Responses of grain sorghum to varying irrigation frequency in the Ord irrigation area. I. Growth, development and yield

Abstract

The effects of five frequencies of furrow irrigation, ranging from every 7 days to once-only-at-sowing, on the growth and yield of six cultivars of grain sorghum were investigated at the Kimberley Research Station during the 1976 dry (winter) season. No rain fell during the experiment. The reduced water supply, both at 42-day intervals and at one irrigation (at sowing), depressed dry matter production and tillering at 42 and 77 days after sowing. The grain yield component most affected was number of grains per head, due entirely to a reduced number of normal florets. All stages of development were hastened by longer irrigation interval, except in the cultivar Q7844, where floral initiation was markedly delayed in all treatments relative to the 14-day irrigation interval. The optimum irrigation interval for grain yield was determined to be in the range of 12-18 days, although there were no significant differences among the three shortest irrigation intervals of 7, 14 and 28 days. The highest grain yield, 5810 kg ha-1, was achieved with the 14-day interval, whilst the lowest, 1980 kg ha-1, was from a single irrigation at sowing. Plant nitrogen yields were reduced at both the longest and shortest intervals.