The effect of sowing date on the growth and yield of three sorghum cultivars in the Ord river valley. I. Agronomic aspects

Abstract

The main aim of the experiment was to elucidate the causes of low sorghum grain yield in the Ord River valley. Three cultivars were studied: two dwarf, insensitive to day length (the hybrid RS610 and the inbred Meloland) and the day length-sensitive Q7844. The dwarf cultivars showed seasonal changes in time to maturity, but no seasonal changes in grain yield; sowing times need therefore depend only on mechanical difficulties of planting or harvesting in the wet season. Q7844 failed to initiate when the day length was longer than c. 12 hr 10 min, but the yield began to fall well before this day length was attained; a high stable yield was obtained only for sowings between about mid January and mid July.

Overall mean yields were: RS610, 4694 kg/ha; Meloland, 4406 kg/ha; Q7844 (stable period only), 5074 kg/ha. Contrary to expectation, the yield of RS610 apparently increased with increase in maximum temperature. Meloland was less sensitive to temperature and to adverse environmental conditions. The causes of occasional yield failures are examined. It is suggested that Meloland deserves more attention than it has hitherto received, and that a dwarf photosensitive line might provide an acceptable 'wet season sorghum' for the Ord.