The growing need for the use of clean energy has led society to seek alternatives to fossil fuels in order to less pollute the environment. Sugarcane has been known to produce enough biomass and to have associative microorganisms, such as plant growth-promoting bacteria (PgPB), which have the potential to improve the yield of crops. The objective of this study is to evaluate the efficiency and the isotopic dilution of 15 N of microbial inoculants containing endophytic diazotrophic bacteria, individually inoculated and in mixture, on productivity, technological quality and biological nitrogen fixation (BNF) of sugarcane variety RB92579. The experiment was conducted for three consecutive years, comprising different crop cycles, in a completely randomized block design with four replications. The evaluations were at 11 months after planting for plant-cane, and at 12 months after cutting for ratoon cane and second ratoon cane. The contribution of BNF by 15 N natural abundance technique to inoculated treatments ranged from 18% to 57.31%. This study showed that no strain promoted the improvement on yield and biological nitrogen fixation during the three cycles of sugarcane (plant-cane, ratoon cane and second ratoon cane). However, industrial characteristics of sugar cane can be affectd by PGPB inoculation.

Studies evaluating the structure and diversity of bacterial communities in arid environments including the rhizosphere of local and adapted plant species are important. Therefore, we used a sequencing of the 16S ribosomal RNA gene for describing the structure and diversity of soil bacterial community in three zones: Agreste, Transition and Sertão. The bacterial community was clustered in 9,838 OTUs in Agreste, 8,388 OTUs in the transition, and 14,849 OTUs for Sertão. Among the most abundant phyla, Proteobacteria and Acidobacteria were abundant in Agreste and Sertão, respectively, while Actinobacteria were abundant in Transition and Sertão. Specifi c taxa of Proteobacteria, in Agreste, and Actinobacteria, in Sertão, exhibited differences according to biotic and abiotic conditions. Thus, the structure and diversity of bacterial community were different in these areas and were infl uenced by environmental and soil conditions.

No abstract