Reducing Nitrogen Fertilizer Dependency in Tropical Pastures Through <i>Azospirillum Brasilense</i> and <i>Pseudomonas Fluorescens</i> Coinoculation

Coinoculation with Azospirillum brasilense and Pseudomonas fluorescens was associated with maintained forage productivity under reduced nitrogen (N) fertilizer rates in tropical pastures. This hypothesis was evaluated in a 2‐year field experiment conducted over two consecutive growing seasons (2022 and 2023) the State University of Goiás, São Luís de Montes Belos, Goiás, Brazil, using Mavuno grass ( Urochloa hybrid cv. Mavuno). Eight treatments were evaluated, combining microbial inoculation and N fertilizer (urea) application: A. brasilense (AZO); A. brasilense and 50 kg ha −1 N (AZO + N50); P. fluorescens (PSD); P. fluorescens and 50 kg ha −1 N (PSD + N50); A. brasilense and P. fluorescens (AZO + PSD); A. brasilense and P. fluorescens and 50 kg ha −1 N (AZO + PSD + N50); synthetic N application at 100 kg ha −1 (N100); and a control with no inoculation or N application. The PSD + N50 and AZO + PSD + N50 treatments resulted in the highest forage yields (8.51 and 9.35 Mg ha −1 , respectively; p &lt; 0.001), and these responses were consistent across both growing seasons. Notably, the 50% reduction in N fertilization maintained forage yields comparable to those obtained with full N fertilization (N100). These findings suggest that coinoculation with A. brasilense and P. fluorescens allows forage productivity to be maintained under reduced N fertilizer rates in tropical pastures, indicating potential to decrease reliance on synthetic fertilizers. The observed responses reflect the combined effect of microbial inoculation and moderate N supply, highlighting improved N use efficiency under coinoculation.