Agronomic Efficiency of a New Liquid Inoculant Formulated with a Mixture of Azospirillum brasilense Strains Ab-V5 and Ab-V6 in Corn (Zea mays L.)

Nitrogen fertilization is a critical factor in maize (Zea mays L.) production, as nitrogen is often the primary limiting nutrient. The use of microbial biostimulants has emerged as a promising strategy to enhance nitrogen use efficiency. This study assessed the field performance of an industrially produced inoculant (Nodusoja™), formulated with Azospirillum brasilense strains Ab-V5 and Ab-V6, under contrasting soil and climatic conditions. The aim of this study is to assess the grain yield of maize cultivated in different edaphoclimatic conditions using the biostimulant, together with lower doses of topdressing fertilization. Field experiments were conducted across double cropping seasons in Sete Lagoas, Minas Gerais (19°28′ S; 44°15′ W), and Palmas, Tocantins (10°8′ S; 48°19′ W), Brazil, during the 2018, 2019, and 2021 harvests. Evaluated parameters included grain yield, shoot dry mass, and nitrogen content. The most pronounced effects were observed on productivity, with maximum grain yields of 8.76 and 9.05 t·ha−1 recorded in the 2019 season, under inoculation without topdressed N and inoculation with 50% of the recommended N dose, respectively. By contrast, uninoculated treatments with 20, 60, and 120 kg N·ha−1 yielded 6.41, 7.13, and 7.49 t·ha−1, respectively. Statistical analyses demonstrated that inoculation with strains Ab-V5 and Ab-V6 increased maize grain yield by up to 40% when combined with 50% of the recommended nitrogen fertilization. These findings highlight the potential of Azospirillum-based inoculants to improve N use efficiency and reduce dependence on synthetic fertilizers in maize cultivation.