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We assessed the impacts of forest-to-pasture conversion on the dynamic of soil microbial communities, especially those involved in the N-cycle, and their potential functions, using DNA-metagenomic sequencing coupled with the quantification of marker genes for N-cycling. We also evaluated whether the community's dynamic was reestablished with secondary forest growth. In general, the microbial community structure was influenced by changes in soil chemical properties. Aluminum and nitrate significantly correlated to community structure and with 12 out of 21 microbial phyla. The N-related microbial groups and their potential functions were also affected by land-use change, with pasture being clearly different from primary and secondary forest systems. The microbial community analysis demonstrated that forest-to-pasture conversion increased the abundance of different microbial groups related to nitrogen fixation, including Bacteroidetes, Chloroflexi, and Firmicutes. In contrast, after pasture abandonment and with the secondary forest regeneration, there was an increase in the abundance of Proteobacteria taxa and denitrification genes. Our multi-analytical approach indicated that the secondary forest presented some signs of resilience, suggesting that the N-related microbial groups and their potential functions can be recovered over time with implications for future ecological restoration programs.

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Several studies have shown that cover crop can increase common bean (Phaseolus vulgaris L.) yield. However, little is known about the influence of cover crop mixtures in association with topdressing N fertilization on common bean seed quality. We, therefore, evaluated the physiological quality of common bean seeds produced under cover crop residues and N fertilized in a no-till farming system. A 5 × 4 factorial experiment (cover crops and N rates) was performed under field conditions in Mato Grosso do Sul, Brazil. Single-specie and cover crops mixtures [pearl millet (Pennisetum glaucum), pearl millet-jack bean (P. glaucum; Canavalia ensiformis), pearl millet-pigeon pea (P. glaucum; Cajanus cajan), pearl millet-sunn hemp (P. glaucum; Crotalaria juncea), and pearll millet-velvet bean (P. glaucum; Mucuna pruriens)] were grown and common bean was planted in succession. Nitrogen fertilizer (50, 100, and 150 kg N ha-1) was topdressed applied to common bean at the V4 stage. At maturity, common bean plants were harvested, and physiological quality of seeds was assessed. The first germination count, final germination, germination speed index, accelerated aging, and N and protein concentration were influenced by cover crop residues and/or N rates (main effect). A cover crop × N rate interaction was observed for seedling dry biomass after germination and accelerated aging. All treatments produced seeds with high physiological quality. Although the cover crops showed variable results, the application of 100 kg N ha-1 in topdressing slightly improved seed quality attributes compared to the other N rate treatments. We conclude that addition of N fertilizer and cover crop treatments does not affect common bean seed quality to a large extent.

Em busca do aumento da produtividade do feijoeiro e de várias outras culturas de interesse econômico, foram realizadas inúmeras pesquisas utilizando reguladores de crescimento, hormônios e nutrientes, principalmente em aplicações foliares com a finalidade de acelerar o desenvolvimento da planta, melhorar suas características agronômicas, garantir maior sanidade e desempenho em campo. A aplicação de reguladores vegetais bioestimulantes com a finalidade de aumentar a produtividade das culturas é prática ainda pouco usual na agricultura. Assim, objetivou-se com este estudo avaliar o efeito da aplicação de bioestimulante vegetal associado a um indutor de resistência nos componentes de produção do feijoeiro. Foram utilizadas cinco doses de um bioestimulante (ácido indolbutírico, cinetina e ácido giberélico), sendo 0; 0,5; 1,0; 1,5 e 2,0 L ha-1, combinado com quatro doses de um indutor de resistência (0,5; 1,0; 2,0 e 3,0 L ha-1) no feijão comum, cv. IAC Formoso, em sistema de plantio direto. O experimento foi conduzido em Selvíria-MS, no ano agrícola 2013/14. O delineamento experimental foi em blocos casualizados, em esquema fatorial (5x4), com quatro repetições. Foram avaliados os componentes da produção e a produtividade de sementes da cultura. O indutor de resistência proporcionou maiores valores de matéria verde (52,08 g planta-1) e seca (17,29 g planta-1) de feijoeiro, respectivamente, nas doses de 2,04 L ha-1 e 2,15 L ha-1. A maior produtividade (3756 kg ha-1) foi obtida na dose de 0,78 L ha-1 do bioestimulante. O uso do bioestimulante vegetal pode ser uma alternativa viável para o aumento de produtividade do feijoeiro.