4 years ago

The Partnership no. 7

  • Text
  • Enza
  • Organic
  • Zaden
  • Partnership
  • Tomatoes
  • Varieties
  • Consumers
  • Breeding
  • Products
  • Cultivation

In Scandinavia,

In Scandinavia, greenhouse vegetable growers have been using grow lights to help their crops through the long, dark winters for many years now. In the past decade this technology has become more popular further south, in the Netherlands, too. Almost one third of the total Dutch tomato acreage is now equipped with artificial light systems, and that proportion is still increasing annually. Growers in countries around the Netherlands, and in North America, too, are also discovering the advantages of extra artificial light. The Netherlands has for many years been Europe’s number-one producer of tomatoes in the summer season. They are all grown in glass greenhouses, most of which are heated with combined heat and power stations or gas-fired boilers. Most growers plant their plants in stone wool slabs in December, to stretch the traditional production period from early April until the end of November. “In the past decade many growers equipped some of their greenhouses with lighting systems,” says Maarten van den Heuvel, Crop Sales Manager Tomato “They answer the growing demand for a continuous supply of tomatoes of a reliably high quality.” The Crop Sales Manager goes on to point out that such lighting systems are now being used in almost 600 ha, corresponding to about thirty percent of the total acreage in the Netherlands. Growers with combined heat and power stations didn’t need much persuasion to start using such a system, as it enables them to generate electricity at relatively low costs. Even so, the cost price of the tomatoes concerned is quite a bit higher. Artificial growing light Technology Product brings advantages Advantages Marc Mens, Crop Specialist Fruity Crops in Northwestern Europe, explains: “Using artificial lights implies several advantages. For a start, it ensures customer loyalty, because buyers can rely on more or less the same quality from their usual suppliers all the year round. In the winter season in particular there used to be substantial shortages in the top segments, and they have now been partly eliminated. And as tomatoes of high quality fetch better prices in the winter they often pay back your investments. An added advantage of spreading your production like that is that you have a slightly smaller supply in the summer period, when prices are usually very low. So you’re killing two birds with one stone.” According to Van den Heuvel, the acreage of tomatoes grown with lighting is in some segments, such as that of snack tomatoes, not increasing as rapidly as that in, say, the segment of tomatoes on the vine. Spain and North Africa are formidable competitors in those segments because of their lower cost prices. Sodium and LED lamps Almost the entire acreage of the greenhouses with artificial lights is equipped with high-pressure sodium lamps of 600 or 1,000 Watt suspended above the crops. A small, but growing number of growers also have LED lamps hanging between the rows of plants. This combination is also known as hybrid lighting. “Sodium lamps generate a lot of thermal radiation besides growing light,” explains Van den Heuvel. LED lamps are far more efficient, and can also be used between the plants. But at this moment they’re still more expensive to buy.” Hybrid lighting Research and practical experience have shown that tomato plants do best under hybrid lighting. The top parts of the plants need heat, which is generated by the sodium lamps. LED lamps can be suspended between the plants, to systematically ensure larger amounts of light lower down the crop so that the plants remain productive over greater lengths. That promotes a slightly higher growth rate, and above all heavier tomatoes. “Profits in Dutch greenhouse horticulture have been under pressure for quite some time, but I expect that more investments will be made in hybrid lighting when the results improve,” says Mens. “I’m pretty certain that’s what’s going to happen in the future.” Different form of control As crops grown with such lighting start to develop far earlier than traditionally grown crops, i.e. in August instead of December, the plants have to grow at a decreasing natural day length for a few months. “In combination with the increasing plant load, such crops call for a different form of control than standard crops,” explains Mens. “For a start, you have to keep your eye on the moisture content. In late summer the relative humidity always rises, while the expanding crop introduces extra moisture into the greenhouse through transpiration. On top of that, energy screens tend to be closed more often as the nights grow colder. So you then have to make sure you discharge enough moisture.” According to Van den Heuvel you need varieties with sufficient generative development combined with vigour for the standard types of tomatoes. The tomatoes must be of a consistent quality and ripen equally. Another aspect that is also important for specialties is taste, which must be consistent. Enza Zaden tests all its varieties intended for greenhouse cultivation to check whether they are indeed suitable for that type of cultivation, of course in greenhouses with lighting systems. Maarten van den Heuvel: “Artificial light is an answer to the growing demand for a continuous supply of tomatoes of a reliably high quality” 32 | The Partnership The Partnership | 33

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