S12 - Session P1 - Using a mobile platform to measure canopy temperature and map plant water status in a nectarine orchard

Authors: Alessio Scalisi *, Mark Glenn O'Connell, James Underwood, Ian Goodwin

In a climate change and water scarcity scenario, precise irrigation management tailored to plant water status (PWS) is paramount for sustainable agriculture. Canopy temperature (T c ), delta temperature [dT = T c - ambient temperature (T a )] and crop water stress index (CWSI) can be used to describe PWS. This study aimed to test a mobile platform sensor system (Green Atlas Cartographer equipped with infrared temperature sensors) for rapid measurements of T c (and derivation of dT and CWSI) in nectarine trees subjected to different irrigation regimes. The study was conducted on mature high density 'September Bright' nectarine trees under different irrigation treatments m 100 % of crop evapotranspiration (ET c ), 40 % of ET c , 20 % ET c and no irrigation (0 % of ET c ) imposed at all fruit development stages. The orchard was scanned using Cartographer ; T c , dT and CWSI were obtained and their relationship with irrigation treatments was verified. Leaf water potential and leaf conductance were related to canopy temperature indices. T c and CWSI were found to be significantly inversely related to irrigation treatments irrespective of fruit development stage or time of the day. The spatial maps of T c revealed a clear visual separation of the deficit irrigation treatments even in days with low evaporative demand and low vapour pressure deficit. We contend that T c can be used per se as a tool to assess spatial variability of PWS at single points in time when measurements are taken in relatively short time whereby T a can be considered constant. However, CWSI and dT are the preferred indices of PWS for comparisons between different days and/or times of the day. Our results confirm the suitability and utility of ground-based vehicles for fast assessments of plant water status in orchards using infrared thermography to achieve precise spatial and temporal irrigation management.