Vol.:(0123456789) 1 3 Sustainable Water Resources Management https://doi.org/10.1007/s40899-018-0250-8 ORIGINAL ARTICLE Optimizing irrigation water levels to improve yield and water use efciency of vegetables: case study of tomato Kidane Welde 1  · Hintsa Libsekal Gebremariam 1  · Kifom Degif Kahsay 1 Received: 27 June 2017 / Accepted: 30 May 2018 © Springer International Publishing AG, part of Springer Nature 2018 Abstract Optimizing irrigation water requirement is necessary to improve productivity of irrigated agriculture. Hence, adapting the knowledge of irrigation scheduling for specifc crop and location is important. Field experiment was then conducted in Raya Alamata district of Tigray, Ethiopia to investigate the impact of diferent irrigation water levels on yield and irriga- tion water use efciency (IWUE) of tomato. Eight treatments (50, 35, 25% above estimated crop water requirement (CWR), estimated CWR, 25, 35, 50% below the estimated CWR and farmers practice) were arranged in randomized complete block design under three replications. Tomato water requirement was estimated using CROPWAT 8 software and it was estimated to be 500 mm throughout the base period. The result indicates signifcant diference between marketable yield (MY), total yield (TY) and IWUE of tomato by the level of irrigation. The application of estimated CWR of tomato gave higher MY (36.37 ton/ha) and TY (38.58 ton/ha). Unmarketable fruit yield of tomato was unafected by level of irrigation. Farmers’ practice gave considerable MY (36.32 ton/ha). But, the depth of water applied by farmers throughout the growing season was 561 mm which was 12.2% above the estimated CWR. The yield obtained per unit of applied water (IWUE) ranges from 0.357 to 0.876 kg/m 3 for the diferent irrigation water levels. This shows that IWUE increases with decreasing depth of water application. In conclusion, defcit irrigation practice could be successful in saving irrigation water up to 35% of tomato CWR without signifcant reduction in fruit yield of tomato in regions where water is a limiting factor for vegetable production. Keywords CWR · IWUE · Marketable yield · Unmarketable yield · Small-scale irrigation Introduction Efcient utilization of irrigation water is becoming increas- ingly essential in developing countries to attain food security (Chun et al. 2010). The increasing worldwide shortage of water and costs of irrigation especially in arid and semiarid regions contributes to give emphasis to methods of irriga- tion that maximize water use efciency (Youssef et al. 2007; Cai and Rosegrant 2003). Hence, sustainable methods to improve irrigation water productivity are getting emphasis in arid and semiarid regions like Ethiopia (Debaeke and Aboudrare 2004). Agricultural practices such as the use of sprinkler and drip irrigation are in expansion in southern zone of Tigray. But with this expansion, there remains a need for advancement in irrigation scheduling and CWR of vegetables. If the applied water is insufcient during the crop grow- ing season, the crop will not produce fully. This results in low quality yield or loss of total yield (Yazar and Sezen 2006). Applying more water than required by crop evapo- transpiration consumptive use (ETc) can result in extra pumping cost, wasted water and increased risk for leaching of valuable chemicals below the rooting zone and possibly in to the ground water (Cabello et al. 2009). Under these conditions, the root zone needs leaching to reduce salinity and water logging (Sun et al. 2006). Efective irrigation is possible only with regular monitoring of soil water and crop development condition in the feld and with the forecast- ing of future crop water needs (Raes et al. 2009; Steduto et al. 2009). Therefore, the irrigator needs to know efective Electronic supplementary material The online version of this article (https://doi.org/10.1007/s40899-018-0250-8) contains supplementary material, which is available to authorized users. * Kidane Welde kidanew2009@gmail.com 1 Tigray Agricultural Research Institute, Alamata Agricultural Research Center, P.O.Box 56, Alamata, Ethiopia