Yield and water use efficiency response of onions to deficit irrigation in Sekota, Northern Ethiopia

A field experiment was conducted in Sekota woreda to investigate the impact of deficit irrigation on the yield and water productivity of the Bombay red variety onion. The experiment used a randomized complete block design with nine treatments and three replications. Crop water requirements and data analysis were estimated via the CropWat model and statistical analysis software (SAS) respectively. The results indicated that deficit irrigation at different growth stages had a significant effect (p < 0.01) on growth and yield parameters. The maximum and minimum marketable yields of 25.2 t/ha and 16.4 t/ha, respectively, were obtained from the treatments receiving 100% and 50% ETc throughout the growing season. The highest crop water use efficiency of 6.39 kg/m3 was obtained from the 50% ETc irrigation application. A severe yield reduction of 55.27% was obtained from a 50% deficit at all stages. Compared with full irrigation, a 25% ETc deficit at the development and late stages resulted in a 6.36% yield reduction and saved 12% of the irrigation water. The highest Ky was obtained from the 25% deficit treatment at the middle and development stages having a value of 1.1. The maximum net income and maximum marginal rate of return were 684130.28 ETB/ha and 969.66%, respectively, which were obtained from treatments in which 25% ETc deficit was applied at the development stage and late stage. The study revealed that increased water savings and water productivity were obtained from 25% deficit irrigation at the development and late stages. Hence, applying 25% less water at the late and development stages can reduce the problem of irrigation under water-scarce conditions, with no significant yield reduction for the study area and similar agro-ecologies and soil types to improve the water productivity of onion.