Articles
THE INFLUENCE OF CULTURAL FACTORS ON THE BULB SHAPE OF THE ONION (ALLIUM CEPA L.) CULTIVAR “PUKEKOHE LONGKEEPER”
The shape can vary from flat to globe to torpedo with different markets having different requirements.
Bulb shape has become an important aspect of New Zealand onion production with European markets now demanding a flattened globe shaped onion for ease of packaging.
Onion bulb shape was assessed by the bulb shape index, this was determined the ratio of bulb height to diameter.
Bulbs having a shape index of greater than 1.2 were regarded as having an unacceptable shape for New Zealand export grade onions.
An experiment carried out during the 1990 – 1991 season showed that increasing the plant density from 50 to 100 plants per square metre increased the percentage of shape rejects from 7.9 to 15.3 %. Increasing the plant density also increased the bulb shape index.
Delaying the sowing time from June to September resulted in a decrease in both shape index and percentage of shape rejects.
In a second experiment during the 1991 – 1992 season, increasing the plant density from 65 to 130 plants per square metre increased the percentage of shape rejects from 9.1 % to 14.2%. Changing the sowing depth did not significantly influence the percentage of shape rejects.
Increasing the row number from five to ten rows per 1.5 m bed resulted in an overall reduction for the percentage of shape rejects from 18.4% to 9.9% at the higher density of 130 plants per square metre.
However there was no significant difference at the 65 plants per square metre density.