Detection of Water Stress in Cotton (Gossypium hirsutum)

Authors: Sassenrath, Gretchen; Thomson, Steven

Submitted to: ASABE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/21/2007
Publication Date: 6/21/2007
Citation: Sassenrath, G.F., Thomson, S.J. 2007. Detection of Water Stress in Cotton (Gossypium hirsutum). ASABE Annual International Meeting.

Interpretive Summary: Cotton (Gossypium hirsutum) is sensitive to water deficit during growth. The goal of our research is to improve crop production through better timing and application of supplemental irrigation water. Key to the correct timing of irrigation is knowledge of the crop water stress. To this end, we are exploring methods of detecting the onset of water stress in cotton. Remote sensing has been used successfully in arid regions to detect crop water deficits, and schedule irrigation. However, water vapor and cloud cover exacerbate attempts to detect early crop water stress in humid areas. Using ground-based measurements, we found a decrease in cotton crop reflectance with water stress, though primarily in the near-infrared spectral range. Visible and thermal aerial images showed similar declines in canopy reflectance. This may have been partly due to increases in soil reflectance due to loss of vegetative growth with water stress in these mature canopies.

Technical Abstract: Insufficient water during growth of cotton (Gossypium hirsutum) plants can inhibit growth and reduce yield and quality. In humid areas, accurate, timely determination of crop water status is hindered by environmental conditions that can interfere with remotely sensed crop temperatures indicative of water stress. Moreover, frequent cloud cover interferes with aerial monitoring of crop status. We are exploring changes in cotton plants and soil with water stress, and correlating physiological and edaphic changes with changes in canopy reflectance. Our goal is to develop an accurate remote sensing system capable of detecting the onset of water stress in cotton prior to canopy closure. Crop and soil temperatures and soil water potential were monitored continuously throughout the growing season, as were crop growth variables. A pair of spectroradiometers mounted on a moveable boom system was positioned over canopy elements to measure the canopy reflectance. Individual leaf temperatures, reflectance, and water potential were determined at different stages of growth. Aerial imagery was collected from thermal and visible cameras mounted on agricultural aircraft. Correlations between physiological, edaphic and reflectance variables are explored to determine the potential utility of remote systems for monitoring crop water status for irrigation scheduling.