Title: Vapor pressure deficit effects on cotton canopy temperature Authors
Submitted to: Functional Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 10, 2013
Publication Date: N/A
Interpretive Summary: Improved irrigation of crop plants is needed to increase the sustainability of agricultural production. The measurement of plant temperature through the use of infrared thermometers is a potentially powerful tool for the determination of when plants require irrigation. Plant temperature is a sensitive measurement of the plant’s need for water. Plant temperature measurement can be automated with 96 measurements per day. In this study an ARS-developed irrigation protocol was tested in the Australian cotton production system. The study showed that plant temperature can be compared to an estimate of the dryness of the air (VPD) to improve the ability to control irrigation in environments where the humidity of the air is relatively high. This modification may result in wider application of the use of plant temperature in cotton irrigation.
Technical Abstract: Crop canopy temperature (Tc) is coupled with transpiration, which is a function of soil and atmospheric conditions and plant water status. Thus, Tc has been identified as a real-time, plant-based tool for crop water stress detection. Such plant-based methods theoretically integrate the water status of both the plant and its environment. However, previous studies have highlighted the limitations and difficulty of interpreting the Tc response to plant and soil water stress. This study investigates the links between Tc, established measures of plant water relations and atmospheric vapour pressure deficit (VPDa). Concurrent measures of carbon assimilation (A), stomatal conductance (gs), leaf water potential ('l), soil water (fraction of transpirable soil water- FTSW) and Tc were conducted in surface drip irrigated cotton over two growing seasons. Associations between the more established methods of water stress physiology (A, gs, 'l and FTSW) and Tc are presented, which are significantly improved with the inclusion of VPDa. Through understanding the interactions between VPDa, Tc and plant water relations, an increased understanding of the response of cotton Tc to water stress is gained. Therefore, to better determine the plant water status of a crop, Tc based irrigation scheduling protocols should consider the use of VPDa. Improved accuracy in water stress detection with Tc, and an understanding of the interaction the environment plays in this response, can potentially provide more timely irrigation water. This will reduce losses in crop yield or quality due to water stress and improve the efficiency of irrigation through a reduction in over irrigation.