Effect of drip lateral spacing and mulching on yield, irrigation water use efficiency and net return of onion (Allium cepa L.) at Ambo, Western Shoa, Ethiopia

Field experiment was conducted at Ambo during the 2017/2018 to investigate effects of drip lateral spacing and mulching on yield, water use efficiency and net return of onion. Eight treatments with three replications were randomized in complete block design to conduct the experiment. Two levels of drip lateral spacing and four levels of mulch were used to evaluate their effects. The result showed that both onion yield and water use efficiency were affected by main effects of drip lateral spacing and mulching but not affected by their interaction effect. The maximum bulb yield 34990 and 35117 kg ha-1 of onion were recorded from onion grown under drip lateral in every row and white plastic mulching, respectively. Water use efficiency of 1.14 and 1.15 kg L-1 were recorded from onion grown under drip lateral spacing in every row and white plastic mulching, respectively. Even though white plastic mulch scores significantly higher yield and water use efficiency, highest net returns of 246,410 and 284,616 ETB ha-1 were obtained from drip laterals in every rows and no mulch, respectively. This suggests that drip laterals in every rows and no mulching is economically feasible for drip irrigated onion production at Ambo. Key words: Drip irrigation, drip lateral spacing, mulching, bulb yield, water use efficiency, net return, Ambo woreda.