Appropriate spacing enables the farmers to keep appropriate plant population in the field. Hence, it can avoid over or less population in a given plot of land which has negative effect on yield and quality of onion. Spacing of 40 × 20 × 10 cm between furrow, row and plants, respectively has been used for onion production in Ethiopia. But producers complain 10 cm intra row spacing produces large bulb size which is not preferred by consumer for home consumption. To optimize onion productivity, full package of information is required. To fill this gap field experiment was conducted to study the effect of inter and intra row spacing on the bulb yield and yield components of onion at Ribb in Fogera, Woramit in Bahir Dar and Koga in Mecha districts in 2014. The interaction of the lowest inter and intra row spacing mature earlier by 15 days compared to highest inter and intra row spacing. Forty nine percent of medium sized bulbs were produced with the interaction of 15 and 6 cm inter and intra row spacing while only 32% of medium sized bulbs were produced by the interaction of 25 and 8 cm inter and intra row spacing. Small sized bulb distribution decreased as intra row spacing increased while large bulb sized distribution increased when intra row spacing increased. The highest bulb weight (102 g) was produced by the interaction of highest inter and intra row spacing while the lowest bulb weight (45 g) was produced by the lowest inter and intra row spacing. Interaction of inter and intra row spacing of 15 and 4 cm respectively, scored the 1st highest marketable bulb yield (39 ton ha-1) and interaction of 15 and 6 cm inter and intra row spacing scored the 2st highest marketable bulb yield (36 ton ha-1). The result revealed that the earlier recommendation (20 and 10 cm inter and intra row spacing) produced more number of medium and large sized bulbs with a yield penalty of 8.0 and 10 ton per ha-1 compared to interaction of inter row spacing of 15 cm with intra row spacing of 6 and 4 cm, respectively. Therefore, the interaction of inter and intra row spacing of 15 with 6 cm is recommended as a first option for producers who wishes to produce maximum bulb yield with maximum medium sized bulbs. It is also confirmed that earlier recommendation is better as a second option for producers who wishes to produce for export market which requires medium and large sized bulbs of onion.
Key words: Onion, inter, intra, spacing, bulb, yield.
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