Artificial Lighting - Exhibition Onions
22nd Jan 1997
There's no doubt at all that the use of artificial lights in it's various forms has greatly improved the size of the large exhibition onions over the past few years. Prior to using the Philips SGR 200 unit and a SON T Aggro lamp, the plants used to be very weak and drawn at this time of year. The difference in the quality of the plants is remarkable, and I'm still amazed how the plants respond to being given full lights for twenty four hours a day for a six week period without even going to seed.
A number of growers use the normal fluorescent tubes as a source of light and they don"t have to be the Gro Lux type either, the normal warm type will do the job just as well provide you have plenty of them. If they are being used in an enclosed environment such as a growing cabinet, always be aware that not only are they a source of light, they also release a fair bit of heat, so do have a maximum / minimum thermometer inside just in case the temperature rises too high.
This year I have incorporated a new 6" diameter fan into a pane of glass at the far end of the second greenhouse, this works very well in conjunction with the other 9" fan inside the growing cabinet. Both fans are connected to a reverse thermostat so that hopefully the plants have as near an ideal growing condition as possible. The Parwin heater is set at a minimum of 55°F and the fans are set at 75°F so in theory the temperature is always set between these two parameters.
There are of course other benefits to be derived from such a set up, firstly the stagnant air that inevitably surrounds the plants in such a warm humid environment is being regularly pushed out of the cabinet whilst the other fan sucks it outside. Secondly the very fact the air is being regularly re cycled means that the foliage of both leeks and onions are gently moved about. This means that the cell walls of the plant are toughened up which most certainly helps the plants to stay more erect, at the end of the day stronger plants will be the result and stronger plants must mean better onions and leeks as well.
Supporting the Foliage
Even though the plants are undoubtedly stronger because of the air movement, it also helps if you support the foliage of both the leeks and onions. For a number of years now I have been using the green plastic plant support clips which are clipped onto split canes and form a circle around the foliage. Later on as plant growth increases, two canes are used with two clips forming a larger circle.
If you haven't already done so, get your onion and leek bed soil analysed, there's no doubt that accurate soil testing has also improved the quality of the plants we produce. Gone are the days when we used to just throw some bone meal in the Winter followed by a balanced fertiliser in the Spring in the hope that it would do the trick. If you have never tested your soil, I strongly urge you to do so as you may well be shocked by the results. I know of one grower who had used bone meal extensively every Winter for a number of years without ever having his soil analysed. He eventually had it tested after a particularly bad year with very poor leeks and onions.
When he had the result through, his phosphate or phosphorous level was so high that he didn't have to apply any for a couple of years, this meant that other elements within the soil were being locked up by the high phosphates. I have mine tested every year by Lancrop Laboratories, The Airfield Industrial Estate, Pocklington, York. YO4 2NR.
It will soon be time to sow your parsnips so be sure that you have everything to hand ready for the job. If you haven't already emptied your beds or drums of the solid sand inside them you must do so now so that they have to time to settle down prior to boring the holes.