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Bioenergy is one of the alternatives to reduce the dependence of global energy on fossil fuels. The short rotation coppice (SRC) of eucalypt species appears as an interesting option for forest biomass production in a short time. However, the harvesting of whole trees (included the crown) in SRC systems has implications on sustainable land use. More information is required on the increase of biomass as renewable energy resource to achieve the sustainability of these crops. The main objective of this research was to evaluate the sustainable use of biomass from very high-density eucalypt plantations, managed at tropical conditions for bioenergy. To accomplish this objective, the tree was fractionated into three fractions: stem, branches, and leaves, and there was determination of the dry matter, energy yield, and nutrients export. This experiment used a short rotation coppice, a hybrid clone of Eucalyptus urophylla  Eucalyptus grandis, of 2 years old. According to the results obtained, the density planting and fertilization levels have a greater influence on the dry matter yield, energy yield, and nutrient exports. The higher density planting reaches mean values of 30.9 tonnes of dry matter per hectare (t DM ha À1) and 743.3 GJ ha À1. Considering the biomass yield and nutrients export of short rotation coppice of eucalypt, the higher density planting with the lower dose of fertilization is more indicative of sustainable use. The leaves have an important participation in nutrients export and should be retained in the soil of forest.

Modified foragers represent a cost-effective option for harvesting high-density short-rotation energy plantations. However, new energy plantations grown in Brazil far exceed the stocking and the stem size characterizing plantations in the Northern hemisphere, which raises the question about the ability of modified foragers to perform effectively. A study was conducted on five eucalyptus plantations, located in different Brazilian States and spanning over a wide range of work conditions in terms of clone, age, planting density and row system (e.g. single or twin rows). Field stocking varied between 90 and 157 t ha À1 , and breast-height diameter between 5 and 8 cm. The tests were conducted with a New Holland 9060 forager, equipped with a 130 FB energy wood header. This machine was capable of negotiating all test fields, and reached a productivity on these sites between 39 and 65 t h À1 , which was comparable with the productivity values recorded in Europe and North America. The machine coped well with the high field stocking and stem size levels encountered in Brazil. Blockages accounted for a very small proportion of total harvesting time, which was similar to that recorded in studies conducted on poplar and willow in the Northern hemisphere. Productivity was directly proportional to field stocking and target chip length. Changing target chip length from 30 to 20 mm resulted in a 20e30% reduction in productivity. These figures reflect work conditions in uncoppiced first-rotation plantations, and they should be applied with some caution to following rotations.

A utilização correta de pneus em tratores, tanto em relação ao seu tipo quanto à calibração de sua pressão interna, e a lastragem ideal para cada condição de carga são fatores que influem significativamente no desempenho do trator. Esta pesquisa teve como objetivo comparar o desempenho de um trator equipado com pneus radiais e com pneus diagonais, para três condições de lastragem líquida (0%, 40% e 75% de água), em três condições superficiais de um Nitossolo Vermelho distrófico (superfície firme, preparada e com cobertura vegetal de resto de milho) e em três velocidades teóricas de deslocamento (4 km h-1, 5 km h-1 e 7 km h-1), informadas no painel do trator, correspondendo às marchas B1, B2 e C1. O melhor desempenho do trator, equipado com pneu diagonal, ocorreu na condição de 75% de água nos pneus, apresentando maior velocidade de deslocamento, menor patinhagem do trator, menor consumo horário de combustível e gerando maior potência na barra de tração. Com pneus radiais, o melhor desempenho do trator ocorreu na condição de 40% de água nos pneus, proporcionando maiores velocidades de deslocamento do trator, menores patinhagens, menores consumos, horário e específico de combustível, e maiores potência e rendimento na barra de tração.

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Soil tillage that maintains the productivity of sugarcane plantations, providing an area for the root development and without traffic on crop rows, has given rise to new technologies in rural areas. the purpose of this study was to evaluate the soil physical properties in two sugarcane plantations, one of which was prepared with deep tilling and the other with conventional tillage. the experiment was conducted in lençóis paulista, São paulo State. Soil penetration resistance and relative density were analyzed. the cone index was lower in deep-tilled soil without traffic in all layers, than in deep-tilled soil with traffic and in conventional tillage. In both tillage treatments, the relative density values were acceptable in the 0.00-0.15 m soil layer, but considered detrimental for sugarcane development in the 0.15-0.30 and 0.30-0.45 m layers.

Changes in physical and chemical characteristics of fermented cocoa (Theobroma cacao) beans with manual and semi-mechanized transfer, between fermentation boxes Cambios en la características físicas y químicas de granos de cacao (Theobroma cacao) fermentados con transferencia manual y semi-mecanizada, entre las cajas de fermentación

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