ESTIMATION OF SOIL MASS AND NUTRIENT LOSS IN GULLIES IN THE ATLANTIC FOREST USING UNMANNED AERIAL VEHICLE IMAGERY

Erosion is a major environmental problem that contributes to soil and nutrient losses. The use of unmanned aerial vehicles (UAVs) has the potential to assist in monitoring and increase the accessibility and accuracy of this information. This study aimed to estimate the loss of soil mass and nutrients in the occurrence of gullies at different stages of development over 3 years in Pinheiral-RJ, Brazil. Aerial photographs of four gullies (initial, juvenile, mature and senile stages) were taken in 2017 and 2020 using UAV. The captured images had a spatial resolution of 0.04 m. Deformed and undisturbed soil samples (0.00–0.10 m deep) were collected inside the gullies in the dry and rainy seasons of 2017. Nutrient content, total organic carbon and soil bulk density were determined, and estimated soil mass and nutrient removal. The senile gully had the highest area, volume, soil density and amount of soil mass and nutrients removed, while in the initial gully the values were lower. After 3 years there was an increase in the removal of soil mass in the gullies, except in the senile stage due to the appearance of tree individuals. Overall, the UAV is a valuable tool for mapping degraded soils.