Effects Of Green Manure On Microbial Community Diversity In Tobacco-Growing Soils

In order to provide a theoretical basis for improving tobacco soil and promoting the rational fertilization mode between tobacco and green manure,green manure intercropping,turning and decomposition experiments were carried out with Lolium perenne L.,Melilotus officinalis(L)pall.,Medicago sativa L.,and Triticum aestivum L.in the tobacco experimental plot of Mudanjiang Tobacco Research Institute in Heilongjiang Province.The effects of green manure and tobacco cultivation patterns on soil microbial diversity were analyzed by high-throughput gene sequencing and Biolog-ECO method in 0-20 cm topsoil.The main results are as follows:1.Effects of intercropping green manure on microbial diversity in tobacco-growing soilsThe content of soil microbial biomass C and N changed significantly with the growing season of tobacco planting,which was the highest in June.Green manure intercropping and green manure intercropping combined with chemical fertilizer treatment were significantly higher than the control treatment in the whole tobacco growing season.The effect of intercropping green manure treatment on microbial biomass carbon and nitrogen was Melilotus officinalis(L)pall.,indicating that intercropping green manure increased soil microbial biomass carbon and nitrogen content.Intercropping green manure had a positive effect on soil microbial community diversity,and soil microbial community showed the highest activity in June.The average color change rate showed that intercropping Melilotus officinalis(L)pall.had the highest carbon utilization,and the diversity index of intercropping Melilotus officinalis(L)pall.was significantly higher than that of other treatments.The utilization of six major carbon sources showed that soil microbial communities had a higher utilization of amino acids,carboxylic acids and carbohydrates.Load factors reflected the diversity of carbon metabolism of tobacco-growing soil microorganisms mainly reflected in amino acids and carboxylic acids.Firmicutes accounted for the largest proportion of 15 soil samples intercropped with green manure.At the genus level,Bacillus accounts for the largest proportion of all soil samples.The community composition of Lolium perenne L and Melilotus officinalis(L)pall.was similar to that of OTU,but the community composition of Triticum aestivum L?Medicago sativa L and the control had little difference.The species of bacteria in tobacco-growing soil intercropped with ryegrass and rhinoceros were the most.Soil microbial biomass carbon and soil microbial biomass nitrogen have great influence on bacterial community composition.2.Effects of Turning Green Manure on Microbial Diversity of Tobacco-growing SoilSoil microbial biomass C and N changed significantly with the growing season of tobacco planting,which was the highest in June.During the whole growing season,the microbial biomass carbon content of overturned Medicago sativa L and Melilotus officinalis(L)pall.was significantly higher than that of other treatments,but there was no significant difference in microbial biomass nitrogen content.The AWCD value showed that the carbon utilization of overturned Triticum aestivum L and Medicago sativa L was the highest,and the AWCD value was the highest in June.The trend of soil microbial community diversity index of Tobacco Planted with different green manure was the highest in June.During the whole growing season,the utilization of six kinds of carbon sources by tobacco-growing soil microorganisms was significantly higher than that of amino acids,carboxylic acids and carbohydrates,other compounds and polymers.Load factors showed that the diversity of microbial carbon metabolism was mainly reflected in carbohydrates,amino acids and carboxylic acids.In the treatment of turning green manure,Firmicutes were the most dominant species at the gate level.Bacillus is the most abundant community at the generic level.The community composition of Melilotus officinalis(L)pall.and other groups differed greatly at OTU level.The bacterial community structure of Lolium perenne L and Triticum aestivum L was similar.Microbial biomass carbon and microbial biomass nitrogen had a great influence on the composition of bacterial community,and there was a positive correlation between soil microbial biomass carbon and soil microbial biomass nitrogen The bacterial species in tobacco-growing soils of overturned Triticum aestivum L and Medicago sativa L were the most.3.Effects of decomposition of green manure on microbial diversity in tobacco-growing soilsThe content of soil microbial biomass C and N changed significantly with the growing season of tobacco planting,which showed that the content in April was higher than that in September.Soil microbial biomass C and N of different green manure bagging treatments were significantly higher than those of control treatments in the whole growing season.The utilization degree of soil microbial community to carbon source was from April to September,Medicago sativa L was the highest in April,and Melilotus officinalis(L)pall.was the biggest one in September.AWCD was the lowest in September and April.The higher utilization of carbon sources by buried green manure are amino acids,carboxylic acids and carbohydrates.Principal component analysis showed that the diversity of microbial carbon metabolism was mainly reflected in carbohydrates,amino acids,carboxylic acids and polymer carbon sources.