两种水稻土磷素渗漏流失及其与Olsen磷的关系

采用田间试验的方法,研究了太湖地区两种水稻土(爽水型水稻土和囊水型水稻土)稻季磷素向下渗漏流失情况及其与土壤Olsen-P浓度的关系.结果表明:在每季度30 kg/hm2常规施磷处理水平下,两种水稻土土壤渗漏水的溶解态磷(Dissolved P,简称DP)平均浓度均远超过了水体富营养化的阈值(0.02 mg/L).施磷处理能显著增加30 cm深度渗漏水磷浓度.土壤磷素渗漏迁移流失的主要形态是颗粒态磷(Particulate P,简称PP).爽水型水稻土和囊水型水稻土各处理土壤渗漏水PP/TP的平均值分别为70.9%和67.0%.囊水型水稻土稻季的磷素渗漏流失量约为每季度469.7 g/hm2大干安镇爽水型水稻土378.5 g/hm2.爽水型水稻土和囊水型水稻土土壤渗漏水中磷浓度各存在一个突变点(Change-point),两者分别为33.0 mg/kg和26.3 mg/kg.即当爽水型水稻土和囊水型水稻土土壤(0～10 cm)中的Olsen-P浓度分别大干33.0 mg/kg和26.3 mg/kg时,土壤30 cm深度的渗漏水磷浓度将随着Olsen-P浓度的增加迅速增大.两种水稻土突变点的差异可能与它们的有机质和黏粒含量不同有关.

Phosphorus Move Down by Leaching and Related to Olsen-P of Surface Soil in Two Paddy Soils

A field plot experiment was conducted to study phosphorus move down by leaching and its relation to the concentration of Olsen-P in surface soil on two types of paddy soils(the permeable paddy soil in the Anzhen site and the waterlogged paddy soil in the Changshu site) in the Taihu Lake region.Commercial NPK compound fertilizer and single superphosphate fertilizer were applied to furnish 0,30,75,150,300 kg/hm2 applied P per season.The results showed that all the Dissolved P(DP) concentrations in leachate samples were much greater than the threshold of 0.02 mg/L caused the eutrophication.Fertilizer P rate had an effect on P concentrations in the leachate.The dominant form of P in the leachate was the Particulate P(PP).The average value for PP/TP in the leachate from the various P treatments on the permeable paddy soil and the waterlogged paddy soil was 70.9% and 67.0%,respectively.Under the normal P application rate of 30 kg/hm2 each season,the P losses by leaching at 30cm depth in the Changshu site was 469.7 g/hm2,and greater than 378.5 g/hm2 in the Anzhen site.The change-point of phosphorus by leaching was 33.0 mg/kg in the permeable paddy,higher than in the waterlogged paddy soil(26.3 mg/kg).This difference was probably associated with the different contents of organic matter and soil clay particle of two paddy soils,and indicating that P loss by leaching in the waterlogged paddy soil would be easier than that in the permeable paddy soil.