Submitted to: International Irrigation Show
Publication Type: Proceedings
Publication Acceptance Date: October 30, 2009
Publication Date: December 2, 2009
Citation: O'Shaughnessy, S.A., Evett, S.R. 2009. Using radiation thermometry to assess spatial variation of water stressed cotton. In: Proceedings of the Annual International Irrigation Show, December 2-4, 2009, San Antonio, Texas. Paper No. IA-09-1012. 2009 CDROM. Interpretive Summary: Producers often encounter problems of poor drainage, non-uniform irrigation, soil variability, or pest infestations within their fields. These conditions can decrease crop yields and are often not obvious to the human eye. In this study, scientist investigated crop water stress based on canopy temperature. The temperatures were measured using remote thermal images and infrared thermometers to calculate an empirical crop water stress index for cotton. Four irrigation amounts were applied, ranging from full to deficit to no irrigation (dryland). The results showed that the daily empirical crop water stress index was a good predictor of crop yields. The least stressed crops provided the highest yields and the most stressed crops provided the lowest yields. In the future, it is possible that thermal imaging sensors combined with computational analysis will provide real-time spatial and temporal information concerning in-field crop water status.
Technical Abstract: The use of infrared thermometry and thermal imagery to investigate unapparent but important field conditions (poor drainage, non-uniform irrigation, soil variability, or biotic infestations) offers a producer improved management tools to avoid yield declines or variability in crop status. This study investigated spatial and temporal crop water stress based on crop canopy temperature extracted from remote thermal images and point infrared thermometry within the imaged area to calculate an empirical crop water stress index for varying levels of manually and automatically irrigated cotton (Gossypium hirsutum L.). The daily empirical crop water stress index calculated from canopy temperature data extracted from thermal imagery was significantly related to midday leaf water potential (LWP), r**2 = 0.88 in 2007 and r**2 = 0.77 in 2008. Data from 2007 indicated a significant inverse correlation between seasonal mean empirical crop water stress index values derived from infrared thermometry and yields, r**2 = 0.86 and 0.77 for manually and automatically irrigated plots, respectively. In 2008, there was also an inverse relationship between the empirical crop water stress index and yield for deficit irrigated cotton in the automatic blocks, r**2 = 1.0. However, there was a positive correlation between the mean empirical crop water stress index and corresponding mean yields in the manually irrigated plots. High temperatures and wind, and heavy rainfall near the period of boll maturation negatively impacted yields and the yield - empirical crop water stress index relationship. In the future, it is plausible that thermal imaging sensors combined with computational analysis will provide real-time spatial and temporal information concerning in-field crop water status.