Precision Water Stress in Tree Crops Using Thermal Imaging and Trunk Hydration.

Moderate water stress of tree crops can save water and improve the fruit quality, but a reliable indicator of tree water status is required to implement precision water stress.  Measurements of soil moisture are unreliable because of the deep and extensive root systems of trees.  Pressure bomb measurements of stem water potential are reliable, but are labor intensive and cannot be automated.  Infrared measurements of the leaf to air temperature gradient  are partly effective, but the gradient is typically  less than 2 C.  Inserting soil water content sensors into tree sapwood may provide a reliable indicator of trunk hydration and tree water status.  Here we report the integration of  these three methods to  precisely water stress trees in orchards.