The Improvement of yield and water productivity of Adama onion (Allium cepa L.) under deficit irrigation using furrow method in West Oromia, Ethiopia

Abstract

Water scarcity is the most severe constraint for agricultural growth in arid and semi-arid areas. To overcome this, there is a need to use the scarce water efficiently and economically which is an important strategy to address present and future water need. This study was conducted from December 2017 to March 2018 in Ambo District, aiming to investigate the effect of deficit irrigation at different growth stages on yield and water productivity of onion. The experiment was laid out in randomized completed block design with three replications and nine treatments namely, T1: control (without deficit irrigation at any growth stage – 100% crop evapotranspiration, ETc); T2: 20% deficit irrigation in all growth stages – 80% ETc; T3: 40% deficit irrigation in all growth stages – 60% ETc; T4: 20% deficit irrigation in development and late stages – 80% ETc, and 40% deficit irrigation in mid stage – 60% ETc; T5: 20% deficit irrigation in development and late stages – 80% ETc, and 40% deficit irrigation in initial stage – 60% ETc; T6: 20% deficit irrigation in initial stage – 80% ETc; T7: 20% deficit irrigation in development stage – 80% ETc; T8: 20% deficit irrigation in mid stage – 80% ETc; T9: 20% deficit irrigation in late stage – 80% ETc. The results indicated that deficit irrigation levels at different growth stages had significantly (p ≤ 0.05) affected the yield and water productivity of onion. The highest marketable yield (28.68 ton ha^-1) was obtained from 20% deficit irrigation at late stage (T9), whereas lowest yield (14.42 ton ha^-1) was recorded from 40% deficit irrigation in all growth stages (T3). The mean values of onion yield obtained in T2, T6, T8, and T9 no differ statistically. The highest water productivity (8.77 kg m^-3) was obtained in T2 (20% deficit in all growth stages), while the lowest water productivity (5.17 kg m^-3) was obtained in T4 (20% deficit irrigation at development and late stages, and 40% deficit irrigation at mid stage). These results confirmed that with deficit irrigation practice it is possible to increase water productivity by saving water and increase income from scarce water. Therefore, it was recommended that the application of deficit irrigation in 20% of crop water requirement throughout season in four days irrigation interval is beneficial for obtaining optimum onion yield and increases water productivity.