RESPONSE OF ONION (ALLIUM CEPA L.) TO DEFICIT IRRIGATION UNDER SURFACE AND DRIP IRRIGATION METHODS IN THE CENTRAL RIFT VALLEY OF ETHIOPIA

Abstract

The study was carried out at the Melkass Agricultural Research Experimental Field, Adama, Ethiopia, to assess the onion response to deficit irrigation under drip and surface irrigation methods. The experiment was laid out in RCBD design, split-plot arrangement and replicated thrice. Irrigation methods were employed for the main plot, and the sub-plots were divided into five irrigation levels: 100% ETc (full irrigation), 85% ETc, 70% ETc, 60% ETc, and 50% ETc. The irrigation was applied throughout the growing season. Onion vegetative parameters and yield were collected and analyzed. The study found that variations in yield, yield parameters, and water productivity were highly significant (P≤ 0.01). The results showed that when water deficit levels increased, onion bulb yield declined. In contrast, higher water productivity was observed as the level of water deficit increased. On average, the highest total onion bulb yield was observed (50.4 t/ha) by applying 100 ETc via drip irrigation method. Although, 85%ETc and 70%ETc irrigation level irrigating via the same irrigation method were shows equivalent and non-significant variation on onion total bulb yield. On the other hand, in furrow irrigation techniques the highest and the lowest onion yield was obtained irrigating conventionally (every other furrow) with 100% ETc irrigation level and vial Alternate furrow irrigation with 50% ETc level of irrigation respectively. However, acceptable yield variation and significantly higher WP were observed when irrigating via Alternate furrow irrigation technique with application of 85%ETc and 70% ETc irrigation level as compared to full irrigation using convectional furrow irrigation method. An Alternate furrow irrigation technique coupled with different level of irrigation could save substantial amount of irrigation water; thereby enable to irrigate more land and different types of crop in area where water was not enough for full irrigation. Therefore, the study reveals that onions could be irrigated via drip and an Alternate furrow irrigation method combined with 85%ETc and 70%ETc of level irrigation to enhance water productivity without considerably reducing total onion bulb yield.