In view of ecological and economic costs of nitrogen (N) fertilization, measures are needed to enhance the sustainability of cereal production in tropical savannah regions. In this context, we investigated the combined effects of N application levels and inoculation with Azospirillum brasilense on maize plant biomass, grain yield, agronomic efficiency (AE), and N content in plants, focusing on the economic feasibility of maize production systems. The field trial involved four N application levels (control, low, average and high, i.e., 0, 50, 100 and 200 kg ha⁻¹, respectively, applied as sidedress) either with seed inoculation with A. brasilense or without inoculation. Inoculation with A. brasilense enhanced AE and N uptake in maize plants with increased shoot, root and grain N accumulation, augmenting grain yield by 7%. The increase in total N accumulation was mainly the result of improved N-NH₄⁺ accumulation in plant roots and shoots. Our results showed that it is possible to reduce the N fertilization level by 50% while increasing the operating profit by 11% with A. brasilense inoculation. Additionally, when inoculation was performed in the presence of a high N level, the operating profit was 11% higher than that for the same N level in the absence of inoculation. Therefore, in view of the low economic cost, ease of application, and high probability of a positive response by maize crops, even in the presence of different N application levels, inoculation with A. brasilense has the potential to be a key technology for improving plant-soil N management, leading to more sustainable maize production under tropical conditions.

鉴于施氮 (N) 施肥的生态和经济成本，需要采取措施提高热带稀树草原地区谷物生产的可持续性。在此背景下，我们研究了施氮水平和接种巴西固氮螺菌对玉米植物生物量、谷物产量、农艺效率 (AE) 和植物中氮含量的综合影响，重点关注玉米生产系统的经济可行性。田间试验涉及四种N施用水平（对照、低、平均和高，即分别作为配施施用的0、50、100和200 kg ha ^{-1 ），其中种子接种有}A. brasilense或没有接种。接种A. brasilense增强玉米植株对 AE 和 N 的吸收，增加茎、根和籽粒 N 积累，使籽粒产量增加 7%。总氮积累量的增加主要是植物根部和芽中N-NH ₄ ^{+积累量增加的结果。}我们的研究结果表明，通过接种A. brasilense可以将 N 施肥水平降低 50%，同时将营业利润提高 11%。此外，当在高氮水平下进行接种时，营业利润比在没有接种的相同氮水平下高出 11%。因此，鉴于经济成本低、施用方便、玉米作物产生阳性反应的可能性高，即使在不同施氮水平的情况下，接种A. brasilense有可能成为改善植物-土壤氮管理的关键技术，从而在热带条件下实现更可持续的玉米生产。