THE EFFECT OF IRRIGATION TIMING ON YIELD AND YIELD COMPONENTS OF WINTER WHEAT

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Abstract
A study was conducted in southwest Kansas to evaluate the effect of limited water applications at critical growth stages on yield and yield components of winter wheat (Triticum aestivum L.). The experiment was a split-plot design. Irrigation treatments were main plots and cultivar × seeding rate combinations were subplots. The irrigation treatments were: Preplant (PP), PP + jointing (JT), PP + flowering (FL), and PP + JT + FL. Two cultivars (Centurk and Newton) were seeded at rates of 22, 45, and 67 kg∙ha−1. The experiment was conducted over a 2-yr period. During the first cropping season grain and straw yields showed a significant (P < 0.05), positive response to irrigation water applications at the JT growth stage, compared to the PP and PP + FL treatments. There was no significant effect of water treatments on heads per square metre, kernels per square metre or kernel weight. The second cropping season resulted in a positive, significant response of straw yields to irrigation treatments, but no significant response of grain. Grain yield response was nullified by greater kernel weight on the treatments that were most limiting in soil water during early reproductive development (PP and PP + FL).Key words: Triticum aestivum L., limited irrigation, moisture stress, seeding rate, kernel number, kernel weight