-This study was conducted in order to evaluate the selectivity of signal grass and congo grass, submitted to post-emergence herbicide application. The experiment was conducted under greenhouse conditions, in Diamantina, Minas Gerais state, and it was arranged in a randomized block design, with five replications. Treatments were set in factor scheme (8 x 2) + 2. Eight herbicides (nicosulfuron; clomazone; glyphosate; fluazifop-p-butyl + fomesafen; lactofen; fomesafen; fluazifop-p-butyl and mesotrione) were applied in doses recommended by the manufacturer on two fodder species: Brachiaria decumbens cv. Basilisk (signal grass) and Brachiaria ruziziensis (congo grass); in addition, there were two control samples without herbicide application, for a total of 18 treatments. The evaluated herbicides showed less intoxication on signal grass when compared to congo grass. Nicosulfuron and glyphosate promoted higher intoxication on both species when compared to the other herbicides. Glyphosate, fluazifop-p-butyl + fomesafen, fluazifop-p-butyl, mesotrione and nicosulfuron affected the ratio variable / maximum fluorescence (Fv/Fm) in both species, indicating an effect provided by these herbicides on the electron transport chain. Results demonstrated that signal grass and congo grass have higher susceptibility to glyphosate, fluazifop-p-butyl + fomesafen, fluazifop-p-butyl, mesotrione and nicosulfuron. congo grass shows higher susceptibility to the studied herbicides when compared to signal grass. Keywords

The aim of this work was to determine the persistence of auxinic herbicides applied on tropical pasture and toxicity for succeeding crops. The herbicides were applied in an area of dystrophic red‒yellow latosol with pasture infested of weeds. At 40, 80, and 280 days after application of herbicide, the soil samples were collected at depths of 0 to 20 cm. Soil with residues of 2,4-D, 2,4-D + picloram, triclopyr, and a soil without herbicide application were analyzed with six replicates. Seven crops were cultivated in these soils: cucumber (Cucumis sativus L.), velvet bean [Mucuna pruriens (L.) DC.], pigeon pea [Cajanus cajan (L.) Millsp.], alfalfa (Medicago sativa L.), lablab bean [Lablab purpureus (L.) Sweet], corn (Zea mays L.), and sorghum [Sorghum bicolor (L.) Moench]. The plants of cucumber, pigeon pea, and alfalfa were the most susceptible to the auxinic herbicide residues. However, the lablab bean was the only one among the dicot evaluated that showed tolerance to the 2,4-D + picloram residual when cultivated in soils at 280 days after application of herbicide. Corn and sorghum showed lower chlorophyll content in soils with 2,4-D + picloram residual up to 80 days after application of herbicide.

No abstract

Objetivou-se, com essa literatura, descrever de maneira sucinta os parâmetros referentes à morfologia, anatomia e fisiologia de plantas forrageiras cultivadas em sistema agrossilvipastoril, correlacionando com os principais mecanismos de produção. Através da avaliação das alterações morfológicas, anatômicas e fisiológicas que ocorrem em plantas sob irradiância reduzida pode acarretar seleção de espécies forrageiras mais adaptadas ao meio, demonstrando a importância significativa dos sistemas agrossilvipastoris que podem ser considerados soluções para problemas relacionados à conservação dos recursos naturais e forma sustentável de utilização das pastagens de baixa fertilidade natural. Os sombreamentos existentes nestes sistemas influenciam o crescimento da forrageira e modificam suas características agronômicas reduzindo o número de perfilhos, porém para trazer benefícios à pastagem, desde que o sombreamento seja moderado. Então pode ser constatado que plantas forrageiras cultivadas em sistemas agrossilvipastoris, em baixa luminosidade, conservam seus estômatos abertos, a fim de aumentar o escoamento dos gases para a realização da fotossíntese. De maneira geral, plantas forrageiras de clima tropical submetidas ao sombreamento apresentam grande vantagem de adaptações morfológicas, anatômicas e fisiológicas com elevados índices de produção de forragem.

O controle de gramíneas infestantes em pastagens ainda é um problema a ser solucionado no manejo das pastagens. Desse modo o uso de herbicidas comumente utilizados em pastagens foi estudado (glyphosate e fluazifop-p-butil) e suas doses determinadas para controle de Brachiaria decumbens (capim-braquiária) e toleradas pela B. ruziziensis (capim-ruziziensis), na formação de pastagens, a partir da intoxicação das mesmas pelos herbicidas. Utilizou-se o delineamento inteiramente casualizado, com cinco repetições, distribuídos no esquema fatorial (2x6), sendo dois herbicidas (glyphosate e fluazifop-p-butil) e seis doses desses herbicidas. As doses dos herbicidas foram equivalentes a 0,00; 0,25; 0,50; 1,00; 1,50; 2,00 vezes a dose comercial indicada pelos fabricantes para controle de gramíneas do gênero Brachiaria. Procedeu-se então avaliações de controle das plantas de capim-braquiária e nível de intoxicação das plantas de capim-ruziziensis, aos 07, 15, 21 e 30 dias após aplicação do herbicida (DAA), por meio de observações visuais, atribuindo-se notas de 0 a 100, para ambas as espécies. O glyphosate proporciona intoxicação de 100% em plantas de capim-braquiária e capim-ruziziensis, mesmo na menor dose de 90 g e.a. ha-1 de glyphosate, podendo ser utilizado com eficiência para o controle dessas espécies no início de desenvolvimento, já o fluazifop-p-butil proporciona intoxicação do capim-braquiária acima de 70%, nas plantas submetidas às doses a partir de 300 g ha-1 e de capim-ruziziensis a partir da dose de 100 g ha-1, demonstrando ser o capim-braquiária mais tolerante a essa molécula herbicida.

The effects of powder sugarcane molasses on silage of leuchena grass (Leucaena leucocephala

This paper aimed to evaluate the influence of management practices of marandu grass, at eucalyptus shading levels in a forest grazing system, on organic carbon (OC) and nitrogen (N) stocks, and on soil chemical characteristics in the Brazilian Cerrado. The experimental design adopted was entirely random with five repetitions. In the plots were allocated the environments with different light availability, and a treatment with marandu grass in full sun. The management of marandu grass pasture was distributed in the subplots with pre-pasture at 30, 40, 50, and 60 cm high. Evaluations were repeated in two crop cycles in year 1 and year 2. Soil chemical characteristics, OC and N stocks were analyzed. The management of marandu grass at 50 cm height in the forest grazing system provided higher levels of OC, N, organic matter in the soil and an increase in fertility, compared to monoculture pasture, with repercussions in two years. The integration of eucalyptus and marandu grass pasture contributes with greater stocks of OC and N in the soil strips closest to the tree row, due to greater nutrient cycling. Marandu grass in forest grazing systems with shading varying from 40 to 60% present greater efficiency and maintenance of soil chemical attributes, demonstrating greater sustainability compared to monoculture pastures.