THE EFFECT OF IRRIGATION INTERVALS ON GROWTH, YIELD AND YIELD TRAITS OF ONION (Allium cepa L.) VARIETIES IN RAMA ADIARBAETE, TIGRAY, ETHIOPIA

Abstract

Onion (Allium cepa L.) is one of the most important vegetable crops in Ethiopia which is used almost daily as a spice and vegetable in the local dish. It is a shallow-rooted crop that requires frequent irrigation to achieve a high yield. Inconsistent or suboptimal irrigation regimes can lead to yield variability among onion varieties. This study was aimed, to investigate the effect of irrigation intervals on the growth and yield traits of onion (Allium cepa L.) varieties and determine optimal irrigation intervals for maximizing crop and water productivity. The experiment was conducted at Rama Adiarbaete, central zone of Tigray, Ethiopia. Split plot design was used to conduct the experiment; by considering four irrigation intervals (5, 8, 11 and 14 days) assigned in the main plot and three onion varieties (Bombay red, Adama red and Red creole) assigned in the sub-plots with three replications. The climatic data of Rama Adiarbaete wereda was taken from Adwa meteorological station. Water requirements of onion were computed using the cropwat model 8.0. The results showed that the onion Bombay red variety irrigated at 5 day interval produces higher marketable bulb yields (12.23 t ha-1), harvest indexes (80%) and water productivity (3.52kg m-3) than Adama red and Red creole. In addition to this, at 8 day irrigation intervals, Bombay red scored the highest harvest index (75.30%), marketable bulb yield (11.05 t ha-1) and water productivity (3.097kg m-3) which was followed by Adama red variety (71.88%, 10.43t ha-1, 2.96kg m-3) respectively. According to the economic analysis, also Bombay red irrigated at 5 days interval resulted in 443% MRR over Bombay red irrigated at 8 days interval and residually ranked first. This could be due to the higher marketable yield of Bombay red when irrigated at 5 days intervals. Therefore, farmers in the study area and similar location should have to use 5 days irrigation interval and use the Bombay red variety when there is accessible labor. However, when there is limited availability of labor in the study area, they have to irrigate the Bombay red variety every 8days interval for higher productivity and profitability. In case of the scarcity of Bombay red seeds, farmers could use Adama red onion seeds as an option in the study area. The findings should be refined further by taking up multi season data and by measuring soil water characteristics in multi locations.