Influence of irrigation on the leaf water potentials and yield of wheat and barley at two dates of sowing

Abstract

Wheat and barley sown in the field at two different dates were given three irrigation treatments: irrigation when 75% of the available soil moisture in the active root zone was depleted, two irrigations at critical stages, and one irrigation at the most critical stage. Diurnal and seasonal changes in leaf water potential were determined using the pressure chamber technique. The effect of frequency of irrigation on leaf water potential was greatest at the grain development stage. The lowest leaf water potentials (−36.8 bar and −31.8 bar in wheat and barley, respectively) were recorded with one irrigation and the highest (−26.2 and −23.7 bars in wheat and barley, respectively) with the most frequent irrigation treatment. Diurnal fluctuations in leaf water potential were marked. At all levels of irrigation, leaf water potentials in barley were higher than in wheat and recovery of water potential by one irrigation was also faster in barley. Although wheat yielded better than barley under the most frequent irrigation treatment, barley yields were reduced less than wheat by water deficit; with one irrigation barley yielded more than wheat at both dates of sowing.