| Biochar is widely used as a soil amendment.Due to its specific physiochemical properties,such as high pH,high porosity,great cation adsorption ability,biochar can improve soil environment and increase crop growth.The arable black soils have been severely degraded over the past several decades because of long-term excessive and inappropriate agronomic practices.Consequently,soil acidification and the decrease of soil organic carbon have threatened the sustainability of agricultural development in the black soil region.Therefore,based on the long-term experimental field trial with different dosages of biochar addition,i.e.,C0(0%),C2(2%),C4(4%)and C8(8%),we investigated the soil physicochemical properties and soil enzymes activities,and the effects of biochar on bacterial,fungal and acidobacterial community using Q-PCR and Illumina Miseq sequencing methods.Moreover,the relationship among biochar,soil physicochemical factors and microbial community structure was discussed in this study.Main results are shown as follows:1.Biochar addition significantly increased the soil pH,total C,total N,total P,NO3--N and available K contents,while decreased the soil total K content.However,some other nutrients,such as available P,available N and NH4+-N,were less affected by biochar addition.In addition,biochar addition stimulated the growth of crop and yield.2.The enzyme activities of catalase,urease and invertase were largely influenced by biochar addition.Application of biochar increased the activities of these three enzymes except individual sampling time,especially observed in C8 treatment.However,the phosphatase activity was not affected significantly by biochar addition.3.Biochar amendment increased the bacterial abundance.Irrespective of sampling date,the average bacterial abundances in the C4 and C8 treatments were increased averagely by 6.3% and 15.2% compared to the C0 treatment,respectively.The biochar addition changed the bacterial community compositions.Taxonomic analyses showed that Proteobacteria,Acidobacteria,Actinobacteria,Chloroflexi and Bacteroidetes were the dominant phyla,and the relative abundances of Acidobacteria decreased but Chloroflexi increased with biochar addition.In addition,biochar addition increased the relative abundances of Bacillus and Pedomicrobium,but decreased the relative abundance of Bradyrhizobium.Canonical correspondence analysis(CCA)revealed that changes in the soil bacterial community composition were closely related to soil characteristics,such as pH,total C,total N and total K,which were highly correlated with amount of biochar,suggesting that the long-term impacts of biochar on the soil bacterial community were indirectly driven by changes in soil properties.4.Biochar addition also increased soil fungal abundance,especially the average fungal abundances in the C8 treatments increased by 31.2% in pairwise comparisons with the C0 treatment irrespective of sampling date.The long-term influence of biochar addition on the fungal community was shown at the genus and OTU levels but not at the phylum level.The findings of the relative abundance of Fusarium and several OTUs which are suspected to be the crop pathogens were decreased with biochar addition,suggesting that biochar amendment may be beneficial for controlling crop disease.In addition,CCA analysis revealed that changes in the soil fungal community composition were closely related to soil characteristics,such as pH,soil moisture,total C,total N,total K and available K.These soil characteristics were highly correlated with biochar addition,suggesting that the impacts of long-term biochar amendment on the soil fungal community occurred indirectly as a result of the alteration of soil chemical properties.5.Soil acidobacterial abundance was also increased by biochar addition.Irrespective of sampling date,the average acidobacterial abundances in the C2,C4 and C8 treatments increased by 4.5%,16.7% and 20.9% in pairwise comparisons with the C0 treatment,respectively.The result of Illumina Miseq sequencing showed that 18 subgroups of acidobacteria were detected,and Gp4 and Gp6 were the dominant subgroups in this study.Biochar addition decreased the relative abundance of Gp4.Moreover,biochar addition also affected the acidobacterial community at the OTU levels,and the OTUs with significant changes in relative abundance were identified as Gp4 and Gp6.In addition,CCA analysis indicated that changes in the soil acidobacterial community composition were closely related to soil characteristics,such as NH4+-N,TP,AP and soil moisture.The influence of biochar addition on soil acidobacterial community composition was stronger than that of growth stages(seasonal changes). |
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