Márcia Vitória Santos

Levantamento fitossociológico em pastagens degradadas sob condições de várzea

An assessment was carried out of two contingently flooded low land areas, located at the Experimental Farm of Leopoldina, owned by Empresa de Pesquisa Agropecuaria de Minas Gerais (EPAMIG)-Brazil-MG. Area 1 (3 ha) was cultivated with Angola-grass (Brachiaria mutica) pasture, not well managed and without any weed control for more than 10 years. Area 2 (5 ha) was occupied by Setaria grass (Setaria anceps cv. Kazungula) pasture which had been established in the previous rainy season, with forage being affected by the slow growth of the plants. For the phyto-sociological study, the inventory square method was applied through a square of 1,0 m2, randomly placed 19 times in area 1 and 41 times in area 2. The species found were identified and recorded. In the Angola-grass pasture, 27 species were identified, distributed in 11 families; in the Setaria grass pasture, 34 species were identified, distributed in 13 families. The most representative families in number of species were: Poaceae (11); Asteraceae (6); Papilionoideae (5); Malvaceae and Euphorbiaceae (4). The most frequent species were: Cynodon dactylon, Sida rhombifolia, Cyperus esculentus, Mimosa pudica, Senna occidentalis, Setaria anceps cv. Kazungula and Paspalum urvillei. In general, both areas were infested with weeds, including toxic, spinescent and rather unpalatable plants, reducing the animal support capacity of the pastures and preventing adequate utilization of the areas by the cattle.

Efficacy and Persistence of Herbicides in Pasture Soils

This work aimed to evaluate the efficacy of the herbicides 2,4-D + picloram (Tordon); fluroxypyr + picloram (Plenum) and triclopyr (Garlon) in the control of Schinus terebintifolius and Eupatorium maximilianii, which are important weeds in pastures. The experiment was developed in a pasture of Melinis minutiflora, arranged in a randomized complete block design, with four replications, distributed in a factorial scheme (3x4+1), using two commercial mixtures and herbicide applied at four rates: 2,4-D + picloram (360 + 96 g ha -1 ; 720 + 192 g ha -1 ; 1.080 + 288 g ha -1 ; 1.440 + 384 g ha-1); fluroxypyr + picloram (120 + 120 g ha-1; 240 + 240 g ha-1; 380 + 380 g ha-1; 480 + 480 g ha -1 ) triclopyr herbicide: 240; 480; 720 and 960 g ha -1 plus a control without herbicide. Intoxication in the pasture was evaluated at 7 and 15 DAA (Days After Application) and weed control at 60 and 180 DAA. The residue in the soil was evaluated through bioassay, in pots in the greenhouse, with soil samples collected in the experimental plots at depths of 0-10 and 10-20 cm, 10, 40, 70, 120, 180 and 360 DAA, with Cucumis sativus used as test plant. Controls over 90% of Schinus terebintifolius and Eupatorium maximilianii were obtained 180 DAA, respectively, as follows 2.78 and 2.46 L ha-1 on Tordon; 1.97 and 2.02 L ha-1 on Plenum; and 1.23 and 1.44 L ha -1 on Garlon. Residues in the soil were verified until 360 DAA for herbicide commercial mixtures containing picloram in their formulation. Triclopyr herbicide residue was verified only at 10 DAA, indicating short persistence in the soil.

Bromatological and microbiological characteristics of sugarcane silages treated with calcium oxide

It was evaluated the addition of calcium oxide (0; 0.5; 1.0; 1.5; and 2.0% of dry matter) effect on the chemical composition and ruminal degradability of the dry matter and neutral detergent fiber, on the losses of dry matter, and on the microbial population in sugar cane silages. A design with five levels of calcium oxide and three replications was used. All the variables were influenced by the addition of calcium oxide in the silages, except the composition in acid detergent insoluble protein, water soluble carbohydrates and lignin. The dry matter content and pH linearly increased while the contents of organic matter, hemicellulose and crude protein linearly decreased with the levels of calcium oxide. Neutral detergent fiber corrected for ashes and protein and acid detergent fiber were adjusted for the quadratic models with calculated minimal values of 33.3 and 22.5% for the levels 1.73 and 1.49% of calcium oxide, respectively. The in vitro digestibility of the dry matter and the content of amoniacal nitrogen adjusted to quadratic models with maximal levels of 80.1% and 9.1% for the levels of 1.8 and 0.7% of calcium oxide, respectively. The minimal production of gas (3.18%) was observed at the level of 1.39% of calcium oxide. Production of effluent and recovery of dry matter of the ensiled mass showed a reduction and a linear increase, respectively, with addition of calcium oxide. The highest lactic acid bacterial population was observed in the silage treated with 1.5% of calcium oxide. The addition of calcium oxide increased degradability of the soluble fraction of the dry matter, which was higher than 50% and reduced the non- degradable fraction of the neutral detergent fiber. Addition of calcium oxide level higher than 1.0% in the sugar cane during ensilage improves in vitro dry matter digestibility and the recovery of dry matter, increases populations of lactic acid bacteria and reduces production of yeasts.

Deposição de serapilheira e de nutrientes no solo em Sistema Agrossilvipastoril com eucalipto e acácia

RESUMO – Este estudo teve como objetivo avaliar o efeito do componente arboreo no aporte de serapilheira e de nutrientes em dois Sistemas Agrossilvipastoris, sendo o sistema 1: milho (Zea mays) + eucalipto (hibrido – Eucalyptus grandis x E. urophylla) + acacia (Acacia mangium) + braquiaria (Brachiaria decumbens); e o sistema 2: milho + eucalipto + braquiaria, que foram comparados com monocultivo de pasto, em Vicosa, MG. A serapilheira do componente arboreo e da forrageira foi coletada mensalmente, a partir dos 34 meses apos a implantacao, no periodo de outubro de 2010 a setembro de 2011, em distâncias a partir das linhas centrais do plantio das arvores, que consistiram nos subtratamentos: 1, 3 e 6 m; e realizadas a analise e quantificacao de nutrientes: N, P, K, Ca, Mg e S. A deposicao da serapilheira da forrageira foi superior no monocultivo de pasto. Entretanto, a maior deposicao de serapilheira total (forrageira + componente arboreo) foi observada em ambos os sistemas agrossilvipastoris, comprovando a influencia positiva do componente arboreo no incremento de material vegetal depositado sobre o solo. A distância da linha de plantio das arvores tambem influenciou a deposicao, que foi maior a 1 m, seguida das distâncias 3 e 6 m. Com excecao do P, os sistemas agrossilvipastoris depositaram maior quantidade de nutrientes por meio da serapilheira, destacando-se o sistema com acacia, que promoveu maior deposicao de N. O componente arboreo, a especie leguminosa e a distância da linha de plantio das arvores dos sistemas agrossilvipastoris influenciaram a deposicao de serapilheira e de nutrientes no solo, indicando a potencialidade desses sistemas para recuperacao e manutencao de pastagens degradadas. Palavras-chave: Sistemas agroflorestais; Ciclagem de nutrientes; Leguminosas. LITTER FALL AND NUTRIENT DEPOSITION ON SO IL IN AN AGROSILVOPASTORAL SYSTEM WITH EUCALYPT AND ACACIA

Controle de Brachiaria brizantha, com uso do glyphosate, na formação de pastagem de Tifton 85 (Cynodon spp.)

This study aimed to evaluate glyphosate efficiency in the control of Brachiaria brizantha, cv marandu, for Tifton-85 pasture formation. The experiment was carried out in the field in 10L capacity polyethylene pots, and arranged in a randomized block design, in a 2 x 8 factorial scheme, with two application times, eight glyphosate rates (0; 90, 180; 360; 720; 1,080; 1,440; and 1,800 g e.a. ha-1), and four replicates. Each plot had a vase with two B. brizantha cv. Marandu and two Tifton 85 plants. The first application time was before B. brizantha plant tillering, when the plants were 10cm high and the second one, when B. brizantha was around 20cm high and showed four or five tillers. For each application time, visual evaluations of B. brizantha control and intoxication in the Tifton85 plants were conducted at 15, 30 and 60 DAA (days of application). At 60 DAA, the plants were cut and dried in a greenhouse, and sprouts were evaluated at 60 DAC days after cut. Control percentage of 90% of B. Brizantha, at 60 DAA, was obtained with 133.60 g ha-1 in the first application and 365.63 g ha-1 in the second. At 60 DAA after the first and second application, respectively, low dosages of glyphosate (133.60 and 365.63 g ha-1), were observed to promote B. brizantha control with absence of sprouts at 60 DAC, and mild intoxication of Tifton 85 without influencing its yield. Due to the higher tolerance of Tifton 85 to glyphosate, it is possible to control B. brizantha by using low doses of glyphosate, without compromising Tifton 85 forage yield.

Morphogenesis of Tanzania guinea grass under nitrogen doses and plant densities

The objective of this work was to evaluate effects of nitrogen fertilization and plant density on morphogenesis of Tanzania guinea grass. It was used a random block design with 12 treatments and two replications in a 4 × 3 factorial arrangement, with four doses of nitrogen (N) (without N application, 80, 160 or 320 kg/ha.year) and three plant densities (9, 25 or 49 plants/m2). Harvest was performed at 25 cm from the ground when the canopy intercepted 95% of the incident light. Rates of leaf appearance and pseudostem elongation were positively and linearly influenced by nitrogen, whereas phillochron and leaf life span were influenced linearly and negatively. Leaf elongation responded positively to two factors, whereas leaf senescence rate and number of live leaves were not influenced by the factors evaluated. Number of total, basal and aerial tillers were greater at the density of 9 plants/m2 and at the nitrogen dose of 320 kg/ha.year. Nitrogen increases production of leaves and tillers in Tanzania guinea grass defoliated at 95% of light interception, but high density of plants reduces the number of tiller per bunch.

Fitossociologia de plantas daninhas em sistemas de integração de sorgo com braquiária sob diferentes formas de implantação da pastagem

Objetivou-se no presente trabalho avaliar o efeito da modalidade de semeadura de Brachiaria brizantha cv. Xaraes sobre a comunidade de plantas daninhas e a produtividade de Sorghum bicolor cv. BRS 160 no sistema de integracao lavoura-pecuaria. Os tratamentos foram constituidos da seguinte maneira: consorcio sorgo forrageiro com braquiaria semeada a lanco com incorporacao leve e sem incorporacao; consorcio sorgo forrageiro com braquiaria semeada em linha unica e em duas linhas na entrelinha da cultura anual; e testemunhas, representadas pelos monocultivos de sorgo, com e sem aplicacao de atrazine, e de braquiaria. Maior producao de massa seca das plantas daninhas foi observada nos tratamentos em monocultivo, sendo a especie Digitaria horizontalis a de maior valor de importância e maior cobertura do solo. Para os cultivos em consorcio, D. horizontalis obteve menores valores de importância e cobertura quando a semeadura da forrageira foi realizada a lanco com e sem incorporacao. A massa seca das plantas daninhas foi semelhante entre os tratamentos consorciados e o tratamento em monocultivo de sorgo com aplicacao de herbicida. As parcelas de sorgo em monocultivo que nao receberam aplicacao de herbicida apresentaram maior infestacao de plantas daninhas. Nos consorcios nao houve diferencas para os valores de massa seca de braquiaria entre os tratamentos, porem as modalidades de semeadura a lanco com e sem incorporacao apresentaram maiores estandes, demonstrando melhor eficiencia da semeadura a lanco para a formacao da pastagem. Contudo, essa forma de semeadura leva ao desenvolvimento de plantas da forrageira proximo a linha de cultivo do sorgo, o que pode comprometer a producao dessa cultura pelo aumento da competicao. A forma de semeadura de B. brizantha interfere na produtividade do sorgo e na infestacao de plantas daninhas.

Efeito da época de semeadura de Brachiaria decumbens e de dessecantes em pré-colheita sobre o rendimento de grãos do feijoeiro e a biomassa forrageira em cultivo consorciado

Com o objetivo de avaliar a epoca de semeadura e os efeitos da dessecacao da Brachiaria decumbens em consorcio com duas cultivares de feijao (Phaseolus vulgaris L.), foi conduzido um experimento, em Coimbra, MG, em esquema fatorial envolvendo cultivares de feijao (Ouro Vermelho e VC3), duas epocas de semeadura da braquiaria (simultânea e na capina do feijao), tres tipos de dessecacao (sem dessecacao, Carfentrazone-ethil e Paraquat), mais dois tratamentos adicionais: os monocultivos do feijao e da braquiaria, em DBC com quatro repeticoes. O feijoeiro foi plantado com semeadora mecanizada, no espacamento de 0,50 m entre linhas. A braquiaria foi semeada com semeadora manual, sempre nas entrelinhas do feijoeiro. Foram avaliados o estande final de plantas e o rendimento de graos do feijao e a biomassa seca da parte aerea da braquiaria, aos 15 e aos 60 dias apos a colheita do feijao. Concluiu-se que a cultivar Ouro Vermelho e mais indicada para o consorcio com B. decumbens na safra das aguas que a VC3. O retardamento da semeadura da braquiaria proporciona maior rendimento de graos do feijao, mas prejudica a producao de biomassa seca da forrageira. A dessecacao na pre-colheita nao influencia a produtividade do feijoeiro, mas, quando e realizada com paraquat, prejudica a producao de biomassa seca da forrageira.

Levantamento fitossociológico e produção de forragem em pasto de capim-gordura

Este estudo foi realizado com o objetivo de efetuar o levantamento fitossociologico em um pasto de capimgordura (Melinis minutiflora P. Beauv.), que vinha sendo pastejado por bovinos de corte, ha mais de dez anos, sem estrategia de manejo definida. A pesquisa foi desenvolvida no campus da Universidade Federal de Vicosa, em Vicosa, MG. Para avaliacao das caracteristicas fitossociologicas e da massa seca das plantas daninhas e da forrageira, utilizou-se o metodo do quadrado inventario, aplicando-se um quadrado de 0,25 m 2 , lancado, ao acaso, 40 vezes, na pastagem, perfazendo uma area amostral de 10 m 2 . Em toda a area experimental, foram identificadas 31 especies e 12 familias botânicas, tendo como destaque as familias Poaceae, com oito especies, e Asteraceae, com sete especies. A forrageira cultivada M. minutiflora P.Beauv., corresponde a 24,26% da producao total de massa seca, entre especies levantadas na area. Estes resultados indicam estadio avancado de degradacao do pasto de capim-gordura, com elevada infestacao por plantas daninhas, inclusive especies consideradas toxicas, epinescentes e de alta competitividade com as forrageiras, o que o caracteriza como pasto de baixa capacidade de suporte. Palavras-chave: diversidade de especies, forrageiras, pastagem degradada, plantas daninhas.

Desempenho produtivo de vacas recebendo dietas com capim-elefante submetido a diferentes adubações e níveis de concentrado

Yield performance of cows fed diets with elephant grass subjected to dif ferent fertilization and concentrate levels The objectives of this work were to determine the total diet dry matter (TDDM) intake, milk production and milk composition, net energy for lactation (TNE) and total digestible nutrients (TDN) of elephant grass in the total diet. The elephant grass subjected to chemical (CF) and organic (OF) fertilization was mixed to the concentrate, at levels of 400, 500 and 600 g, in dry matter basis (DM). The treatments were arranged in a 6 x 6 Latin square, in a 2 x 3 factorial design (fertilizer x concentrate level). The average TDDM contents, in fed basis, and NDF, CP, Ca and P of the total diet, in DM basis, were different (P 0,05). Concentrate levels did not influence digestion of TDDM, MO and PB of total diet. NDF digestion decreased (P<.05) with increasing concentrate levels. Digestion of DM, OM