LED systems clearly add value to year-round growth concepts for cucumbers. Jan Biemans of Tielemans Groentekwekerij from Boekel, the Netherlands and Eric van den Eynde from Kontich, Belgium have determined this after their first cultivation under a hybrid grow light solution. In 2020, they both upgraded their existing HPS installations with Philips LED toplighting systems from Signify. Despite the differences in their greenhouses, installations, and goals, their conclusions were unanimous: LED contributes to an efficient, high winter production of excellent quality.
Eric and Lander van den Eynde’s company near Antwerp consists of 2 ha of unlit tomatoes and 2,1 ha of lit, high-wire cucumbers. “We have been growing under HPS lights for two years already, which complemented the natural light with 180 µmol/m²/s,” says Eric. “However, in winter the fruits did not reach the desired weight of 350 to 400 grams. Therefore, light had to be added and LED is the most efficient solution for that. Our question to Signify was how we could fulfill that in the smartest way.” Multiple light plans were calculated in consultation with their installer and the plant specialists from Signify. Because of the limited height of the greenhouse (gutter height 5 meters), the Philips GreenPower LED toplighting linear was chosen because that gives the most uniform light distribution.
Half of the HPS lamps were removed, and for each removed lamp 2,9 linear LED modules were installed. This brought the total light intensity to 223 µmol/m²/s, divided between 87µmol/m²/s HPS and 136 µmol/m²/s LED in red, blue and a bit of white working light. The total installation gives 24% more PAR-light, while the energy usage (at equal lighting hours) is about 7% less.
“The light division is nice and equal, even when only the LED lights are on”, the grower continues. “The latter is the case every now and then in the spring and autumn in particular, when the heat radiation from the HPS lights is not always wanted.”
More and heavier fruit
The new installation was ready in September of 2020. To take maximum advantage of the higher light level, a planting distance of 50 cm (2,5 plant/m2) was chosen. Lighting was begun directly after planting on October 2nd. Van den Eynde: “The plants reacted well. Our goal is to have a growth speed of six new leaves per week, and we could keep up with that pace effortlessly. The higher density of the stalks did ask for an altered pruning policy, but that did not have any effect on our labor planning. The most important goal was a higher average fruit weight. That was realized right away. Furthermore, we cut more cucumbers and they were of good color. Our customer is very satisfied, and therefore so are my son and I.”
Tielemans Groentekwekerij consists of 12 ha of greenhouses at two locations in Boekel. Cucumber is the most important crop. The company realizes two high-wire growths per year, from the beginning of January till the end of November, which formerly received 95 µmol/m²/s extra PAR-light from HPS lamps during the lighting season.
“In 2020 we received the request from our producers’ association to adapt 3,0 ha for winter production”, says growth manager Jan Biemans. “In order to realize sufficient production, weight, and quality in the darkest period, quite some additional light had to be installed. We looked at different options and made calculations. The choice was made for Signify’s Philips GreenPower LED toplighting compact, in combination with the GrowWise control system. With that we can dim the LED installation and tune the light level even better to the crop’s needs.”
Longer light in the evening
According to the light plan, the toplighting compact grow lights (providing 2.600 µmol in red and blue for optimal efficiency) were attached to the trellis in between the rows of HPS lights, raising the light level with 144 µmol/m²/s to 240 µmol/m²/s. The stalk density was chosen at 2,25 stalks per m2. Biemans: “We are content with the achieved winter production, and I am happy with this hybrid solution’s flexibility. The LED installation enables us to continue lighting longer in the evening without the additional heat. The plants did fine and got through the winter well.”
The growth manager thinks he can get even more out of it by decreasing the width of the row distance. “In the future I think we can benefit even more by adding far-red light”, he adds. “One variety showed some contracted leaves in darker periods, but the other variety did not do this at all. Overall, we are happy with the results.” Erik Stappers, plant specialist at Signify adds: “Full LED with far-red has proven itself by now. The role of far-red light in a hybrid installation with more LED than HPS is being investigated at the moment. Indeed, we do see differences between the varieties there.”