Yao Jianwu

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

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.

Effect of amendment on Cd uptake by Brassica chinensis in Cd-contaminated soils.

The effects of 4 amendments [lime,calcium-magnesium phosphate (Ca-Mg-P fertilizer),alkali slag and peat] on biomass,Cd uptake of Brassia chinensis,and pH and DTPA-extracted Cd in Cd-contaminated soils were investigated in a pot experiment of two continuous crops of B.chinensis.The results show insignificant effects on B.chinensis biomass of additions of 1 mg·kg-1 and 5 mg·kg-1 Cd.However,some form of promotion of biomass is noted under 1 mg·kg-1 Cd addition.Amendments do not significantly improve biomass,but remarkably decrease shoot Cd content in B.chinensis in Cd-polluted soils.The order of efficiency of the 4 amendments on reducing shoot Cd content is lime≈peatalkali slagCa-Mg-P fertilizer.4 amendments present different Cd-reduction effects on B.chinensis root.In the first and second crop,peat and lime decrease root Cd under all Cd treatments,while Ca-Mg-P fertilizer shows the same effect only under 0 and 1 mg·kg-1 Cd.Alkali slag shows not effect.There is a significantly negative correlation between soil DTPA-extracted Cd and pH.Lime,peat and Ca-Mg-P fertilizer increase soil pH,and decrease DTPA-extracted Cd,resulting in decreasing shoot Cd content in B.chinensis.Peat increases soil pH,but does not decrease DTPA-extracted Cd as much as pH.The main mechanism of Cd-reduction effect of peat on B.chinensis shoot could be related with the formation of organic-chelated Cd,which is difficult for B.chinensis to uptake.Comparison between the two crops indicates that amendments have a significantly decreasing effect on Cd content in B.chinensis in the second crop.