Abstract:
The problem of irrigation water scarcity is the major production constraints in the arid and semi-arid areas of Dire Dawa. The objective of this study wasto evaluatethe effect of deficit irrigation on water productivity and yield of onion crop. The experiment was conducted at Tony farm experimental station of Haramaya University in Dire Dawa under the furrow irrigation system. Seven irrigation treatments were replicated three times in RCBD. In the treatment combination, a full application of irrigation water (100% ETc) was used as a control treatment and Bombay red onion variety was subjected to six deficit level of treatments 90% ETc, 80% ETc, 70% ETc, 60% ETc, and 50% ETc and 40% ETc throughout the growing season. The study revealed that maximum seasonal water demand for onion (423.8 mm) was consumed by control treatment and minimum seasonal water demand was consumed by 40% ETc application level. The study revealed that full application of irrigation water (100% ETc) produces a high number of leaf per plant, plant height, leaf height, and leaf diameter than the others treatment. Maximum yield (38.09 ton/ha) was obtained by non-deficit treatment (T1) while the lowest application level of irrigation water had the lowest yield of 22.23 ton/ha. Maximum WP (12.85 kg/m3) was obtained by T7 and minimum WP (9.36 kg/m3) was obtained by T1 (control treatment). Statistically, no significantdifference was observed between T4, T5, T6,and T7 in the case of WP. By saving 30% of irrigation water T4 (70% ETc application level) produce optimum WP (11.20kg/m3) than T1, T2 and T3. This implies that WP decreases with increasing application level of irrigation water up to 30% deficit. The result has shown that the minimum yield response factor (ky) was produced by T4 (application of 70% ETc) by saving 30% of irrigation water. The water saved by T4 can irrigate additional land of 0.43 hector which can produce 13.97 tons of additional onion bulb yield. The benefit cost ratio obtained by 70% ETc application of irrigation level was better than other treatments. Even though the net income of control treatment was high the benefit-cost ratio obtained by this treatment was small. Generally, the finding revealed that 70% ETc application level was the best application-level than the other treatment based on water productivity, economic visibility, total yield, and percent of yield reduction and yield response factor
