Effects Of Biochar And Arbuscular Mycorrhiza Fungi On Maize Growth Under Lead Stress

With the rapid development of industrialization and urbanization,sewage irrigation,household waste,and car exhaust can cause serious soil lead pollution.Lead in soil will be enriched to human body through the food chain and food web,causing great potential harm to human health.It is urgent to prevent and reduce soil lead pollution.In recent years,biochar has shown good potential in soil lead pollution remediation due to its unique physicochemical properties,low price,and environmentally friendly characteristics.Arbuscular mycorrhiza fungi（AMF）can coexist with host plants,promote plant growth and improve lead tolerance.However,it is not clear whether biochar and Arbuscular mycorrhiza fungi have a synergistic effect on plant growth and the remediation of lead pollution in soil.Therefore,in this study we used a common crop maize（Zea mays L.）to study the the mechanism of biochar and Arbuscular mycorrhiza in remediation of soil lead pollution.The main research findings are as follows:（1）Under lead stress,the accumulation of nutrients（P,K,Ca,etc.）,plant height,stem diameter,leaf number,and biomass in maize were all decreased.Lead pollution significantly reduced the AMF colonization rate by 22.89%,and the total biomass of soil fungi,bacteria,and microorganisms decreased.（2）The addition of biochar significantly reduced the concentration of ammonium nitrogen and nitrate nitrogen in the soil,while significantly increased the concentration of available phosphorus.Moreover,the addition of biochar significantly increased plant height,stem diameter,leaf number,biomass,and nutrient accumulation of maize.Furthermore,the application of biochar significantly increased the root biomass of maize by 1218.75%and the root to shoot ratio by 92.63%.Whether or not lead was added,the addition of biochar significantly reduced the colonization rate of AMF.The addition of biochar can significantly reduce the extractable Ca Cl₂ and DTPA lead in soil,and significantly reduce 23.87%of weak acid extractable lead in soil,but significantly increasing 10.50%of oxidizable lead.Meanwhile,the addition of biochar significantly reduced the shoot lead content,root lead content and lead enrichment coefficient by 51.36%,49.53%and 46.91%,respectively.（3）AMF inoculation significantly reduced the concentration of soil nitrate nitrogen while significantly increased the concentration of soil alkaline phosphatase.AMF inoculation also significantly increased the plant height,stem diameter,leaf number,and biomass of maize,as well as the absorption of nutrients and chlorophyll content.Moreover,AMF inoculation significantly reduced the extractable Ca Cl₂ and DTPA lead in the soil.Following AMF inoculation,the lead concentration in the maize shoot significantly decreased by 42.58%,the lead concentration in the root system significantly decreased by 30.61%,and the lead enrichment coefficient significantly decreased by 35.79%.（4）The combined application of biochar and AMF significantly reduced the content of soil ammonium nitrogen,nitrate nitrogen,and neutral phosphatase,while significantly increased the content of available phosphorus.The combined application of biochar and AMF also significantly increased the plant height,stem diameter,leaf number,biomass,and K,Ca,Mg,and Mn contents in the aboveground parts of maize.Under lead stress,the combined application of biochar and AMF reduced the accumulation of malondialdehyde and hydrogen peroxide in leaves,and the concentration of superoxide dismutase（SOD）,peroxidase（POD）and catalase（CAT）decreased significantly,while the concentration of ascorbic acid peroxidase（APX）increased significantly under dual application of AMF and biochar.Moreover,the combined application of biochar and AMF significantly reduced the extractable Ca Cl₂ and DTPA lead in soil,and the extractable lead in weak acid state in soil was significantly reduced by 13.08%,while the residual lead was significantly increased by 12.15%.Furthermore,the combined application of biochar and AMF significantly reduced the maize shoot lead concentration by 45.30%and the transfer coefficient by70.86%,but significantly increased the maize root lead concentration by 80.87%.n summary,the toxicity of lead to corn is mainly manifested in the reduction of corn biomass,photosynthetic pigments,and nutrient element absorption.At the same time,it also disrupts the antioxidant mechanism of corn and reduces the biomass of soil microorganisms.The addition of biochar and AMF both reduced the lead content in maize and reduced the toxicity of lead to maize.Although the combined application of biochar and AMF has a good effect on improving soil nutrient status,promoting corn growth,and alleviating lead toxicity,the effect is not as good as applying biochar alone.This may be because the addition of biochar increases the soil available phosphorus content,and the higher available phosphorus content limits corn’s ability to obtain more benefits through symbiosis with AMF.