The objective of this study was to assess the impact of Azospirillum brasilense in conjunction with nitrogen fertilization on structural, morphogenetic, yield-related, and chemical characteristics of Urochloa humidicola cultivated in the Amazon savannah. Treatments consisted of five nitrogen application rates (0, 50, 100, 150, and 200 kg ha-1), both with and without A. brasilense inoculation. The experiment was laid out in a completely randomized design with a 5×2 factorial arrangement, including four replications. The morphological composition of the pastures, morphogenetic and structural characteristics and chemical composition of the forage were evaluated. The utilization of A. brasilense, either alone or combined with nitrogen fertilization, did not influence the enhancement of forage yield. However, nitrogen fertilisation led to consistent increases in production, primarily through an increase in leaf and culm components and a reduction in the proportion of dead material in pastures. It also led to a linear increase in the proportions of NDF, ADF and CP in the forage. The use of A. brasilense does not alter the production and chemical composition of the forage, while nitrogen fertilization favors the management of pastures with U. humidicola grown in Amazonian savanna soil.

Objetivou-se neste trabalho avaliar modelos matemáticos comparando os parâmetros cinéticos na produção de gás in vitro em diferentes genótipos de capim-elefante. O delineamento foi inteiramente casualizados com três repetições com cincos tratamentos que foram os genótipos de capim-elefante (BRS Canará, Napier, Vruckwona, Cameroon e CNPGL 93-41-1) com idade de maturidade de rebrota aos 45 dias. O inóculo ruminal foi obtido através de dois bois Nelores machos inteiros mantidos em piquetes formados por Urochloa brizantha cv. Marandu, no período seco do ano. As incubações foram consecutivas mensurando as leituras de pressão de produção de gás realizadas em 2; 4; 6; 8; 10; 12; 19; 24; 36; 48; 60; 72; 84 e 96 horas. A determinação da cinética de produção de gases foi testada dois modelos não lineares que são: Monomolecular e o Logístico. Onde foram estimados o volume final ( /mL), taxa média de produção de gás ( /h-1), o tempo de latência de produção ( /h) e o tempo médio de digestão (TMD/h-1). Os modelos testados, o Logístico com latência apresentou melhor ajuste para todos os perfis das cultivares. A cultivar BRS Canará e CNPGL 93-41-1 e Wrockwona, apresentam estimativas dos parâmetros cinéticos de produção de gás semelhantes e melhores aos comparados das cultivares Cameroon e Napier.

Resumo O objetivo com este estudo foi avaliar os efeitos do Azospirillum brasilense associado ao uso da adubação nitrogenada sobre as variáveis estruturais, morfogênicas, produtivas e químicas de Urochloa humidicola cultivada na savana Amazônica. Os tratamentos foram constituídos de cinco doses de nitrogênio (0, 50, 100, 150 e 200 kg ha-1) associadas a inoculação ou não de Azospirillum brasilense, em delineamento inteiramente casualizado, em esquema fatorial 5x2, com quatro repetições. Foram avaliadas as composições morfológicas dos pastos, as características morfogenéticas e estruturais, e a composição química da forragem. O uso de Azospirillum brasilense, isolado ou em associação com a adubação nitrogenada, não foi determinante para o aumento de rendimento de produção da pastagem. No entanto, a adubação nitrogenada proporcionou ganhos lineares em produção, principalmente no aumento dos componentes folha e colmo, e redução na proporção de material morto nos pastos, bem como aumentou linearmente as proporções de FDN, FDA e PB da forragem. O uso de A. brasilense não altera a produção e a composição química da forragem, enquanto a adubação nitrogenada favorece o manejo de pastos com U. humidicola cultivados em solo da savana Amazônica.

Agricultural soils are major sources of nitrous oxide (N₂O) and important regulators of methane (CH₄), but field interpretation remains difficult because observed fluxes depend on the coincidence of system type, hydrothermal conditions, substrate availability, and microbial context. This challenge is especially relevant in tropical production landscapes where integrated crop-livestock systems are increasingly promoted, yet side-by-side field datasets that jointly measure greenhouse-gas fluxes, mineral nitrogen, and microbial indicators remain limited. We compared an integrated crop-livestock system, a long-term monoculture pasture, and native vegetation in the Atlantic Forest biome of Brazil over two years. We quantified N₂O and CH₄ with static chambers, measured soil temperature, water-filled pore space, ammonium, nitrate, and qPCR abundance of nitrogen-cycle marker genes, and summarized patterns with phase-wise comparisons, correlation analysis, and principal component analysis. N₂O varied strongly through time, with seasonal totals ranging from 0.13 to 1.72 kg N₂O-N ha⁻¹, but cumulative values did not differ among systems. CH₄ showed clearer system separation: annual balance was negative in the monoculture pasture and positive in native vegetation and the integrated crop-livestock system. Marker-gene abundances, particularly AOA and nirK, more consistently separated native vegetation from managed systems than did mineral N alone, while ordination summarized a dominant contrast between native vegetation and managed systems and a second pattern associated with hydrothermal variation. These results show that, in the studied landscape, CH₄ balance differentiated systems more strongly than cumulative N₂O and that flux variability was best interpreted from the joint context of hydrothermal conditions, mineral nitrogen, and selected microbial indicators.

Nitrogen fertilization plays a central role in the intensification and sustainability of tropical pasture systems by influencing forage production, animal performance, and greenhouse gas (GHG) emissions. Although the individual components of these systems have been extensively studied, studies that simultaneously integrate soil nitrogen processes, forage responses, animal performance, and environmental outcomes within a unified framework remain scarce in the literature. This structured narrative review aimed to synthesize current knowledge on the role of nitrogen in tropical pastures, addressing soil–plant–animal–environment interactions with a focus on nitrogen use efficiency, productivity, and GHG emissions. Studies were selected from Google Scholar using keywords related to nitrogen fertilization, tropical forages, GHG emissions, and animal performance, prioritizing research conducted with C4 forage species. The reviewed evidence demonstrates that nitrogen fertilization consistently increases forage accumulation, tillering, crude protein concentration, stocking rate, and animal productivity per unit area; however, nitrogen recovery efficiency decreases at high application rates. The timing of nitrogen application, dose splitting, and the choice of nitrogen source are key management strategies to reduce N losses through volatilization, leaching, and gaseous emissions, improving nitrogen use efficiency in tropical pasture systems. Future studies should focus on providing integrated answers that simultaneously consider soil, plant, animal, and environmental components, in order to support more efficient and sustainable nitrogen management in tropical livestock systems.