The search for sustainable agriculture has increased interest in using endophytic bacteria to reduce fertilizer use and increase stress resilience. Stress-adapted plants are a potential source of these bacteria. Some species of these plants have not yet been evaluated for this, such as pangolão grass, from which we considered endophytic bacteria as potential plant growth promoters. Bacteria from the root, colm, leaves, and rhizospheric soil were isolated, and 132 strains were evaluated for their in vitro biological nitrogen fixation, IAA and siderophores production, and phosphate solubilization. Each mechanism was also assessed under low N availability, water stress, and low-solubility Fe and P sources in maize greenhouse experiments. All strains synthesized IAA; 63 grew on N-free media, 114 synthesized siderophores, and 46 solubilized P, while 19 presented all four mechanisms. Overall, these strains had better performance than commercial inoculant in all experiments. Still, in vitro responses were not good predictors of in vivo effects, which indicates that the former should not be used for strain selection, since this could lead to not testing strains with good plant growth promotion potential. Their heterologous growth promotion in maize reinforces the potential of stress-adapted plant species as potential sources of strains for inoculants.

N deficiency is one of the significant causes of tropical pasture degradation, and including legumes may be a sustainable strategy to prevent pasture degradation in tropical environments. The objective of this study was to investigate the use of forage peanut (Arachis pintoi), butterfly pea (Clitoria ternatea), calopo (Calopogonium mucunoides) and stylosanthes (Stylosanthes sp.) intercropped with signal grass to determine soil biomass and microorganismal activity in a tropical subhumid zone. Soil sampling was performed at the legume rows and, three meters away from them and in the soil of pastures with single signal grass with or without an application of N-fertilizer, two years after legume implantation and during the dry and rainy seasons. The estimate of carbon and nitrogen of microbial biomass, C-CO2 emission, and soil metabolic quotient of each legume were compared between the dry and rainy seasons, at two distances and with both single signal grass treatments. Although the rainy season decreased soil basal respiration in all treatments, forage peanut (~332 mg kg-1), and butterfly pea (~280 mg kg-1) showed pronounced soil microorganismal biomass, surpassing 27% and 14% the estimate for single signal grass not fertilized, respectively. The soil microorganisms with forage peanuts and stylosanthes also emitted more C-CO2 (~1.0 mg kg−1 h−1) in the dry season, indicating an effective microorganismal activity in these soils, mainly due to the absence of disturbances, as noted in the low metabolic quotients in both climatic seasons (less than 1%).Keywords: Soil respiration rate; Silvopastoral system; Soil microbial activity; Pasture. Biomassa e atividade microbiana do solo em pastagem degradada de Brachiaria decumbens após implantação de leguminosas herbáceaResumoA deficiência de N é uma das principais causas da degradação de pastagens tropicais e a inclusão de leguminosas pode ser uma estratégia sustentável para prevenir a degradação de pastagens em ambientes tropicais. O objetivo deste trabalho foi investigar o uso de amendoim forrageiro (Arachis pintoi), cunhã (Clitoria ternatea L.), calopogônio (Calopogonium mucunoides Desv.) e estilosanthes (Stylosanthes sp.) consorciados com capim-braquiária para avaliar a biomassa e atividade microbiana do solo em uma zona subúmida tropical. A amostragem do solo foi realizada nas fileiras das leguminosas e a três metros de distância delas e no solo das pastagens com capim-braquiária com ou sem adubação nitrogenada, dois anos após a implantação da leguminosa e nas estações seca e chuvosa. A estimativa de carbono e nitrogênio da biomassa microbiana, emissão de C-CO2 e quociente metabólico do solo de cada leguminosa foram comparados entre as estações seca e chuvosa, em duas distâncias e com ambos os tratamentos de capim-braquiária. Embora a estação chuvosa tenha diminuído a respiração basal do solo em todos os tratamentos, o amendoim forrageiro (~332 mg kg-1) e a ervilha borboleta (~280 mg kg-1) apresentaram pronunciada biomassa microbiana do solo, superando em 27% e 14% a estimativa para capim-braquiária não fertilizada, respectivamente. Os microrganismos do solo com amendoim forrageiro e estilosante também emitiram mais C-CO2 (~1,0 mg kg−1 h−1) na estação seca, indicando uma atividade microbiana efetiva nestes solos, principalmente devido à ausência de distúrbios, como indicado pela baixa quocientes metabólicos em ambas as estações climáticas (menos de 1%).Palavras-chave: Taxa de respiração do solo; Sistema Silvipastoril; Atividade microbiana do solo; Pastagem.

Brazil is one of the largest grain producers worldwide, with yields heavily dependent on ecologically and financially expensive inputs. One possible approach to reduce these inputs is inoculation with plant-growth-promoting bacteria, whose large-scale use depends on a continual search for new genotypes for inoculant production. Several bacteria with potential for this have been isolated from plants that are more adapted to stressful environments. Thus, we aimed to evaluate the potential of pangolão grass (Digitaria eriantha cv. Suvernola) endophytic bacteria both in vitro and on maize growth. To this end, endophytic bacteria were isolated from pangolão grass of a tropical semiarid climate and a random subset of 80 strains was evaluated for biological nitrogen fixation, HCN, IAA and siderophore production and calcium phosphate solubilization, and later for maize growth promotion. All strains were positive for at least one of these in vitro growth promotion mechanisms and some strains increased maize plant height and root length, including some with better results than plants receiving commercial inoculants, confirming the potential of endophytic bacteria from stress-adapted plants. In vitro results had poor correlation with plant growth promotion, which indicates that the common practice of using these laboratory techniques as a pre-selection tool before a subset of strains is evaluated for plant growth promotion might result in the rejection of potentially interesting strains.

Water scarcity has a significant impact on global agriculture, particularly in semi-arid regions, hindering economic development. The use of recycled urban wastewater in agriculture is a sustainable practice; however, it is essential to assess its impact on soil carbon stocks and microbial activity. This study hypothesized that the use of wastewater in soil cultivated with forage cactus and amended with 8 or 12 tons of sorghum straw as soil cover could increase carbon stocks, microbial biomass, and microbial activity compared to bare soil, even after only 8 months. The experiment was conducted in a tropical semi-arid region of Brazil, based on a factorial design with different cactus intercropping systems and soil cover treatments under wastewater irrigation. Overall, soil carbon stocks did not increase significantly compared to the control, although they increased by approximately 21% over the study period. However, soil cover increased C-CO₂ emissions by 70% after 4 and 8 months. Microbial biomass carbon increased by 65% compared to the baseline (time 0), particularly in treatments with soil cover. Soil cover and consortium under wastewater irrigation improved microbial activity and biomass, even over a short experimental period, indicating a sustainable soil management strategy to enhance soil organic matter quality and microbial properties.