Effect of Plant Density and Seeding Date on Early- And Late-Maturing Sunflower Hybrids

Field experiments were conducted in 1983, 1984 and 1986 to determine the response of Sun M 20 (early) and 894 (late) sunflower (Helianthus annuus L.) hybrids to three plant densities (30 000, 45 000 and 60 000 plants ha −1 ) at two seeding dates (18–24 May and 13–16 June). With increase in plant density, achene yields followed the same trends in each seeding date for both hybrids. Yields were similar at the 30 000 and 45 000 plant densities, but lower at the 60 000 density. Plant height and oil content of achenes increased while achene weight decreased with increase in plant density. Plant height was greater but achene weight, oil content and achene yield were lower in the late than the early seeding.Key words: Sunflower, Helianthus annuus L., plant density, seeding date