Desenvolvimento de mesa para medição do perfil de distribuição de pulverização com drones e calibração para otimização da aplicação na cafeicultura

Abstract

To meet the global demand for high-quality and sustainable coffee, new technologies such as spraying drones are being adopted by coffee growers to assist in cultivation of crop with restricted access with limited labor. Since application efficiency depends on proper calibration, this work aimed to identify the distribution pattern of different spray volumes and flight heights and to evaluate the application efficiency of sprays with different volumes and flight speeds in coffee trees of two different ages in the upper, middle, and lower thirds. In the first study, a table was developed for evaluating volumetric distribution, using materials that are easily accessible and manageable. The treatments included four spray volumes (8, 12, 16, and 20 L ha-1) and three flight heights (2, 3, and 4 m), with three repetitions. The application uniformity was evaluated through graphs and the coefficient of variation, and the swath width was quantified. Flights at 2 meters showed greater variation in the center of the application swath, while flights at 3 and 4 meters showed a more uniform distribution closer to normality. A direct relationship was observed between the spray volume and the applied swath width. The highest application uniformity was obtained with 8 L ha-1, regardless of the height used. The low-cost system developed proved efficient, indicating that flight height and spray volume significantly influence the spray distribution pattern by drones. The best application uniformity was observed with a 3-meter height and 8 L ha-1. The second study was conducted in 2.5- and 6.5-year-old coffee plantations. The treatments consisted of four spray volumes (8, 12, 16, and 20 L ha-1) and two flight speeds (12 and 15 km h-1), with three repetitions. Hydrosensitive papers were distributed in different thirds of the plants. The reading was performed by DropScope, providing data on DMV, DMN, relative amplitude, Dv 0.9, and Dv 0.1. In the analysis, spray volume, flight speed, and paper position were considered factors. There was a difference in application efficiency in coffee trees of different ages. While in the younger coffee plantation the paper position on the plant showed little difference, in the older one, a larger droplet size was observed in the upper third. Overall, in the 2.5-year-old plantation, spraying at 15 km h-1 produced droplet sizes indicative of good spray penetration, demonstrating the potential for using higher flight speeds in younger plantations. In contrast, in the 6.5-year-old plantation, spraying at 12 km h-1 resulted in finer droplets, indicating better coverage at lower flight speeds. Therefore, it is important to calibrate the spraying drone according to the plant age, considering that different spray volumes and flight speeds influence the application distribution and penetration.