Influence of size of achenes sown and depth of sowing on growth and yield of dryland oilseed sunflowers (Helianthus annuus) on the Darling Downs

Abstract

Large achenes of sunflower (Helianthus annuus) exhibited a slightly higher germination percentage and greater mean hypocotyl length than small achenes, resulting in a higher field emergence percentage at sowing depths exceeding 6 cm. Size of achenes sown had no effect on achene yield, provided plant populations from large and small achenes were equal. Plants grown from small achenes produced achenes of higher kernel percentage in both seasons, resulting in higher protein percentage in one season and higher oil percentage in the other. Performance of ungraded achenes was equal to that of graded achenes of the same mean size. Deep sowing reduced emergence percentage considerably, especially when small achenes were sown, but the effect of deep sowing on growth and yield was confounded with effects of reduced plant density (because of reduced emergence) and effects of delayed emergence causing slightly later timing of growth and development processes in relation to environmental factors.