Sowing time effects on the development, yield and oil characteristics of irrigated sunflower (Helianthus annuus) in semi-arid tropical Australia

Abstract

The effect of sowing time on development, yield and oil characteristics of irrigated sunflowers was studied in an experiment at the lrrigation Research Station, Ord lrrigation Area (15¦ 30'S, 128¦ 43'E), Western Australia in 1978. Sunflower cultivars Hysun 10, Hysun 30, Sunfola 68-2 and Polestar were sown at monthly intervals between mid-February and mid-August. Delay in sowing from February to June increased the period from sowing to physiological maturity by between 10 d (Hysun 10) and 24 d (Hysun 30), due mainly to an increase in the period from emergence to bud visible. Results showed that May sowing of the late maturing hybrid Hysun 30 was the best combination, with a seed yield of 2.3 t/ha. Oil content and quality (% linoleic acid) were highest with April sowing, 47.0 and 57.0%, respectively. Sowings from April to July gave acceptable yields (1.8-2.0 t/ha) and oil contents (45-47%). However, oil quality, although responding to sowing date, was always lower than the accepted level of 60% linoleic acid. Seed yields, which were considerably lower than those recorded for irrigated sunflower in southern Australia, are discussed in terms of the environmental limitations of the region