Determination of Optimal Irrigation Using Soil Moisture Depletion on Yield and Water Productivity of Potato (Solanum tuberosum L.) at Odo Shakiso District, Southern Ethiopia

Irrigation technologies that save water are necessary to ensure the economic and environmental sustainability of agriculture. Accurate irrigation planning is critical to improving irrigation efficiency. Therefore, this activity aimed to evaluate the responses of potato plants to the irrigation system (when and how much) and to determine the water productivity (WP) under optimal irrigation system. During the 2020 and 2021 irrigation season, a field trial of five irrigation treatments (20% ASMDL, 40% ASMDL, 60% ASMDL, 80% ASMDL and 100% ASMDL (FAO recommended ASMDL) irrigation) was conducted in Odo Shakiso district. The experiment was set up in a randomized complete block design (RCBD) with three repetitions. For the Irrigation Treatment at Allowable Soil Moisture Depletion (ASMDL), irrigation was scheduled when 35% of the total available water was depleted. Results showed that potato tuber yield, number of tubers per plant, and water productivity were significantly affected between treatments (P<0.05). Plant height, tuber weight and non-marketable tuber yield did not vary significantly between treatments. The highest marketable tuber yield (32.91 t ha^-1) was achieved using irrigation water with 100% ASMDL. Reducing soil moisture loss from the recommended level (0.35) did not increase water productivity. However, no significant difference in water productivity was observed between irrigation water application at 60% of the ASMDL and irrigation water application at 100% of the ASMDL (FAO recommended depletion limit). Therefore, it can be concluded that the application of the FAO recommended ASMDL can provide the highest marketable tuber yield and water productivity of potatoes in the study area and in a similar agro ecology. Therefore, further investigation and verification work under different climatic conditions is recommended.