Under shade, tiller population leaf area and forage mass index were higher in the second year than in the first. Forage neutral detergent fiber value was higher at full sunlight than in the shade, while the crude protein content and in vitro dry matter digestibility were higher under the trees. Moderate shading increases crude protein and reduces neutral detergent fiber, therefore improving forage digestibility of grasses growing under trees.

Resumo -O objetivo deste trabalho foi avaliar, nas diferentes estações do ano, as características morfogênicas e estruturais e a produção de matéria seca de Brachiaria decumbens Stapf., cultivada em três graus de sombreamento: área de pastagem exclusivamente com B. decumbens, área próxima ao bosque e área com bosque de Eucalyptus grandis consorciado com leguminosas arbóreas (0, 18 e 50% de sombreamento, respectivamente). O delineamento experimental foi o de blocos ao acaso, com arranjo em parcelas subdivididas no tempo, com quatro repetições. O sombreamento induziu à elevação das taxas de alongamento de folhas e colmos. A taxa de aparecimento de folhas e o número de folhas vivas por perfilho não foram influenciados pelos graus de sombreamento. Em geral, no inverno houve redução nos valores das variáveis morfogenéticas e estruturais do dossel, assim como das taxas de produção de forragem, independentemente do sombreamento. A braquiária apresenta plasticidade fenotípica, em resposta às variações climáticas sazonais e aos níveis de sombreamento ambiental, o que confere a essa espécie elevado potencial para uso em sistemas silvipastoris.Termos para indexação: Brachiaria decumbens, morfogênese, perfilhamento, sistema silvipastoril, taxa de alongamento de folhas, taxa de aparecimento de folhas. Growth of signalgrass influenced by shading levels and season of the yearAbstract -The objective of this work was to evaluate, in different seasons of the year, the morphogenetic and structural traits and dry matter production of Brachiaria decumbens Stapf., established under three shading conditions: exclusive B. decumbens pasture, area distant 12 m from trees, and area under trees cultivated with Eucalyptus grandis mixed with leguminous trees (0, 18 and 50% shading level, respectively). The experimental design was the randomized blocks, in a split plot array in time, with four replications. Shade caused an increase of leaf and stem elongation rates. Shading levels have not influenced leaf appearance rates and leaf number per tiller. Morphogenetic and structural traits and herbage production rates reduced during winter, independently of shading level. Signalgrass presents phenotypical plasticity and responded to seasonal climatic variations and shade conditions; therefore, it has a good potential to be used in silvipastural systems.

Panicum maximum is important for cattle production in tropical regions, and it responds well to nitrogen (N) fertilization. Many cultivars have exhibited potential for use in silvopastoral systems, although there is limited information on how different levels of N can influence plant growth and nutritive value under shading. Morphogenetic and structural traits, biomass production and nutritive value of two P. maximum cultivars (Tanzânia and Massai) were investigated under three shading levels (0, 37 and 58%) and four N rates (0, 50, 100 and 150 mg N dm À3 ). Plants were grown in pots under shade. Leaf and stem elongation rate and leaf blade length increased with shading and in response to N. Tiller density was reduced with shading, but showed a linear increase fashion with N under full sun and moderate shading. Under intense shading, the tillering showed a quadratic response to N. Plant biomass production increased linearly with N under full sun and moderate shade, but it increased quadratically under intense shade. Crude protein (CP) content increased with shade and N and was greater for Tanzânia than Massai under shade. Contents of NDF and ADF were greater for Massai than Tanzânia. Acid detergent insoluble protein was reduced in Tanzânia under shade, but it increased for Massai. It is suggested that the positive shading effect on CP content may not result in increased nutritional value. Although N fertilization was important for increasing biomass production under full sun and moderate shade, it should be avoided under intense shading.

Resumo -Os objetivos deste trabalho foram avaliar os efeitos de árvores dispostas em renques sobre as características produtivas e nutricionais de Urochloa decumbens e identificar a distância média, na qual ocorre o melhor aproveitamento do sombreamento moderado, em um sistema agrossilvipastoril. Os tratamentos consistiram em distâncias dos pontos de observação ao renque das árvores (0, 3, 6, 9, 12 e 15 m) e foram distribuídos em blocos ao acaso, com quatro repetições. A densidade de perfilhos e a massa e a taxa de acúmulo de forragem e a composição química do pasto foram avaliadas. A densidade de perfilhos, a massa e a taxa de acúmulo de forragem aumentaram com a distância do renque, com valores máximos de 392 perfilhos m -2 , 1.347 kg ha -1 e 30,1 kg ha -1 por dia, respectivamente, a 9,1, 10,4 e 8,8 m de distância. Os teores de fibra em detergente neutro não variaram com a distância, enquanto os de fibra em detergente ácido e os de lignina variaram, mas sem um padrão definido de resposta. Os teores de proteína bruta diminuíram quadraticamente com a distância do renque e apresentaram valor máximo sob a copa das árvores (9,8%) e mínimo a 13,5 m de distância (6,5%). A região entre 7 e 10 m de distância do renque apresentou maior benefício da sombra moderada sobre as características do pasto.Termos para indexação: Brachiaria decumbens, Urochloa decumbens, fibra em detergente neutro, massa de forragem, perfilhamento, proteína bruta, sombreamento. Productive and nutritional traits of pasture in an agrosilvopastoral system, according to the distance from treesAbstract -The objectives of this work were to evaluate the effects of trees arranged in rows on yield and nutritional characteristics of Urochloa decumbens and to identify the average distance in which there is a better use of moderate shading in an agrisilvipasture system. The treatments consisted of distances from measure points to tree rows (0, 3, 6, 9, 12 and 15 m) and were distributed in randomized blocks, with four replicates. The tiller density, forage mass, forage accumulation rate and chemical composition of pasture were evaluated. The tiller density, forage mass and rates of forage accumulation increased with the distance from tree rows, reaching the highest values of 392 tillers m -2 , 1,347 kg ha -1 and 30.1 kg ha -1 per day, respectively, at 9.1, 10.4 and 8.8 m of distance. The contents of the neutral detergent fiber did not vary with distance, while the acid detergent fiber and lignin content varied, but without a clear pattern of response. The crude protein contents reduced quadratically with distance from tree rows and had the highest values under trees (9.8%) and the lowest at 13.5 m of distance (6.5%). The site of pasture, between 7 and 10 m of distance from the tree rows showed the highest benefits of moderate shading on pasture traits.

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-It was studied the effects of shading (0, 36 and 54%) and of four nitrogen doses (0, 50, 100 and 150 mg N/dm 3 of soil) on the morphogenetic traits and on the tillering of grasses of Brachiaria genus (B. decumbens, B. ruziziensis and B. brizantha cv. Marandu and cv. Xaraes), cultivated in pots with 5 kg substrate. It was used a complete random design, in a 3 × 4 × 4 factorial scheme with three replications. Nitrogen promoted increase in leaf appearance rate and in average leaf blade length, whereas shading increased stem elongation rate. Leaf elongation rate and tillering varied with the interaction among shading percentages and nitrogen doses. Shading increased response efficiency of leaf elongation rate to nitrogen doses, but reduced for tillering, evidencing priority existing tillering growth in detriment to appearance of new tillers when there is light restriction for the plants. Phenotypic adjustments, in response to light reduction, indicate that the studied grasses present tolerance to moderate shading.

The silvopastoral system (SPS) has been suggested to ensure sustainability in animal production systems in tropical ecosystems. The objective of this study was to evaluate pasture characteristics, herbage intake, grazing activity and milk yield of Holstein × Zebu cows managed in two grazing systems (treatments): SPS dominated by a graminaceous forage (Brachiaria decumbens) intercropped with different leguminous herbaceous forages (Stylosanthes spp., Pueraria phaseoloides and Calopogonium mucunoides) and legume trees (Acacia mangium, Gliricidia sepium and Leucaena leucocephala), and open pasture (OP) of B. decumbens intercropped only with Stylosanthes spp. Pastures were managed according to the rules for organic cattle production. The study was carried out by following a switch back format with 12 cows, 6 for each treatment, over 3 experimental years. Herbage mass was similar ( P > 0.05) for both treatments, supporting an average stocking rate of 1.23 AU/ha. Daily dry matter intake did not vary ( P > 0.05) between treatments (average of 11.3 ± 1.02 kg/cow per day, corresponding to 2.23 ± 0.2% BW). Milk yield was higher ( P < 0.05; 10.4 ± 0.06 kg/cow per day) in the SPS than in the OP (9.5 ± 0.06 kg/cow per day) during the 1 st year, but did not significantly differ ( P > 0.05) in subsequent years. The highest ( P < 0.05) values for herbage mass and milk yield were observed during the 3 rd year. In the SPS, with moderate shade (19% shade relative to a full-sun condition), the grass CP was higher ( P < 0.05) than in the OP, although the NDF content and digestibility coefficient were not modified. The animals spent more time ( P < 0.05) idling in the SPS than in OP. The higher legume proportion in the SPS was associated with the higher CP level in B. decumbens relative to the OP, which could explain the better ( P < 0.05) performance of the cows in silvopastoral areas during the 1 st year. However, during the 2 nd and 3 rd years, similarities in the legume percentages of both systems resulted in similar ( P > 0.05) milk yields. Low persistence of Stylosanthes guianensis was observed over the experimental period, indicating that the persistence of forage legumes under grazing could be improved using adapted cultivars that have higher annual seed production. The SPS and a diversified botanical composition of the pasture using legume species mixed with grasses are recommended for organic milk production.

RESUMO -Lâminas foliares e segmentos de colmo das gramíneas forrageiras capim-braquiária (Brachiaria decumbens), capimgordura (Melinis minutiflora) e capim-bermuda Tifton 85 (Cynodon sp) foram analisados quanto aos teores de proteína bruta (PB), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), celulose, hemicelulose e lignina e aos coeficientes de digestibilidade in vitro da matéria seca (DIVMS), em duas estações de crescimento: verão e outono. As lâminas, amostradas no momento da exposição da lígula e 20 dias após, situavam-se nas posições inferior e superior do perfilho. Os segmentos de colmo avaliados foram os situados imediatamente abaixo da lâmina da posição superior. O colmo de capim-bermuda Tifton 85 apresentou 8,5 unidades percentuais a menos de FDA que os das outras duas gramíneas, que não diferiram entre si. Os teores médios de PB de lâminas foliares exibiram pequena variação entre as espécies e diminuíram de 18,8 para 14,6%, após 20 dias de expansão, e de 18,9 para 14,5%, entre as lâminas das posições inferior e superior do perfilho. Lâminas da posição superior apresentaram mais elevados teores de FDN e lignina, independente da espécie, da estação e da idade. Os coeficientes de DIVMS reduziram a partir do momento da expansão da lâmina foliar e foram maiores em lâminas situadas no nível inferior e colhidas no outono. Entre as espécies, a DIVMS não variou em lâminas recém-expandidas, mas foi mais elevada em capim-bermuda Tifton 85 e mais baixa em capim-braquiária em lâminas com 20 dias após completa expansão. A DIVMS do colmo foi mais baixa em capim-braquiária (56,9%) e mais elevada em capim-bermuda Tifton 85 (59,6%) e capim-gordura (60,5%), que não diferiram entre si.Palavras-chave: Brachiaria decumbens, Cynodon sp, fibra em detergente neutro, Melinis minutiflora, proteína bruta, valor nutritivo Chemical Composition and In Vitro Digestibility of Leaf Blades and Stems of Forages Grasses, According to Level of Insertion on Grass Tiller, Age and Season of GrowthABSTRACT -Chemical composition and the in vitro dry matter digestibility were evaluated in blades and stems at two stages of development and two insertion levels on tillers of signalgrass (Brachiaria decumbens), molassesgrass (Melinis minutiflora) and tifton 85 bermudagrass (Cynodon sp), in two seasons of the year (summer and autumn). Lower and upper leaf blades were sampled from the tillers, on the day of ligule exposure and 20 days thereafter, and stems segments located below of the upper leaf blade. The crude protein contents of leaf blades showed little differences among the species, but decreased with development from 18.8 to 14.6% and level of insertion from 18.9 to 14.5% from lower to upper position. Leaf blades of higher insertion level had a greater neutral detergent fiber and lignin concentrations. The IVDMD decreased as leaf aged and exhibited greater values when situated at lower insertion level and sampled in the autumn. The IVDMD of old leaf blades were higher to tifton 85 bermudagrass and lower to signalgrass. The a...