Response of Onion (Allium Cepa L.) to Soil Moisture Stress Conditions at Different Growth Stages under SemiArid Area of Ethiopia

摘要

Soil moisture stress condition is the most critical factor affecting crop yield and water productivity. Under changing climate and increasing human population the evaluation of effect of soil moisture stress on crop production is critical issue for the increasing water scarcity. An experiment was conducted for three consecutive seasons to investigate the effect of water stress imposed at different growth stages on bulb yield and water productivity of onion (Allium cepa L.). Sixteen treatments were used depriving irrigation at different combinations of the four growth stages: at each growth stages, at two growth stages, at three growth stages, irrigated at establishment only and full irrigation (control). The treatments were replicated three times in a randomized complete block design. The study result indicated that onion bulb yield and water productivity were significantly (p<0.05) affected with soil moisture stress imposed at different growth stages. The maximum bulb yield (31.50t/ ha) was obtained from fully irrigated onion at all stages (the control). Water stress imposed at combinations of initial and late season stage didn’t affect bulb yield, but soil moisture stress imposed at combinations of development and bulb formation stage decreased bulb yield highly. Withholding irrigation at initial and late season stage increased onion water productivity and reduced yield response factor by saving 29.3% water. While withholding irrigation at development stage followed by bulb formation stage decreased water productivity to 3.41 Kg/m3 causing higher yield response factor of 1.19. Thus, moisture stress at mid-season stage should be avoided especially when combined with moisture stress imposed at development stage for higher bulb yield. Moreover, moisture stress imposed at initial and late season stages enhance water productivity without significantly reducing the yield from the control.