Abstract
ABSTRACT THE canopy temperature of four winter wheat varietiesTAM-105, TAM-108. Sturdy, and Scoutwas studied under four irrigation regimes. Non-water-stressed baselines for the crop stress index (CWSI) were developed for the individual varieties and for both pre-and post-heading phenology using three data smoothing techniques. Non-transpiring (stressed) baselines were developed from the unstressed baselines and compared to canopy-air temperature differentials that were measured in water-stressed plots. Wind speed did not affect the non-transpiring baselines in the high windspeeds common to the Southern Great Plains. Aerodynamic and canopy diffusion resistances were predicted using the baseline relationships and energy balance theory. The predicted aerodynamic resistance was similar between pre- and post-heading phenology and between the values predicted from the non-transpiring and non-water-stressed baselines. The predicted canopy resistance increased from pre- to post-heading. The CWSI was related to midday leaf water potential (LWP) of winter wheat, but the relationship depended on phenology. The phenology response in LWP may be due to differences in water relations between winter wheat flag leaves and canopy leaves. The CWSI was useful for evaluating crop water stress in winter wheat in this region and should be useful for timing of spring irrigations for winter wheat.
Published Version
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