**3.4 UAV images and NDVI**

UAV images were taken at midday on April 3rd, 6th, and 9th at three different zones of the plantation. Many trees in the multispectral images (19 + 10) had null NDVI changes after 1 week. In the 19 trees, irrigation was maintained and the other 10 marked with a blue cross (**Figure 9b**) had only one sprinkler removed. After 1 week, those trees without irrigation showed NDVI changes (**Figure 11a** and **b**). Trees grown in loam soil are marked with circles filled with white, being more stressed than those grown over clay soil (red circles). After calculating the NDVI index, trees in loam soil decrease their value from 0.85 to 0.82, as schemed by the blue columns (**Figure 11b**), even when only one sprinkler was removed. The NDVI index of trees standing on clay soil had no variation during the first 4 days when the four sprinklers were removed as shown by the brown column in **Figure 11b**. After 7 days, NDVI index of trees grown on clay soil decreased to 0.81.
