土壤磷素的流失风险研究

Risk Assessment on Phosphorus Potential Loss in Agricultural Soil

以附近水田落干土样为对照,选取29个蔬菜地表层土壤样品;通过对比由室内模拟径流实验测得的溶解态磷DRP、生物可利用磷BAP和不同浸提剂提取的土壤有效磷水平以及等温实验得到的相关参数,探讨了特定条件下两种不同土地利用方式土壤磷素的流失风险。结果表明,与附近水田落干土样相比,蔬菜地土壤中溶解态磷DRP含量是水田的2.5倍,生物可利用磷BAP含量是水田的3.6倍,蔬菜地表层土壤磷素流失风险比水田落干后明显增加;影响水土界面磷素径流流失的主要因素是土壤有效磷素水平,室内模拟径流实验测定的生物可利用磷BAP的变化量与Olsen-P、M1-P、M3-P、Pw、DPS和EPC0的变化量之间存在显著的正相关关系,且采用Mehlich3法提取的有效磷水平(M3-P)和土壤吸持饱和度(DPS)比其他指标更能准确地预测磷素流失潜能(R2=0.7345、0.7122,P<0.01)。

29-paired agricultural topsoil （0～20 cm） samples obtained from Boluo county of Huizhou city, the risk of agricultural soil phosphorus loss to surface waters were estimated by comparing the quantities of dissolved reactive phosphorus （DRP） and bio-available phosphorus （BAP） in laboratory simulated runoff with soil test phosphorus levels used by different extractants as well as some isothermal sorption parameters. The results showed that the loss quantity of DRP and BAP in vegetable farm soils were 2.5 times and 3.6 times as much as those of corresponding paddy field soils, respectively. Therefore, vegetable farm soils would produce a greater risk for river eutrophication than that of paddy field soils by air-drying process. The principal component analysis indicated the phosphorus runoff loss in agricultural soils mainly through soil-water interface. BAP was a key issue for controlling eutrophication in agriculturally impacted watersheds. Change of the concentrations of BAP was significantly correlated with change of soil Olsen-P, Mehlichl-P, Mehlich3-P, water-extractable P（Pw）, and soil equilib- rium phosphorus concentration（EPC0） （R^2=-0.380 3, 0.666 9, 0.734 5, 0.430 6, 0.358 9,P〈0.01）. A linear relationship （R^2=0.734 5, 0.712 2, P 〈0.01） was also obtained between BAP and degree of phosphorus sorption saturation （DPS）. Among all the parameters, Mehlich3-P and DPS gave the best estimates of BAP loss.