Effects Of Long-term Fertilization On Heavy Metals Accumulation In Protected Soil Tomato System

Protected land planting is an effective way to solve the problem of off-season fruit and vegetable supply,improve agricultural efficiency and increase farmers' income.Due to the high output and good benefit,the input of fertilizer,especially organic fertilizer,is large,which to a certain extent leads to the accumulation of heavy metals in the soil,resulting in the risk of safe production of agricultural products.Therefore,it is of great practical significance to study the effect of long-term fertilization on heavy metal accumulation in soil crop system for the prevention and control of soil pollution and the safety of agricultural production.Based on the scientific research base of tomato long-term fertilization experiment of Shenyang Agricultural University,this paper analyzed the soil and tomato plant samples in the facility for 10 years,studied the relationship between the accumulation of heavy metals and the physical and chemical properties of soil in the facility soil tomato system under different fertilization measures for a long time,and estimated the effects of soil on Cu,Zn,Pb,Cd,Cr,Hg,As under different fertilization conditions The environmental capacity of elements,the law of heavy metal accumulation and migration in soil tomato system,and the environmental and health risks of heavy metals in soil and edible part of tomato were evaluated in order to provide scientific fertilization basis for environmental quality of soil and quality control of vegetable products.The main conclusions are as follows:(1)Ten years of long-term fertilization promoted the accumulation of heavy metals in the soil(0~20cm),but they did not exceed the screening value of soil pollution risk.The content of Zn,Cr and Hg in the soil treated with MRKCa was higher than that before the experiment,which was 59.0%,63.1% and 65.8% higher than that before the experiment;the content of Cd in the soil treated with MRK was the highest,which was 55.2% higher than that before the experiment;the content of Cu,Pb and As in the soil treated with MR was the highest,which was 14.8%,61.4% and 58.5% higher than that before the experiment.(2)The accumulation characteristics of heavy metals in different parts of tomato plants were different under different fertilization treatments.The enrichment characteristics of heavy metals in different parts of tomato:Cd and Zn had a certain enrichment ability and the difference was very significant(P<0.01),other heavy metals had no enrichment ability.The migration characteristics of heavy metals in different parts of tomato were as follows: root stem(TF1): Cd > Zn > Cu > Cr > As > Pb > Hg;stem leaf(TF2): Hg > As > Pb > Zn > Cd >Cu > Cr;the migration ability of heavy metals in leaf fruit(TF3)was different among different treatments,and the migration ability of heavy metals was the strongest in TF2.(3)Under different fertilization treatments,soil physical and chemical properties(p H,organic matter,CEC)have different effects on heavy metals in soil tomato system.p H was negatively correlated with Cu,Zn,Pb,Cd,Cr and As in soil(P<0.01),and p H was negatively correlated with Cd,Cr and Hg in tomato fruit(P<0.01).The decrease of p H decreased the accumulation of some heavy metals in the soil tomato system.The organic matter was positively correlated with Cu,Zn,Pb,Cd and Cr in the soil(P<0.01),and the organic matter was positively correlated with Cu,Zn and Cr in the tomato fruit(P<0.01).CEC had asignificant positive correlation with Zn and Cr in soil(P<0.01),CEC had a significant positive correlation with Cr in tomato fruit(P<0.01),while the increase of organic matter and CEC would increase the accumulation of some heavy metals.(4)Heavy metals in soil tomato system with long-term fertilization did not have ecological risk.The single factor pollution index and comprehensive pollution index of soil are less than 1,and the ecological risk is small.The content of heavy metals in the edible part of tomato fruit conforms to the national food safety standard(GB2762-2012)issued by the Ministry of health.To sum up,10 years of long-term fertilization has a trend of accumulation of heavy metals in the soil tomato system,which may lead to serious problems in agricultural production and food safety.Therefore,under different fertilization conditions,the accumulation of heavy metals needs continuous attention.