Assessment of vineyard water status variability by thermal and multispectral imagery using an unmanned aerial vehicle (UAV)

The goal of this study was to assess the water status variability of a commercial rain-fed Tempranillo vineyard (Vitis vinifera L.) by thermal and multispectral imagery using an unmanned aerial vehicle (UAV). The relationships between aerial temperatures or indices derived from the imagery and leaf stomatal conductance (g (s)) and stem water potential (I-stem) were determined. Aerial temperature was significantly correlated with g (s) (R (2) = 0.68, p < 0.01) and I-stem (R (2) = 0.50, p < 0.05). Furthermore, the thermal indices derived from aerial imagery were also strongly correlated with I-stem and g (s). Moreover, different spectral indices were related to vineyard water status, although NDVI (normalized difference vegetation index) and TCARI/OSAVI (ratio between transformed chlorophyll absorption in reflectance and optimized soil-adjusted vegetation index) showed the highest coefficient of determination with I-stem (R (2) = 0.68, p < 0.05) and g (s) (R (2) = 0.84, p < 0.05), respectively. While the relationship with thermal imagery and water status parameters could be considered as a short-term response, NDVI and TCARI/OSAVI indices were probably reflecting the result of cumulative water deficits, hence a long-term response. In conclusion, thermal and multispectral imagery using an UAV allowed assessing and mapping spatial variability of water status within the vineyard.