Growing consultant Willem Valstar of StarGrow Consultancy was not complaining about the weather on Wednesday afternoon. That is simply because he was in Portugal for a while, for consultancy work. In the Netherlands, it's a different kettle of fish. "Dealing with moisture is what it's all about for lighting growers now," he points out. "And making sure you keep crops productive."
The exposed crops are halfway there. Some growers combine LED lighting with dehumidification technology. Others work with just LED, trying to rid their greenhouses of moisture without new techniques. "Under 300 micromol LED, you have quite a bit of moisture," the crop consultant signals. "Dehumidification techniques solve part of it, but from what I see with the current systems, not all of it yet."
Additional tube heating
The shortest route growers can then take is to put in extra tube heating, and this is done in abundance where growers have enough heat available. However, not every grower has that luxury. Not everywhere are tomato growers connected to geothermal heat sources, and also, when making the move to LED, some have opted for less CHP capacity. "At the moment, you have to be able to generate enough heat to get the moisture out of your greenhouse and get things up to temperature. That's where things do pinch here and there."
Looking to the future, there is still a challenge here for illuminated crops, Willem points out in trials with LED lighting in recent years. "We want to grow more energy-efficient crops, but under winter conditions like now, that's still difficult. LED is more economical, but you have to put in a bit more heat."
For the October plantings, which are just coming into production, it is still a bit hard to say, but it seems that the expected productions are not quite achieved yet, given the conditions. For the slightly longer-running crops, the story is similar. "There, too, it is currently difficult to make the most of it in terms of production. With growers who have more heat available, things are generally going better."
Edema and pollination
Pest pressure in the exposed tomato crop is currently limited. However, the crop consultant does see problems with edema rearing their heads here and there. "That problem is back. Inflated leaf cells due to excess moisture you didn't really see in HPS-exposed crops."
For growers facing it, he advises growing drier. "Fewer screens and letting in more daylight can help," he says. But that is where the foggy weather of the past week immediately comes into play. "It's just super tough growing right now," he says.
Pollination is also another challenge given the growing conditions at the moment. It is grey and cold, and with less radiant heat from the LED lights, growers are opting to screen more. "But then your bumblebees also fly less well again. Bumblebee flight is also a challenge."
Despite the necessary challenges, Dutch tomato cultivation with LED lighting is well on its way, emphasizes Willem. He acknowledges that it is a puzzle but points out that at the moment, it is mainly the details that need to be improved. It's all about setting accents. "I see a lot of potential in LED cultivation," he says.
Unlit cultivation is slow
For unlit cultivation, the current weather is especially tricky. "There is an icebox strategy here," laughs the cultivation consultant. "With this weather, planting in December makes little sense. You just have to take it easy to avoid losing bunches."
With the lessons of the previous dark spring also in mind, it is expected that productions will be delayed here. "In the whole of December, we only had 3,000 joules in some areas. An average of 100 joules a day, which is really bizarrely little." January is no better for now. "Week 1 was bad, week 2 moderate, and anyone who looked outside this week understands that week 4 was not anything to write home about either."
For more information:
StarGrow Consultancy
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www.stargrowconsultancy.nl