Dessecação pré-colheita do feijoeiro: taxa de aplicação, adjuvantes e monitoramento por RPA

Abstract

Pre-harvest desiccation of common beans is a strategic practice, but its effectiveness depends on optimizing application technology and precise monitoring methods. This study aimed to evaluate the impact of different application rates and the addition of adjuvants on desiccation efficacy, integrating scientometric analysis, field trials, and physicochemical characterization in the laboratory. Initially, a global bibliometric mapping was performed in the Scopus and Web of Science databases to assess the evolution of the use of remotely piloted aircraft (RPAs) and the NDVI index in agriculture. In the field, the effect of three application rates (50, 100, and 150 L ha-1) and the addition of an organosilicone adjuvant on spray deposition, defoliation, and grain moisture was evaluated over two growing seasons. Simultaneously, the accuracy of NDVI indices obtained by multispectral and RGB sensors in monitoring senescence was validated. In the laboratory, the droplet spectrum, surface tension, and viscosity of the spray solutions were determined in a completely randomized design (3 x 4 factorial), combining the three application rates with four spray solution compositions (without adjuvant, polydimethylsiloxane, D'limonene, and nonylphenol ethoxylate). Scientometric analysis showed the exponential growth of publications on ARPs and NDVI, consolidating them as technological pillars of modern agricultural monitoring. In the field, the 100 L ha-1 application rate promoted deposition and efficacy similar to 150 L ha-1 and superior to 50 L ha-1. The organosilicone adjuvant did not alter the physical deposition of the spray solution, but significantly accelerated moisture loss from the grains, suggesting optimization in absorption. In monitoring, the correlation of the RGB sensor degraded after application, rejecting the hypothesis that it can replace the multispectral sensor with the same accuracy. In the laboratory, polydimethylsiloxane provided the greatest reduction in surface tension and the greatest increase in volume median diameter (VMD), resulting in the lowest percentage of droplets susceptible to drift (%<100 µm). It is concluded that a rate of 100 L ha-1 represents the best technical and operational balance. Its association with the organosilicone adjuvant enhances the effectiveness of desiccation. Furthermore, the use of air-induction nozzles overrides the physicochemical effect of adjuvants in primary atomization, ensuring application safety, a process that should preferably be monitored by multispectral sensors mounted on UAVs.