Evapotranspiration adjustments for deficit‐irrigated corn using canopy temperature: A concept

Abstract

Sustainability of irrigated agriculture with declining water supplies is a critical agricultural issue in the US Great Plains. Imposing water deficits on crops during noncritical 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 stress indicators 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. The objective of this study was to investigate use of a ratio of canopy temperature ( T c ) measured over fully irrigated and water‐stressed corn ( Zea mays L.) as a substitute for the water stress coefficient presently used in the reference ET‐crop coefficient concept. Preliminary results indicated that the T c ratio is a reasonable quantitative water stress coefficient for calculating crop ET under water stress conditions. This ratio allows application of the crop coefficient method for scheduling deficit irrigation. Furthermore the T c ratio lends itself to hourly incorporation of plant stress effects on crop ET since canopy temperature can be measured continuously throughout the day. Published in 2010. This article is a US Government work and is in the public domain in the USA.

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