Determination of Optimum Irrigation Scheduling and Water Productivity for Onion Production in Mandura District, North-West Ethiopia

Knowing how much water a plant has access to and how effectively it can use it is crucial for irrigation scheduling in order to prevent overwatering or under watering. To assess how onions responded to the irrigation schedule, a field experiment was carried out. (When and how much) and to identify water productivity under optimal irrigation regime. The recommended levels of soil moisture depletion for onions served as the basis for setting the treatments. Then, in order to assess the best irrigation timing, there are five degrees of available soil moisture depletion namely, 60% Available Soil Moisture Depletion Level, 80% Available Soil Moisture Depletion Level, 100% Available Soil Moisture Depletion Level, 120% Available Soil Moisture Depletion Level and 140% Available Soil Moisture Depletion Level of the FAO recommended value of onion were used. Three replications of the experiment were set up using a Randomized Complete Block Design. The highest total bulb yield obtained at 60% Available Soil Moisture Depletion Level that was 211.65 q/ha followed by 80%, 100% and 120% Available Soil Moisture Depletion Level with the values of 210.85q/ha, 191.89q/ha and 188.18q/ha respectively without any significant difference. The highest irrigation water productivity of onion to convert irrigation water to bulb yield were obtained under 60% Available Soil Moisture Depletion Level which had 3.87kg/m<sup>3</sup>/ha followed by 80%, 100% and 120% Available Soil Moisture Depletion Level with the values of 3.77, 3.63 and 3.37 kg/m<sup>3</sup>/ha respectively without any significant difference. Therefore, according to the current findings, the highest bulb production and irrigation water productivity are obtained when irrigation scheduling is applied for onions in the research and related agroclimatic areas and soil types at 60% Available Soil Moisture Depletion Level.