Effect Of Biomass Charcoal And Foliar Selenium Fertilizer On Cadmium Content In Lettuce

With the rapid development of industry and the extensive use of pesticides and fertilizers in agricultural production,the pollution of the heavy metal Cadmium(Cd)in farmland soil has become more and more serious.Vegetables are essential foods in people’s lives,and cadmium pollution in the production area is the main problem facing the safety of vegetables.Among them,the absorption capacity of leafy vegetables to Cd is significantly higher than that of other types of vegetables,and more attention should be paid to the problem of Cd pollution.Therefore,taking effective measures to inhibit the absorption and accumulation of Cd in the soil by vegetables,reduce the content of Cd in vegetables,improve the quality of vegetables and ensure food safety is one of the problems that need to be solved urgently.In this study,lettuce(Lactuca sativa L.)was used as the research object through a pot experiment.Under the condition of soil cadmium pollution,different amounts of biomass charcoal(10g/kg;20g/kg;30g/kg)and different concentrations of foliar selenium(1mg/L;3mg/L;5mg/L)were applied,Which the effect of fertilizer on the absorption and accumulation of cadmium and growth of lettuce.The ability of lettuce to absorb and accumulate Cd was found to respond to biomass charcoal and foliar selenium fertilizer,and it clearly affected the absorption of lettuce.The main influencing factors of accumulated Cd are designed to provide reasonable technical support for the production of safe and high-quality vegetables on cadmium-contaminated soil.The main conclusions are as follows:1.Under soil Cd pollution conditions,the application of biomass charcoal or foliar selenium fertilizer can reduce the adsorption and accumulation of cadmium on lettuce,enhance its physiological resistance,and promote the growth of lettuce;the effect of adding biomass charcoal at 30g/kg is the best.Under different levels of Cd contaminated soil conditions,the effect of foliar selenium fertilizer on the absorption and growth of lettuce is as follows: when the soil Cd content is 1mg/kg(Cd1),the effect of spraying foliar selenium fertilizer with a concentration of 1mg/L is the most effective.Good;when the soil Cd content is 2mg/kg(Cd2)and 3mg/kg(Cd3),5mg/L is the best treatment.2.Compared with the single application of biomass charcoal and foliar selenium fertilizer,the combination treatment of foliar selenium fertilizer and biomass charcoal at an appropriate concentration can significantly reduce the adsorption and accumulation of lettuce on Cd,and enhance the activity of SOD and CAT,reduces the content of MDA,increases the content of chlorophyll and promotes the growth of lettuce.Under the conditions of this experiment,under the stress of Cd1,the combination of biomass charcoal addition of 30g/kg and foliar selenium fertilizer spraying concentration of 1mg/L can reduce the Cd content in the shoots of lettuce from 0.31mg/kg to 0.05mg/kg;under Cd2 stress,the combination of biomass charcoal addition of 20g/kg and foliar selenium fertilizer spraying concentration of 3mg/L can reduce the Cd content of lettuce shoots from 0.46mg/kg to 0.09 mg/kg.Under Cd3 stress,the combination of the two treatments when the addition amount of biomass charcoal is 30g/kg and the spraying concentration of foliar selenium fertilizer is3mg/L can reduce the Cd content of lettuce from 0.79mg/kg to 0.08mg/kg.And they are all lower than the limit value of 0.2mg/kg(GB2762-2017)of the national food safety standard.3.The interaction of biomass charcoal and foliar selenium fertilizer has a significant impact on the ability of lettuce to absorb and enrich Cd and regulate the growth of lettuce.The effect of spraying foliar selenium fertilizer is higher than that of adding biomass charcoal.4.The application of biomass charcoal can change the distribution of Cd form by increasing soil p H and organic carbon content,thereby affecting the absorption of Cd by lettuce.The distribution of acid extractable cadmium is the main influencing factor that affects the absorption and accumulation of Cd by lettuce;Foliar selenium fertilizer can adjust the physiology of lettuce by affecting the absorption and accumulation of Cd by lettuce.In summary,the addition of biomass charcoal and the application of appropriate concentration of foliar selenium fertilizer can prevent the absorption and accumulation of Cd by lettuce,and the combined application of the two has a superimposing effect,which will further reduce the absorption of each Cd by lettuce.Accumulate and achieve the effect of "enriching selenium and reducing cadmium";the optimal combination plan needs to be determined according to the actual Cd pollution of the soil;this provides a certain reference method for the cultivation of safe and high-quality lettuce in different degrees of Cd contaminated soil.