Study On Repairing Heavy Metal Contaminated Soil By Sorghum Under Different Planting Density And Fertilization Level

In order to explore the bioremediation approach of heavy metal contaminated soil,a density test and a fertilization level test were designed to study the remediation effect of biomass sorghum on heavy metal contaminated soil.The breed N5D6 was used as test material,in the density treatment experiment,to research Biological production of sorghum and repairing effect of biomass sorghum on cultivated land heavy metal pollution under five different planting densities?16.50?14.63?12.75?10.88?9.00 ten thousand plants/hm²?.The breed N2562,N5D61and M4264 were used as test material,in fertilization level test,and four different fertilization?N,P₂O₅,K₂O:150,90,150;225,135,180;300,180,210;375,225,240 kg/hm²?levels were designed,to analysis the effects of different fertilization levels on the biomass production,nutrient utilization rate and heavy metal absorption of the three sorghum varieties.The main results are as follows:The planting density and fertilization level product certain effects on biomass sorghum blades growth.The leaf area index reached maximum when the density ranged from 146300to 165000 plants/hm²;And planting density has no significant effect on SPAD value of chlorophyll content.The leaf area index of N2562 reached maximum when using 375kg/hm²pure nitrogen;The leaf area index of N5D61and M4264 both reached maximum,above 5.5,when using 300kg/hm² pure nitrogen.It showed that increasing fertilization amount was beneficial to improve chlorophyll content,to some extent.The planting density and fertilization level product certain effects on the stem growth and root activity of biomass sorghum.The diameter of sorghum base decreases with increasing density and increases with increasing fertilizer application.When it comes to biomass sorghum root activity,planting density of 127500 plants/hm² was superior to other density treatments in the most vigorous stages of vegetative and reproductive growth.Under different fertilization levels,stem bleeding sap amount of N2562 and M4264 reached maximum when using 225kg/hm² pure nitrogen however,the root activity was most vigorous when using 300 kg/hm² pure nitrogen.Planting density and fertilization product significant effects on biomass of sorghum.Under 165000 plants/hm² density treatment,biomass on unit area was highest,reached67.0t/hm² of fresh weight.The breed N5D61 would have a high biomass when using225kg/hm² pure nitrogen.Biomass potential of three varieties would be full played when using 300kg/hm² pure nitrogen and it showed that M4264>N2562>N5D61.Planting biomass sorghum had an obvious remediation effect on heavy metal contaminated soil.before the study,the Cd content of experimental field was 0.64mg/kg,surpassing the national food security standard;While it reduced about 0.22mg/kg after the study.Undoubtly,there was an obvious improvement effect.Except Pb,the content of other several heavy metals reduced greatly.Therefore,Planting the tested cultivars had a considerable remediation effect on heavy metal contaminated soil.Absorption capacity was the largest under 165500 plants/hm² treatment for repair and reuse of various heavy metals.The results of fertilization level test revealed that absorption effect of three varieties for five heavy metals was very approximative,and it barely showed that N5D61>M4264>N2562.The suitable fertilization amount is pure nitrogen 225 kg/hm²,which can not only meet the potential of nutrient demand,but also The biological yield,economic benefit and heavy metal absorption were good.Therefore,the use of sorghum N5D61 varieties is an ideal material for repairing heavy metal Cd and Cr in arable land soil.The optimal planting density is 16.5 million plants per hm²,and the suitable fertilization amount is 225 kg/hm²,P₂O₅ 135 kg/hm²,K₂O 180 kg/hm²can not only meet the potential of nutrient demand,but also obtain a high biological yield,and can obtain a good amount of heavy metal absorption,to achieve the purpose of repairing heavy metal pollution in arable land.