RESUMO A qualidade e o valor da bebida do café podem ser afetados pela contaminação de impurezas durante a torra e moagem. Métodos que permitem o controle de qualidade do produto comercializado são importantes para atender aos padrões exigidos pelos consumidores e pela indústria. Objetivou-se neste estudo estimar o percentual de impurezas contidas no café usando descritores texturais e colorimétricos obtidos a partir de imagens digitais. Os grãos de café arabica (Coffea arabica L.) com 100% de pureza foram submetidos a processos de torra e moagem, e o café moído inicialmente puro foi gradativamente contaminado por impurezas. As imagens digitais foram coletadas em amostras de café com 0, 10, 30, 50 e 70% de impurezas. A partir das imagens, foram obtidos os descritores texturais de histogramas (média, desvio padrão, entropia, uniformidade e terceiro momento) e os descritores colorimétricos (espaço de cores RGB e espaço de cores HSI). O método de regressão de componente principal (PCR) foi aplicado ao grupo de dados de descritores texturais e colorimétricos para o desenvolvimento de modelos lineares para estimativa de impurezas do café. Os modelos selecionados para o grupo de dados dos descritores texturais e o grupo de dados dos descritores colorimétricos foram compostos por dois e três componentes principais, respectivamente. O modelo dos descritores colorimétricos apresentou maior capacidade de estimativa da porcentagem de impurezas no café quando comparado com o modelo dos descritores texturais.

ABSTRACT The quality and price of coffee drinks can be affected by contamination with impurities during roasting and grinding. Methods that enable quality control of marketed products are important to meet the standards required by consumers and the industry. The purpose of this study was to estimate the percentage of impurities contained in coffee using textural and colorimetric descriptors obtained from digital images. Arabica coffee beans (Coffea arabica L.) at 100% purity were subjected to roasting and grinding processes, and the initially pure ground coffee was gradually contaminated with impurities. Digital images were collected from coffee samples with 0, 10, 30, 50, and 70% impurities. From the images, textural descriptors of the histograms (mean, standard deviation, entropy, uniformity, and third moment) and colorimetric descriptors (RGB color space and HSI color space) were obtained. The principal component regression (PCR) method was applied to the data group of textural and colorimetric descriptors for the development of linear models to estimate coffee impurities. The selected models for the textural descriptors data group and the colorimetric descriptors data group were composed of two and three principal components, respectively. The model from the colorimetric descriptors showed a greater capacity to estimate the percentage of impurities in coffee when compared to the model from the textural descriptors.

ABSTRACT The use of Precision Agriculture tools and soil attributes has contributed to local agricultural management in the identification of different productive potentials and quality of pastures. The present study aimed to use Precision Agriculture tools to investigate the spatial variability of soil organic matter fractions and soil chemical and physical attributes and to delineate management zones in pasture soils cultivated under tropical conditions. The study was conducted on a hay production farm located in Seropédica, Brazil. Fifty points were collected on a irregular grid and soil samples were taken at depths of 0-0.20 and 0.20-0.40 m and crop productivity was evaluated. Chemical and physical soil organic matter fractionation was performed to obtain data on fulvic acid, humic and humin fractions, mineral-associated and particulate organic carbon, and light organic matter. Geostatistics and multivariate analysis (principal component analysis and k-means clustering) were performed to define the management zones. The results obtained contributed to the division of the pasture area into two regions that can be managed in different ways aiming to increase soil organic matter in a localized manner with the possibility of reducing the use of inputs and directed management that respects the productive potential of the pasture on the farm.

ABSTRACT In recent years, the coffee has undergone major changes, and in case of transplanting operation, the use of machinery has proved to be a viable alternative to producers. Prior knowledge of the influence of the variables that influence the operational capability of these machines can generate models to estimate precisely these parameters, thus enabling the optimization and management of mechanized operations. One of this tool is the use of the response surface methodology, which allows checking the influence of different independent variables and the response generated to allow a great value. This study aims to verify the use of the response surface method to determine parameters of mechanized operations in coffee plant implantation. The results show that the number of seedlings deposited increases with the increase in operating speed. In contrast, the adoption of higher speeds decreases the efficiency of the evaluated field operations. The response surface methodology was an important tool to check the effect of variables on performance parameters, and the generated models showed high significance allowing the identification of the effects of the operational speed and the average length of the cultivation line.

RESUMO A qualidade do café é um aspecto imprescindível para o aumento do seu valor comercial e para que a cafeicultura brasileira continue com destaque no mercado mundial. O estádio de maturação dos frutos no momento da colheita é um dos fatores importantes que interfere na qualidade e no valor comercial do produto. Com a realização deste trabalho, objetivou-se desenvolver um classificador para determinação do momento de colheita do café pela força de desprendimento. A força de desprendimento dos frutos e o valor percentual do estádio de maturação foram mensurados durante a janela de colheita de 75 dias. As coletas foram realizadas quinzenalmente, resultando em cinco momentos distintos no período de colheita. Um classificador foi desenvolvido a partir de redes neurais para distinguir frutos verdes e cerejas nos momentos de colheita analisados. Os resultados demostraram que a primeira quinzena de junho foi o momento em que o classificador supervisionado apresentou a maior porcentagem de acerto na distinção de frutos verdes e cerejas, sendo este, o momento adequado para realização de uma colheita seletiva para as condições deste experimento.

ABSTRACT Coffee quality is an essential aspect to increase its commercial value and for the Brazilian coffee business to remain prominent in the world market. Fruit maturity stage at harvest is an important factor that affects the quality and commercial value of the product. Therefore, the objective of this study was to develop a classifier using neural networks to distinguish green coffee fruits from mature coffee fruits, based on the detachment force. Fruit detachment force and the percentage value of the maturity stage were measured during a 75-day harvest window. Collections were carried out biweekly, resulting in five different moments within the harvest period. A classifier was developed using neural networks to distinguish green fruits from mature fruits in the harvest period analyzed. The results show that, in the first half of June, the supervised classified had the highest success percentage in differentiating green fruits from mature fruits, and this period was considered as ideal for a selective harvest under these experimental conditions.

RESUMO Objetivou-se, neste trabalho, avaliar o desempenho de um sistema de distribuição de fertilizantes a uma taxa variável para a cultura do café aplicando dois produtos simultaneamente. Realizaram-se dois tipos de ensaio: o de deposição transversal e de deposição longitudinal utilizando-se, nesses ensaios, delineamento inteiramente casualizado (DIC) em esquema fatorial sendo realizado o teste de Scott-Knott a 0,05 de probabilidade. Nos ensaios de deposição transversal objetivou-se quantificar as variações entre as doses programadas e aplicadas enquanto os ensaios de deposição longitudinal tiveram, como objetivo, a determinação das características de distribuição do equipamento ao longo da linha de deslocamento analisados através de valores de frequência relativa; outro fator analisado foi o comportamento de aplicação das doses nos dois lados de distribuição do sistema; observou-se que a variação de aplicação no ensaio de deposição transversal com lonas foi de -1,59%; o sistema de distribuição a uma taxa variável se manteve estável em relação à deposição longitudinal independente de qualquer interação.

ABSTRACT The objective of this study was to evaluate the performance of a variable-rate fertilizer distribution system for coffee crop, simultaneously applying two products. Two types of tests were performed: transversal deposition and longitudinal deposition. The transversal deposition test, with tarps, aimed to quantify the variations between programmed and applied doses, using a completely randomized design (CRD), in a factorial scheme, and the Scott-Knott test at p < 0.05. The longitudinal deposition test aimed to determine the distribution characteristics of the equipment along the displacement line, based on relative frequency values. In addition, the application rates on both sides of the distribution system were analysed using a CRD and the Scott-Knott test at p < 0.05. The application variation in the transversal deposition test with tarps was 1.59%. The variable-rate distribution system remained stable regarding the longitudinal deposition, regardless of any interaction.

Ao se utilizar pressão de inflação e a capacidade de carga (lastro) adequadas, pode-se obter um rendimento maior e um prolongamento da vida útil do pneu; além disso, minimizam-se os problemas de perda de tração, aumento de patinhagem e consumo de combustível. O presente trabalho teve como objetivo avaliar o consumo de combustível de um trator agrícola operando com pneus novos e desgastados, em três condições de lastragem e três pressões de inflação, ao trafegar sobre solo compactado com cobertura vegetal. O experimento foi realizado na unidade experimental do Departamento de Zootecnia da Universidade Federal de Lavras, Lavras-MG, em um solo compactado pelo pisoteio de bovinos e com cobertura vegetal. Utilizou-se um trator 4x2 TDA, com potência de 65,62 kW no motor. Os pneus foram do tipo R1, diagonal (dianteiros: 12,4-24; traseiros: 18,4-30), sendo que a altura média das garras dos pneus novos foi de 0,3 e 0, 35 m para os pneus dianteiros e traseiros, respectivamente, e nos pneus desgastados, 0,018 e 0,0045 m para os pneus dianteiros e traseiros, simultaneamente. Os resultados evidenciaram vantagens para o trator quando equipado com pneus novos.

When using appropriate inflation pressures and load capacity (ballast), it may obtain a higher yield and prolongation of the life of the tire, besides it may minimize the problems of loss of traction, increased slippage and fuel consumption. This study aimed to evaluate the fuel consumption of a tractor operating with new and worn tires in three conditions of ballasting and three inflation pressures, when driving on compacted soil with vegetation cover. The experiment was conducted at the experimental unit from the Department of Animal Science, Federal University of Lavras, state of Minas Gerais, Brazil, in an agricultural soil compacted by cattle trampling and with vegetation cover. It was used a tractor 4x2 with front wheel assist, of a 65.62 kW engine power. The tires were of R1 type, diagonal (front: 12.4 to 24; and rear: 18.4 to 30), the average height of the clutches of the new tires were 0.3 and 0.35 m for front and rear tires, respectively, and for the worn tires were 0.018 and 0.0045 m, for the front and the rear tires, respectively. The results showed advantages for the tractor equipped with new tires.