Effects Of Microbial Fertilizer On Tobacco Quality And Soil Bacterial Diversity

In order to accelerate the recycling of straw and livestock manure,and improve the yield and quality of tobacco in Northeast China,this study selects excellent strains for preparing microbial fertilizer through enrichment,culture and separation,proposes the optimized preparation process of cattle manure microbial fertilizer,and studies the fertilizer Influence on soil physical and chemical properties,fertility,microbial community structure and tobacco agronomic characteristics.The main findings are as follows:120 cellulose-degrading strains were isolated from forests,tobacco fields and cow dung,and the best strains with fast growth rate and high-efficiency degrading cellulose were selected as Ureibacillus thermosphaericus.The medium formula of U.thermosphaericus is 50 g of peptone,50 g of filter paper,50 g of sodium chloride,20 g of calcium carbonate,10 g of yeast extract and 10 L of distilled water.The best culture conditions are as followed:inoculation volume 20%,temperature 30～35℃,pH value 7.0,rotation speed 400 r/min and ventilation volume 100 ln/h.The best ratio for preparing microbial fertilizer is 1000 kg of cow dung,25 kg of straw,7.5 kg of bacterial liquid and 2.5 kg of water.After adding water in proportion,the bacterial solution is mixed with cow dung and straw,covered with plastic cloth to avoid water evaporation.The bottom diameter of the compost is 145 cm and the height is 95 cm.The initial moisture content of the mixture is controlled at 60±1%.The compost is turned over every 3 days during the heating and high temperature phase for 1～6 weeks,and every 7 days during the cooling phase of 6～12 weeks.During the composting process,the water content is maintained at 60±5%.During the accumulation of microbial fertilizer,the pH value is between 7.3 and 7.8.The total nitrogen content first decreases and then increases but the content of NH4+-N and NO3--N changes in opposite trends.The content of ammonium nitrogen showed a downward trend,the content of nitrate nitrogen showed an upward trend and the content of hydrolyzed nitrogen showed an overall upward trend.When the height is 40 cm,the content of available phosphorus and available potassium are the highest,at 17.60 g/kg and 15.60 g/kg,respectively.Also,it has a promoting effect on the germination rate of tobacco seed"Longjiang 911" and the promotion effect is the most significant compared with the control and other treatment groups(p<0.05).Through high-throughput analysis,the dominant bacteria phyla developed from Firmicutes to Proteobacteria,Bacteroidetes,Chloroflexi and Actinobacteria during the composting process,forming a new microbial fertilizer community.The artificial addition of Ureibacillus thermosphaericus was among the top 50 bacterial genera in relative abundance at different composting periods.With the extension of the composting time,the bacterial community composition changed significantly,and the bacterial communities were significantly different in the early,middle and late stages of composting.The relative abundance of Ureibacillus showed a trend of first decreasing and then increasing,indicating that this genus can exist stably during the refining period and has a certain impact on the diversity and richness of the microbial community during the refining process.Then,the importance of Proteobacteria,Actinomycetes,Firmicutes,Gemmatimonadetes and Chloroflexus in the development of microbial communities was determined by constructing an ecological network diagram.The mixed application of microbial fertilizer 382.5 kg/hm2+ tobacco special fertilizer 375 kg/hm2 can significantly improve soil pH to the optimum range for tobacco growth,increase soil hydrolyzed nitrogen content,available potassium content,organic carbon content,organic matter content and invertase activity.At the same time,it has the best promotion effect on tobacco plant height,stem circumference,leaf area,yield,nitrogen and potassium content.The application of microbial fertilizer can significantly improve the physical and chemical properties of the soil and promote the accumulation of tobacco metabolites.The effect of single application of 1080 kg/hm2 of microbial fertilizer on soil total porosity(51.2±2.1%),available phosphorus content(25.26 mg/kg),catalase activity,and urease activity was the best among the experimental groups.At the same time,the total sugar,reducing sugar and protein content of the tobacco treated with a single application of microbial fertilizer 1080 kg/hm2 was the highest,the tobacco total nitrogen/nicotine ratio was the best,and the tobacco smoking quality score was the highest.Single application of special fertilizer for tobacco will reduce the diversity of soil bacteria,while the application of microbial fertilizer or mixed application of microbial fertilizer and special tobacco fertilizer can help improve the bacterial diversity in the soil.However,there was a big difference in the community composition between the treatments with single application of tobacco special fertilizer and single application of microbial fertilizer.Redundant analysis of soil bacterial diversity and physical and chemical properties showed that available phosphorus,organic carbon,pH,invertase activity,and catalase activity are all important driving forces for the differences in soil bacterial communities.This study optimized the cow dung-straw composting technology,formulated high-efficiency microbial fertilizer,and proposed a microbial fertilizer composting and fertilization technology that can effectively improve soil fertility,improve soil bacterial diversity,and improve tobacco quality and yield in Northeast China.