Time and Frequency of Irrigation Effects on Sunflower Production and Water Use

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Abstract
Sunflower (Helianthus annuus L.) production has greatly increased in the U. S. in recent years, with some being produced under irrigation in the Southern Great Plains. However, because of limited water supplies in the Southern Great Plains, sunflower usually is not fully irrigated. The objective of this study was to determine the influence of limited irrigation on sunflower growth, seed yield and quality, oil percent and quality, and water use and use efficiency. Treatments providing one or two irrigations at readily identifiable growth stages were compared with treatments providing no, adequate, and full irrigation. Sunflower irrigated before flowering averaged 17 cm taller than those not irrigated between emergence and flowering. Seed yields averaged highest (2.49 t/ha) with full irrigation, but in individual years, differences between full irrigation and other treatments were not always significant. Usually, the highest seed yield resulted from flowering or late flowering irrigations. These irrigations usually also resulted in the highest seed test weight and weight/seed. Oil percent averaged highest (48.8%) for the emergence plus late flowering irrigation treatment and lowest (43.4%) with the emergence plus budding treatment. Irrigation treatments significantly affected linoleic and oleic acid concentrations of the oil, but the maximum difference among treatments was only four and five percentage units for linoleic and oleic acids, respectively.Total water use increased with increased number of irrigations, but yield increases were not proportional to water use, especially for the adequate and full irrigation treatments. With these treatments, water‐use efficiency was less than for limited irrigation treatments that provided adequate water from flowering to late flowering.