| This experiment is mainly aimed at the problem of cadmium(Cd)pollution in acidic soil in Henan Province.Corn was used as a remediation plant.The pot experiment was used to study the mechanism of different concentrations of wood vinegar to strengthen the remediation of soil Cd by corn,and the concentration of wood vinegar suitable for corn planting was selected.The field experiment was used to study the remediation effect of wood vinegar combined with densification and corn straw off-field measures on moderately and slightly Cd-contaminated soil,which provided a scientific theoretical basis for the remediation of acid Cd-contaminated farmland soil while production.The results are as follows :(1)In the pot experiment,with the increase of the concentration of wood vinegar,the plant height and biomass of maize showed a trend of increasing first and then decreasing.The plant height,aboveground and underground biomass increased by 2.05 % ~ 6.03 %,15.09 % ~ 29.87 %,11.48 % and 85.25 % respectively compared with the water treatment(CK).Compared with CK treatment,the Cd content,accumulation,enrichment coefficient and transfer coefficient of maize shoot treated with wood vinegar increased by 12.34 %-46.98 %,29.29 %-90.18 %,19.76 %-59.25 % and 2.37 %-10.88 %,respectively.The net photosynthetic rate of maize treated with wood vinegar was 16.02 % ~ 57.66 % higher than that of CK treatment,and the highest net photosynthetic rate of maize treated with 100 times wood vinegar(T100)was 16.08 μmol·m-2·s-1.The application of wood vinegar significantly increased the root length,root surface area,root average diameter,root volume,root tip number and root branch number of maize.The application of 200 times wood vinegar treatment(T200)increased the O2-clearance rate of maize by 5.29 %compared with CK treatment.The MDA content of maize treated with wood vinegar increased by7.58 % ~ 111.35 % compared with CK treatment.The SOD activity increased by 17.07 % ~28.68 % compared with CK treatment,and the CAT activity increased by 15.61 % ~ 29.33 %compared with CK treatment.In addition,the application of wood vinegar treatment increased the activities of soil urease,sucrase and catalase,which were 36.85 %-63.17 %,4.85 %-35.07 % and 4.33 %-7.01 % higher than CK treatment,respectively.Wood vinegar promoted the transfer of residual Cd(RE)and Fe-Mn oxidized Cd(OX)to exchangeable Cd(EX)and organic bound Cd(OM)in soil.The proportion of EX and OM in soil increased by 41.61 % ~ 69.00 % and 18.17 % ~ 107.11 %,respectively,compared with CK treatment.The proportion of RE and OX in soil decreased by9.61 % ~ 51.63 % and 6.76 % ~ 58.68 %,respectively,compared with CK treatment.Wood vinegar enhanced the absorption of Cd by maize,resulting in lower Cd content in rhizosphere soil of each treatment than CK treatment.The lowest Cd content in soil of T200 treatment was 0.701mg·kg-1,which was 9.43 % lower than CK treatment.Compared with CK treatment,the application of wood vinegar treatment increased the Simpson index and OTU number of rhizosphere soil microorganisms.At the phylum level,the application of wood vinegar treatment significantly increased the proportion of Actinobacteriota and Acidobacteriota.At the genus level,the proportion of Burkholderia-Caballeronia-Paraburkholderia and Acetobacteraceae was significantly increased by applying wood vinegar.T200 treatment significantly improved the function of microbial Carbohydrate transport and metabolism,Cell wall/membrane/envelope biogenesis,and Signal transduction mechanisms,compared with CK treatment increased by5.19 %,5.01 %,and 6.03 %,respectively.(2)In the field experiment,the application of wood vinegar treatment and densification combined with wood vinegar treatment could increase the biomass of maize grains and straw.The biomass of maize grains and straw in each treatment increased by 8.95 %-16.13 % and 7.03 %-42.31 %,respectively,compared with straw returning treatment(HCK).The application of wood vinegar and densification measures had a significant effect on Cd content in stems,leaves and roots of maize,but had no significant effect on Cd content in grains.The Cd content of maize grains in each treatment was 0.032 mg·kg-1~0.047 mg·kg-1,which was much lower than the national food safety standard(GB2762-2017).The highest content of Cd in maize stem was0.534 mg·kg-1 in the treatment of 200 times wood vinegar(T200),which was 59.67 % higher than that of HCK treatment.The highest content of Cd in maize leaf was 1.378 mg·kg-1 in the treatment of 400 times wood vinegar(T400),which was 55.02 % higher than that of HCK treatment.The enrichment coefficients of maize stem and leaf in each treatment were 9.63 % ~70.03 % and 12.74 % ~ 67.42 % higher than that of HCK treatment,respectively.(3)The application of wood vinegar and densification measures had a significant effect on the proportion of Cd forms in rhizosphere soil.The proportion of EX,OM and RE forms of Cd in each treatment was lower than that of HCK treatment,and the proportion of carbonate-bound Cd(CA)was significantly increased.The proportion of EX form of Cd in soil treated with 200 times wood vinegar(ZT200)under densification measures was the lowest,which was 24.56 % lower than that of HCK treatment,and the proportion of RE form was 127.89 % higher than that of HCK treatment.The Cd content in the rhizosphere soil of each treatment after maize planting was lower than that before planting.The Cd content in the soil treated with 100 times wood vinegar(ZT100)under the densification measure decreased the most,from 0.794 mg·kg-1 before planting to 0.676mg·kg-1,which was 14.90 % lower than that before planting,indicating that the combination of wood vinegar and densification measures can make maize absorb more Cd,reduce the content of Cd in the soil,and improve the remediation effect of maize on Cd-contaminated farmland.(4)The Cd content of grain,straw and root in wheat season was decreased by the measures of enhanced remediation in maize season and crop straw removal,and the biomass of wheat grain and straw did not decrease significantly compared with HCK treatment.Compared with the HCK treatment,the Cd content of wheat grain decreased by 7.54 %-23.24 %,and the Cd content of straw decreased by 23.45 %-45.63 %.By measuring the microbial diversity of rhizosphere soil after wheat ripening,the results showed that the Chao index,Shannon index and ACE index of rhizosphere soil microorganisms in wheat season were reduced by maize straw leaving the field,and the Simpson index of rhizosphere soil microorganisms in wheat season was increased by applying wood vinegar.The straw removal in maize season reduced the number of OTUs in rhizosphere microorganisms in wheat season and increased the dominant bacteria in soil microorganisms.For example,the application of 100 times wood vinegar treatment(T100)significantly increased the relative abundance of Actinobacteriota,which was 27.85 % higher than that of HCK treatment.ZT200 treatment significantly increased the relative abundance of Acidobacteriota,which was 11.29 % higher than that of HCK treatment.Each treatment in the maize season significantly affected the function of microorganisms in the rhizosphere soil.Under normal planting conditions,the Amino acid transport and metabolism and Transcription of soil microorganisms treated with wood vinegar in the maize season were significantly increased,which were 10.82 %-14.23 % and 8.14 %-11.13 % higher than HCK treatment,respectively.Under the condition of dense planting,the functions of Carbohydrate transport and metabolism,Transcription and Cell wall / membrane / envelope biogenesis of soil microorganisms were significantly improved by applying wood vinegar in maize season,which were 9.54 % ~ 9.86 %,7.74 % ~ 10.70 % and 11.02 % ~ 12.87 % higher than those of HCK treatment,respectively. |
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