No abstract

Agroforestry systems (AFS) are considered alternative land use options to help prevent soil degradation and improve soil microbial biomass and organic C status. However, it is unclear how different densities of babassu palm [Attalea speciosa (syn. Orbignya phalerata)], which is an important tree in Northeast Brazil, affect the soil microbial biomass. We investigated the soil microbial biomass C and activity under AFS with different densities of babassu palm associated with Brachiaria brizantha grass. Soil microbial biomass C (MBC), soil microbial biomass N (MBN), MBC:total organic C ratio, fluorescein diacetate hydrolysis and dehydrogenase activity showed highest values in plots with high density of babassu palm. On the other hand, the respiratory quotient (qCO 2 ) was significantly greater in plots without babassu palm. Brachiaria brizantha in monoculture may promote C losses from the soil, but AFS with high density of babassu palm may increase the potential of soils to accumulate C. ResumenLos sistemas agroforestales (AFS, por sus siglas en inglés) son opciones alternativas de uso de la tierra que ayudan a prevenir la degradación del suelo y mejorar la biomasa microbiana y el estado del carbono (C) orgánico. Babasú [Attalea speciosa (syn. Orbignya phalerata)] es una importante palma nativa que forma bosques en los estados Maranhão y Piauí, nordeste de Brasil; no obstante no se conoce su efecto sobre la biomasa microbiana del suelo cuando crece en diferentes densidades. En el estudio se evaluaron los efectos sobre el C y la actividad de la biomasa microbiana del suelo en AFS con 3 densidades de babasú en pasturas de Brachiaria brizantha. El C y el nitrógeno de la biomasa microbiana (MBC resp. MBN) del suelo, la relación de MBC:C orgánico total del suelo, la hidrólisis de diacetato de fluoresceína y la actividad de la deshidrogenasa mostraron valores más altos en las parcelas con alta densidad de babasú. Por otra parte, el cociente respiratorio (qCO2) fue significativamente mayor en las parcelas sin babasú. El pasto B. brizantha en monocultivo puede promover la pérdida de C del suelo, pero los AFS con alta densidad de la palma pueden aumentar el potencial de los suelos para acumular C.

SUMMARY This study aimed to determine the area occupied by different tissues present in the leaf blade and the in situ degradability of leaf and stem of elephant grass (Pennisetum purpureum Schum.) under different defoliation frequencies (30, 45, 60, 75 and 90 days). Plants were classified into three levels of insertion in the tiller (apical, medial and basal). The results were presented as a proportion of the area of each tissue in relation to the total area of the leaf blade, namely, parenchyma tissue (PT), lignified vascular tissue (LVT) and non-lignified vascular tissue (NLVT). The proportion of tissue in the leaf blade is altered in accordance with the insertion in the tiller and increase in cutting age of the plant. PT has greater proportion at lower cutting ages, LVT increases with frequency and NLVT is higher at 60 days. The parameters of DM degradation in the two fractions evaluated decreased significantly with increasing maturity of the plant. The effective degradability of CP in leaf and stem decreased with the increase in the rate of passage (2, 5, and 8% h-1). The highest rate (c) of CP degradation for the leaf fraction was obtained with a frequency of 60 days, for the stem, with 45 days. The advance in plant maturity increases the proportion of lignified vascular tissue, thus influencing the ruminal degradation parameters of elephant grass. The defoliation frequency of 60 days offers an optimal point regarding the proportion of anatomical tissues correlated with the degradation of elephant grass.

This study aimed to evaluate the agronomic characteristics and nutritional value of Massai grass (Megathyrsus maximus 'Massai') pastures fertilized with different nitrogen levels and subjected to deferred grazing. A completely randomized experimental design (CRD) was adopted, with including five nitrogen levels (zero, 100, 200, 300, and 400 kg ha −1 ), and five replications (plots). The degradability trial used a CRD including a 6 × 5 factorial arrangement, consisting of six rumen-incubation times (6, 24, 48, 60, 84, and 96 h) and five levels of nitrogen in different plots. One fistulated sheep, with a live weight of 60 kg, was used in the experiment. Total herbage biomass, dead herbage biomass, and height showed a quadratic response to nitrogen fertilization levels of 100 to 200 kg ha -1 resulted in greater tillering. Protein and dry matter content increased linearly with nitrogen fertilization level, leading to increase in fibrous components. The increase in NDF and ADF contents might be a consequence of the reduction in NCE, and the high flowering rate of the grass, owing likely to the reduction in metabolism of the grass in an attempt to extend its lifetime. Nitrogen levels of 300 kg ha −1 or higher affected the productive characteristics positively, whereas the chemical characteristics were negatively affected. Key words: Deferred period. Degradability of dry matter. Megathyrsus. Nitrogen fertilization. ResumoObjetivou-se avaliar as características agronômicas e valor nutritivo do capim-Massai (Megathyrsus maximus 'Massai') submetido a diferimento e doses crescentes de nitrogênio. O delineamento experimental adotado foi o inteiramente casualizado (DIC) com cinco doses de nitrogênio (zero, 100; 200; 300 e 400 kg de N ha -1 ) com cinco repetições (parcelas). O ensaio de degradabilidade foi estruturado em DIC, com arranjo fatorial 6x5, seis tempos de incubação no rúmen (6, 24, 48, 60, 84 e 96 h) e cinco doses de N em parcelas diferidas. Utilizou-se um ovino fistulado com peso vivo de 60 kg. A biomassa de forragem total, morta e a altura respondeu à adubação nitrogenada de forma quadrática. A adubação nitrogenada nas doses 100 a 200 kg de N ha -1 proporcionou maior perfilhamento. A adubação nitrogenada proporcionou resposta linear sobre os teores de proteína e matéria seca em consequência também aumentou os constituintes fibrosos. O amento dos teores de FDN e FDA pode ser uma consequência da redução da ECN e da taxa de florescimento da gramínea, devido provavelmente à redução no metabolismo na tentativa de prolongar sua vida útil. A partir da dose de 300 kg de N ha -1 resultou em redução da degradação da matéria seca do capim-Massai. As doses de N influenciaram positivamente as características produtivas e negativamente as características químicas. Palavras-chave: Adubação nitrogenada. Degradabilidade da MS. Megathyrsus. Período de diferimento.

401Composição químico-bromatológica e degradabilidade in situ de capim-Marandu em sistemas silvipastoris formados por babaçu e em monocultivoChemical Composition and bromatologic degradability in situ of Marandu grass in silvopastoral systems formed by babassu and monoculture systems

The lack of information on the growth of forage grasses in semi-arid environment, especially from the perspective of irrigation, is one of the obstacles to regular forage supply, as well as to the rational use of irrigation water. The objective with this study was to evaluate the leaf gas exchanges, biomass flow and structural characteristics of buffel grass cultivar Gayndah under different water supplies (30, 60, 90 and 120% of the reference evapotranspiration -ETo) during the dry season and dry-rainy season, in completely randomized design in a split-plot scheme with three repetitions. The experiment was conducted in Sobral, CE, Brazil (3° 45' 00.77" S and 40° 20' 38.55" W, altitude of 101 m) from September 2015 to January 2016. A higher photosynthetic rate was verified during the dry season, evidencing the adaptability of buffel grass to environments with water restriction. Overall, the best morphogenic and structural characteristics and the biomass production were observed in the dry season. The 90% ETo regime leads to maximum amount of forage accumulation, whereas the 30% ETo allows the maintenance of the cultivar Gayndah of buffel grass in a state of latency during the dry season.Morfofisiologia do capim-buffel cultivado sob diferentes suprimentos hídricos na estação seca e estação seca chuvosa RESUMO: A carência de informações sobre o crescimento de gramíneas forrageiras em ambiente semiárido, sobretudo sob a perspectiva de irrigação, é um dos entraves para a oferta regular de forragem, assim como para o uso racional da água de irrigação. Diante do exposto, objetivou-se avaliar as trocas gasosas foliares, o fluxo de biomassa e as características estruturais do capim-buffel cultivar Gayndah em diferentes suprimentos hídricos (30, 60, 90 e 120% da evapotranspiração de referência -ETo na estação seca e estação seca chuvosa, em delineamento inteiramente casualizado em esquema de parcelas subdivididas com três repetições. O experimento foi conduzido em Sobral, CE (3° 45' 0.77" S e 40° 20' 38.55" O, altitude de 101 m) no período de setembro de 2015 a janeiro de 2016. Foi verificada maior taxa fotossintética durante a estação seca, evidenciando adaptabilidade do capim-buffel a ambientes com restrição hídrica. De maneira geral, as melhores características morfogênicas e estruturais e a produção de biomassa foram observadas na estação seca. O regime de 90% da ETo proporciona o máximo de acúmulo de forragem, ao passo que o tratamento de 30% da ETo, possibilita a manutenção do capim-buffel, cultivar Gayndah em estado de latência durante o período de estiagem. Palavras-chave:Pennisetum ciliare, fluxo de biomassa, lâminas de irrigação, semiárido, trocas gasosas

Resumo: Este artigo estuda a eficiência técnica e a produtividade total dos fatores (PTF) da agricultura dos países da América Latina e do Caribe. Para tanto, utilizaram-se a abordagem de fronteira estocástica de produção e o índice de produtividade de Malmquist. Os dados de valor da produção e a quantidade de insumos agrícolas abrangeram os anos de 1991 a 2012. Os resultados mostraram que todos os países apresentaram ineficiência técnica de produção agrícola ao longo do período. As variáveis que explicaram significativamente a ineficiência da produção agrícola foram o crédito e o consumo de energia na agricultura, o que representou uma inovação nessa temática. O índice de produtividade de Malmquist mostrou que não houve ganhos de produtividade total dos fatores.

The objective was to evaluate the intake, digestibility, nitrogen balance, and metabolic profile of lactating goats fed diets containing detoxified castor cake (DCC) by alkaline solutions during 150 days of lactation. Twenty-four Saanen and Anglo Nubian goats, approximately 17 months old (first lactation) and body weights of 43±2.97 kg, were distributed in a completely randomized block design with eight replicates. Treatments consisted of three diets, one containing soybean meal (SM) and two others containing DCC, with calcium hydroxide [Ca(OH) 2 ] and sodium hydroxide (NaOH). The diets significantly influenced the intake of dry matter (DM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF), and total digestible nutrients (TDN). We observed a higher dry matter intake (DMI) in goats fed SM, similar to that of goats fed Ca(OH) 2 DCC. Intake of nutrients followed the same trend as DMI. There was no significant effect of diets on digestibility of DM, CP, EE, and NDF; however, we observed a significant effect of diets on the levels of nitrogen intake (NI) and urinary nitrogen (UN). The goats fed SM consumed a larger quantity of nitrogen, but all had the same nitrogen balance, indicating that goats fed DCC were more efficient. The diets did not influence renal and hepatic parameters. Inclusion of castor cake in the diet of goats in confinement is an attractive option, considering that goats fed DCC present lower feed conversion, and its use does not cause hepatic and renal alterations, suggesting that SM can be completely replaced.