The effect of plant density on the reproductive structure of safflower in the Ord River valley

Abstract

Safflower (Carthamus tinctorius L., variety Gila) was grown under irrigation at the Kimberley Research Station as a row crop at plant densities of 25,000 to 133,000 plants an acre and as a drilled crop at 593,000 plants an acre. The main effect of increasing plant density, within the range examined, was to reduce plant size (dry weight of tops and number of seed heads) ; the mean size of individual heads (number of seeds and their weight) showed little change. Though the relative seed and oil yield per head of primary, secondary, and tertiary heads remained fairly constant with increasing plant density, the increasing proportion of primary heads and the decreasing proportion of tertiary heads brought about corresponding changes in the contribution by primary and tertiary heads to total seed and oil yield. In contrast, the proportion of secondary heads and their contribution to seed and oil yield remained relatively stable.