USE OF INFRARED THERMOGRAPHY ON CANOPIES AS INDICATOR OF WATER STRESS IN 'ARBEQUINA' OLIVE ORCHARDS

Irrigation scheduling is critical for olive orchards, since it affects both fruit yield and olives composition. Regulated deficit irrigation (RDI) strategies have been applied with positive results in the past. However, to successfully regulate stress levels, it is necessary to have accurate measurements of plant water status, which is usually done using a pressure chamber. Canopy temperature (T_c) is another potential accurate indicator of water stress. Therefore, the objective of this study was to evaluate three methods to obtain T_c values from infrared thermal images to calculate the crop water stress index (CWSI). Furthermore, the relation between CWSI and midday stem water potential (MSWP) was also studied. The methods used to obtain T_c were: i) T_c1 obtained from a region of interest within the image; ii) T_c2 obtained from whole image; iii) T_c3 obtained from a filtered image using an interactive filtering process to exclude non-leaf material (low and high temperature values). The infrared thermal images were obtained using an infrared camera (Model i40, FLIR Instruments) in parallel with MSWP measurements from trees under different RDI strategies in a drip irrigated olive orchard (Olea europaea L. ‘Arbequina’) located in Pencahue valley, Maule Region, Chile (35°23’L.S; 71°44’L.W; 96 m a.s.l.) during the 2011-2012 season. Results obtained in this study showed that CSWI₃ calculated using T_c3 had a better correlation with MSWP compared to the two other methods studied. The interactive filter process to obtain T_c values could be used in olive orchards as a fast and cheap indicator of water stress. Further studies are required to automate the analysis process.