RESPONSE OF ONION( Allium Cepa L, )TO DIFFERENT IRRIGATION LEVELS UNDER DRIP AND CONVETIONAL FURROW IRRIGATION WITH AND WITH OUT MULCH AT MELKASSA , CENTRAL RIFT VALLEY OF ETHIOPIA

Abstract

Water is a scarce resource in Central Rift Valley of Ethiopia and is a 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 dry season to identify irrigation method and irrigation application level with and whithout mulch that maximizes productivity of onion per unit of water consumed and enhanced onion crop production. The experiment was carried out using split plot design inRCBD having twelve treatments with three replications.The FAO’s recommended allowable Manageable depletion level of onion is 25%. In this study 75%, 100% recommended and 125% were tested. The experiment consisted of two irrigation methods viz.,furrow irrigation and drip irrigation as main plot and three levels of Manageable allowable depletion viz., 125%, 100% and 75% with and whith out mulch 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 plant height, 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 drip irrigation under 75% MAD with mulch and furrow irrigation under125% MAD without mulch, respectively. Further, their interaction had a significant effect on total bulb yield and water productivity. Nonetheless, they had no significant effect on number of leaves per plant, plant height, leaf height, bulb diameter, marketable bulb yield and bulb height.The maximum total bulb yield (37.1 ton/ha), marketable bulb yield (33.1 ton/ha), bulb diameter (5.6 cm), crop water use efficiency (0.78 kg/m3 )and irrigation water use efficiency, (0.60 kg/m3 ) were observed from drip irrigation method at 75% MAD with mulch application, while significantly lower as (30.5 ton/ha), (26.7 ton/ha), (5.0 cm), (0.53 kg/m3 )and (0.40 kg/m3 ) respectively were recorded from furrow irrigation method at 125% MAD with out mulch application. Generally, drip irrigation was working efficiently according to its design and economically acceptable. Among all tested treatments drip irrigation method under 75% MAD with mulch was the best practice because of its high yield and water productivity