Effects of Planting Date on Seed, Oil, and Forage Yields of Irrigated Sunflowers

Cool climates with short growing seasons of high intermountain areas, such as Central Oregon, limit the kinds of crops that can be grown. A wider choice of crops is needed for crop rotations and production changes. A substitute for corn (Zea mays L.) silage to supplement livestock energy requirements is also needed. Sunflower (Helianthus annuus L.) is a short season plant potentially useful for seed, oil, and forage crops. Sunflower forage has substituted for corn in silage in other areas. This study evaluated sunflowers for use as a new crop in Central Oregon. Eleven sunflower cultivars were planted in the field on 11-14 April, 28-29 April, 12 May, and 26-28 May in 1975 and 1976. The effects of planting date on seed, oil, and forage yields were determined. Seed yields ranged from 1,694 to 2,082 kg/ha for the 1975 planting dates. The 28 April and 12 May planting dates resulted in highest yields. Seed yields among cultivars ranged from 1,560 to 2,183 kg/ha. In 1976, a late frost in June stilled all cultivars planted on all dates except 12 May and reduced average seed yields to 412 kg/ha for the 12 May planting. Oil contents ranged from 38.5 to 41.8% for the 1975 planting dates. The three earliest dates recruited in highest oil contents. Oil contents were not determined in 1976 because of frost damage. Oil yields ranged from 707 to 873 kg/ha for the 1975 planting dates. Highest yields were from 28 April and 12 May planting dates. Oil yields among cultivars ranged from 700 to 900 kg/ha. Forage yields were determined only for the 12 and 26 May 1975 and 12 May 1976 planting dates. Dry for-age yields averaged 9.9 metric tons/ha. This study showed that sunflowers are adapted to high intermountain conditions and that seed, oil, and forage yields would be sufficient to warrant their use. Mid-May would be the optimum planting time for highest yields and least risk of frost damage.