Effect Of Different Organic Materials Combinations On Carbon And Nitrogen Characteristics And Microbial Community Structure Of Tobacco Growing Soils In Central Henan Province

Returning agricultural organic materials to the field is an effective measure to eliminate agricultural waste,improve soil quality and improve the yield and quality of tobacco leaves.However,there are relatively few studies on the carbon(C)and nitrogen(N)ratio of organic materials impacts to the C,N and microecological characteristics of tobacco growing soil.Through field,pot and indoor simulated leaching experiments from 2020 to 2021,taking sandy,loamy and cohesive tobacco planting soils as the research objects;taking biochar,earthworm dung and barley straw as the sources of organic materials.This study designed five organic material C/N ratio treatments of CK,CN15,CN20,CN25 and CN30,and discussed the effects of organic material C/N ratio on tobacco planting soil C and N regulation,physical and chemical quality improvement,microecological characteristics,tobacco plant growth and development and tobacco yield and quality.The main research results are as follows:1.The treatment group can significantly improve the soil carbon pool.In addition to microbial entropy,the increase of soil carbon pool characteristic value and soil respiration rate increased with the increase of C/N ratio.Low C/N ratio treatment(CN15)could significantly increase the soil nitrogen pool and cumulative nitrogen mineralization before the long-term prosperity of tobacco plants,and the lifting effect decreased gradually with the growth period of tobacco plants.The volume of leaching solution and the leaching amount of ammonium and nitrate nitrogen were negatively correlated with the ratio of C to N.The effects of different soil texture factors on soil C and N components and mineralization are similar: the soil treated with high C to N ratio had higher C pool level and lower N mineralization potential energy,and the C and N parameters in cohesive soil were more affected by the treated C to N ratio.2.Soil C/N ratio,microbial biomass C/N ratio,electrical conductivity,cation exchange capacity,electrical conductivity,cellulase,sucrase,catalase activities and phosphorus and potassium contents increased positively with the change of organic material C/N ratio,but there were significant differences among treatment groups.Soil pH,catalase activity and the contents of iron,calcium and zinc were less affected by the change of C/N ratio.Soil bulk density and urease activity decreased linearly with the increase of C/N ratio.3.The treatment group can improve the soil bacteria and fungi α Diversity,while improving the abundance of some bacterial and fungal populations.Actinobacteria(actinobacteria),Proteobacteria(Proteobacteria)and chlorobi(Campylobacter)were the dominant bacterial populations of each treatment.The higher the C/N ratio of organic materials,it was more conducive to improve the abundance of Chlorobi(Campylobacter)and Firmicutes(Firmicutes),and inhibited the abundance of Proteobacteria(Proteobacteria)and Methylmirabilota(methylated bacteria).The relative abundance of nitrospirae increased by 2.5%-6.4% in the treatment groups,and the increase range of CN30 treatment was the highest,indicating that the high C/N treatment has a higher abundance of nitrogen mineralizing microbial flora than the treatment.The results of redundancy analysis showed that soil bulk density,C/N ratio and microbial biomass C/N ratio were the key environmental factors affecting the structure of fungal and bacterial flora in the rhizosphere soil.4.Organic material treatment with different C/N ratio can improve the agronomic properties of tobacco plants,promote root development,increase the dry matter accumulation in various parts of tobacco plants,coordinate the content of mineral nutrients in tobacco leaves,and improve the photosynthetic rate and the activity of key enzymes of C and N metabolism.The improvement effect of CN15 was the most obvious before the prosperous period,and the improvement effect of CN25-CN30 was the best at the later stage of tobacco growth.The final performance was the more coordinated content of conventional chemical components and richer content of neutral aroma substances(CN25)in the treatment of high C/N ratio,as well as the increase of the proportion of medium and high-grade tobacco(5.34%-11.23%),the yield of tobacco(2.36%-7.58%)and the output value(8.75%-16.27%).In conclusion,higher C/N ratio of organic materials tends to have better soil C and N storage capacity,improvement effect of physical and chemical properties,microbial abundance and yield and quality of tobacco leaves.