Abstract:
Water is scarce resource in Central Rift Valley of Ethiopia and is major limiting factor for crop production. Onion is one of the major economically important vegetable crops grown under irrigation in central rift valley. The field experiment was conducted at Melkasa agricultural research center during the off-season to identify irrigation method and irrigation application level that maximizes productivity of onion per unit of water consumed and enhanced onion crop production. The experiment was carried out using split plot design in RCBD having six treatments with three replications. The experiment consisted of two irrigation methods viz., furrow irrigation and drip irrigation as main plot and three levels of Manageable allowable depletion viz., 120%, 100% and 80% of manageable allowable depletion as sub-plot. The analysis of variance revealed that irrigation methods and management allowed depletion levels had a significant (p<0.01 and p<0.05) effect on onion vegetative parameters like number of leaves per plant, plant height and leaf height and yield parameters like bulb diameter, bulb height, total bulb yield, marketable bulb yield, and water productivity. The highest and lowest onion vegetative and yield parameters were obtained from drip irrigation and furrow irrigation method respectively. Moreover, the highest and lowest onion vegetative and yield parameters were obtained from 80% and 120% management allowed depletion respectively. Further, their interaction had a significant effect on bulb diameter, total bulb yield, marketable bulb yield and water productivity. Nonetheless, they had no significant effect on number of leaves per plant, plant height, leaf height and bulb height. The maximum total bulb yield (41.76 t/ha), marketable bulb yield (38.39 t/ha), bulb diameter (6.02 cm) and water productivity (13.05 kg/m3) were observed from drip irrigation method at 80% management allowed depletion application, while significantly lower of 34.48 t/kg, 31.6 t/ha, 5.11 cm, and 6.84 kg/m3 respectively were recorded from furrow irrigation method at 120% management allowed depletion application. Generally, drip irrigation was working efficiently according to its design and economically acceptable. Among all tested treatments drip irrigation method with 80% MAD was the best practice because of its high yield, water productivity and good return
