Increasing the efficiency of solar dryers with ensuring that the system remains accessible to all users can be achieved with their automation through low-cost and easy-to-use technique sensors. The objective was to develop, implement and evaluate an automatic system for monitoring drying parameters in a hybrid solar-electric dryer (HSED). Initially, an automated data acquisition system for collecting the parameters of sample mass, air temperature, and relative air humidity was developed and installed. The automatic mass data acquisition system was calibrated in the hybrid solar-electric dryer. The automated system was validated by comparing it with conventional devices for measuring the parameters under study. The data obtained were subjected to analysis of variance, Tukey test and linear regression at p ≤ 0.05. The system to turn on/off the exhaust worked efficiently, helping to reduce the errors related to the mass measurement. The GERAR Mobile App showed easy to be used since it has intuitive icons and compatibility with the most used operating systems for mobile devices. The responses in communication via Bluetooth were fast. The use of Arduino, a low-cost microcontroller, to automate the monitoring activity allowed estimating the mass of the product and collecting the drying air temperature and relative air humidity data through the DHT22. This sensor showed a good correlation of mass and air temperature readings between the automatic and conventional system, but low correlation for relative air humidity. In general, the automatic data acquisition system monitored in real time the parameters for drying agricultural products in the HSED.

Results of evaluations using optical evaluation methods may be correlated with tomato quality and maturation. In this context, the objective of this study was to evaluated the correlation between tomato colorimetric and physico-chemical variables, clustering them as a function of maturation stages, using multivariate analysis. The experiment was conducted using 150 fruits and three maturation stages (immature, light red and mature). The physico-chemical variables were evaluated through traditional methods. The colorimetric variables were assessed on images in RGB color model taken with a digital camera. The correlation between colorimetric and physico-chemical variables was analyzed using the Pearson’s coefficient. Principal components analysis and k-means clustering method was applied to three data set: RGB isolated variables; colorimetric variables calculated by relation between the RGB bands (colorimetric indexes); and physico-chemical variables. The colorimetric variables present higher explanatory capacity of the maturation variation than physico-chemical variables. The colorimetric indexes presented higher performance in clustering (accuracy of 0.98) tomatoes as a function of maturation.

O balanço energético permite identificar as possíveis entradas e saídas de energia no processo de produção, resultando no saldo energético final do processo produtivo. O objetivo do trabalho foi avaliar os fluxos de energia e a demanda energética de dois sistemas de manejo do solo para a produção de sorgo silageiro na região metropolitana do estado do Rio de Janeiro. Foram realizados o estudo da eficiência energética e o balanço energético, quantificando o coeficiente energético de cada componente envolvido no processo de produção e determinando as matrizes de consumo energético nas formas de insumos, mão-de-obra, equipamentos, produção de silagem e restos culturais. Utilizou-se delineamento de blocos casualizados com cinco repetições, onde os tratamentos foram constituídos por sistema de preparo convencional do solo (SC) e sistema de preparo convencional com gradagem pré-plantio (SCG). Para os dados das entradas e saídas de energia, do balanço energético e da eficiência, os mesmos, quando significativos, foram submetidos ao teste de comparação de média Scot-Knott a 5 % de probabilidade. Os resultados indicaram que a contribuição do dispêndio energético dos fertilizantes e combustíveis foi determinante para o elevado consumo energético dos sistemas de cultivo estudados, sendo o efeito contrário para as energias referentes às fontes de origem biológica. Para as condições do presente experimento, sob o ponto de vista energético, o sistema com gradagem adicional (SCG) apresentou-se energeticamente mais viável, apresentando maior produtividade e eficiência na conversão de energia.

Comparação de parâmetros de qualidade obtidos por métodos destrutivos e óptico para classificação de tomates

O entendimento e conhecimento das características operacionais de conjuntos mecanizados se tornou uma preocupação cada vez mais frequente na agricultura moderna. Por conta do alto valor agregado, conhecer a viabilidade econômica dos custos de produção é essencial, pois são diretamente afetados pelo desempenho operacional das máquinas agrícolas envolvidas. Objetivou-se avaliar o desempenho operacional e determinar os custos operacionais nos diferentes conjuntos mecanizados na produção de feno do Tifton 85 (Cynodon spp.). O experimento foi conduzido na fazenda Feno Rio, localizada no campus de Seropédica da Universidade Federal Rural do Rio de Janeiro, em uma área total de 60 hectares cultivadas por Tifton 85 (Cynodon spp.). Foram determinados o desempenho operacional e os custos das diferentes operações mecanizadas realizadas durante a produção do Tifton 85. A mecanização na produção do Tifton 85 para a região da Baixada Fluminense se mostrou viável, apresentando lucratividade de 32,21% e margem líquida de 4.690,16 R$ ha^-1. Conclui-se que os custos com a etapa de colheita refletem 56% de todo o custo com mecanização agrícola no processo de produção do Tifton 85.

Diversified cropping systems offer an alternative to sustainable agriculture, but they present high spatial variability. This study aims to develop and evaluate an automated irrigation system and a variable-rate water application for areas with diversified vegetable crops. The prototype comprises a mobile drip line, a winding reel, and an electronic control system. The drip line irrigates plants individually, with irrigation depths along the beds controlled by the displacement speed and between beds by adjusting the timing of electrical pulses to activate the water flow control valves. To evaluate the drip line, irrigation depths were defined for different crops, followed by performance assessments, which included evaluating the uniformity (Christiansen’s Uniformity Coefficient—CUC) of the line under constant and variable rates. A hydraulic evaluation of the system was also carried out, as well as the calculation of the potential irrigable area. The drip line showed CUC ≥96% for depths under a constant rate and 95% for depths under a variable rate. The application efficiency reached 93.4% for a degree of suitability of 83%, considering variable depths along and between beds. The potential irrigable area obtained was 360 m² day⁻¹. The developed drip line effectively meets the spatial variability of crop water requirements in diversified cropping systems by adopting the variable-rate irrigation technique. The control of irrigation depth through valve activation via electrical pulses allows for the application of variable depths between the beds.