3% increase in cucumbers in high-wire cultivation under lights

January 1, 1

A trial carried out last year at Hortus in Futuro in Maasbree demonstrated that high-wire cucumbers in 7.5 cm high Grodan Plantop NG2.0 blocks produced a 1.5% higher yield in natural light and a 3% increase under lights compared with plants in 6.5 cm blocks. Moreover, an increase in fruit weight was noted.

Detail of cucumber crop in greenhouse

Hortus in Futuro in Maasbree, a family business that specialises in high-wire cucumbers, has two harvests annually: a winter harvest of the Hi Power variety (planting date: 28 December) and a summer harvest with Hi Force, a mosaic-resistant variety with a planting date around the longest day.

Manager Marcel Huibers places high demands on his plants and substrates. This makes excellent communication with propagator Grow Group extra important. "We request a strongly generative plant. We don't mind if it's smaller, as long as it contains sufficient dry matter to produce a strong crop."

He starts with a plant density of 1.7 plants/m2, amounting to 3.4 stems/m2. During the first harvest he keeps one extra stem as of 3 February, as the outside light starts to increase sharply. For summer harvesting he uses topped plants, topped at the fourth leaf. "Grow Group, our propagator, ensures that the lower shoots and the top leaf have been removed, leaving a shoot only on the third and fourth leaf."


The nursery of 10ha, run by Hay and Paul van Lipzig, is innovative in many ways. Assimilation lighting was installed last winter in the entire nursery. Lighting ensures earlier harvesting, as well as better shelf life of the cucumbers," Huibers clarifies.

5.8ha has been equipped with diffuse glass with a 70% haze factor, the other part with a haze factor of 50%. Both are doubly AR-coated. This ensures much more uniform climate conditions in the summer, according to Huibers. Trials are carried out continuously as well: variety trials, growing system trials and trials with new stone wool blocks and slabs. He also takes an interest in trials carried out by, among others, the propagator.

Better plants from the propagator

A few years ago production manager Wien Hermans performed trials with sweet peppers in higher blocks in a Grow Group trial greenhouse in Baarlo because of issues with elephant feets. The plants produced bigger leaf area.

He started experimenting with cucumbers in higher blocks from 2014 to find out if the same thing would happen here. Hermans concluded that 'you measure increased leaf surface area and a higher dry matter content ". He summarised the results in a chart demonstrating that plants grown in Plantop NG2.0 blocks of 7.5 cm are heavier after 26 days and have bigger cotyledons than those grown in 6.5 cm blocks (see table).

Higher volume blocks also provide more growing convenience. "The higher volume enables us to irrigate a little less frequently. 6.5 cm blocks are irrigated four times per crop cycle in the spring, whereas with the higher blocks we only have to irrigate three times during a 30-day crop period. Irrigation takes place relatively more often during the second crop. The higher blocks provide an optimal oxygen to water ratio, which enables the plants to grow more vigorously and develop stronger roots. When we open the blocks, we observe more roots inside the blocks and at the base."

Increased production with growers

Hermans trialled the higher blocks in 2015 at various sites. Hortus in Futuro picked up on the development. Immediately in the first year, the plants propagated on higher blocks were stronger and more robust than those on lower blocks.

In consultation with Hans van Herk, a GRODAN propagating specialist, Huibers decided to carry out a trial of 2ha (32,000 blocks) during the second crop of the 2016 production year, with 7.5 cm GRODAN Plantop NG2.0 blocks in combination with 133x20x10cm Grotop Master slabs. "A 27 litre volume for four plants is rather high in comparison with others, but we are convinced of the positive effects of a higher slab volume."

"We counted and weighed results in a trial row with Hi Force alongside the variety tests. Fruit weight was higher and we had an 8% increase in cucumbers of more than 40 cm. Greenhouses without lighting produced 1.5% more cucumbers while illuminated greenhouses saw a 3% increase in the crop from 21 June until mid-November. Production gains were achieved throughout the entire growing process rather than at the start and end only. The crop appeared to have more stamina towards the end of the season."

Given these promising results, this year Hortus in Futuro is making the switch to 7.5cm GRODAN Plantop NG2.0 blocks for the entire business. 'Higher blocks cost a few cents more per block, but we can more than earn it back." Growers in study clubs and their circles have been taking a great interest in the trials at Hortus in Futuro. Some of them have already converted to higher blocks, while others have set up trials.


In Hortus in Futuro's 2016 trial with higher blocks, GRODAN Plantop blocks with Next Generation 2.0 technology were used. This is GRODAN's latest substrate technology, which has been available since 2016. Huibers carried out a small trial with higher blocks in 2016, based on a trial that the propagator also carried out with this new generation of stone wool. Huibers used them in combination with Grotop Master slabs that use the same NG2.0 technology.

Propagator and grower alike think it's still too early for firm conclusions. "I believe in them, the blocks and slabs combine well. It seems like we have to irrigate a little less often and that the blocks are more uniform when they are dried and then re-saturated. It could be that the NG2.0 technology has a positive effect when problems arise that prevent us from irrigating during certain times. It should be easier to re-saturate the slabs compared with the old ones," according to Huibers' first impressions.

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