Promoting black oat and ryegrass growth via Azospirillum brasilense inoculation after corn and soybean crop rotation

Inadequate management of nitrogen fertilization, due to high costs, compromises the nutrition and productivity of winter forage plants, highlighting the need to adopt sustainable alternatives, such as using nitrogen-fixing bacteria. This research evaluated the growth promotion of black oat (Avena strigosa) and ryegrass (Lolium multiflorum) plants inoculated with Azospirillum brasilense rhizobacteria. The experiments were carried out over two consecutive harvests in Santa Maria, Brazil. The sowing density was 300 viable seeds per square meter for black oats and 100 viable seeds per square meter for ryegrass. A dose of 5 ml per kg of seeds from the consortium was used as an inoculant. Following sowing, the seeds were incorporated into the soil through light harrowing. At the beginning of tillering, 50 kg of N ha-1 was applied to create treatments with and without nitrogen. Plant emergence, plant height, number of leaves and tillers were evaluated. In the first year, an inoculation response was observed for the number of black oat plants emerged m-2. In the second year (corn residue), an inoculation response was observed for the number of leaves and height of black oats. Under soybean straw for oat leaf number and ryegrass tiller number. The current research highlights the effectiveness of inoculation with Azospirillum brasilense in promoting significant improvements in the morphological components of forage crops. Following corn, an increase in the number of leaves and tillers was observed, as well as in the height of black oats. Similarly, following soybeans, there was an increase in the number of black oat tillers and the number of ryegrass leaves. The results emphasize the importance of inoculation as an effective practice to enhance crop development and performance in agricultural systems, improving sustainability and productivity under soybean and corn residues.