Brachiaria and Cynodon are important pasture grasses in Brazil. Convert HD 364 (Dow AgroSciences, São Paulo, Brazil) brachiariagrass (Brachiaria hybrid CIAT 36087; also known as Mulato II) is a new hybrid released for use in a broad range of environments. It has high nutritive value and yield, but there are no year‐round comparisons, including the dry season, with other pasture grasses. Forage accumulation and crude protein (CP), neutral detergent fiber (NDF), and in vitro digestible organic matter (IVDOM) concentrations were evaluated for Convert HD 364, Marandu palisadegrass {B. brizantha (Hochst. ex A. Rich.) R. D. Webster [syn. Urochloa brizantha (A. Rich.) Stapf]; CIAT 6297}, and Tifton 85 bermudagrass (Cynodon spp.) during dry and rainy seasons from 2011 to 2013. Irrigated and rainfed plots were harvested every 28 and 42 d. Convert HD 364 had similar or greater forage accumulation (17.9–22.8 Mg DM ha−1) than Marandu and Tifton 85 (15% greater than Marandu and 12% greater than Tifton 85 when irrigated and harvested every 28 d). Tifton 85 CP concentration was 140 g kg−1, greater than that of the other grasses when harvested every 28 d and irrigated. Convert HD 364 (537 g kg−1) NDF concentration was least, regardless of irrigation, harvest frequency, or season. This was associated with IVDOM concentration greater than 650 g kg−1, similar to that of Marandu. Convert HD 364 is a viable option for diversification of pasture‐based animal production systems in tropical areas due to high forage accumulation and nutritive value when fertilized and well managed.

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Brachiaria and Cynodon are two of the most important pasture grasses worldwide. Computer model simulations can be used to study pasture species growth and physiological aspects to identify gaps of knowledge for genetic improvement and management strategies. The objective of this research was to compare the performance relative to calibrated parameters of the CROPGRO‐Perennial Forage Model (CROPGRO‐PFM) for simulating three different species (“Marandu” palisadegrass, “Convert HD 364®” brachiariagrass and “Tifton 85” bermudagrass) grown under similar management. The field experiment consisted of two harvest frequencies, 28 and 42 days, under irrigated and rainfed conditions. Data used to calibrate the model included regular forage harvests, plant‐part composition, leaf photosynthesis, leaf area index, light interception and plant nitrogen concentration. The simulation of biomass production of the three grasses presented d‐statistic values higher than 0.80, RMSE ranging from 313 to 619 kg/ha and ratio observed/simulated ranging 0.968 to 1.027. Harvest frequency treatments of 28 and 42 days were well simulated by the model. A sensitivity analysis was conducted to evaluate the most influential parameters needed for model calibration and to contrast the grasses, showing that the differences among the three grasses are mostly driven by plant‐part composition and assimilate partitioning among plant organs.

(1) Recebido para publicação em março de 2008 e aprovado em fevereiro de 2010.

The aim of this study was to investigate the effect of nitrogen (N) concentration during the establishment period of Mombasa grass (Panicum maximum Jacq.). The experiment was conducted using four different N concentrations (0, 30, 60 and 90 kg N/ha) during the establishment period in order to evaluate the effect of nitrogen on the plant. These effects were assessed using different indexes, including the efficiency of nitrogen use and agricultural, physiological and nutritional efficiencies. We also determined the total dry matter and nitrogen accumulation in the plant. The recovery of applied N and the agronomic efficiency of Mombasa grass were found to be greater with increasing N concentrations, and all indexes tested were found to be affected by the concentration of applied N. Based on the indexes studied, 90 kg N/ha was found to be most suitable for Mombasa grass during the establishment period. Key words: Agronomic efficiency. Nitrogen fertilizer. Panicum maximum Jacq. Nitrogen recovery. ResumoO presente trabalho teve como objetivo estudar o efeito de doses de nitrogênio (N) em pasto de capimMombaça (Panicum maximum Jacq.) durante o período de estabelecimento. Foi realizado experimento com quatro doses de N (0, 30, 60, 90 kg.ha -1 ), durante o período de estabelecimento, para avaliação do efeito do nitrogênio na planta, através de índices de eficiência de utilização, eficiência agronômica, fisiológica e nutricional, avaliou-se ainda a matéria seca total e o acúmulo de nitrogênio na planta. Concluiu-se que a recuperação do N aplicado e a eficiência agronômica pelo capim Mombaça aumentou com o incremento das doses. Sendo que, para todos os índices ocorreu influência das doses aplicadas. A dose de 90 kg de N.ha -1 , com base nos índices estudados, é a mais indicada para o período de estabelecimento do capim-Mombaça. Palavras-chave: Eficiência agronômica. Adubo nitrogenado. (Panicum maximum Jacq.). Recuperação do N aplicado.

IntroductionTropical grasslands represent an important resource for the Brazilian cattle industry, which is heavily dependent on grazed pastures. Total pasture area in the country totals 196 Mha (23% of the country's land area) (FAO 2013 (Barbosa 2006). Mulato II is a new hybrid brachiariagrass cultivar, which has been developed to improve agronomic characteristics, broaden the range of adaptation, and ensure high forage production and nutritive value. It has also been viewed as a means of reducing the dependence on the Marandu palisadegrass monoculture (Argel et al. 2007).The use of new cultivars should be based on adequate understanding of physiological processes and growth potential under a range of management practices. Morphogenic characteristics allow for accessing herbage accumulation potential through the measurement of tissue synthesis and senescence in forage plants. Management practices such as defoliation frequency can modify assimilate partitioning in the forage plant, affecting morphogenic characteristics related to growth rate and forage nutritive value. The objective of this research was to describe and explain morphogenic differences between Marandu palisadegrass and Mulato II brachiariagrass as affected by harvest frequency. MethodsThe experiment was conducted in the Department of Animal Science ESALQ/USP, Piracicaba, SP, Brazil (22°42' S, 47°30' W; 580 m asl). Average annual rainfall is about 1,300 mm and temperature ranges between 10 °C and 35 °C. The soil at the experimental area is a Kandiudalfic Eutrudox. Plots were established with Brachiaria brizantha cv. Marandu and Brachiaria cv. Mulato II in October 2010. The evaluation occurred during the summer season (December 22, 2011−March 20, 2012. Two experiments were conducted simultaneously in adjacent areas, one irrigated and another non-irrigated. The design of each experiment was a randomized complete block in a 2 x 2 factorial arrangement, with the 2 grasses and 2 harvest frequencies (28 and 42 days) and 4 replications, totaling 16 experimental units of 20 m² (4 m x 5 m). Harvests were made 10 cm from the soil surface.Ten tillers were evaluated for the following characteristics: (a) leaf blade length and (b) leaf type, classified as expanding, expanded, senescing and dead. Leaves were classified as: expanding, when their ligules were not exposed; expanded, when the ligule was visible and/or growth ceased; senescing, when part of the leaf blade showed signs of senescence (yellowing and necrosis); and dead, when more than 50% of the leaf blade was senesced. Degree of leaf senescence was estimated visually. The stem length was measured from the soil level to the ligule of the youngest fully expanded leaf. Means were calculated using "LSMEANS" statement, and comparisons made with "PDIFF" based on a Student t-test (P<0.05). Data for the experiment were analyzed using the GLM Procedure of SAS.

Understanding plant growth may help to identify factors limiting forage production and contribute to the identification of optimal harvest management. The objective of this study was to describe and explain the effect of two harvest intervals (28 and 42 d) on the growth of Convert HD 364 (Dow AgroSciences, São Paulo, Brazil) hybrid brachiariagrass (Brachiaria spp., syn. Urochloa spp.), ‘Marandu’ palisadegrass [Brachiaria brizantha (Hochst. ex A. Rich.) RD Webster, syn. Urochloa brizantha (A. Rich.) Stapf; CIAT 6297], and ‘Tifton 85’ bermudagrass (Cynodon spp.). The experimental design was a randomized complete block with a factorial combination of three grasses and two harvest intervals (n = 4). The following variables were evaluated during two consecutive years: leaf area index (LAI), crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and leaf weight ratio (LWR). Marandu palisadegrass showed the least CGR (44.4 kg ha−1 d−1) compared with Convert HD 364 and Tifton 85 (∼52 kg ha−1 d−1). Longer harvest interval resulted in greater CGR (55.4 vs. 43.5 kg ha−1 d−1), but generally a lesser RGR, suggesting a reduction in efficiency of growth under 42‐d harvest intervals. Tifton 85 uses less leaf area to produce similar or greater herbage mass due to greater leaf photosynthetic efficiency, as it had greater NAR and lesser LAI, but similar CGR compared with Convert HD 364. The harvest interval of 28 d results in greater C partitioning to leaf and to build leaf area, increasing the leaf proportion in harvested forage.

ResumoO objetivo deste trabalho foi demonstrar a utilização da estatística como ferramenta para minimizar o risco em operações de hedge de boi gordo, tendo como base a série histórica de preços na cidade de Itapetinga no estado da Bahia. Os preços no mercado futuro foram obtidos junto ao Centro de Estudos Avançados em Economia Aplicada [CEPEA] Esalq/USP. Os preços do mercado físico foram levantados junto a Secretária da Agricultura, Pecuária, Irrigação, Pesca e Aquicultura [SEAGRI-BA]. Foi calculada a correlação entre os preços nos mercados físico e futuro com o objetivo de saber o quanto a variação de um acompanha a variação do outro. Foram calculadas as bases para todos os dias do período de tempo em análise, em seguida foram encontrados a média e o desvio padrão da base. Encontrado o risco de base das operações de hedge, tendo como referência a tabela da distribuição normal-padrão, foram simulados contratos de compra e venda diariamente no período de um ano, utilizando o conceito de custo de base para determinar o preço objetivo, aumentando a segurança nas operações. Sugeriu-se na prática encerrar algumas posições e assumir outras à medida que o mercado se movimenta a favor ou contra a posição do hedge. Desta forma, estratégias hedge em mercados futuros se mostram como excelentes opções para se precaver contra a variação de preços de boi gordo. Palavras-chave: base, boi gordo, hedge, Itapetinga AbstractThe