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.
