Formas de aplicação de Azospirillum brasilense na produção de forragem do campo nativo

Abstract

Azospirillum brasilense is a bacterium that can improve nitrogen utilization and stimulate root growth in grasses; however, studies on its use have focused on cultivated plants. This study aimed to evaluate the response of native grasslands to the use of this bio-input in two application methods: in-furrow and foliar spray.The experiment was conducted in a greenhouse at DZ/FAEM/UFPEL, using native grassland samples as monoliths placed in plastic trays. Three experimental treatments were applied in a randomized complete block design with four replications: 1) Control (no application of A. brasilense); 2) A. brasilense applied as a foliar spray; 3) A. brasilense applied in-furrow. The first forage evaluation cut was made when the average plant height reached 12 cm, with the plants being cut back to 6 cm. Subsequent cuts were made when the average plant height reached 10 cm, with the plants being cut back to 5 cm. For each cut, the green and dry forage mass, dry matter content, accumulation rate, and botanical composition of the sample components (grasses, legumes, and other species) were determined. The results were analyzed using analysis of variance and Tukey's mean comparison test (P≤0.05), considering the possible interaction between the three cuts and the three A. brasilense application methods. The results showed that both in the first cut and the sum of the three cuts, A. brasilense applied in the soil had greater efficiency in producing green forage mass and dry forage mass; however, these higher values were driven by a greater percentage of other species. A. brasilense applied via foliar spray resulted in shorter intervals between cuts compared to the control and soil-applied A. brasilense. The inoculation of A. brasilense in native grasslands, whether by foliar spray or directly in the soil, effectively altered the mass of forage produced. Direct soil inoculation influenced the frequency of species from different botanical families, increasing plant diversity. The use of A. brasilense on native grasslands is entirely feasible; however, due to the plant complexity in this environment, further studies should be conducted to detail its effects.