氮素形态对烟草根际镉的有效性及镉吸收的影响

Effects of nitrogen forms on bioavailability of cadmium in rhizosphere and its uptake by tobacco

采用盆栽实验,研究了不同氮素形态对酸性紫色土和中性紫色土中烟草根际有效镉含量及烟草吸收镉的影响。结果表明,氮素形态对烟草根际有效镉含量的影响不显著,但铵态氮(AN)和铵态氮+硝化抑制剂双氰胺(AN+DCD)使非根际有效镉含量显著提高。2种土壤中,烟草的生物量均以AN+DCD处理最高;烟草地上部镉含量在酸性紫色土中以硝态氮(NN)处理最高,中性紫色土中则以AN+DCD处理最高;烟草地上部镉累积量均以AN+DCD和AN+NN处理最高。从植物修复角度,2种土壤宜以铵态氮与硝态氮混合或铵态氮与双氰胺混合方式施用。

The effects of nitrogen forms,including ammonium nitrogen（ AN）,nitrate nitrogen（ NN）,ammonium nitrogen ＋ nitrate nitrogen（ AN ＋ NN）,ammonium nitrogen ＋ dicyandiamid（ AN ＋ DCD） and urea（ CO） on the bioavailability of cadmium in the rhizosphere and its uptake by tobacco grown on an acid purple soil and a neutral purple soil,were studied using a pot and rhizobag experiment. The results showed that the application of different nitrogen forms did not significantly affect the content of bioavailable cadmium in the rhizosphere,but the treatments of AN and AN ＋ DCD significantly increased the content of bioavailable cadmium in the nonrhizosphere（ p 0. 05）. In both soil types,the highest biomass resulted from the AN ＋ DCD treatment,while the highest cadmium content in the tobacco shoots was obtained from the NN treatment in the acid purple soil,and from AN ＋ DCD treatment in the neutral purple soil. However,the highest cadmium accumulation was observed after the treatments of AN ＋ DCD and AN ＋ NN for both soils. Therefore,it is suggested that ammonium nitrogen be applied together with nitrate nitrogen or DCD,to enhance the phytoextraction efficiency of cadmium by tobacco from polluted soils.