Effects Of Chicken Manure Compost On Soil Cd Fractions, Microbiological Properties And Wheat Growth In Cd-contaminated Soils

Brown-red soil used in this experiment was collected nearby shizi mountain,Wuhan, then treated with various levels of Cd(0～50 mg Cd kg^-1 soil) and compost(0～120 g kg^-1). The experiment was conducted to evaluate the effect of compost on the immobilization and bioavailability of Cd,soil microorganism and wheat growth in winter wheat(Triticum aestivum L.) potted soils.The objectives of the present study were to evaluate the remediating effect of compost on Cd-contaminated soils by pot experiments under greenhouse conditions.1.Soil pH,OM and total P increased with the increasing amount of compost application in Cd-treated soils.Compared to without compost application,soil pH increased by 0.5～1.2 units after compost application,the content of soil OM and total P increased by 0.2～1.9 and 0.2～3.2 times,respectively.2.In Cd-treated soils,compost application resulted in more than 70%lower soluble/exchangeable Cd(KNO₃),the concentration of organic-bound(NaOH) Cd increased by 0.9～7.8 times,and inorganic precipitates(EDTA) Cd increased by 0.6～1.5 times in soils.3.Compost application increased the number and activity of soil microorganisms and soil enzyme activities in Cd-contaminated soils.With increasing level of compost application,microbial biomass carbon(MBC) significantly increased by 1.1～13.4 times compared to without compost.After compost application,soil urease activities increased by 0.4～1.9 times,soil protease activities increased by 0.35～2.5 times,soil sucrose activities increased by 0.34～1.81 times and neutral phosphatase activities increased by 0.74～4.22 times.4.Compost application improved wheat growth,increased dry yield matter of wheat seeds and decreased the Cd content in wheat seeds and stems.With increasing compost application,wheat seeds yield increased by 1.73～3.34 times and 1.14～2.34 times compared to without compost in Cd 0 and 2 treated soils,respectively.In low levels of soil Cd, compost application decreased Cd content by 33～61.4%in wheat seeds and 56.3～89.1%in wheat stems.Compost was more effective for the decrease of Cd in wheat seeds and stems in high levels of soil Cd.5.The alleviating effect of compost on the toxicity of Cd to soil microorganisms and wheat could be assigned to the redistribution of Cd species in soils affected by compost. Soluble/exchangeable Cd was converted to organic-bound and inorganic precipitates forms after compost application.Alleviation of Cd phytotoxicity by compost was attributed primarily to the increase of soil pH,complexation of Cd by the organic matter and coprecipitation with P content.The conversion of bioavailable Cd species to inert ones is vital in governing the uptake of Cd by plants and the phytotoxicity of the element.The remediation effect of compost on Cd-contaminated soil was influenced by the amount of compost addition and soil Cd level.Therefore compost amendment of Cd-polluted soil decreased the bioavailability of Cd,improved the performance of crops and reduced the uptake of Cd by wheat seeds and stems,while increased the content of soil organic matter and nutritions.There is a good application prospect of compost on the remediation of Cd-contaminated soil by pot experiment study.The remediating effect of compost on Cd-contaminated soil depends on soil type,particular metal and the nature of compost.In practice,the amount of compost application and the combine with other repair technology should be further studied.