Determination of Optimal Irrigation Scheduling for Onion (<i>Allium cepa</i> L.) in Gumara Scheme, North Western Ethiopia

Abstract

The experiment was performed at Gumara irrigation scheme farm in the 2017/18 and 2019/19 irrigation seasons, with the objective of determining the optimum irrigation schedule based on the available soil moisture depletion levels. The experiment was carried out in RCBD with three replications, randomly assigned to the experimental plots with treatments. Six available soil moisture depletion levels (60, 80, 100, 120, 140, and 160%) were use. The results obtained of two years of research showed that different rates of levels of soil moisture available had a very highly significant effect (P<0.0001) on bulb mass, bulb diameter, marketable yield, and water productivity. The highest marketable bulb yield and water productivity (35222.2 kg ha^-1 and 7.06kg/m³) were recorded at 80% and available soil moisture depletion levels (ASMDL) and also the lowest non-marketable bulb yield (1513.9 kg/ha) was recorded at 80% ASMDL. However, the lowest marketable yield, lowest water productivity and highest non-marketable bulb yield (28722.2 kg ha^-1, 5.29 kg/m³ and 5236.1 kg /ha) was recorded at 160 percent ASMDL Very highly significant (P < 0.0001) plant height and bulb length differences were observed due to the treatments. The highest plant height and bulb length were recorded at 60 per cent AMADL (66.33 cm and 5.62 cm respectively). However, different soil moisture depletion levels showed no significant difference in the stand count of onion. The highest efficiency of water use on onion yield (7.06 kg/m³) was attained at 80 percent ASMDL, whereas the minimum efficiency of water use (5.29 kg/m³) was recorded at 160 per cent ASMDL. Therefore, based on the findings of the current experiment, it is recommended that using 80%ASMDL for furrow irrigation system for onion to be grown in areas around Fogera and similar agroecology as best options to increase yield and water use efficiency for the production of onion.