Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2005
Publication Date: 1/4/2006
Citation: Gonzalez-Dugo, M., Moran, M.S., Mateos, L., Bryant, R. 2006. Canopy temperature variability as an indicator of crop water stress severity. J. Irrig. Sci. 24:233-240. Interpretive Summary: Irrigation is a significant means of raising production in agricultural crops. It is essential in arid environments, and is often used to increase crop productivity in semi-arid and humid areas. This study uses the within-field variability of canopy temperature, measured by airborne sensors, to measure field-scale water stress and improve irrigation scheduling. This approach worked well to identify low and moderately stressed crops, and thus, assist with irrigation timing. On the other hand, the approach was also sensitive to irrigation uniformity, field root zone water holding capacity, and some basic meteorological conditions such as wind speed, vapor pressure deficit and air temperature. These sensitivities could limit the operational application of this remote sensing approach for irrigation scheduling. Nonetheless, for large irrigation districts, this may be an economical option for minimizing water use and maximizing crop yield.
Technical Abstract: Irrigation scheduling requires an operational means to quantify plant water stress. Remote sensing may offer quick measurements with regional coverage that cannot be achieved by current ground-based sampling techniques. This study explored the relation between variability in fine-resolution measurements of canopy temperature ( ) and crop water stress in cotton fields in Central Arizona USA. Using both measurements and simulation models, this analysis compared the to the more complex and data intensive Crop Water Stress Index (CWSI). For low water stress, field was used to quantify water deficit with some confidence. For moderately stressed crops, the was very sensitive to variations in plant water stress and had a linear relation with field-scale CWSI. For highly stressed crops, the estimation of water stress from is not recommended. For all applications of , one must account for variations in irrigation uniformity, field root zone water holding capacity, basic meteorological conditions such as wind speed, vapor pressure deficit and air temperature and spatial resolution of Tc data. These sensitivities limit the operational application of for irrigation scheduling. On the other hand, was most sensitive to water stress in the range in which most irrigation decisions are made, thus, with some consideration of daily meteorological conditions, could provide a relative measure of temporal variations in root zone water availability. For large irrigation districts, this may be an economical option for minimizing water use and maximizing crop yield.