Always a clean greenhouse
Even when prices are poor few companies cut back on cleaning the inside and outside of the greenhouse. This indicates that in practice the importance of good light transmission has sunk in.
Contractor De 3 Koningen (The Three Kings), of Steenbergen, the Netherlands, specialises in cleaning. This particular company name was chosen when brothers René and Frank de Koning (King) joined forces with their younger brother Robert. The company also has five permanent employees and when necessary takes on temporary personnel.
“We recommend that vegetable greenhouses, the segment in which we by far the most work do, are cleaned three times per year. Some vegetable nurseries even clean four times per year. The realisation that glass should be clean the entire year round is becoming more and more noticeable,” says René de Koning. That includes flushing out and cleaning the gutters because these can also cause the glass to become dirty again.
Contractor De 3 Koningen
Many large greenhouses have their own (stationary) roof washer. However, De Koning notices that some growers are moving away again from self cleaning. “Their machines often lie idle for quite some time, such as during the summer. This standing still combined with lack of maintenance means they can go wrong. Such growers then call us, either to do the maintenance, or to take over the entire cleaning with our well-maintained machines. These have improved a lot over the years and now have wider brushes and double gutter brushes.”
De 3 Koningen has four large roof cleaners (4 metres wide) and a smaller one (3.20 m). Annually these are used to clean some 4 million m² of greenhouse roofing. In addition to the normal cleaning the company can also remove coatings such as ReduClean. The contractor is also increasingly asked to apply coatings at the beginning of the season. Due to the structure of its customer base (mostly vegetable growers), this is usually ReduFuse.
Crop change over
Another branch of the business is cleaning the inside of greenhouses in between the old and new crops. During a six week period they clean some 250 ha. “This is a very busy period in order to get everything planned in. Many greenhouses change crops at the same time. In order to get everything done we then work through the weekend,” he says.
Firstly the whole greenhouse is sprayed using radio-operated spraying vehicles. Then the greenhouse is sprayed again, this time manually using a hydrocart. “We notice that GS-4 is used more and more often. We used to think that you needed a very aggressive fluoride substance but we now realise that the greenhouse can stay clean with environmentally friendlier substance, such as GS-4. Therefore some customers no longer want to use aggressive substances due to the vapour given off and its risk to humans and the crop. Sometimes it’s necessary to use a little more on the walls and this works perfectly.”
Anne Elings explains why crops grow better with more light
For a good part of the year, the level of natural light is below optimal for most crops. Any additional light that then enters the greenhouse contributes to improved production and quality, says Anne Elings, Plant Physiologist at Wageningen University & Research.
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