Effects Of Biochar On Mineral Nutrition And Rhizosphere Soil Microecology Of Flue Cured Tobacco

In recent years,the unreasonable application of chemical fertilizers and pesticides in the process of tobacco cultivation and management in China has led to serious pollution of tobacco planting soil,aggravation of soil nutrient non-uniformity,serious impact on soil carbon and nitrogen cycle process and micro ecological environment,resulting in a sharp decline in tobacco yield and quality,threatening the production of high-quality tobacco.In this paper,the effects of biochar on Rhizosphere microecology,mineral nutrient absorption and tobacco production were systematically studied from the aspects of soil carbon and nitrogen components,available nutrients,microbial diversity,tobacco growth and development,tobacco mineral nutrient absorption,and tobacco quality in Yanshan tobacco experimental station of Shaowu from 2018 to 2020.The main results are as follows:1.Biochar is beneficial to soil health cultivationBiochar application can improve soil physical and chemical properties and reduce soil bulk density.Compared with CK2,the four biochar treatments decreased by 14.76%,18.12%,24.83%and 26.17%respectively;the soil acidity decreased,and the pH value of the four biochar tre atments increased by 0.63%,6.17%,2.68%and 2.05%respectively.The content of soil organic matter,available phosphorus,available potassium and total nitrogen increased in varying degrees.T3 treatment had the highest content of soil organic matter,increased by 9.85%,8.96%,10.92%and 14.67%respectively compared with CK2 treatment;the content of available phosphorus increased by 23.69%,20.11%,22.33%and 24.18%respectively compared with CK2 treatment;the content of available potassium increased by 34.49%,34.32%and 38.72%respectively compared with CK2 treatment The total nitrogen content increased by 17.43%,12.56%,12.58%and 17.45%respectively compared with CK2,T1,T2 and T4 in the same period.2.Biochar increased soil microbial diversity and significantly affected soil microbial community structure.Compared with the conventional treatment,the diversity index of fungal community in T3 was the highest,increased by 11.0%,and that of bacterial community in T2 was the highest,increased by 3%.The relative abundance of Ascomycota T3 decreased by at least 18%,that of Chloroflexi increased by 33%,39%,21%and 15%,and that of Acidobacteria increased by 47%,78%,65%and 63%,respectively.3.Biochar is beneficial to the production of high quality tobacco and promotes the balance of mineral nutrients in tobaccoIn the early stage of tobacco growth,biochar inhibited the growth and development of tobacco plants,and promoted the growth and development in the middle and late stage.Compared with CK treatment,the plant height,leaf length,leaf width and stem circumference of tobacco plants increased by 11.83%,16.88%,6.70%and 10.80%,respectively.The disease index of bacterial wilt in T3 treatment also decreased by 9%.The application of biochar could improve the net photosynthetic rate of tobacco leaves.The net photosynthetic rate of T3 was the highest,T1 was the highest,T2 and T4 were the second,and CK2 was the lowest.Biochar can optimize the physical properties of cured tobacco,increase the tensile force and thickness of tobacco,reduce the stem content,and improve the availability of tobacco.The tensile force of biochar T2 treatment is the largest,increased by 57.66%compared with CK2.The neutral aroma components of flue-cured tobacco,such as furfural,benzyl alcohol,Solanone,dehydrodihydro-?-ionone,megastigmatrienone and neophytadiene,were significantly higher in T2 treatment than in other treatments.The results showed that the proportion of biochar in T2 treatment was very good,which was beneficial to increase the content of aroma components in flue-cured tobacco.With the extension of transplanting time,the contents of Ca,Mg,P,K,Na,B,Mn,Cu,Fe and Zn in tobacco leaves increased first and then decreased.At 60 days after transplanting,the contents of Ca,Mg,P and Cu reached the maximum in T4 treatment,increased by 3.78%,2.01%,1.99%and 10.51%respectively compared with CK2 treatment.4.Biochar regulates plant rhizosphere soil microecological environmentAfter biochar application,sucrase,urease,catalase and neutral phosphatase increased by 63.73-166.37%,117.52-174.03%,12.98-23.59%and 60.84-119.71%respectively compared with CK2 treatment.Correlation analysis showed that soil C/N ratio was the key factor affecting soil enzyme activity,and catalase activity was the key factor affecting bacterial community structure.5.Biochar can regulate the microbial community structure of rhizosphere soil of tobacco plants with bacterial wilt and reduce the disease index of tobacco plantsAfter biochar application,the diversity of bacterial ? increased,but the difference was not significant.Under the same fertilization conditions,bacterial a diversity and community richness of rhizosphere soil of bacterial wilt tobacco plants were lower than that of healthy soil;compared with healthy rhizosphere soil,the rhizosphere soil of diseased tobacco plants without biochar increased the abundances of Gemmatimonadetes(4.42%),Acidobacteria(8.59%),and decreased the abundances of Proteobacteria(2.08%)and Actinomycetes(1.16%).Biochar application can alleviate the bacterial abundance decline caused by bacterial wilt,reduce the relative abundance of pathogenic bacteria,and drive relative growth of functional promoting bacteria(Gemmatimonadetes),thus reducing the incidence rate of bacterial wilt,and preliminarily clarify the mechanism of biochar on the regulation of bacterial wilt disease in tobacco planting.