The effect of sowing date on the growth and yield of three sorghum cultivars in the Ord river valley. II. The components of growth and yield

Abstract

Thirteen measurements were obtained from 59 successive sowings of three cultivars of sorghum. Principal component analyses showed that growth could be regarded as consisting of three largely independent components: crop density, total photosynthate, and extension. The correlations of these components with environmental measurements are examined. There is a high negative correlation between grains per head and heads per plot; grain weight is independent of crop density or spacing; the relationship between grain weight and number varies with the cultivar, attaining a high negative value for the hybrid RS610.

Compared with sorghum grown elsewhere in the world, grain weights in the Ord are normal, but the number of grains per head is unusually low. This does not appear to be a high temperature effect, since in the dwarf cultivars higher maximum temperatures resulted in an increased number of smaller grains. It is suggested that African dwarf cultivars sensitive to day length might be more appropriate for the Ord than the American cultivars currently grown.