长沙市郊不同种植年限菜地土壤磷状况及淋失风险分析

Phosphorus Status and Risk of Phosphate Leaching Loss from Vegetable Soil of Different Planting Years in Suburbs of Changsha

目的提出长沙市郊蔬菜土壤磷淋失临界值,对不同种植年限对土壤淋失风险的影响进行评价。方法选择长沙市郊3种不同种植年限蔬菜土壤为研究对象,采用化学测试方法分析菜地土壤有效磷含量与磷素淋失风险之间的关系。结果Olsen-P与CaCl2-P和土壤溶液中磷浓度之间存在极显著的正相关,并且随着Olsen-P浓度的增加,CaCl2-P和土壤溶液中磷也随之增加并存在一个明显的突变点。通过分析Olsen-P含量与CaCl2-P含量和土壤溶液中磷含量之间的关系,确定80mg·kg-1为长沙市郊菜地土壤磷淋失的临界值。利用GIS和指示克立格法得到长沙市郊蔬菜土壤超过临界值的磷淋失概率并划分为4个淋失风险等级,结果表明,超过30年的老蔬菜基地(陈家渡)和15年左右种植年限的蔬菜基地(黄兴镇)均存在高强度磷淋失风险,磷淋失风险系数分别为3和2.93。1-2年新开辟蔬菜基地(宁乡)磷淋失风险最低,淋失风险系数为0.06,基本不存在磷淋失的风险。结论长沙市郊菜地土壤磷淋失风险严重,种植年限越长,淋失风险越大。

Objective The aim of the study was to develop an index to assess the environmental risk of P loss potential in vegetable soils with chronic difference of plantation in the suburbs of Changsha. Method Chemical methodology was used to study soil phosphorus status and the relationships between available P in soil and potential soil leaching P. Result The results showed that there was a significant linear relationship between Olsen-P and CaCl2-P or P concentration in soil solution. Olsen-P increased sharply when either CaCl2-P or P concentration in soil solution reached a certain level. It was confirmed that 80 mg·kg-1 of Olsen-P was the critical value of soil P leaching in the vegetable soil. P leaching probability over the critical was assessed by GIS and indicator kriging and four secondary risks of phosphorus leaching loss were defined. In the area with vegetable cropping for over 30 years （Chenjiadu） and 10-15 planting years （Huangxingzhen）, the indices of phosphorus leaching loss risk were 3 and 2.93, respectively. These two areas belonged to strong secondary of risk of phosphate leaching loss. In the new vegetable planting field less than 2 years （Ningxiang）, the index was 0.06, which was almost no risk of phosphorus leaching. Conclusion In vegetable soil in the suburban region of Changsha, the phosphorus leaching peotential is high and the phosphorus leaching loss is related to chronic length of vegetable cropping.