Blocking effect of paraffin wax and amino acid waste mother liquor powder on the adsorption heavy metal Cd of tobacco
Tobacco is an important cash crop with strong enrichment of cadmium(Cd).In order to reduce the absorption of Cd by tobacco,the contaminated soil in mining area(Cd content is 0.678 mg·kg-1)is used as planting substrate.In this experiment,tobacco special fertilizer(nitrate nitrogen)was used as control,the amino acid waste mother liquor powder was a new nitrogen fertilizer(amino acid nitrogen),and paraffin wax(food-grade)as soil microbial carbon source was applied separately.The purpose is to promote the continuous increase of soil microbial population and quantity(the degradation rate of paraffin wax is slow.),and reduce the soil available Cd content through biochemical regulation of microorganisms,thereby reducing the absorption of Cd by tobacco leaves.The results showed that:(1)Paraffin wax and amino acid waste mother liquor powder(T4 treatment)significantly(P＜0.05)increased the soil microbial richness,the ACE reached 4464.47,the chaol reached 3888.30,the amino acid waste mother liquor powder(T3 treatment)soil microbial Shannon diversity was the best,and the Shannon reached 6.4066;(2)the application of amino acid waste mother liquor powder(T3,T4 treatment)could significantly increase soil pH(P＜0.05),and the maximum increases in the three periods were 0.23、0.49 and 0.35 units.(3)Paraffin wax and amino acid waste mother liquor powder significantly(P＜0.05)reduced the soil effective Cd content,which was reduced by 14.8％—20.7％,18.6％—34.5％and 20.5％—36.7％compared with the tobacco special fertilizer group(T1 treatment)in the three periods.(4)Paraffin wax and amino acid waste mother liquor powder significantly(P＜0.05)reduced the Cd content of tobacco leaves,and decreased by 0.6％—10.2％,8.2％—26.2％and 13.8％—38.9％compared with tobacco special fertilizer(T1 treatment)in the three periods.Therefore,the combination of paraffin wax and amino acid waste mother liquor powder can effectively improve the richness and diversity of soil microorganisms and reduce the soil effective Cd content.Finally,the absorption of Cd by tobacco is reduced.
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