Increasing nitrogen use efficiency (NUE) remains a crucial topic in contemporary agriculture. Inoculation with endophytic diazotrophic bacteria offers a potential solution, but the results vary with the N-fertilization regime. Here, we examined the efficacy of inoculation with Herbaspirillum seropedicae strain HRC54 in enhancing NUE and promoting the growth of Marandu palisadegrass with varying levels of N-urea (0, 25, 50, and 100 mg N kg soil⁻