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The usage of fertilizer with high nitrogen content in many countries, as well as its enormous surplus, has a negative impact on the soil ecological environment in agricultural system. This consumption of nitrogen fertilizer can be minimized by applying biochar to maintain the sufficient supply of nitrogen as nutrient to the near-root zone. This study investigated the effects of various amounts of biochar application (450, 900, 1350, and 1800 kg/hm2) and reduction of nitrogen fertilizer amount (10, 15, 20, and 25%) on the nutrients and microorganism community structure in rhizosphere growing tobacco plant. The microorganism community was found essential in improving nitrogen retention. Compared with conventional treatment, an application of biochar in rhizosphere soil increased the content of soil available phosphorus, organic matter and total nitrogen by 21.47%, 26.34%, and 9.52%, respectively. It also increased the abundance of microorganisms that are capable of degrading and utilizing organic matter and cellulose, such as Actinobacteria and Acidobacteria. The relative abundance of Chloroflexi was also increased by 49.67–78.61%, and the Acidobacteria increased by 14.79–39.13%. Overall, the application of biochar with reduced nitrogen fertilizer amount can regulate the rhizosphere microecological environment of tobacco plants and their microbial population structure, thereby promoting soil health for tobacco plant growth while reducing soil acidification and environmental pollution caused by excessive nitrogen fertilizer. [Display omitted] • Biochar can compensate N 2 fertilizer in supplying nutrient to rhizophere soil. • Biochar increases organic matter, phosphorus, and nitrogen in rhizophere soil. • Biochar favors a healthy rhizosphere microecological environment for plants. • Soil microbial diversity is enriched and provides active pool for plant nutrients. • Biochar with reduced N 2 fertilizer promote soil health with less acidification. [ABSTRACT FROM AUTHOR]

• The association between soil microbiota and tobacco quality was studied after applying fertilizers. • Biochar and high-carbon fertilizers increased the aroma through changing the soil microbiota. • Forty microbial phylotypes involved in tobacco growth and aroma increasement. Fertilizers promote plant growth through increasing plant nutrition and changing soil microbial communities. Here, the association between soil microbial communities and tobacco (Nicotiana tabacum L.) quality was investigated via high-throughput MiSeq sequencing and LC-GC-MS after applying fertilizers in purple soil. Biochar + chemical fertilizer (BC) and a high-carbon fertilizer + chemical fertilizer (HC) improved soil properties, including soil carbon and nitrogen pool, and increased the aroma of tobacco leaves by 19.38 % and 28.90 %, respectively. Biochar and high-carbon fertilizer increased the microbial diversity and altered their distribution, including improvement of unique bacteria, and Chao1 and Shannon indexes. Linear discriminant analysis identified 40 key phylotypes in response to fertilizers, including plant growth-promoting bacteria such as the genera Sphingomonas , Pseudomonas, Sphingobium, Haliangium and families Rhizobiaceae and Micrococcaceae, which are potentially associated with the quality of soil and tobacco plants. This study elaborates the mechanism underlying tobacco quality improvement by fertilizers and provides understanding of the methods for improving tobacco aroma. [ABSTRACT FROM AUTHOR]