Biological Impact of Nickel Pollution on Pakchois in Drab Soil and Its Critical Value

In a pot experiment impact of Ni addition on growth and Absorption and accumulation of mineral nutrients of pakchois in the drab soil was studied.Variation of pakchoi biomass,Ni content in pakchois and available Ni content in soil are three major indexes to characterize critical value of Ni toxicity.Results show with Ni application rate rising from（0-25） mg·kg^-1,the fresh weight of pakchois increased,but its dry weights decreased.With Ni application rate rising on,the biomass of pakchois decreased remarkably.Ni content in pakchois was negatively related to the biomass of the plant.Ni application affected the plant adsorption and accumulation of other mineral nutrients,which showed certain synergia or antagonism.With the reduction of biomass by 10% as an index,the critical value of Ni toxicity in drab soil was defined to be（57.22） mg·kg^-1 and 8.59 mg·kg^-1 for total Ni and available Ni（extracted by DTPA）in the soil respectively,and 20.51 mg·kg^-1 Ni in stems and leaves of pakchois.