氮肥对镉在土壤-芥菜系统中迁移转化的影响

Effect of nitrogen fertilization on cadmium translocation in soil-mustard system

以芥菜为研究对象,采用盆栽试验,探讨了不同用量的5种氮肥对污染农田土壤中镉(Cd)在土壤-根系-地上部迁移累积的影响。结果表明:5种氮肥均促进了芥菜根系对Cd的吸收,且根系Cd含量随施氮量的增加而增加;但根系吸收转运Cd的能力随氮肥施用量的增加呈先降后增的变化趋势。在≤200mg(N)·kg-1(土)的施氮水平下,CO(NH2)2和Ca(NO3)2处理能显著降低芥菜地上部Cd含量,降低幅度分别为13%～29%和24%～30%。在施氮量相同的条件下,NH4Cl和(NH4)2SO4显著降低了土壤pH,增加了土壤DTPA-Cd含量,促进了芥菜对Cd的吸收。本试验条件下,200mg(N)·kg-1(土)的CO(NH2)2在增加芥菜产量和降低芥菜地上部Cd含量等方面优于其他氮肥处理。

A pot experiment was conducted to study the effect of urea [CO（NH2）2],ammonium nitrate （NH4NO3）,ammonium chloride （NH4Cl）,ammonium sulfate [（NH4）2SO4] and calcium nitrate [Ca（NO3）2] on cadmium （Cd） translocation and accumulation in the soil-root-shoot system of mustard （Brassica juncea Coss.）.The results indicate that the nitrogen fertilizers significantly promote Cd absorption in roots.Cd translocation ability of roots initially declines and later increases with increasing nitrogen dose.At doses less than 200 mg（N）·kg-1（soil）,urea and calcium nitrate significantly reduce Cd content in mustard shoot in the range of 13%～29% and 24%～30% respectively.At the same level of nitrogen input,ammonium chloride and ammonium sulfate obviously reduce soil pH,increase soil DTPA-Cd content and promote shoot Cd absorption.From the point of view of increased output and lowered Cd content in mustard shoot,200 mg（N）·kg-1（soil） of CO（NH2）2 is superior to other nitrogen treatments.