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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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DETERMINAÇÃO DO COEFICIENTE DE CULTIVO (Kc) DO CAPIM  TANZÂNIA IRRIGADO NO NORTE DE MINAS GERAIS  BRENON DIENNEVAN SOUZA BARBOSA¹; FLÁVIO GONÇALVES OLIVEIRA² E FLÁVIO PIMENTA DE FIGUEIREDO3 ¹Graduando em Engenharia Agrícola e ambiental. Universidade Federal de Minas Gerais. Instituto de Ciências Agrárias da Campus Montes Claros-MG., ICA/UFMG. .e-mail: b.diennevan@outlook.com²Engenheiro Agrícola, Doutor, Instituto de Ciências Agrárias,  Universidade Federal de Minas Gerais. ICA/UFMG, campus Montes Claros-MG           .flagiogoliveira@ibest.com.br²Engenheiro Agrícola, Doutor, Instituto de Ciências Agrárias,  Universidade Federal de Minas Gerais. ICA/UFMG, campus Montes Claros-MG           figueiredofp@ica.ufmg.br  1 RESUMO O período de estiagem na região norte mineira, que pode perdurar até 8 meses, estendendo-se de Março até final de Outubro, é um grande problema para a produção de pastagem. A pecuária é umas das principais atividades econômicas desta região e, nestas condições, o uso da irrigação, é imprescindível para reduzir os efeitos do déficit hídrico na produção de forragem. Este estudo visou a determinação do coeficiente de cultivo (Kc) do capim Tanzânia, nas condições climáticas da safra 2012 – 2013 na região norte de Minas Gerais. Os valores de coeficiente de cultivo (Kc) foram determinados em lisímetros de drenagem que recebiam uma lâmina de irrigação correspondente a 120% da evapotranspiração de referência (ETo). Estes lisímetros foram selecionadas em decorrência da maior produtividade em relação aos tratamentos recebendo 30, 60, 90 e ETo e da igualdade de produtividade, 38 ton/ha/ano, em relação aos lisímetros recebendo 150% da Eto. No verão, os valores médios de Kc, correspondentes a quatro repetições, apresentaram valores variando desde 0, 67, logo após o corte, até 1,2, aproximadamente trinta dias após o corte. No inverno, o valor médio de Kc foi igual a 1. Palavras-chave: Forragicultura, manejo de irrigação, irrigação de pastagem  BARBOSA, B. D. S.; OLIVEIRA, F.G.; FIGUEIREDO, F. P. DEDETERMINATION OF CROP COEFFICIENT (Kc ) OF TANZANIA GRASS IRRIGATION IN GENERAL MINES NORTH  2 ABSTRACT The dry season in the northern region of Minas Gerais state, which can last up to 8 months, stretching from March to end of October, is a major problem for pasture production. Livestock is one of the main economic activities of this region and , in these conditions , the use of irrigation , it is essential to reduce the effects of drought on forage production. This study aimed to determine the crop coefficient (Kc ) of the Tanzania grass, in the climatic conditions of the 2012 - 2013 season in the northern region of Minas Gerais. The crop coefficient values (Kc) were determined in drainage lysimeters receiving irrigation depth corresponding to 120 % of the reference evapotranspiration ( Eto). These lysimeters were selected because they achieved the same yield level, around 38 ton / ha / year, of the lysimeters in which it were applied 150% of Eto and a higher productivity in relation to the lysimeters in which were applied 30, 60, and  90% of ETo. In summer, average Kc values, corresponding to four replications, presented values ranging from 0.67, soon after cutting, to 1.2, approximately thirty days after the cut. In the winter, the average value Kc is equal to 1.0. Palavras-chave: Forragicultura, manejo de irrigação, irrigação de pastagem

This study aimed to evaluate the energy efficiency of a center pivot irrigation system operating in a terrain of variable topography. Values of Pumping Energy Efficiency (PEE), Supply Energy Efficiency (SEE), Global Energy Efficiency (GEE) and Specific Energy (Es in kWh m -3 ) computed at 18 different angular positions of the lateral line were used as energy efficiency indicators. An ultrasonic flow meter, digital pressure transducers and a power quality analyzer were used in order to evaluate hydraulic (total system flow-Q and total dynamic head-TDH) and electrical parameters (active electrical power -AEP) of the center pivot pumping unit that were required for evaluating the selected energy efficiency indictors. Topographic elevations of the water source, the pumping unit and of the center lateral line were also determined. For the center pivot lateral line, it was necessary to determine, at the 18 angular positions considered, the altitude of the track of each center pivot support tower. Results indicated that currently, even after more than 10000h of use, the center pivot system operates with satisfactory energy efficiency, as indicated by an average GEE value equal to 42.5%, that is classified as "good". Statistical analysis indicated that the topographic disposition of the center pivot lateral line, as characterized by a uphill or downhill disposition, resulted on different PEE, SEE and GEE values, while the average Es value (0.42 kWh m -3 ) was not affected by the lateral line disposition.

Leaf area is a component of crop growth and yield prediction models. Few studies have used the structure from motion (SfM) algorithm, which is based on the principles of traditional stereophotogrammetry, to obtain the leaf area index (LAI). Thus, the objective of this study was to follow the evolution of the LAI and percentage of land cover (%COV) in coffee plants, using pre-established equations and plant measurements obtained from generated 3D point clouds, combined with the application of the SfM algorithm to digital images recorded by a camera coupled to a UAV (unmanned aerial vehicle). The experiment was conducted in a coffee plantation located in southeastern Brazil. A rotary wing UAV containing a conventional camera was used. The images were collected once per month for 12 months. Image processing was performed using PhotoScan software. Regression analysis and spatial analysis were performed using R and GeoDa software, respectively. The resulting %COV data had R 2 and RMSE values of 89% and 3.41, respectively, while those for LAI had R 2 and RMSE of 88% and 0.47, respectively. Significant %COV results were obtained in the months of January, February and March of 2018. There was significant autocorrelation for the LAI values from January to May 2018, with most blocks in the central and centerwest regions presenting LAI values > 3.0. It was possible to monitor the temporal and spatial behavior of the LAI and %COV, allowing for the conclusion that this methodology generated results that are consistent with the literature.

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