Effects of Deficit Irrigation and Mulch Levels on Growth, Yield and Water Productivity of Onion (<i>Allium cepa</i> L.) at Werer, Middle Awash Valley, Ethiopia

Abstract

Enhancing water productivity of irrigated crops through Agricultural water management is a vital option in water scarce areas, such as, Rift valley. Accordingly, a field experiment was conducted at Werer Agricultural Research Center to evaluate the effects of deficit irrigation and straw mulching levels on growth, yield and water productivity of onion (<i>Allium cepa</i> L.). The experiment was laid out in a randomized complete block design in factorial arrangement of three levels of irrigation (100, 80 and 60% of Crop Evapotranspiration and four levels of straw mulch (0, 3, 6 and 9ton wheat straw per ha) in three replications. The output of Cropwat model indicated that the highest seasonal water requirement of onion was 422.5 mm at 100% ETc while; the lowest was 253.5 mm at 60% ETc. The analysis of variance revealed that there was significant (p<0.05) difference in growth parameters and yield parameters were highly significant (p<0.01) influenced by the interaction effects of deficit irrigation and straw mulch levels. The highest marketable bulb yield (33.47 t/ha) was obtained from an experimental plot treated with combined application of 100% of ETc and 6 t/ha straw mulch, while the lowest (21.10 t/ha) was obtained from plots treated with 60% ETc irrigation level and no mulch treatment. Water productivity was also highly significant (p<0.01) influenced by the interaction effects of deficit irrigation and straw mulching levels; the highest (10.22 kg/m³) and the lowest (6.11 kg/m³) were recorded from the plots treated with 60% ETc and 9 t/ha straw mulch, and 100% ETc and no mulch treatments, respectively. Therefore, in terms of marketable bulb yield and water productivity, irrigating with 80% ETc with 6 t/ha straw mulch would be recommended for production of onion in the study area.