EFFECT OF IRRIGATION INTERVAL AND NITROGEN RATE ON YIELD AND YIELD COMPONENTS OF ONION (Allium cepa L.) IN ARBA MINCHSOUTHERN, ETHIOPIA

Abstract

Onion is an important cash crop for smallholder farmers in the Central Rift Valley of Ethiopia. However, its productivity is low owing to a number of factors including inappropriate irrigation water and nitrogen management. A field experiment was, therefore, conducted at Amibar farm, Arba Minch, Ethiopia, during 2018/19 dry season to determine the effect of irrigation interval and nitrogen rates on growth, yield and yield components of onion (Bombay Red variety). The treatments comprised four irrigation intervals (3, 6, 9 and 12 days of crop water requirement, ETc) and four nitrogen levels (0, 50, 100 and 150 kg N ha-1). The experiment was laid out in a split-plot design using irrigation intervals as main plots and nitrogen rates as subplots with three replications. There was significant increase in growth parameters, yield components and final yield of onion with decrease in irrigation interval up to 6 days, but further decrease in irrigation interval upto3 days did not have significant improvement in various parameters. The increasing N rate increased significantly the growth and yield components up to 150 kg N ha-1, but response was significant only up to 100 kg N ha-1 on final yield of crop. The growth and yield contributing parameters, showing enhancement with frequent irrigation and higher N rates, had a significant bearing on the final yield and quality of onion. The irrigation at 6 days interval combined with 100 kg N ha-1 gave higher marketable yield (30.21 t ha-1), net return (Birr 288,458 ha-1) and marginal rate of return (8586%). As such, irrigation at an interval of 6 days and fertilizer at the rate of 100 kg N ha-1 may be recommended for higher productivity and profitability of onion at Arba Minch, Gamo-Gofa, Southern, Ethiopia.