Water scarcity is one of the most significant constraints on agricultural production in the world, notably in Ethiopia. In the location where this study was conducted, production is only possible once a year. To make the most use of available water, effective water application technologies must be used, and the feasibility of producing crops in water-stressed scenarios must also be researched. In areas of water shortage, deficit irrigation was an essential approach for raising water production and improving water use efficiency. For this purpose, a field experiment was carried out at Alage ATVET College in Ethiopia's Central Rift Valley during the 2019/20 dry season. The regularly grown cash crop pepper was chosen for experimentation under drip irrigation. The study aimed were to investigate the influence of deficit irrigation levels on agronomic performance and water productivity. Seven deficit levels (DI) namely 60, 50, 40, 30, 20, 10 and 0% were laid out in a randomized complete block design with three replications by using drip irrigation. Water application was used in all deficit levels by managing the demand side. Full irrigation produced the maximum plant height, branch number, fruit weight per plant, fruit diameter, fruit length, marketable and total yield. However, at 20% DI levels, stem diameter, flower and fruit number per plant increased. There were only significant variations in total dry yield at 50% and 60% deficiency levels. Marketable yield was significantly different across all deficit levels. It was not possible to determine the water stress threshold level of pepper due to the large variation in yield, but at 30% DI, the yield reduction was about one-quarter of the 0% deficiency level by withholding 33.4% water. CWUE was significantly different at all deficit levels, demonstrating that as stress levels rise, so does CWUE. IWUE exhibited significant difference only at 0 and10% DI. As a result, it is possible to conclude that using at 30% deficit by withholding 33.4% of water can be used to optimize the yield and water productivity of pepper production at Alage and other areas with comparable agro-ecology.
