Azospirillum brasilense in the Planting Furrow of Sugarcane to Minimize the Use of N Fertilizer

Sugarcane (<i>Saccharum</i> spp.) stands out in the context of sustainable agricultural production due to its versatility and energy potential. However, management challenges, such as nitrogen (N) fertilization associated with microbiological action, require improvement. In this context, the use of the bacterium <i>Azospirillum brasilense</i> has been studied as an alternative to reducing the use of mineral fertilizers. The objective of this study was to evaluate the application of <i>Azospirillum brasilense</i> in the planting furrow of sugarcane in terms of leaf diagnosis, nutrient uptake, yield and technological quality of the stalks, and total fresh and dry biomass of the aerial parts of the plants. The experiment was conducted under field conditions at two locations during the 2022/2023 growing season. The soils in Areas 1 and 2 were classified as medium-textured oxisol and sandy-textured oxisol, respectively. The experimental design was a randomized block design with four replications. The treatments were as follows: (T1) 28 kg ha^-1 of N; (T2) 14 kg ha^-1 of N; (T3) T2 + 0.2 L ha^-1 of inoculant; (T4) T2 + 0.4 L ha^-1 of inoculant; (T5) T2 + 0.6 L ha^-1 of inoculant; (T6) T2 + 0.8 L ha^-1 of inoculant. In Area 1, treatment T5 showed a total fresh biomass yield of the aerial parts that was 34% higher than T2. Total dry biomass, tillering, stalk yield, and technological parameters did not differ significantly between treatments in either area. In terms of nutrient uptake, treatment T5 consistently ranked among those with the highest averages for P, K, Ca, Mg, S, Fe, Mn, and Zn in both experimental areas. The dendrogram showed similar results between treatments T1 and T5. The application of 0.6 L ha^-1 of the solution containing <i>Azospirillum brasilense</i>, combined with 50% of the recommended N dose, increased total fresh biomass production. Total dry biomass, stalk yield, tillering, and technological variables of the crop were not affected by the presence of the bacterium.