Com o objetivo de determinar os efeitos de períodos de controle e de convivência das plantas daninhas na produtividade da cultura do algodoeiro (Gossypium hirsutum), cultivar Delta-Opal, realizou-se um experimento que constou de dois grupos de tratamentos. No primeiro, a cultura permaneceu livre da competição das plantas daninhas desde a emergência até 7, 14, 21, 28, 35, 42, 49, 56, 63 dias e colheita (159 dias). No segundo, a cultura permaneceu em competição com a comunidade infestante desde a emergência até os mesmos períodos descritos para a primeira série de tratamentos. Dentre as espécies de plantas daninhas encontradas na área experimental, destacaram-se a tiririca (Cyperus rotundus), o fedegoso (Senna obtusifolia), a anileira (Indigofera hirsuta) e o capim-carrapicho (Cenchrus echinatus). Pelas condições edáficas, climáticas e florísticas sob as quais foi conduzida a cultura de algodão, o Período Anterior à Interferência (PAI) dessa comunidade que reduziu em 5% a produtividade da cultura foi de oito dias após a emergência da cultura (DAE); o Período Total de Prevenção da Interferência (PTPI) foi de 66 DAE; e o Período Crítico de Prevenção da Interferência (PCPI) foi dos 8 aos 66 DAE.

Field experiments were conducted at Morro Agudo county, SP, Brazil, to determine the critical period of weed control in peanut. A different cultivar was planted for each experiment (runner cultivars: 'Caiapó ' and Runner 'Tégua', and erect cultivars: 'ST-Tatu', 'IAC-1075' and 'IAC-22'). Treatments consisted of increasing initial periods of weed maintenance or weed control, in a randomized block design with four replications. The predominant weed species were Brachiaria plantaginea (Link) Hitchc. (alexander grass), Digitaria horizontalis Willd. (crabgrass) and Bidens pilosa L. (hairy beggarticks). In the absence of weeds the most productive cultivar was 'Caiapó ', followed by Runner 'Tégua', 'IAC-22', 'ST-Tatu' and 'IAC-1075'. Weed interference resulted in maximum yield losses between 74 and 92%. Assuming a level of 5% in peanut yield loss, the critical time of weed removal was 7 to 16 days after planting (DAP) and the critical weed-free period was 26 to 65 DAP. Thus, to ensure the high yield for all cultivars the critical period for weed control should begin at 7 DAP and continue until at least 65 DAP.

Despite being considered renewable, corn (Zea mays) ethanol still generates much debate over the use of fossil fuels in its production and is considered less sustainable than sugarcane (Saccharum spp.) ethanol. In Brazil, corn ethanol is starting to be produced in the Center-West and is expected to increase with the RenovaBio, a promising policy for biofuels adoption. In this context, energy cane (Saccharum spp.) is a biomass crop with high yields that can provide bagasse to supply the energy demand of the corn ethanol industry and provide juice with about 10% sugar content. However, the effects of introducing its juice in the production process are unknown. For these reasons, the objective of this study was to assess the effects of adding energy cane juice in corn ethanol production. Energy cane juice brings several advantages: (i) It provides sugars that can reduce by almost 50% the amount of corn and enzymes used, (ii) reduces the amount of water needed for ethanol production, and (iii) increases significantly the fermentation efficiency from 86.4% to 90.8% by providing minerals that support yeast growth. Therefore, energy cane can be integrated into the corn ethanol production process, making the fermentation more efficient and the production systems more sustainable.

A indústria açucareira tem como principal subproduto o melaço que é produzido na proporção de 40 a 60 quilos por tonelada de cana-de-açúcar processada. O melaço oriundo de uma tonelada de cana-de-açúcar processada pode produzir cerca de 12 litros de etanol, além do açúcar fabricado. Deste todo modo, constata-se que, na maioria dos países latino-americanos com produção açucareira, o melaço pode constituir uma fonte de etanol relevante e precursora para o atendimento das necessidades internas de combustível (HORTA NOGUEIRA, 2004). Na busca por alternativas para aperfeiçoar o processo de produção do etanol nas usinas, este trabalho visou mostrar a influência da clarificação e esterilização no preparo do melaço a ser empregado no processo fermentativo, determinando assim condições ótimas para a produção de etanol. Foram realizados três tipos de tratamentos no mosto para que a fermentação ocorresse: T1- Melaço não clarificado e não estéril. T2- Melaço estéril e não clarificado. T3- Melaço estéril e clarificado. O tratamento T3 foi o que apresentou maior produtividade e rendimento, devido ao procedimento de esterilização e clarificação que se mostraram influentes no processo fermentativo.

The objective of this study was to evaluate the technical and economic feasibility of installing central pivot irrigation systems in current days (Scenario A) and in two future scenarios, one with a 10% increase in rainfall (Scenario B1) and the other with 10% reduction in rainfall (Scenario B2). For both future scenarios, an increase of 2ºC in the global temperature and the concentration of atmospheric carbon dioxide (CO2) increasing to 528 ppm (parts per million) were considered. For the study, the recommendation for an area of clayey soil and with the sugarcane cycle was evaluated on three different planting dates: May 15, August 15 and November 15. The DSSAT/CANEGRO model was used, and under the current conditions, the simulations indicated greater yield for planting in May, both for rainfed and irrigated. For scenario B1, there was an increase in yield of 22% for rainfed and 33% for irrigated. In addition, irrigation provided yield gains in the two future scenarios of 13% and 14% for B1 and B2, respectively. Based on the results obtained, central pivot irrigation proved economically viable in the simulated climatic conditions. Therefore, the increase in sugarcane production provided by irrigation in agronomic management was sufficient to make investment in the region in question feasible. It is suggested to repeat the study in other regions, since the existing synergy between the factors that define agricultural yield can change the decision making about the implantation of irrigation systems in the production environment.