Effects Of Heavy Metal Compound Pollution And Fixed Repair On The Growth And Physiological Characteristics Of Sweet Sorghum

Environment in Guangxi features typical karst rocky desertification in southwestern China.Due to local residents' requirements for production and remediation of farmland soil heavy metals,it is necessary to explore agricultural activities in heavy metal-contaminated soils.In this paper,potting was used to plant sweet sorghum and study its effects on the growth and physiological characteristics of sweet sorghum and its absorption and accumulation of heavy metals such as Pb,Zn,As.At the same time,it digs into changes in soil physical and chemical properties,changes in heavy metal content and availability after the single application of chemical fertilizers and the addition of exogenous organic matter(straw,organic fertilizer and biochar produced at 350° C after anaerobic burning)with NPK fertilizers as well as on this basis,after planting sweet sorghum,the effect on the growth and physiological characteristics of sweet sorghum to investigate the toxic effects of heavy metals on sweet sorghum,the cumulative effects of heavy metals on sweet sorghum and the changes of microbial and respiratory and the remediation of heavy metal-contaminated soil by exogenous organic matter so as to provide scientific evidence for the improvement of heavy metal-contaminated soil in farmland with exogenous organic matter.The main findings are as follows:(1)The heavy metals Pb,Zn,As,and Hg-extractables in multiple heavy metal co-contaminated soil in Guangxi had a significant inhibitory effect on the accumulation of plant height and biomass dry weight of sweet sorghum.With the increase of heavy metal pollution,sweet sorghum plant height and biomass accumulation decreased first and then increased.The accumulated amount of heavy metals in sweet sorghum increased with the increase of pollution degree.The accumulated amount of aboveground part far exceeded the cumulative amount of grain and the accumulated amount in plant was ranked by Zn>As>Pb>Hg.At the same time,with the increase of heavy metal content,the activity of chlorophyll and SOD increased at first and then decreased,but the activities of MDA and POD decreased first and then increased.According to Pearson's correlation,PI was positively correlated with SOD in leaves and negatively correlated with other enzymes,plant height and biomass.The difference was not significant.Hg,As,Pb-extractables were positively correlated with Chl and SOD,but negatively correlated with other growth physiological indicators and the heavy metal-extractables of the latter two were significantly negatively correlated with POD(P < 0.05).The Zn-extractables was positively correlated with plant height,Chl,MDA and negatively correlated with others.(2)The pH value and organic matter content in the multiple heavy metal co-contaminated soil treated with single application of chemical fertilizer and addition of exogenous organic matter all increased.At the same time,the content of plumbum(Pb),zinc(Zn),and cadmium(Cd)-extractables increased first and then decreased with the increase of straw application amount.Applying organic manure,biomass charcoal and NPK fertilizer can significantly increase the soil pH value,greatly reduce the content of heavy metalextractables in the soil and decrease the content with the increase of organic fertilizer and biomass carbon.Under the treatment of exogenous organic matter,the absorption of heavy metals such as Zn,Pb,Cd by sweet sorghum showed a downward trend,which in turn significantly increased the plant height and biomass dry weight of sweet sorghum.Chl,superoxide dismutase(SOD),and peroxidase(POD)activities increased at the seedling and heading stages of sweet sorghum and malondialdehyde(MDA)content showed a downward trend with the addition of exogenous organic matter,indicating that the application of NPK fertilizer with exogenous organic matter can effectively improve the soil quality,reduce the heavy metal-extractables content of multiple heavy metals co-contaminated soil,reduce the accumulation of heavy metals in sweet sorghum and reduce the toxic effects on sweet sorghum.After integrating all treatment effects,the order of the advantages and disadvantages is organic fertilizer> biomass charcoal> straw> NPK> PK.