Efeito da compactação na produtividade de cultivares de soja em latossolo vermelho

Na agricultura moderna, o tráfego de máquinas sobre o solo é a principal causa da compactação, que, muitas vezes, causa decréscimos da produtividade de soja. O objetivo deste estudo foi avaliar o desenvolvimento de cultivares de soja, considerando os níveis de compactação do solo. Para tal, foi realizado um experimento em Jaboticabal, SP, em Latossolo Vermelho textura média. Os tratamentos de compactação foram: T0 = 0; T1* = 1; T1 = 1; T2 = 2; T4 = 4 e T6 = seis passadas, no mesmo local, de um trator de 11 t, uma ao lado da outra, perfazendo toda a superfície do solo. No tratamento T1*, a compactação ocorreu quando o solo estava mais seco para obter um menor nível de compactação. O delineamento experimental foi inteiramente casualizado em parcelas subdivididas (seis níveis de compactação e quatro cultivares), com quatro repetições. Foram coletadas amostras indeformadas de solo nas camadas de 0,03-0,06; 0,08-0,11; 0,15-0,18 e 0,22-0,25 m, para determinação dos atributos físicos. em dezembro de 2003, foram semeados os cultivares de soja (Glycine max) IAC Foscarin 31, MG/BR 46 (Conquista), BRS/MG 68 (Vencedora) e IAC 8-2. O cultivar de soja IAC Foscarim 31 foi o mais produtivo no Latossolo Vermelho, quando comparado aos cultivares MG/BR 46 (Conquista), BRS/MG 68 (Vencedora) e IAC 8-2. Os valores de resistência do solo à penetração a partir dos quais a produtividade dos cultivares de soja decresceu foram de 2,24 a 2,97 MPa, conforme os cultivares.

Efeitos da subsolagem e da adubação verde nas propriedades físicas do solo em pomar de citros

O presente trabalho teve por objetivo avaliar o efeito da subsolagem e da adubação verde nas propriedades físicas de um Latossolo Vermelho distrófico típico, cultivado com citros (laranjeira Valência). Os tratamentos empregados foram: manejo mecânico das plantas invasoras com roçadora (Testemunha); subsolagem em um lado da planta na entrecopa; subsolagem nos dois lados da planta na entrecopa, e semeadura direta de Crotalaria spectabilis na entrecopa. As propriedades físicas do solo avaliadas foram: porosidade total, macroporosidade, microporosidade, densidade, resistência mecânica à penetração vertical e condutividade hidráulica. Na avaliação efetuada na safra 2001-2002, obtiveram-se os maiores valores de densidade do solo e resistência do solo à penetração vertical, e os menores valores de macroporos e condutividade hidráulica do solo nas entrecopas com e sem tráfego no pomar, em relação à região da copa, principalmente na camada de 0,0-0,2 m de profundidade. Os tratamentos aplicados não surtiram efeitos positivos significativos nas propriedades físicas do solo.

Estudo do comportamento no estado fresco e endurecido do concreto com incorporação de resíduo de corte de botão

This works aims at investigating the effects of adding waste from RCBP-polyester button manufacturing to Portland cement concrete, particularly regarding its consistency and mechanic strength. The RCBP used came from a button factory located in Parnamirim, RN, Brazil. The waste was added to the concrete on different ratios: 5 %, 10 %, 15 % and 20 % of the total cement mass. A sample of concrete without the RCBP was used as reference, 1:1,33:2,45:0,50. For the mechanic strength test four samples were tested with different ages (3, 7 and 28 days old) and mixtures. Furthermore, a Slump Test was also conducted in order to verify the concrete s consistency. A tendency to a reduction in the compression resistance was noticed for all samples. For the samples with 5 % and 10 %, there was also an increase in the traction resistance during inflexion, regarding the reference concrete. In the microstructural analysis, the RBCP was observed to show an irregular and porous surface, thus explaining the consistency decrease

Avaliação de concreto com adição de fibras de PET submetido a altas temperaturas

The concrete for centuries constituted an essential structural element in the construction industry due to its relative ease of forming, before the weather durability, low cost, its lower maintenance compared to other materials such as steel. However, when the concrete is exposed to high temperatures tends to lose its mechanical characteristics, and may even result in loss of section, which undermines the stability and mechanical strength of structural elements. The pathologies resulting from exposure to elevated temperatures ranging from cracks, pops up chipping explosives (spalling). Recently, the technology of concrete is closely related to the study of its microstructure. The use of fibers added to concrete has been revealed as a solution to increase the mechanical strength of the concrete, it acts directly on the distribution of efforts to act in the play within the microstructure. In this work we used recycled PET fibers embedded in concrete with 15x2mm fck = 30MPa, water/cement ratio of 0.46, in works made for verification of mechanical strength of this mixture submitted to high temperature. The specimens of concrete with addition of PET fibers were tested after exposure to temperatures: ambient (30ºC), 100°C, 200°C, 300°C, 400°C, 600°C and 900°C. It was found that the concrete loses significant strength when exposed to temperatures above 300°C, however the use of fiber PET may delay the risk of collapse of structures for the formation of a network of channels that facilitate the escape of vapor 'water, reducing the pore pressure inside the structural element

Avaliação da incorporação de cinzas de lodo de esgoto como adição mineral em concretos de cimento Portland

O desenvolvimento das grandes cidades tem gerado um dos maiores desafios ambientais enfrentados na atualidade, que é a gestão eficaz de resíduos sólidos. A grande variedade e quantidade dos resíduos produzidos diariamente, tem tornado a destinação ecologicamente correta e sustentável destes materiais cada vez mais difícil. Dentre os vários resíduos produzidos diariamente destacam-se os lodos oriundos de estações de tratamento de esgotos, denominados de lodos de esgoto, cuja destinação final segura tem sido discutida mundialmente em diversos estudos, tendo em vista que a tendência de geração deste tipo de resíduo tende a crescer com o aumento do saneamento das cidades. Uma forma amplamente difundida nos países desenvolvidos para destinação dos lodos de esgoto é a incineração destes materiais para posterior envio das cinzas geradas neste processo a aterros sanitários. Porém, tem-se estudado formas alternativas de disposição, destacando-se a utilização destas cinzas como adição mineral em concretos e argamassas de cimento Portland. Sabe-se que o desempenho de resíduos de incineração como adição mineral em matrizes cimentícias, depende em grande parte da capacidade de atuação destes materiais como elementos pozolânicos ou como fileres, podendo estas características serem influenciadas pela temperatura de queima ao qual estes resíduos foram submetidos. Neste sentido, verificou-se com esta pesquisa a influência da temperatura empregada na queima dos lodos sépticos no índice de atividade pozolânica (IAP) das cinzas geradas como resíduo deste processo, aqui denominadas de cinzas de lodo séptico (CLS), sendo em seguida, avaliadas as implicações técnicas e microestruturais da utilização deste resíduo em teores de 10%, 20% e 30% como adição mineral em concretos de cimento Portland. Os resultados obtidos demonstraram não haver alterações significativas no IAP das CLS em decorrência da temperatura utilizada durante o processo de queima dos lodos de esgoto. Além disso, verificou-se que embora a utilização das CLS tenham provocado diminuição da trabalhabilidade dos concretos para todos os teores de incorporação, estas melhoraram a resistência mecânica à compressão, o índice de vazios, a absorção de água e o comportamento microestrutural dos concretos contendo 10% e 20% de resíduo

Compactação do solo e intervalo hídrico ótimo no crescimento e na produtividade da cultura do milho

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Compactação do solo no crescimento radicular e produtividade da cultura do milho

As modificações estruturais causadas no solo pelos diferentes sistemas de manejo podem resultar em maior ou menor compactação, que poderá interferir na resistência mecânica à penetração, densidade e porosidade do solo, influenciando o crescimento radicular e, por fim, a produtividade das culturas. O objetivo deste trabalho foi avaliar os efeitos da compactação sobre determinadas características de um Latossolo Vermelho textura média e associá-las ao crescimento radicular e à produtividade da cultura do milho. Os tratamentos principais foram constituídos por seis níveis de compactação, proporcionados pelo tráfego controlado de tratores, e duas camadas, como subtratamentos, com quatro repetições. Foram coletadas amostras indeformadas do solo nas camadas de 0-0,10 e 0,10-0,20 m, para determinação da resistência do solo à penetração, densidade e porosidade do solo. Para determinação de densidade, superfície, diâmetro e massa seca das raízes, foram retiradas amostras do solo nas camadas de 0-0,10 e 0,10-0,20 m, em cada parcela. O tráfego de tratores sobre o solo provocou maiores níveis de compactação na camada superficial, proporcionando maior densidade e superfície radicular. O diâmetro radicular e a massa seca das raízes aumentaram linearmente com o aumento da resistência à penetração do solo. Verificou-se que valores de resistência à penetração variando entre 1,03 e 5,69 MPa provocaram alterações na morfologia do sistema radicular do milho, reduzindo a produtividade da cultura em 2,581 Mg ha-1, mas não foram impeditivos ao enraizamento.

Nitrogen and silicon fertilization of upland rice

O silício não é considerado um elemento essencial para o crescimento e desenvolvimento das plantas, entretanto, sua absorção traz inúmeros benefícios, principalmente ao arroz, como aumento da espessura da parede celular, conferindo resistência mecânica a penetração de fungos, melhora o ângulo de abertura das folhas tornando-as mais eretas, diminuindo o auto-sombreamento e aumentando a resistência ao acamamento, especialmente sob altas doses de nitrogênio. O presente trabalho teve por objetivo avaliar os efeitos da adubação nitrogenada e silicatada nos componentes vegetativos, nos componentes da produção, na altura da planta e na produtividade da cultivar de arroz IAC 202. O experimento foi constituído da combinação de três doses de nitrogênio (5, 75 e 150 mg de N kg-1 de solo) aplicado na forma de uréia e quatro doses de silício (0, 200, 400 e 600 mg de SiO2 kg-1 de solo), aplicado na forma de silicato de cálcio. O delineamento experimental utilizado foi o inteiramente casualizado em esquema fatorial 3 ´ 4 (N = 5). A adubação nitrogenada aumentou o número de colmos e panículas por metro quadrado e o número total de espiguetas, refletindo na produtividade de grãos. O perfilhamento excessivo causado pela adubação nitrogenada inadequada causou redução na porcentagem de colmos férteis, na fertilidade das espiguetas e da massa de grãos. A adubação silicatada reduziu o número de espiguetas chochas por panícula e aumentou a massa de grãos sem, contudo, refletir na produtividade de grãos.

Influência da adição de rejeitos cerâmicos nas propriedades de cerâmica vermelha da região do Recôncavo Baiano

The study of the physical and mechanic properties is an analysis of unquestioned importance on the production of the ceramic materials. In the region of the Recôncavo Baiano, there are ceramic and small brick factories, that still use rudimentary techniques, where the necessity of characterization of raw materials is denounced by the quality of the final product. The present work has for objective to study the behavior of the clay proceeding from the region of the Recôncavo, between the cities of Candeias and Camaçari/Ba, with addition of 5, 10 and 15% by weight of brick scraps, trying to optimize the physic and mechanical properties of the final product, aiming a better possibility of being manufactured, mechanic resistance, low linear retraction and water absorption. The brick scraps and the clay were characterized by FRX, DRX, TG, ATD and the granulometric analysis. Samples for testing where prepared by uniaxial pressing at 25Mpa, in 60x20x5mm size. The evaluated technological properties were: linear retraction, water absorption, apparent porosity and flexural strength. The samples were burned in electric oven in the temperatures of 850º, 950º and 1050ºC and compared its mechanical properties and the gresification. With addition of 15% by weight of brick scraps and burning at 900º-1000ºC the samples showed properties superior to that clay

Adição de geomanta e tecido não tecido de polipropileno em cimentos geopoliméricos de pega rápida

Geopolymers are cementing materials that depict a number of advantages compared to Portland cement. Contrary to the latter, geopolymers are synthesized at room temperature, thus significantly reducing the emission of CO2 to the atmosphere. Moreover, the composition and synthesis reactions can be tailored to adjust the setting time of the material as well as its compressive mechanical strength. It is then possible to produce geopolymeric cements with short setting times and high compressive strength, although relatively brittle. The objective of the present study was to produce and characterize composite materials by reinforcing fastsetting geopolymeric matrixes with polypropylene geosynthetics (geomats and geotextiles) in an attempt to improve the toughness and tensile strength of the cementing material. Geosynthetics have been increasingly used to reinforce engineering structures, providing higher strength and better toughness. In particular, polypropylene nonwoven and geomats depict other attractive properties such as low density, durability, impact absorption and resistance to abrasion. Fast-setting geopolymers were then synthesized and reinforced with polypropylene nonwoven and geomats. The mechanical strength of the materials, reinforced or not, was characterized. The results showed that relatively short setting times and adequate flowing behavior were achieved by adjusting the composition of the geopolymer. In addition, it is possible to improve the fracture resistance of geopolymeric cements by adding polypropylene geosynthetics. The best results were achieved by reinforcing geopolymer with polypropylene TNT

Anodização para obtenção de membranas cerâmicas

This a study on the achievement of alumina membranes by the method of anodizing. From this method got up a layer of aluminum oxide on the anodic metal, who presented the basic properties necessary for the application as a support for the production and acquisition of nanomaterials, such as porosity nano and resistance to high temperature, and other properties, as resistance to corrosion, and chemical, high ranking of the structure and pore size of the pores. The latter, ranging from 10 to 100nm depended on the electrolyte used, which in this study was the H2SO4. To remove all remaining aluminum, it is a bath of dissolution with HCl and CuCl where the residual aluminum has been withdrawn, and the deep pores were opened after chemical treatment with NaOH. After the dissolution, the membranes were calcined at temperatures of 300, 600 and 900° C, and sintered at temperatures of 1200 and 1300º C to win mechanical strength, porosity and observe the desired crystallization. Then went through analyses of composition through X-ray diffraction and morphology of the microstructure through a scanning electron microscope. The method was effective for obtaining alumine membranes applied in the processes of production of materials in nano

Obtenção de cerâmicas à base de tricálcio fosfatos utilizando óxido de magnésio como aditivo

The tricalcium phosphate ceramics has been widely investigated in the last years due its bioresorbable behavior. The limiting factor of the application of these materials as temporary implants is its low strength resistance. The tricalcium phosphate presents an allotropic transformation β→α around 1250 ºC that degrades its resistance. Some studies have been developed in order to densify this material at this temperature range. The objective of this work is to study the influence of the addition of magnesium oxide (MgO) in the sintering of β-TCP. The processing route was uniaxial hot pressing and its objective was to obtain dense samples. The samples were physically characterized through density and porosity measurements. The thermal behavior was studied through dilatometric, thermal differential and thermogravimetric analysis. The mechanical properties were characterized by three point flexure test and Vickers microhardness measurements, analyzed of the microstructure. The addition of magnesium oxide doesn t cause an improvement of the mechanical strength in relation to material without additive.

Estudo da Potencialidade da produção de tijolos de adobe misturado com outros materiais: uma alternativa de baixo custo para a construção civil

The production of the red pottery brick, made traditionally with clay, is a technique that is already stabled. However, in spite of the little complexity that involves the conventional process of these bricks production, it are exposed to many problems that begin in the fase of exploration of the mines, the problems get worse because of the lack of the clay's characterization, and they continue through the steps of the dough preparation, conformation of the products, the drying and the burning process. The wastefulness is shown and so is the low quality of the material produced. Among other factors, the high use of energy in the burning makes the cost of this material inaccessible to the low income consumer. Besides this, the destruction of the environment around the mines and the use of native vegetation to produce wood - the most used fuel in the pottery industry - make serious environmental damage. The production technique of a new type of simple brick (adobe), that has low cost and no environmental damage, can be the viable altemative to lower the cost of this part of the civil construction, and, consequently, in the building of cheaper houses. In this paper, the results of the mechanical resistance of the adobe brick are shown, using in its composition, clay, natural vegetable fibers, cement and plaster in a process that is completely handcrafted and manual. It is intented to make clear that are possible alternatives to be put in practice, with the simple process, using "raw earth" that has been used in the construction of houses in thousands of years, trying to solve these severe problems. Analysis and tests were performed to find results that could prove the possibility of the utilization of this kind of material. Other studies are in progress, and the new researches are necessary to enrich this work, but it stays the certainty that there is potential to produce bricks from adobe, as an alternative that has low cost to civil construction

Obtenção de cerâmicas à base de tricálcio fosfatos utilizando óxido de manganês como aditivo

The calcium phosphate ceramics have been very investigated as material for bone implants. The tricalcium phosphate (β-TCP) had a great potential for application in temporary implants like a resorbable bioceramic. This material presents a limitation in its sintering temperature due to occurrence of the allotropic transformation β → α at temperatures around 1200°C, not allowing the attainment of dense ceramic bodies. This transformation also causes cracks, what diminishes the mechanical strength, limiting its use to applications of low mechanical requests. This work studies the influence of the addition of manganese oxide in the sintering of β-TCP. Two processing routes were investigated. The first was the powder metallurgy conventional process. The test bodies (samples) were pressed and sintering at temperatures of 1200 and 1250°C. The second route was uniaxial hot pressing and its objective was to obtain samples with high relative density. The samples were physically characterized through density and porosity measurements. The thermal behavior was studied through dilatometric, thermal differential and thermogravimetric analysis. The mechanical properties were characterized by three point flexure test and Vickers microhardness measurements. The microstructure was analyzed by scanning electron microscopy. The addition of manganese oxide caused an improvement of the mechanical strength in relation to the material without additive and promoting the stabilization of β-TCP to greater temperatures

Efeito da introdução de resíduo de cinza de forno cerâmico em massa para cerâmica estrutural

The red ceramics and structural ceramics, as they are known, include ceramic materials made by blocks of seals and structures, bricks, tiles, smail flagstones manacles, rustic floors and ornamental materials. Their fabrication uses raw material such as clay and clay sites, with some content of impurity. It has good durability and mechanical strength to compression, low cost, making it one of the mainly used materials in civil engineering. The incorporation of many industrial activities residue to ceramic products is a technological alternative for reducing the environmental impact caused by its carefree disposal. This incorporation can promote chemical change and inertness of metals from residue, by fixation in the glassy phase of ceramic during the burning stage. The main aim of this project is to study the technical feasibility of the addition of ceramic oven ash into formulations of mass for structural ceramics. In this project two kinds of clay (plastic and non-plastic) were used, as well as the ash from firewood used in the process of burning of structural ceramics. A group of experiments was outlined, which permitted the evaluation of the influence of the burning cycle in different temperatures of the ash content in formulations for ceramic blocks through technological properties, mechanical behavior and microstructure. Five samples were processed of each one of the masses of plastic and non-plastic clay without addition of ash and with addition of ash on the percentages of 10 % and 20 %, for temperatures of 850 °C, 950 °C, 1050 °C and 1150 °C, obtained through sinterization process. Among the studied compositions, the one which presented best performance was the mass of clay with 10 % of ash, at temperature of 1150 °C, with the smallest absorption of water, the smallest apparent porosity, specific apparent mass a bit over the others and greatest mechanical resistance to flexion. The composition made confirmed the technical feasibility of the use of ash in the mass for structural ceramics with maintenance of its necessary characteristics for its purposes