Effect of sowing time on growth, yield, and oil characteristics of irrigated sunflower in southern New South Wales

Abstract

The effect of sowing time on the growth, yield, and oil characteristics of irrigated sunflower was studied for 3 consecutive seasons at Leeton (34¦28ÆS., 146¦25'E.), in southern New South Wales. The hybrid cultivar Hysun 32 was sown at monthly intervals from late October to late January. Duration of growth from sowing to physiological maturity was reduced by I5 days when sowing time was delayed from late October to late December. Dry matter production at flowering was lowest from the late December sowing, and harvest index was always lowest from the late January sowing. Late October and late November sowing produced similar yields (>4 t/ha), but delaying sowing further to late December and late January reduced yields by 18 and 37%, respectively. Effect of sowing time on yield was mainly related to effects on seed number per head. Seed oil content averaged 50%, with the late November sowing producing the highest value in all seasons. To be confident of producing a linoleic acid level >62% as required for the margarine industry, sowing should be delayed until mid November.