| Abstract: | To determine the effects of ethephon (2‐chloroethyl) phosphonic acid] on yield and yield components of rainfed barley in arid (150 mm rainfall) and semiarid (346 mm) regions, the present study was conducted during the growing seasons of 1999–2001. Ethephon was applied at the tillering, stem elongation and flowering stages. Acomparison of the effect of ethephon on rainfed and irrigated barley performed at the semiarid location in the following season confirmed the results. Ethephon decreased grain yield when sprayed at tillering and stem elongation compared with the later flowering stage for both the arid and semiarid locations. All arid‐location barley plants had lower grain yields than the semiarid‐location plants. There was a reduction in spikes m?2 in the tillering and stem elongation stage sprayings compared to the control for both locations. In the semiarid and arid locations no difference in earliness (50 % heading) was observed between spraying times but ethephon always delayed heading. All arid‐location plants were earlier than semiarid‐location plants. However, when ethephon was used with supplementary irrigation it was found to increase grain yield, spikes m?2 and earliness. |
