Abstract:
Satellites, airborne imaging systems and hand held instruments are frequently proposed as indicators of crop stress caused by water, soil compaction, lack of nutrients, diseases and mites. Laboratory experiments have shown this is possible, but many of these studies focus on stresses far greater than any good farmer would allow their crop to endure. In the absence of any field studies reporting cotton canopy reflectance in Australia, a study was conducted to investigate how crop reflectance and temperature changes with the onset of water stress in the green, red, near infrared and thermal infrared wavelengths of the electromagnetic spectrum. These wavelengths are the most commonly used by remote sensing tools. The objective of this experiment was to determine if crop reflectance measurements could detect water stress before it was visible to the human eye. The emphasis of this project was not on the effects of prolonged water stress that are clearly visible to the eye, but rather subtle changes in the crop water status that farmers contend with as a crop irrigation approaches. Pre-visual detection of water stress using handheld radiometers, airborne or satellite imagery would permit more accurate tinting of irrigations before crop yield is adversely affected.
