Optimal Irrigation Scheduling of Garlic (Allium sativum L.) using Allowable Soil Moisture Depletion for Water Scarce Areas of Ethiopia

The main objective of this study was to evaluate the responses of garlic to the irrigation regime (when and how much) to irrigate. The field experiment was conducted at the main station of Debre Zeit Agricultural Research Center in 2016 and 2017. Five treatments for allowable soil moisture depletion levels (ASMDL) of irrigation at 60%, 80%, 100%, 120%, and 140% were used. Application of irrigation water for garlic was scheduled when 30% of the total water available in the soil profile was depleted. Treatments’ were laid out in RCBD experimental design with three replications for each treatment. In the study, it was observed that there was a significant difference in marketable yield and water use efficiency (WUE) between treatments. The maximum marketable bulb yield (7.5 t/ha) and WUE were observed by applying irrigation water at 20% more than the recommended ASMDL and the lowest (4.68 t/ha) was recorded at 40% less than the recommended ASMDL. Reducing the allowable soil moisture depletion level by 40% and also by 20% from the recommended fraction (0.30) has significantly increased the water use efficiency. Generally, from this study it has been observed that irrigating garlic at a shorter frequency enhance yield and water productivity. Therefore, managing the soil moisture content above the allowable depletion level (i.e 60% ASMDL and 80% ASMDL) was better than using the recommended allowable depletion and the other lower levels. Hence, to have a higher yield and maximum water productivity, it was recommended to irrigate garlic frequently.