Effects Of Biochar And Biochar Compound Fertilizer Application On Soil Enzyme Activity And Microbial Community In Soybean Field

As a soil amendment,biochar has been regarded as a promising way to improve soil quality and fertility.It was frequently reported that biochar could improve soil nutrients and have positive effects on crop growth,yield and quality.However,the responses of soil enzyme activity and microbial community to biochar and biochar compound fertilizer application have not been thoroughly elucidated and the results are inconsistent.To investigate the effects of biochar and biochar compound fertilizer on the soil properties and enzyme activities(urease,invertase,alkaline phosphatase and catalase),and microbial community,a field experiment was conducted under the soybean-wheat rotation in Huang-Huai-Hai Plain.The abundance,diversity and composition of microbial communities were measured using quantitative real-time PCR and Illumina high-throughput sequencing methods.The treatments contained chemical fertilizer(CK),straw-returning combined with chemical fertilizer(CS),biochar compound fertilizer(BCF),low rate of biochar combined with chemical fertilizer(LB)and high rate of biochar application combined with chemical fertilizer(HB).The results are as follows:1.Effects of biochar and biochar compound fertilizer on soil enzyme activityHB treatment significantly increased urease activity in bulk soil and LB treatment significantly increased urease activity in the rhizosphere when compared with the CK.BCF treatment significantly increased invertase activity in bulk soil but decreased in the rhizosphere.The treatments of biochar and biochar compound fertilizer significantly increased alkaline phosphatase in bulk soil,while there was no significant change in the rhizosphere.And the treatments of biochar and biochar compound fertilizer significantly increased soil catalase activity in both bulk and rhizosphere soil.2.Effects of biochar and biochar compound fertilizer on soil microbial communityThe results showed that the abundance and diversity of bacteria had no significant response to the amendment of biochar in both bulk and rhizosphere soil.In terms of fungi,the number of gene copies was 8.72%-23.56% higher in the rhizosphere than that in the bulk soil under all treatments.And the biochar(LB and HB)significantly increased the fungal abundance when compared with the CK.The correlation analysis showed that fungal gene abundance was significantly positively correlated with SOC(P < 0.01)and TN(P < 0.05).LB also increased the fungal alpha diversity which including Chao1,ACE and Shannon indices.Nonmetric multidimensional scaling analysis(NMDS)demonstrated that biochar treatments remarkably changed the microbial communities.Furthermore,the dominant phyla of bacterial community across the treatments were Proteobacteria,Actinobacteria,Acidobacteria,Planctomycetes and Chloroflexi.LB significantly decreased the relative abundance of Bacteroidetes in the bulk soil when compared with the CK.The dominant phyla of soil fungi were Ascomycota,Mortierellomycota and Basidiomycota.LB significantly decreased the relative abundance of Ascomycota but increased the relative abundance of Mortierellomycota.Redundancy analysis(RDA)indicated that changes in community structure of bacteria and fungi were significantly affected by soil properties,such as SOC and TN contents.This study was expected to provide more theoretical basis and practices for the application of biochar in agricultural application.