Ingénierie des systèmes d’irrigation et de drainage

Improving Water Use Efficiency for Onion Through Deficit Irrigation in Southern Ethiopia

Abstract

Kedrala Wabela, Sirak Tekleab

Deficit irrigation is one of agricultural water management practice in arid area in which the irrigation water management has to be improved so that water supply to the crop can be reduced while still achieving high yield. The main objective of this study was to improve agricultural water use efficiency (WUE) of onion under different deficit irrigation levels. Randomized complete block design (RCBD) with eleven treatments and three replications was used. The treatments were: full irrigation (0% deficit as a control), and 25% and 50% of crop water requirement (CWR) deficit throughout growing season, and one period deficit treatments (25% and 50% of CWR deficit at initial, development, bulb formation and maturity stages). Treatment 10 (50% of CWR deficit at bulb formation stage) showed the minimum harvest index (0.68) and 25% of CWR deficit at initial and maturity stages respectively showed the maximum harvest index. Yield response factor (ky) indicated that onion was sensitive (yield reduced) for water deficit at development and bulb formation stages. The maximum water use efficiency (4.98 kg/m³) was observed at 50% of CWR deficit throughout growing season and the minimum (3.22 kg/m³) was observed at 50% of CWR deficit at bulb formation stage. Water deficit at initial and maturity growth periods had insignificant impact on WUE of onion. Generally, this result indicated that water deficit at bulb formation growth period of onion reduce more water use efficiency than water deficit on other growth periods.