J. F. Valentim

Crescimento de gramíneas e leguminosas forrageiras tropicais sob sombreamento

O objetivo deste trabalho foi avaliar o efeito de niveis de sombreamento artificial (0%, 30%, 50% e 70%) nas taxas de acumulo de materia seca de quatro gramineas (Brachiaria brizantha cv. Marandu, B. humidicola cv. Quicuio-da-amazonia, Panicum maximum cv. Massai e Paspalum notatum cv. Pensacola) e tres leguminosas forrageiras (Arachis pintoi cv. Belmonte, A. pintoi BRA-031143 e Pueraria phaseoloides), em Rio Branco, Acre. No periodo de novembro de 1999 a abril de 2001, foram realizados nove cortes para medicao das taxas de acumulo de materia seca. Os capins marandu e massai tiveram o melhor desempenho entre as gramineas, aliando boa tolerância ao sombreamento e alta capacidade produtiva, constituindo opcoes importantes na composicao de sistemas silvipastoris em areas com solos bem drenados. O quicuio-da-amazonia apresentou menor tolerância ao sombreamento, podendo ser usado em sistemas silvipastoris com baixa densidade arborea, em areas com chuvas bem distribuidas ou com solos mal drenados. O capim-pensacola apresentou alta tolerância ao sombreamento, mas baixa capacidade produtiva, nao sendo recomendado para a regiao. O Arachis pintoi cv. Belmonte demonstrou maior capacidade produtiva e tolerância ao sombreamento que as demais leguminosas.

Grazing management strategies for massaigrass-forage peanut pastures: 1. dynamics of sward condition and botanical composition

Este estudo foi realizado com o objetivo de avaliar a dinâmica e a composicao botânica de uma pastagem consorciada de capim-massai (Panicum maximum x P. infestum, cv. Massai) e amendoim forrageiro (Arachis pintoi Ac 01), manejada sob lotacao rotacionada em tres niveis de oferta diaria de forragem (9,0; 14,5 e 18,4% do peso vivo). A condicao da pastagem foi caracterizada em cada ciclo de pastejo, em termos de altura, massa de forragem e porcentagem de solo descoberto (pre e pos-pastejo). A composicao botânica da pastagem (graminea, leguminosa e invasoras) foi monitorada antes de cada periodo de ocupacao. Houve aumento linear da altura e da massa de forragem da pastagem com o incremento dos niveis de oferta de forragem (OF), observando-se maiores valores durante o periodo de maxima precipitacao. A porcentagem de solo descoberto, por sua vez, aumentou, principalmente no menor nivel de OF. A porcentagem de amendoim forrageiro aumentou progressivamente ao longo do periodo experimental, sobretudo nas pastagens mantidas com dossel mais baixo e mais aberto, criado com o uso de menores niveis de OF. No ultimo trimestre do periodo experimental, a leguminosa representou 23,5; 10,6 e 6,4% da massa seca da pastagem, respectivamente, do menor para o maior nivel de OF. Estes resultados sugerem que o amendoim forrageiro pode ser consorciado satisfatoriamente com o capim-massai, desde que a altura da pastagem na condicao pre-pastejo seja mantida abaixo de 65-70 cm para evitar o sombreamento excessivo da leguminosa.

Velocidade de estabelecimento de acessos de amendoim forrageiro na Amazônia Ocidental

O objetivo deste estudo foi avaliar a velocidade de estabelecimento de acessos de amendoim forrageiro (Arachis repens e Arachis pintoi), visando selecionar materiais adaptados aos sistemas intensivos de producao pecuaria do Acre. O delineamento experimental utilizado foi de blocos casualizados, com quatro repeticoes. Os tratamentos consistiram de dois acessos de A. repens, sete acessos e duas cultivares de Arachis pintoi identificados como promissores para as condicoes ambientais de Rio Branco, Acre. Foi adotado como testemunha A. pintoi cv. Amarillo. Os acessos Ap 65, Ap 39 e Ar 10, com desempenho semelhante as cultivares Amarillo e Belmonte, destacaram-se por apresentar excelente velocidade de estabelecimento, com indice de sobrevivencia das mudas e cobertura do solo superiores a 80% e comprimento dos estoloes acima de 85 cm, respectivamente, aos 50, 70 e 120 dias apos o plantio. Estes genotipos apresentaram produtividade de materia seca (MS) superior a 2.300 kg/ha, taxas de acumulo de MS iguais ou superiores a 20 kg/ha/dia e teor de proteina bruta variando entre 17,9 e 21,7%, no final do periodo de estabelecimento. Entre os quatro grupos heteroticos, o formado pelo acesso Ap 39 destacou-se dos demais, por apresentar valores medios a altos para todas as caracteristicas avaliadas, de acordo com a analise de agrupamento realizada pelo Metodo de Otimizacao de Tocher, com base na distância generalizada de Mahalanobis. Para que os materiais promissores possam ser recomendados para uso nos sistemas intensivos de producao de bovinos no Acre, devem ser desenvolvidos estudos adicionais com relacao a: 1) produtividade e qualidade de MS nos periodos chuvoso e seco; 2) ocorrencia de pragas e doencas; 3) producao de sementes; 4) adaptacao a solos de baixa permeabilidade; 5) compatibilidade com gramineas forrageiras e especies arboreas e arbustivas perenes; 6) producao animal e persistencia sob pastejo.

Árvores de Baginha (Stryphnodendron guianense (Aubl.) Benth.) em Ecossistemas de Pastagens Cultivadas na Amazônia Ocidental

The effect of isolated trees of baginha (Stryphnodendron guianense (Aubl.) Benth.) on some aspects of cultivated pasture ecosystems was studied in the Western Amazon of Brazil. Soil fertility, nutrients in the litter, soil water content, light transmission to sward, herbage availability, and chemical and morphological composition of the grasses (mixture of Brachiaria decumbens and B. brizantha cv. Marandu) were assessed under the canopies of baginha trees and in the adjacent open areas. The trees had positive effect on soil fertility, especially with respect to soil organic matter and nitrogen content, with the great deposition of litter rich in nitrogen being the main contribution. The shaded grass leaves were richer in N and K, and poorer in Ca, than the unshaded ones. The canopies of the baginha trees presented low density, allowing the transmission of 27% of the incoming photosynthetically active radiation at noon. The high ground cover (superior to 85%) and good herbage availability under the canopies of baginha trees, in addition to other attributes, confirms the potential of this legume as shade tree for pastures and as component of other kinds of silvopastoral systems in the humid tropics.

Seleção de genótipos de amendoim forrageiro para cobertura do solo e produção de biomassa aérea no período de estabelecimento utilizando-se metodologia de modelos mistos

Objetivou-se estimar parâmetros geneticos e selecionar genotipos de amendoim forrageiro para maior cobertura do solo e producao de biomassa aerea durante o periodo de estabelecimento nas condicoes ambientais do Acre. A area experimental foi estabelecida em dezembro de 2005. O experimento foi realizado em delineamento de blocos ao acaso com quatro repeticoes utilizando-se 21 genotipos de amendoim forrageiro, incluindo tres cultivares (Amarillo, Alqueire 1 e Belmonte). A selecao dos genotipos foi realizada considerando a cobertura do solo e a producao de materia seca. As avaliacoes de cobertura do solo foram realizadas entre janeiro e outubro de 2006, em intervalos de quatro semanas. A producao de materia seca foi mensurada 304 dias apos o plantio. Os componentes de variância foram estimados pelo Metodo da Maxima Verossimilhanca Restrita (REML) e os valores genotipicos foram preditos pelo metodo da Melhor Predicao Linear Nao-Viesada (BLUP), conforme metodologia dos modelos mistos. Verificou-se a presenca de variabilidade genetica para ambas as caracteristicas. As herdabilidades individuais foram de magnitude mediana, com valores de 0,36 a 0,58 para as caracteristicas cobertura do solo e producao de materia seca, respectivamente. A maior variabilidade entre os genotipos para cobertura do solo ocorreu entre a 12a e a 16a semana apos o plantio, indicando que esse intervalo e o mais adequado para a selecao de genotipos de cobertura mais rapida do solo. Os valores genotipicos para producao de materia seca variaram de 1.609 a 4.132 kg/ha para os genotipos BRA 015083 e BRA 040550, respectivamente. Os genotipos selecionados para maior cobertura do solo e producao de biomassa aerea durante o periodo de estabelecimento foram Belmonte, Amarillo, BRA 040550, BRA 039187, Alqueire 1, BRA 039799 e BRA 035033.

Desempenho de doze espécies arbóreas nativas e introduzidas com potencial de uso múltiplo no estado do Acre, Brasil

The objective of this study was to evaluate the performance of tree species with multiple use potential, in the local environmental conditions of the western Brazilian Amazon, in order to recommend these species as components of agroforestry systems and for reclamation of degraded areas. The experiment was established at the Experimental Station of Embrapa Acre, with 12 native and introduced species, using 1.5 by 1.5 m spacing between rows and plants. The experimental design was a randomized complete block, with four replications and five plants in each replication. The evaluations at four and a half years after planting showed that: a) all species presented survival indexes above 80%, with exception of Cedrela odorata (75%), Aspidosperma vargasii (65%) and Spondias lutea (65%); b) the mean annual increment in total height was greater in Acacia mangium (2.91 m) and Acacia pollyphylla (2.66 m), followed by Leucaena leucocephala, Calycophyllum spruceanum and Gliricidia sepium, with means of 2.38 m, 1.56 m and 1.40 m, respectively; c) the mean annual increment in basal diameter was greater in Acacia mangium (4.98 cm) and Acacia pollyphylla (3.92 cm), followed by E. fusca (3.06 cm), Spondias lutea (2.37 cm), Erythrina poeppigiana (2.17 cm) and E. berteroana (2.12 cm); d) the annual increment in tree crown diameter was greater in A. pollyphylla (2.50 m), G. sepium (1.03 m), Torresea acreana (0.98 m) and E. fusca (0.87 m). These results suggest good adaptation of the introduced species, which presented development superior to most of the native species, especially in terms of capacity for establishment and initial growth.

Adaptation, productivity and persistence of Arachis pintoi under different levels of shading

The experiment was conducted to determine the forage potential of the Arachis pintoi submitted to 0, 30, 50 and 70% of shading, in silvopastoral systems and as ground cover in agroforestry systems. The experimental design was a completely randomized design with four replications. An evaluation was carried at the end of the rainy season and another at the end of the dry season, using the caracteristics height and plant vigor, ground cover, and total, above and below ground biomass. The results showed that A. pintoi presented good adaptation and persistence in the studied levels of shading. Although its productivity decreased with the increase of the levels of shading, it was considered adequate, even in the highest levels of shading. This indicates that it is possible to use this legume as ground cover in agroforestry systems and as forage in silvopastoral systems.

Productivity, utilization efficiency and sward targets for mixed pastures of marandugrass, forage peanut and tropical kudzu

This study was carried out to evaluate the productivity and utilization efficiency of a mixed marandugrass (Brachiaria brizantha cv. Marandu), forage peanut (Arachis pintoi cv. Mandobi) and tropical kudzu (Pueraria phaseoloides) pasture, rotationally stocked at four daily forage allowance levels (6.6, 10.3, 14.3 and 17.9% of live weight), in order to define sward management targets for these mixtures. In each stocking cycle, dry matter (DM) accumulation rates, defoliation intensity (%), grazing depth (%) and grazed horizon (cm) were evaluated. Sward targets were defined according to the sward condition that best conciliated the grass-legume balance and the equilibrium between forage production and utilization. Pastures submitted to higher forage allowance levels showed higher productivity, but were less efficiently utilized. It was not possible to establish sward management targets for marandugrass-tropical kudzu pastures. For marandugrass-forage peanut pastures the best sward state was set with forage allowance of 10.3% of live weight. Under rotational stocking, the following sward targets were suggested for these pastures in the Western Amazon: pre-grazing height of 30-35 cm (June to September) or 45-50 cm (October to May) and post-grazing sward height of 20-25 cm (June to September) or 25-30 cm (October to May).

Dynamics of sward condition and botanical composition in mixed pastures of marandugrass, forage peanut and tropical kudzu

This study was carried out to evaluate the dynamics of sward condition and botanical composition of a mixed pasture of marandugrass (Brachiaria brizantha cv. Marandu), forage peanut (Arachis pintoi cv. Mandobi) and tropical kudzu (Pueraria phaseoloides), rotationally stocked at four daily forage allowance levels (6.6, 10.3, 14.3 and 17.9% of live weight). Sward condition was characterized in each stocking cycle by measuring pre- and post-grazing sward height, forage mass and percentage of bare ground. Botanical composition (grass, forage peanut, tropical kudzu and weeds) was evaluated before each stocking period. Swards under smaller forage allowances presented lower height, forage mass and ground cover. This condition favored the growth of forage peanut, which constituted 21.1, 15.2, 8.4 and 3.8% of forage mass in the last quarter of the experimental period, from the lowest to the highest forage allowance, respectively. Tropical kudzu was sensitive to all forage allowance levels and its percentage in the botanical composition was strongly reduced along the experimental period, especially during the dry season (July to September). Forage peanut cv. Mandobi and marandugrass form a more balanced mixture when pre-grazing sward height is maintained shorter than 45 cm. Tropical kudzu is intolerant to intensive grazing management systems when associated to marandugrass.

Grazing management strategies for massaigrass-forage peanut pastures: 2. productivity, utilization and sward structure

This study was carried out to evaluate the productivity, utilization and sward structure of a mixed massaigrass (Panicum maximum x P. infestum, cv. Massai) and forage peanut (Arachis pintoi Ac 01) pasture, intermittently stocked at three daily herbage allowance levels (9.0, 14.5 and 18.4% of live weight). In each grazing cycle, dry matter (DM) accumulation rates, defoliation intensity (%), grazing depth (%) and grazed horizon (cm) were evaluated. The structure of massaigrass tussocks was characterized in both dry and rainy seasons by measuring its pre-grazing morphological composition and post-grazing height and density (tussocks/m). Pastures submitted to higher herbage allowance (HA) levels showed higher productivity, but were less efficiently utilized. On average, over the experimental period, DM accumulation rates increased linearly from 56.8 to 81.3 kg/ha/day as HA levels increased from 9.0 to 18.4% of live weight. However, defoliation intensity and grazing depth declined linearly with increasing HA levels. During the dry season, pre-grazing morphological composition of massaigrass was characterized by 41% of green leaf blades, 10% of pseudostems and 49% of dead material, irrespective of HA levels. In the rainy season, however, it showed higher percentage of green leaf blades and lower percentage of pseudostems when submitted to lower HA levels, although there were not differences in relation to percentage of dead material. The structure of massaigrass tussocks tended to deteriorate at high HA levels.