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.