Thermal imaging for estimating and mapping crop water stress in cotton

Water is a scarce resource and a major factor limiting crop productivity. Precision irrigation might promote water saving. In order to implement precision irrigation, efficient techniques for estimating spatial crop water status are needed. Thermal and visible images of cotton canopies were used in this study for estimating and mapping leaf water potential (LWP) and their application in cotton fields. Data were collected from cotton canopies representing a range of plant water status, phenological stages, growing seasons, species and locations. Fusion of visible and thermal images was used for detecting temperatures of sunlit canopy. The crop water stress index (CWSI) statistics were calculated using canopy temperatures and theoretical and empirical references. Models for estimating LWP from the thermal index CWSI were built. The models that were based on empirical references showed good correlation with measured LWP. The accuracy of the LWP-CWSI model was highest during the last phenological stage. The model was then used for generating LWP maps of plots with different water status.