Abstract

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 degrees 23'L.S; 71 degrees 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.