Developing optimal irrigation scenario for onion (Allium cepa L.) in view of leaching requirement and drainable excess water at Werer Agricultural Center, Amibara, Middle Awash, Ethiopia

The field experiment were performed on the site of Werer Agricultural Research Center (Ethiopia)  to study optimal irrigation scenario by taking in account leaching requirement and drainable excess water for three successive years. Six treatments evaluated at different growth stages onion plant namely initial stage four event  23 mm (T1), 16.2 (T2) 21.0 (T3), 13.8 (T4), 27.0 (T5), 19.8 (T6), development five event 32.4 23.4 (T2), 28.8 19.2 36.6 mid 53.4 37.2 48.0 31.8 60.6 44.4 late two 58.0 40.8 35.4 67.2 49.2 (T6) applied respectively. amount added had no significant difference bulb diameter length across highest marketable yield (21784 kg/ha) use efficiency (1.89 kg/m3) recorded first year. maximum from T6 (5.41 cm) lowest T2 (4.81 cm). Treatment recommended production middle awash. developed scheduling can be used as a guide potential allocation decision related soil salinity management.  Key words: Drainage, optimal, leaching, onion.  &nbsp