RESUMO -Bidens pilosa é uma das mais importantes plantas daninhas que ocorrem em lavouras anuais e perenes da região Centro-Sul do Brasil. A grande capacidade de produção de aquênios é uma das suas principais estratégias de sobrevivência, e o conhecimento das condições fundamentais para germinação e emergência das plântulas é essencial para predição do crescimento populacional e para a elaboração de plano de manejo de suas infestações e de seus biótipos resistentes aos herbicidas. Foram conduzidos ensaios em condições de casa de vegetação, onde foi avaliada a emergência de aquênios de B. pilosa em diferentes profundidades (0, 1, 2, 3, 4 e 5 cm). Os experimentos foram conduzidos nos meses de maio, agosto e novembro de 2006 e em março de 2007. Os resultados mostraram que a emergência de plântulas de picão-preto foi bastante afetada pela localização do aquênio no perfil do solo, ocorrendo expressiva redução a partir de 2 cm de profundidade. Essa característica da biologia reprodutiva do picão-preto é importante para a formação de densos bancos de sementes em solos submetidos ao preparo convencional, onde grande parte da chuva de sementes é nele incorporada.Palavras-chave: picão-preto, germinação, biologia reprodutiva.ABSTRACT -Bidens pilosa is one of the major weeds in annual and perennial crops in mid-southern Brazil. High seed production is one of its most important survival strategies and the knowledge of the fundamental conditions for seedling germination and emergence is essential to establish prediction models of its population growth and to elaborate management models for control and prevention of herbicide resistant populations. This research aimed to understand the importance of B. pilosa seed depth in the soil profile to enhance its germination and seedling emergence potential. Thus, four assays were carried out under greenhouse conditions and the seeds were sown at 0, 1, 2, 3, 4, and 5 cm from the soil surface. The emergence of B. pilosa seedlings was reduced as sowing depth was increased, with drastic reduction from two centimeters. This reproductive biology feature presented by B. pilosa is very important for the formation of dense seed banks in soils submitted to conventional tillage system.

The usage of biodiesel, a renewable and biodegradable fuel, is becoming increasingly popular. The objective of the study was to evaluate the operational performance-tractor forward speed, drawbar power, and fuel consumption-and smoke density of an agricultural tractor using biodiesel, diesel, and biodiesel/diesel mixtures as fuel in a tilled field. Soybean biodiesel, murumuru biodiesel, and three combinations of soybean biodiesel and murumuru were used: 90S10M (90% soybean and 10% murumuru), 80S20M (80% soybean and 20% murumuru), and 70S30M (70% soybean and 30% murumuru). The biodiesel/diesel ratios were: B0, B5, B15, B25, B50, and B100; the letter B indicates the presence of biodiesel and the number is the percentage of biodiesel in the diesel. The results showed an increase in specific fuel consumption (SFC) of 10.13%, 16.66%, 12.69%, 14.59%, and 17.42% for murumuru, soybean, 90S10M, 80S20M, and 70S30M, respectively, when comparing B100 to B0. SFC was influenced by the type of biodiesel, B100 of soybean, 90S10M, 80S20M, and 70S30M consumptions were, respectively, 7.8%, 2.9%, 5.2%, and 8.8% higher than those of murumuru. The hourly volumetric consumption (HVC) of 90S10M was 4.8% higher than soybean and murumuru. The tractor's forward speed and drawbar power did not have any significant difference. Smoke density was reduced by 51.6%, 23.04%, 30.41%, 37.8%, and 36.9% for Murumuru, Soybean, 90S10M, 80S20M, and 70S30M, respectively, when comparing B100 to B0. For Murumuru, the smoke density was 59.0%, 43.8%, 28.6%, and 30.5% lower for this variety of biodiesel when compared to soybean at 90S10M, 80S20M and 70S30M, respectively. The results demonstrate the potential usage of biodiesel as a substitution for diesel.

Experiments were performed on a laboratory scale fluidized bed gasifier to characterize the gasification products of almond shell and hull removed in nut processing operations and to determine the effect of gasifying media on bed agglomeration. The higher heating value of syngas during air gasification of almond biomass ranged from 4 to 6 MJ m −3 while gas concentrations ranged from 14 to 18% H 2 , 3-4% CH 4 , 43-50% N 2 , 16-19% CO, and 16-17% CO 2. For steam gasification, higher heating value was 10-12 MJ m −3 and gas concentrations were 35-40% H 2 , 5-7% CH 4 , 17-21% N 2 , 18-21% CO, and 16-18% CO 2. The high level of potassium in the almond shells led to strong corrosion and bed agglomeration due to flue gas transport of potassium compounds. These resulting pervasive kalsilite reactions were significantly worse under air gasification than under steam gasification. As a result of prolonged duration and elevated temperature approaching 1,000 • C, the corrosinal reaction changes to formation of an adhesive potassium distillate melt locally forming strong bonds. This latter is interpreted as a result of aerosol transported of melt particles.

Biodiesel is an alternative fuel to diesel engines. This study aimed to evaluate fuel consumption and smoke density of agricultural tractors fueled by biodiesel, diesel, and biodiesel/diesel mixtures in a tilled field. Treatments consisted of distilled methyl ester (biodiesel) of babassu (Orbinya martiana) and seven combinations of it with two standard diesel fuels (B S1800 and B S50). The blending ratios were 0, 5, 15, 25, 50, and 100% biodiesel in diesel oil (B0, B5, B15, B25, B50, and B100, respectively). Regarding the results for hourly volumetric consumption, no difference was found between B0 and B100 when using B S1800, whereas an 8% increase was observed when using the S50. The weighted hourly consumption increased by 11.29 and 16.9% from B0 to B100 using B S1800 and B S50, respectively. Similarly, the specific fuel consumption increased by 11.1% and 14.3% from B0 to B100 using B S1800 and B S50, respectively. Yet, when comparing B0 and B S1800, the smoke density reduction was 68.6% and between B S50 and B100 was 58.0%. Our findings show that babassu biodiesel is a suitable substitute for diesel oil, without causing any damage to the tractor's engine.

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