddy rice soil No.20 from Qianjiang Hubei Province,had low risk of P leaching occurrence.