Potential use of infrared thermometry for the detection of water deficit in apple and peach orchards.

摘要

The present work was carried out to define a methodology for the detection of plant water deficit in orchards by using ground-based infrared thermal imagery. The measurements were carried out in Michigan, USA, during the summer of 1999 in apple (cv.Empire/Mark) and peach (cv. Redhaven) orchards. Real-time digital, still thermo-images (thermograms) and videos were captured on single canopies of well-watered trees and trees subjected to water shortage, using an infrared imaging radiometer. Simultaneously, the principal atmospheric factors were monitored. A measurement routine (i.e. corresponding environmental parameters and same geometrical configuration among sun/canopy surface/view axes) was adopted, which allowed the comparison of the thermograms acquired in the two treatments. Image processing and analysis provided central tendency values higher in the non-irrigated plants compared to those of well-watered trees (due to the lower transpiration activity, which induces a readjustment of leaf energy budget through an increase in the sensible heat component), even when leaf net photosynthetic activity and fruit size were not yet adversely affected by water shortage. The results of this study support the use of digital infrared thermal imagery andcomputer imaging to timely detect plant water deficit in orchards. However, the successful application of this remote sensing technique still requires a high level of proficiency in capturing the suitable images, especially when the target is represented by an adult tree, and in conveniently processing them.