Study On The Mechanism Of Biochar On Soil Carbon And Nitrogen Cycle And Neutral Aroma Components In Tobacco Leaves

Jiangxi is an important producing area of high-quality tobacco leaves in China.The main soils for planting tobacco are paddy soil and purple soil.The burnt sweet aroma of the tobacco leaves is prominent,and the mellow sweetness is obvious.It is loved by industrial enterprises.However,in recent years,due to the pursuit of high yields in large agriculture,excessive application of chemical fertilizers has caused prominent problems such as the degradation of tobacco planting soil quality,the decline of tobacco leaf quality,and the reduction of aroma.Therefore,in this context,improving tobacco planting soil and tobacco aroma are important ways to improve the quality of tobacco in Jiangxi.Biochar is an important material for research in recent years.According to research reports,the application of biochar in the soil can improve the physical and chemical properties of the soil and improve the quality of tobacco leaves.However,the research content is relatively fragmented,lacks in-depth systematic research,and has not done any research on the main tobacco-growing soil in Jiangxi.In this study,Jiangxi paddy soil and purple soil were taken as research objects,and biochar was used as a means of regulation to study the effects of biochar on the three from the soil-microbial-tobacco neutral aroma substance triad system.Below are key research findings:1.Soil carbon and nitrogen components are important ecological indicators of tobacco planting soil in Jiangxi Province,and are closely related to the content of neutral aroma components in tobacco leaves.The analysis of physical and chemical properties of 175 typical tobacco planting soil samples(100 paddy soils and 75 purple soils)in Jiangxi Province and the neutral aroma content of tobacco leaves cultivated in corresponding soils shows that:with the application of biochar,the neutral aroma content of upper tobacco leaves and middle tobacco leaves in paddy soils increased by 14.76%and 12.02%,respectively;the neutral aroma content of upper tobacco leaves and middle tobacco leaves in purple soils increased by 23.18%and 20.74%respectively;The analysis on the principal component of soil physical and chemical properties showed that soil carbon,nitrogen environment,and carbon pool activity were the important ecological indicators of tobacco-growing soil in Jiangxi province,and had a significant positive correlation with the content of neutral aroma substances in tobacco leaves.2.Application of biochar increased soil carbon pool content and soil carbon pool management index.Under the field conditions,the impact of different amounts of biochar(0 kg/hm2,5400 kg/hm2,7200 kg/hm2,and 10800 kg/hm2)and the application of biochar(7200 kg/hm2)for 2 consecutive years on paddy soil and purple soil carbon cycling were analyzed.The results showed that the application of biochar supplemented the soil carbon pools in tobacco rhizosphere soil,0-20 cm and 20-40 cm soil layer,especially increased soil active organic carbon content such as soil dissolved organic carbon(DOC)and easily oxidized carbon(EOC);The application of biochar improves the soil carbon pool management index and is beneficial to soil fertility;Biochar dosage tests show that biochar has different effects on microbial biomass carbon(MBC)in two types of soil.Medium and high doses are more conducive to the increase of MBC content in paddy soil,but higher doses of biochar decrease MBC content in purple soil;The effect of continuous application of biochar on soil carbon pool replenishment is better than only one year,but continuous application of biochar further promotes soil CO2 emissions and accelerates soil carbon pool mineralization.3.The application of biochar is beneficial to replenish soil nitrogen pools,reduce soil N2O emissions,and is beneficial to the growth of microorganisms related to nitrogen cycling in the soil.Under field conditions,effects of different amounts of biochar(0 kg/hm2,5400 kg/hm2,7200 kg/hm2,and 10800 kg/hm2)and the application of biochar(7200 kg/hm2)for 2 consecutive years on paddy soil and purple soil nitrogen cycling were analyzed.The results showed that:the application of biochar had a beneficial effect on the supplementation of nitrogen pool in tobacco rhizosphere soil,0-20 cm and 20-40 cm soil layers,but biochar reduced the ammonium nitrogen content of purple soil;The application of biochar promoted the increase of soil MBN/TN and increased the biological retention of nitrogen;The application of biochar improves the abundance of bacteria involved in the nitrogen cycle,especially the abundance of denitrifying bacteria;Application of biochar reduced N2O emissions from the soil.4.Application of biochar increased the richness and diversity of soil microorganisms,changed the soil microbial community structure,and facilitated the plant growth promote bacteria(PGPR).Effects of biochar and biochar fertilizer on microbial population abundance and community structure in paddy soil and purple soil were studied through pot experiments.The results showed that the addition of biochar and biochar fertilizer increased the microbial biomass in paddy soil and purple soil,increased soil microbial richness and diversity,and effectively improved the soil microbial community structure.Biochar also significantly increased the abundance of plant growth promote bacteria(PGPR)in soil plants.For example,it has promoted the increase in the abundance of microorganisms such as Bacillus,Pseudomonas and Sphingomonas.5.Application of biochar increased neutral aroma content in tobacco leaves.Field and pot experiments were conducted to study the effect of biochar on the content of neutral aroma substances in tobacco leaves.The results showed that biochar could improve the aroma component content of tobacco leaves in paddy soil and purple soil,the higher dose of biochar is more conducive to increasing the content of neutral aroma substances in paddy soil,However,a lower amount of biochar in purple soil is more conducive to the improvement of tobacco leaf quality.The input of biochar increased the content of tobacco plastid pigments(chlorophyll and carotenoids),and increased the content of such aroma substances in tobacco leaves;Biochar input caused differential gene enrichment in the photosynthesis process of tobacco leaf,which may be the reason for the increase in the plastid pigment content of tobacco leaf.6.The mechanism of the effect of biochar on the aroma content of tobacco leaves was clarified.The effects of biochar on the three aspects of the soil-microbe-tobacco trinity system were studied in a pot experiment.The results showed that the application of biochar affected soil carbon and nitrogen environment and microbial abundance,changes in these factors can affect the neutral aroma content of tobacco leaves.By establishing a partial least squares model,it was found that the main reason for the increase in aroma content of tobacco leaves caused by the application of biochar was the change of soil microorganism;Changes in soil carbon and nitrogen environment directly affect the growth of soil microorganisms and indirectly affect the aroma content of tobacco leaves;In paddy soil,the main microorganisms affecting aroma substances are Burkholderiaceae,Novosphingobium,Bacillus,Chitinophagaceae,Sphingomonas,Acidobacteriaceae,Flavobacterium and Acidobacteria while the purple soil is Sphingobium,Haliangium,Rhizobaceae,Comammonadaceae,Rhodospirillales,etc.