Troy at the Bos brothers in Ouwerkerk

Agricultural trade journal Boerderij recently published an article by Nico Rodenburg about the farm run by brothers Mariën and André Bos in Ouwerkerk. As well as growing sprouts, potatoes, sugar beet and celeriac, the brothers also grow overwintering onions. Their choice fell on the onion set variety Troy, which is supplied under the Quality inside label.

Apart from the season, growing winter onion sets is similar to growing spring onion sets,’ says Bos. After the onions emerge, soil herbicides are applied to keep the crop as clean as possible as it enters the winter months. Bos states that ‘it’s an illusion to think that every conventional onion grower can produce winter onions. The actual technicalities of growing are not that different, but the suitability of the fields used to grow winter onions is far more important’. Bos farms on a light, sandy clay soil with a lutum percentage between 7 and 25%. Good drainage is an aspect the brothers devote a lot of attention to. ‘Taking good care of your soil is absolutely essential, year in year out.’

The brothers have experience with overwintering onions. The planting time is crucial as far as bolters are concerned; the onions must not be too large when winter starts. However, if planted too late, frost can cause high losses. The Troy variety is geared for the Dutch market. ‘Normally, traditional overwintering varieties like Jagro and Jetset produce plenty of bolters if they are planted before the winter. That is absolutely not the case with Troy,’ comments Mariën in the article. The onions can be planted until mid-October and measure about 10cm when winter arrives.

On 2 October the onion sets were planted using the demo precision planter from Machinefabriek Koning in Alkmaar. The result should be even higher uniformity in sizes. ‘This is another step taken to reduce the risk of a failed harvest, as there are risks enough as it is,’ says Bos. A good example is the recent snow and frost, which has had an effect on the foliage of the Troy onions. On the otherwise very uniform looking plot, some leaves on the plants have frozen and died off. The consequences this will have on the final yield partly depend on the conditions in spring.

 

Published 22 Febuary 2010