Effect Of Planting Leguminous Green Manure And Applying Nitrogen Fertilizer On Soil Nitrate And Heavy Metal Content Of A Wheat Field In Dryland Condition

Weibei Dryland is an important area for cereal production in Shaanxi Province. Limited precipitation and barren soil for local farmyard.Plant leguminous green manure can improve the soil physical and chemical properties, improve soil fertility to some extent. But there are less studies showed the influence of planting green manure on soil heavy metal content.This study is a field experiment.using a split-plot design,The main processing set three leguminous green manure(soybeans, mung beans, Huai beans) and a control treatment(Leisure),deputy treatment provided four kinds of nitrogen levels N0(0 kg/hm2)、N1(108 kg/hm2)、N2(135kg/hm2)、N3(162 kg/hm2),to study the effect of utilize leguminous green manure and nitrogen fertilizers on soil nitrate nitrogen and heavy metal content of a wheat field in dryland conditions,to evaluate whether the soil have been polluted,green manure species whether have an impact on soil heavy metals.Thereby providing a basis for soil fertility and guarantee the safety of agricultural products.The results showed that:Before green manure incorporation, with the soil depth, soil nitrate nitrogen have no significant change;Before wheat sowing 0-120 cm, with soil depth, soil nitrate nitrogen continues to decrease, 120-200 cm, with soil depth, soil nitrate nitrogen have no significant change;After wheat harvesting 0-60 cm with soil depth, soil nitrate nitrogen continue to decrease, 60-200 cm, with soil depth, soil nitrate nitrogen increased,huai bean processing nitrate nitrogen was significantly higher than other treatments.Planting three leguminous green manure can reduce the soil content of Hg, planting mung beans can significantly reduce soil As, Zn, Cd content,soybeans can significantly reduce the soil content of Cu, planting huai beans can significantly reduce soil Cr content. Planting three leguminous green manure significantly increased the soil content of Pb, Ni;different nitrogen levels have a significant impact on soil Hg, Cd content, there is no significant effect on other heavy metal content;Soil As, Cu, Pb, Ni content exceeds the background value, but not exceed the reference value of heavy metals, no significant effect on the crop.