Deficit irrigated corn evapotranspiration estimates using canopy temperature data
Bausch, Walter, author
Trout, Thomas, author
Buchleiter, Gerald, author
U.S. Committee on Irrigation and Drainage, publisher
Sustainability of irrigated agriculture with declining water supplies is a primary agricultural issue in the U.S. Great Plains. Consequently, the paradigm of maximizing production through full irrigation must be abandoned. Imposing water deficits on crops during non-critical growth periods must be implemented to maximize net economic output per unit of water consumed by the plant. An irrigation timing and amount determination for such a scenario is not a simple, straight-forward procedure. Methods that monitor plant parameters would appear to be most promising. Several canopy temperature based irrigation timing techniques exist that determine when to irrigate but do not indicate how much to irrigate. The reference ET-crop coefficient procedure for determining crop ET which is used in fully irrigated crop conditions would be easiest to implement; however, the water stress coefficient used in that procedure may not be applicable for prolonged periods of water stress. Thus, the objective of this paper was to investigate use of a ratio of canopy temperature (Tc) measured over fully irrigated and water stressed corn as a substitute for the water stress coefficient presently used in the reference ET-crop coefficient concept. Preliminary results indicated that the Tc ratio (Tc of fully irrigated corn divided by the Tc of water stressed corn) may be a reasonable quantitative water stress coefficient for calculating crop ET under water stress conditions. Furthermore, it lends itself to hourly incorporation of plant stress effects on crop ET if canopy temperature is continuously measured throughout the day.
Presented at the fifth international conference on irrigation and drainage, Irrigation and drainage for food, energy and the environment on November 3-6, 2009 in Salt Lake City, Utah.