EFFECT OF PLANTING DATE AND PLANT SPACING ON ONION ( Allium cepa. L. ) YIELD UNDER RAIN-FED IN SEMI-ARID CONDITIONS OF JORDAN

A field experiment was carried out during 2006/2007 growing season at the Agricultural Research Station, Mu'tah University, Jordan, to study the effect of planting date and plant spacing on onion yield under rain-fed in semi-arid conditions of Jordan.Treatments were arranged in a split plot design with 3 replicates.The main plots were assigned for planting on (Dec. 1, Dec. 15, Jan. 1, Jan. 15 and Feb. 1), while the sub-plots were assigned for plant spacings (10, 15, 20 and 25 cm).Onion bulb yield and bulb weight were decreased with delaying planting date.The highest yield was produced with the earliest planting date (Dec.1).Neck thick diameter, bulb diameter and bulb height were significantly decreased with delaying planting.Wide plant spacing reduced onion bulb yield, but it significantly increased individual bulb weight, neck thickness and bulb diameter.In general, maximum onion bulbs yield (23.71 ton ha -1 ) was obtained from early planting date with the closest plant spacing.In conclusion, the best onion yield in terms of quantity and bulb characters was obtained when onion transplants were planted on Dec. 1 or Dec. 15 at the closest plant spacing under semi-arid conditions.