Effect of Regulated Deficit Irrigation and Mulch Levels on Quality and Economic Importance of Onion (Allium cepa L.) at Werer, Middle Awash Valley, Ethiopia

In Ethiopia, the Onion is one of the most significant vegetables produced by smallholder farmers mainly as a source of cash income and for seasoning the local stew. The rift valley area is a semi- arid with limited water resources and cumulative demand for water combined with high evapotranspiration rates limits the production and productivity of the Onion crop. The experiment was conducted to develop best irrigation water management scenario. Hence, alternatives need to be explored for effective and efficient use of the existing water resources. Thus, a field experiment was conducted at Werer Agricultural Research center to evaluate the response of onion (Allium cepa L) Quality and Economic Importance under deficit irrigation and straw mulching levels. The experiment was laid out in a randomized complete block design in factorial technique of three levels of irrigation (100, 80 and 60% of ETc) and four levels of straw mulch (0,3,6 and 9ton wheat straw per ha) in three replications. The output of the Cropwat model showed that the highest seasonal water requirement of onion was 422.5 mm at 100% ETc while; the lowest was 253.5 mm at 60% ETc. The analysis of variance revealed that statistically, there was a significant (p<0.05) difference in leaf diameter, neck and bulb diameter, and marketable bulb yield by interaction effect of deficit irrigation and straw mulch levels; and Total soluble solid and bulb dry matter content were highly significant (p<0.01) influenced by the main effects of deficit irrigation and straw mulch levels. The highest marketable bulb yield (33.47 t/ha) was obtained from an experimental plot treated with a combined application of 100% of ETc and 6 t/ha straw mulch, while the lowest (21.10 t/ha) was obtained from plots treated with 60% ETc irrigation level and no mulch treatment. Partial budget analysis revealed that the most economically attractive combination for small-scale farmers with lower cost of production and higher net benefits was from the application of 80% ETc and 6 t/ha straw mulch.  Therefore, in terms of marketable bulb yield and water profitable productivity, irrigating with 80% ETc with 6 t/ha straw mulch would be recommended for production of onion in the study area.