Evapotranspiration, Yield, and Water Use Efficiency of Corn Hybrids Differing in Maturity

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Abstract
Short‐season corn (Zea mays L.) hybrids may reduce irrigation requirements and permit earlier harvest. We measured and compared evapotranspiration (ET) of a short‐season (SS, Pioneer 3737) and full‐season (FS, Pioneer 3245) hybrid under full irrigation in 1994 at Bushland, TX, and examined differences in growth, yield, and water use efficiency (WUE). Both hybrids were planted the same day in contiguous 4‐ha fields (each field with a weighing lysimeter to measure ET directly), were irrigated simultaneously until the SS hybrid reached mid grain fill (R5 dent stage), and were managed for high productivity. Harvest was at the normal field‐dried grain water content of 136 g kg−1 for the region. Rainfall was 320 mm; 465 and 577 mm of irrigation was applied to the SS and FS hybrid fields, respectively. Seasonal ET was reduced with the SS hybrid (SS, 673 mm; FS, 802 mm), with the primary reduction after SS anthesis. Peak daily ET rates (some >10 mm d−1) were not affected by hybrid type. Grain yields (dry basis) declined from 1322 to 1130 g m−2, but grain water use efficiency (WUEg = grain yield/ET) was similar across hybrids: SS, 1.68 kg m−3; FS, 1.65 kg m−3. Dry matter (DM) was reduced by >390 g m−2 for the SS hybrid, but DM water use efficiency (WUEd = DM/ET) was identical for the two hybrids, at 3.02 kg m−3. The SS hybrid reached physiological maturity 12 d earlier than the FS hybrid and was harvested 11 d sooner. Leaf area index was >5.5 m−2 m−2 for the FS hybrid, but barely >4 m−2 m−2 for the SS hybrid. The WUEd, WUEg, and peak daily ET rates were not appreciably different for the two hybrids when fully irrigated, although seasonal ET was less with the SS hybrid. A shorter‐maturity hybrid can reduce ET and seasonal irrigation requirement, but it will not reduce the needed irrigation capacity (flow per unit area) by more than 5 to 10%, as that is largely dictated by the near‐maximum daily ET rate needed to avoid soil water deficits and a corresponding yield reduction. With prevailing regional pumping and production costs, the reduced production income with a SS hybrid would be more than six to eight times the saving in irrigation water cost, but this could be offset by higher grain marketing prices with an earlier harvest and by the opportunity for grazing income from a winter wheat (Triticum aestivum L.) double‐crop.

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