Effect Of The Cellulose Degrading Bacteria On Composting Of Cattle Manure And Wheat Straw And Promoting Function Of The Compost Products On Corn Cultivation

China is an agricultural country,which produced a large number of crop wastes and livestock manure every year.Aerobic composting is an effective treatment method for crop waste and livestock manure,which usually contain high levels of refractory organic components such as lignocellulose.Lignocellulose is the most stable organic compound in the composting substrates with the most stable structure and a complex chemical composition.It is also one of the main reasons that lead to the decrease of compost fermentation rate and hinder the formation of humus.In order to promote the effective degradation of lignocellulose and improve the quality and efficiency of compost,this paper screened and identified highly efficient cellulose degrading bacteria from different sources of soil and cattle manure samples,studied the biological properties of degrading bacteria.Taking cattle manure and wheat straw as composting raw materials,the paper studied the changes of parameters of aerobic composting process in cattle manure and wheat straw under different proportions,and optimized fermentation conditions.The promoting effect of cellulose degrading bacteria on aerobic composting of cattle manure and wheat straw and related mechanisms were studied,in order to provide a theoretical basis for the efficient and comprehensive utilization of crop waste and livestock manure.The main research results are as follows:1)Twelve strains of cellulose degrading bacteria were isolated from soil and cattle manure samples by carboxymethyl cellulose sodium medium.Further,through the filter paper strip disintegration test,cellulase activity determination and straw degradation test,three high-efficient cellulose degrading bacteria were screened out.The three strains have been named F-6,T-B and R-1,respectively.The cellulase activities of the three strains were 18.51U/m L,7.01 U/m L and 4.11 U/m L,respectively.Straw degradation rates of strain F-6,T-B and R-1 were 12.49%,11.37%and 9.53%,respectively.Through the morphological characteristics of bacteria,physiological and biochemical characteristics and 16S r DNA sequence analysis,the strain F-6 was identified as Bacillus methylotrophicus,T-B as Bacillus velezensis and R-1 as Bacillus haynesii.2)Wheat straw and cattle manure ratios of 3:1,1:1,1:3,1:5,and 1:7 of mixed organic matter was set respectively to study the aerobic composting process of mixed substrates.Composting maturity was analyzed by measuring the changes of temperature,p H,electrical conductivity（EC）,E4/E6,ammonia nitrogen,nitrate nitrogen,moisture content and organic matter.The contents of C/N ratio,total nitrogen,total phosphorus,and total potassium at the end of composting were determined.Through comprehensive data analysis,it was determined that the optimal ratio of wheat straw and cattle manure organic matter was 1:5,the temperature lasted for 3 days above 50℃,and the highest temperature reached 61.9℃.At the end of composting,NO₃^--N content was 0.18 g/kg,NH₄⁺-N/NO₃^--N was 0.89.The content of TN+TP+TK was 13.86 g/kg.3)Different cellulose degrading bacteria were added to the mixture of cattle manure and wheat straw for 45 d of aerobic composting.It was found that the inoculation of Bacillus extended the thermophilic period of aerobic composting for 1～2 d,and reduced the NH₄⁺-N/NO₃^--N value,E4/E6 and Respiration activity for four days（RA₄）of the final composts.The contents of total nutrients（TN+TP+TK）in compost products were increased by 4.56%～8.06%,and the compost maturity was promoted.At the end of composting,the cellulose degradation rates in DCW（dried cow manure and straw compost,distilled water 200m L）,CW0（dried cow manure,wet cow manure and straw compost,distilled water 200 m L）,CW1（dried cow manure,wet cow manure and straw compost,F-6 200 m L）,CW2（dried cow manure,wet cow manure and straw compost,F-6 100 m L+T-B 100 m L）and CW3（dried cow manure,wet cow manure and straw compost,F-6 66.7 m L+T-B 66.7 m L+R-1 66.7 m L）treatment groups were 20.05%,25.06%,29.50%,36.75%and 35.78%,respectively,while the hemicellulose degradation rates were 29.52%,30.83%,35.93%,40.36%and 36.86%,respectively.The degradation rates of lignin were 13.79%,14.44%,18.39%,25.29%and22.09%,respectively,indicating that Bacillus inoculation greatly promoted the biodegradation of cellulose,hemicellulose and lignin.The infrared spectrum analysis showed that the infrared spectra of different composting treatments were basically similar during the composting maturity stage,but the absorption intensity of different peaks was different.The research shows that adding cellulose degrading bacteria was more conducive to increasing the aromaticity of composting.After composting,polysaccharides and fats in CW1,CW2 and CW3 treatment groups decreased,and aromatic structural components increased.Compared with DCW and CW0,the humification degree was higher and the structure was more stable.4)Bacterial communities at typical stages of composting were analyzed by high-throughput sequencing techniques.It was found that the top ten bacterial phyla with higher relative abundance in the sample were Firmicutes,Proteobacteria,Bacteroidetes,Actinobacteria,Planctomy,Gemmatimonadetes,Halanaerobiaeota,Patescibacteria,Chloroflexi,and Verrucomicrobia.The dominant phyla are Firmicutes（relative abundance:4.04%～78.84%）,Proteobacteria（relative abundance:3.71%～49.63%）,Actinobacteria（relative abundance:3.93%～16.99%）and Bacteroidetes（relative abundance:0.53%～45.47%）.The relative abundance of Firmicutes,Actinobacteria and Bacteroidetes was improved by the application of bacterial agents.At the level of genus classification,the top ten bacterial genus with higher relative abundance in the sample were Bacillus,Atopostipes,Halocella,Oceanbacillus,Corynebacterium,Galbibacter,Proteiniphilm,Ammoniibacillus,Thermobifida,Luteimonas.The relative abundance of Atopostipes,Proteiniphilum and Thermobifida in CW1,CW2 and CW3 treatment were higher than those in DCW and CW0during the compost maturity.5)Compost products of different treatments are used in corn cultivation.The results showed that the leaf length,plant height,aboveground biomass and underground biomass increased by 4.75%～53.12%,6.09%～37.86%,41.34%～118.20%and 21.04%～53.25%respectively in different treatment groups.Chlorophyll increased by 27.52%～70.80%,malondialdehyde decreased by 39.93%～55.69%,soluble sugar decreased by 67.73%～79.23%,and the growth promoting effect of CW2 treatment group was the best.Pearson correlation analysis was conducted between corn growth indexes and the relative abundance of bacterial community at the genus level in compost products during the compost maturity.The results showed that total nitrogen,total phosphorus,total potassium,and the relative abundance of Atopostipes,Proteiniphilum and Thermobifida in compost were positively correlated with plant growth.