The study was conducted at Wondo Genet Agricultural Research Center, SNNP Region, Ethiopia, 7°05’ N latitude, 38°37’ E longitude and 1785 m.a.s.l for three years (2015/16 to 2017/18) based on the objective to determine the level of deficit irrigation levels and furrow irrigation water application techniques on yield and water productivity of lemongrass (Cympopogon citratus (DC) Stapf). Three types of furrow irrigation techniques (alternate, fixed and conventional furrow) combined with different irrigation levels (100, 75 and 50% ETC) with three replications were
used in randomized complete block design. Different furrow irrigation application methods and irrigation levels highly significantly (p<0.01) affected fresh biomass, dry biomass and water use efficiency of lemongrass during 2015/16 and 2017/18. Moreover, essential oil yield of lemongrass was significantly (p<0.05) affected due to different furrow irrigation application methods and irrigation levels both during 2015/16 and 2017/18. However, no significant (p ≥ 0.05) variation was observed in number of tillers per hill and essential oil content of lemongrass due to different furrow irrigation methods and deficit levels during 2015/16 and 2017/18. Higher fresh biomass (9610, 7348 and 4458 kg/ha) and dry
biomass (2507, 2136 and 1408 kg/ha) were obtained at 100% ETC under conventional furrow method during the three successive years. Similarly, maximum essential oil yield of 62.5 and 40.1 kg/ha was obtained at conventional furrow irrigation method with 75 and 100% ETC during 2015/16 and 2017/18, respectively. On the other hand, minimum fresh biomass (7123, 4689 and 2296 kg/ha) and dry biomass (1903, 1308, 704 kg/ha) during the three successive year, and essential oil yield of 44.9 and 20.0 kg/ha were obtained at fixed furrow with 50% ETC during 2015/16 and
2017/2018, respectively. In addition to these, higher water productivity of 0.080, 0.075 and 0.052 kg/m3 was obtained due to alternate furrow irrigation with 50% ETC during three successive years. On the other hand, the minimum water productivity of 0.024, 0.026 and 0.021 kg/m3 was obtained at conventional furrow technique with 100% ETC during 2015/16, 2016/17 and 2017/18, respectively. Therefore, for maximizing essential oil yield under no water limiting scenario, lemongrass could be irrigated with conventional furrow irrigation methods with 100% ETC. However, under limited water resource condition, the main objective will be to maximize the water use efficiency without significantly reducing the oil yield. Therefore, in this case lemongrass could be irrigated with alternate furrow technique with 100% ETC at Wondo Genet and similar agro-ecology and soil type.