The objective of this study was to evaluate the potential of the practical application of unmanned aerial vehicles and RGB vegetation indices (VIs) in the monitoring of a coffee crop. The study was conducted in an experimental coffee field over a 12-month period. An RGB digital camera coupled to a UAV was used. Nine VIs were evaluated in this study. These VIs were subjected to a Pearson correlation analysis with the leaf area index (LAI), and subsequently, the VIs with higher R2 values were selected. The LAI was estimated by plant height and crown diameter values obtained by imaging, which were correlated with these values measured in the field. Among the VIs evaluated, MPRI (0.31) and GLI (0.41) presented greater correlation with LAI; however, the correlation was weak. Thematic maps of VIs in the evaluated period showed variability present in the crop. The evolution of weeds in the planting rows was noticeable with both VIs, which can help managers to make the decision to start crop management, thus saving resources. The results show that the use of low-cost UAVs and RGB cameras has potential for monitoring the coffee production cycle, providing producers with information in a more accurate, quick and simple way.

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Precision coffee-growing technologies contribute to increased yield, operational efficiency, and final product quality. In addition, they strengthen coffee growing in the global agricultural scenario, which makes this activity increasingly competitive. Scientific research is essential for technological development and offering security regarding its application. For relevant research identification, bibliometric revision methods expose the best studies and their relationships with countries and authors, providing a complete map of research directions. This study identified the main contributions and contributors to academic research generation about precision coffee growing from 2000 to 2021. Bibliometric analysis was performed in VOSViewer software from the referential bases Scopus and Web of Science that identified 150 articles. Based on the number of citations, publications about precision coffee-growing showed Brazilian institutions at the top of the list, and Brazil’s close relationships with North American and South African institutions. Geostatistical analysis, remote sensing and spatial variability mapping of cultivation areas were used in most experimental research. A trend in research exploring machine learning technologies and autonomous systems was evident. The identification of the main agents of scientific development in precision coffee growing contributes to objective advances in the development and application of new management systems. Overall, this analysis represents wide precision coffee growing research providing valuable information for farmers, policymakers, and researchers.

Mechanized operations on terrain slopes can still lead to considerable errors in the alignment and distribution of plants. Knowing slope interference in semi-mechanized planting quality can contribute to precision improvement in decision making, mainly in regions with high slope. This study evaluates the quality of semi-mechanized coffee planting in different land slopes using a remotely piloted aircraft (RPA) and statistical process control (SPC). In a commercial coffee plantation, aerial images were collected by a remotely piloted aircraft (RPA) and subsequently transformed into a digital elevation model (DEM) and a slope map. Slope data were subjected to variance analysis and statistical process control (SPC). Dependent variables analyzed were variations in distance between planting lines and between plants in line. The distribution of plants on all the slopes evaluated was below expected; the most impacted was the slope between 20–25%, implementing 7.8% fewer plants than projected. Inferences about the spacing between plants in the planting row showed that in slopes between 30–40%, the spacing was 0.53 m and between 0 and 15% was 0.55 m. This denotes the compensation of the speed of the operation on different slopes. The spacing between the planting lines had unusual variations on steep slopes. The SCP quality graphics are of lower quality in operations between 30–40%, as they have an average spacing of 3.65 m and discrepant points in the graphics. Spacing variations were observed in all slopes as shown in the SCP charts, and possible causes and implications for future management were discussed, contributing to improvements in the culture installation stage.

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Adobe is an efficient construction material for several reasons, such as its thermal comfort, sustainability, and lower energy cost, as well as the simplicity of its production and execution. However, challenges such as water absorption, capillarity, and compressive strength should be investigated to improve its physical and mechanical properties. "Synthetic termite saliva" (STS) is an excellent stabilizer with high cohesive and hydrophobic power. Therefore, the objective of this work was to evaluate the effects of STS incorporation into adobe, analyzing its physical, mechanical and thermal properties. Five treatments were studied: 0 (control); 0.1; 0.2; 0.4 and 0.8% STS by mass. These adobe samples were evaluated according to bulk density, linear shrinkage, capillarity, water absorption, thermal conductivity and compressive strength, according to Norma Técnica de Edificación (NTE) E0.80 testing using a new methodology. Linear shrinkage decreases from 2.7 to 1.91 cm with 0.4% STS. Capillarity decreases with the increasing amounts of STS. Water absorption decreased from 12.03 to 6.31% using 0.4% STS, and its mass was reduced from 779 to 19 grams. The thermal conductivity showed no differences between concentrations. The compressive strength was reduced but was still acceptable based on NTE E.080. The stabilization of the adobe using STS showed an improvement in its physical properties, mainly due to its hydrophobic power.

No abstract

Pela praticidade e simplicidade de construção, nos últimos anos, os biodigestores tubulares, também conhecidos como canadense, têm sido utilizados para o manejo e tratamento de resíduos da suinocultura. Contudo, a escassez de informações acerca da composição energética destas estruturas limita a realização de estudos relacionados às análises energéticas nesses biossistemas. O objetivo deste trabalho foi contabilizar a energia empregada na construção de biodigestores anaeróbios de fluxo tubular utilizados para o manejo e tratamento de resíduos da suinocultura. Para tanto, foram quantificados os componentes envolvidos na construção dos biodigestores e, em seguida, para transformação em unidades de energia desses componentes, multiplicou-se a quantidade destes pelos seus respectivos coeficientes energéticos. Os resultados indicaram que a construção dos biodigestores consumiu 490.179,59 MJ de energia, sendo que o componente energético mais expressivo no consumo energético foram as geomembranas flexíveis de PVC (29,33%), seguido pelas tubulações de PVC e lonas de impermeabilização com 28,45% e 21,06% da energia consumida, respectivamente. Considerando o volume útil dos biodigestores, o índice energético determinado foi de 225,89 MJ m-3.