Effect Of Fertilization On The Heavy Metal Content And Pollution Evaluation Of Farmland Topsoil

To more accurately and more comprehensively evaluate the effect of fertilizer application on heavy metal content accumulation in soil,this study used CNKI and Web of Science as the source of literature.First set up two keywords search for"fertilization"and"heavy metal",based on the title and abstract,we collected Chinese and English literature on the effect of fertilization on heavy metals in China between 2000 and 2018 Papers.Then re-screened based on research objects,test methods and project measurement methods,and finally got 33 valid papers.According to the different fertilization periods and fertilizer dosages of inorganic fertilizer,organic fertilizer and organic-inorganic（combination）fertilizers,the data of soil heavy metals Cu,Zn,Cr,Cd,and Pb were sorted and classified,and 790effective data groups were obtained.Using SPSS for data integration analysis,the effects of different fertilization periods and fertilizer dosages of three fertilizers on the content of heavy metals in the surface soil of farmland were discussed.On this basis,further use<Risk control standard for soil contamination of agricultural land>,single factor pollution index,and individual potential ecological risk index to analyze the different fertilization conditions on the soil Possible impact on environmental quality.The results show:（1）The application of inorganic fertilizer treatment significantly increased the Cu,Zn,and Cr contents in the soil,but Cd and Pb not significantly accumulated.When the inorganic fertilizer dosage was D<400 kg·ha^-1·y^-1,the Zn content in the soil would be greatly affected when the inorganic fertilization period was Y≥20 year.However,when the inorganic fertilizer dosage was D≥400kg·ha^-1·y^-1,the contents of Cu,Zn,and Cr in the soil increased significantly,even if the application period was less than 20 years.（2）The application of organic fertilizer treatment significantly increased the Cu,Zn,Cr,Cd,and Pb contents in the soil.Among them,the effect on the contents of Cu,Zn,and Cr was stronger,even under low fertilization dosage(D<25,000 kg·ha^-1·y^-1),the contents of these three heavy metals in soil increased significantly.However,the contents of Cd and Pb in soil only increased significantly under the condition of high fertilizer application(D≥25,000 kg·ha^-1·y^-1).（3）The application of inorganic-organic（combination）fertilizers treatment significantly increased the Cu,Zn,Cr,Cd,and Pb contents in the soil.Among them,under the conditions of low fertilization dosage(D<25,000 kg·ha^-1·y^-1),the Cd content in the soil was significantly higher than that without fertilization,and with the increase of the application period,the growth rate also increased.However,the content of Cu and Zn in the soil was not much different from that of non-fertilization treatment when the inorganic-organic（combination）fertilizers dosage was D<25,000 kg·ha^-1·y^-1,and it would take a longer period of application for significant accumulation.Application of inorganic-organic（combination）fertilizers had relatively little effect on the content of Cr and Pb in soil,and accumulation was obvious only when the fertilization dosage was high(D≥25,000 kg·ha^-1·y^-1)and the fertilization period was high（Y≥20 year）.（4）According to<Risk control standard for soil contamination of agricultural land>,the contents of Cu,Zn,Cr and Pb in farmland soils with different fertilizers did not exceed the pollution risk screening value under the corresponding p H standard,but some Cd content reached between the pollution risk screening value and the regulated value.According to the evaluation results of single factor pollution index,geological accumulation index and individual potential ecological risk index,after the application of inorganic fertilizer and inorganic-organic（combination）fertilizers,although the contents of Cu,Zn,Cr,Cd and Pb in the soil have increased to varying degrees,they are still safe or low pollution level,the pollution level has not increased.Application of organic fertilizer is still low,the single factor of soil Cd and the evaluation level of potential ecological risk pollution have been increased from heavy pollution to serious pollution.