Evapotranspiration Measurements in Pasture Classes, Crops, and Native Cerrado Based on Sensors Embodied on Uavs

Abstract In Brazil, agriculture consumes most of the available freshwater, especially in the Cerrado biome, where the rain cycle is marked by long periods of drought. This study, conducted at Embrapa Arroz e Feijão Rice and Beans unit in Santo Antônio de Goiás, Goiás, estimated evapotranspiration (ET) in different crops and soil cover. Using multispectral Unmanned Aerial Vehicle (UAV) images and weather station data, we applied the "Simple Algorithm for Evapotranspiration Retrieving" (SAFER) to calculate ET in bean, pasture, and Semideciduous Seasonal Forest areas. The results showed a good agreement between UAV and satellite data, with R² = 0.84, also validated with flow towers by the eddy covariance method. UAV-based ET was observed to correspond well to tower (EC) during full vegetative development of beans but is underestimated at the beginning of planting and in the final periods of plant senescence, due to the influence of soil or straw cover. These findings contribute to a better understanding of water dynamics in the system and to enhancing sustainable agricultural practices. This method, adapted for multispectral aerial imaging, can be applied flexibly and on demand, in different contexts and ground cover. The study highlights the importance of integrated agricultural practices for better management of water resources and preservation of the Cerrado in balance with cultivation areas.