Comparison of methods for field scale mapping of plant water status using aerial thermal imagery

In previous studies, a model for assessing leaf water potential (LWP) in cotton plants based on Crop Water Stress Index (CWSI) calculated using ground thermal imagery and artificial wet reference (AWR), as the minimum temperature, was developed and validated. The AWR cannot be measured from aerial thermal images and in order to implement this approach, it is essential to characterize the minimum boundary reference temperature and to evaluate the validity of the CWSI-LWP relationship. Four types of minimum references were examined: artificial, theoretical, plant and virtual. Three aerial thermal images were acquired above a cotton field. The best relationship was found between calculated and measured LWP using the virtual reference: high correlation and 1:1 fit. This means that a reliable LWP map of a cotton field can be created using only an aerial thermal image and air temperature. Using the LWP-CWSI relationship, the LWP can be mapped for each pixel or for each area of interest such as an irrigation section or pre-defined management zone.