EFFECT OF DEFICIT IRRIGATION ON YIELD AND WATER PRODUCTIVITY OF ONION (Allium cepa L.) UNDER CONVENTIONAL FURROW IRRIGATION SYSTEM IN BENNATSEMAY WOREDA, SOUTHERN ETHIOPIA

Abstract

Enhancing water productivity is an important strategy for addressing future water scarcity in arid and semi-arid regions. Hence, innovations are needed to increase the water use efficiency that is available. Deficit irrigation is believed to improve water productivity without causing severe yield reductions; which the crop is exposed to a certain level of water stress either during a particular period or throughout the whole growing season. The field experiment was conducted in Bennatsemay Woreda Weyito experimental site of Jinka Agricultural Research Center, Southern Ethiopia, during 2018 season with objective of investigating the effect of deficit irrigation on yield and water productivity of Onion under conventional furrow irrigation system. Six treatments (T1=100% ETc, T2=85% ETc, T3=70% ETc, T4=50% ETc, T5=100% ETc Is, 85% ETc Ds, 70% ETc Ms, 50% ETc Ls and T6=85% ETc Is, 70% ETc Ds, 50% ETc Ms, 0% ETc Ls) were imposed on Onion (Allium cepa L.) Bombay red variety and laid out in randomized complete block design (RCBD) with four replications. Results indicated that the different deficit irrigation levels had highly significant (p < 0.01) effect on vegetative growth, yield, yield components and water use efficiency of Onion. Onion bulb yield was reduced with increased water stress, where as water productivity was increased with stress level increased. The highest bulb yield of 21.3 t/ha were obtained from T1 which was significantly different to all other treatments while yield from T6 (12.86 t/ha) was recorded as the lowest one. Similarly, the highest IWUE (2.41 kg/m3 ) and CWUE (4.02 kg/m3 ) were obtained from T6 which was significantly superior to all other treatments. But, at T4 and T6 high yield reduction was recorded which may not be attractive for producers. On the other hand, the total bulb yield, yield components, IWUE and CWUE observed under T3 and T5 irrigation application levels had no statistically significant variation (p < 0.01). However, under T5 the relative yield reduction was greater when compared to T3. So, instead of T5, using T3 (applying 70% ETc) is advisable. Accordingly, made T5 out of the role, compared T1, T2, T3, T4 and T6, high IWUE was observed under T6 and T4 with high yield reduction penalty. From resources conservation point of view, maximum water productivity may be our attention, which could be obtained under this severe deficit irrigation. However, such consequences on yield may not be tolerable from producers view point (at T4 and T6). Therefore, it could be concluded that increased water saving and water productivity through irrigation at 70% ETc deficit irrigation level under conventional furrow irrigation system can solve the problem of water shortage and would ensure the opportunity of further irrigation development in the study area and similar agro-ecology