Linking rhizosphere bacterial diversity and soil fertility in tobacco plants under different soil types and cropping pattern in Tanzania: A pilot study

Tobacco (Nicotiana tabacum L.), one of the major crop plants in Tanzania, cropping affects the level of soil fertility, but the reason has not been known. Plant rhizosphere plays an important role in affecting soil fertility through changing microbial composition. We planned a pilot study to understand the changes in microbial composition and soil nutrients in the rhizosphere soils of tobacco in three agro-ecological zone, namely Sikonge, Tabora and Urambo in Tanzania. This study assessed bacteriota composition using 16S rRNA sequencing and soil fertility in the rhizosphere of tobacco plants. The results showed that bacterial diversity in tobacco rhizosphere soils belonged to Proteobacteria phyla, associated significantly (p < 0.05) with solubilization of insoluble P, K and S. The solubilization of P, K and S in soils facilitates the availability of these nutrients to the tobacco plants (a heavy feeder crop) allows low levels of these nutrients in the soils for the subsequent crop. The Proteobacteria phyla also associated with an increase in soil N content through fixation. Therefore, bacteria diversity in tobacco rhizosphere influence solubilities of macronutrients (P, K, S) and quickly up taken by the tobacco plant and reduces their levels in soils, some bacteria involved in fixing N and increases total N in the soil.