According to sweet pepper grower Wim Gubbels and his assistant Geert Colbers, plants propagated in 7.5-cm-high blocks have more mass than those they used to receive from their propagator in the lower, 6.5-cm-high blocks. They are also more uniform. These are great advantages especially in the case of the four-stem system used by kwekerij Gubbels Siberië.
Kwekerij Gubbels, run by Wim Gubbels and his son Erik, is a leading modern sweet pepper farm comprising two establishments, one with an area of 16 ha in Maasbree and one with 4 ha of land in Velden. The largest establishment grows red and yellow peppers while the farm in Velden produces green ones.
In spite of the poor economic conditions the farm has grown and makes every effort to produce good-quality sweet peppers in a sustainable, innovative way. Heat is provided by a total energy system, with the returned electricity being sufficient for around 9000 households.
Since 2010 the growers at the largest farm have been using the Covent system of Cogas Zuid to dehumidify the greenhouse air. They work according to the ‘New Cultivation’ principles.
This year a large-scale trial using the higher, 7.5-cm blocks is being carried out at the Maasbree farm. “Last year GRODAN informed us that we would be able to increase our production by around 3 to 4 percent by using blocks that are one centimetre higher, so we decided to organise a large-scale trial to test GRODAN’s higher Vitagreen and Plantop Delta blocks alongside our standard blocks,” says Gubbels.
Lei Goertz of Fortaplant BV, specialising in the propagation of tomato, cucumber and sweet pepper plants, propagated the plants in the higher blocks. He treated the plants in the same way as all the others, watering them three times during the propagation phase. By the end of that phase the plants were found to be 10 to 15% heavier than those propagated in the lower blocks. The propagator regards the high blocks as one of the decisive factors, alongside the variety, EC and CO2, for arriving at good-quality vegetative plants.
In the propagation phase there aren’t yet any differences as far as the type of block is concerned. All the plants in high pots grew better.
That’s not surprising, explains Hans van Herk, one of GRODAN’s propagation specialists. “Every time the plants are watered they have a larger volume of water at their disposal. And more water is converted into more fresh weight/leaf mass. You don’t start to see the differences between the different types of blocks until after the longest day, when the plants are at the pepper farm.”
From vegetative to generative
What surprises the growers is that the plants switch so easily from vegetative to generative growth once they have arrived at the farm. Around February the plants were found to be more generative than those in the standard-height pots.
The propagation specialist has an explanation for this, too. The higher the block, the more strongly the water is drawn downwards. The top part of the block remains drier, containing more oxygen. This is favourable for the production of new roots.
And the fact that the roots have to search a little harder for water has a generative effect on the plant.
Geert Colbers noted that the plants flower higher and set fruit more easily, leading to a slightly higher plant load and slightly smaller peppers in March. How things will proceed later this year is yet to be seen.
The benefits of the higher blocks are most evident in the case of the new pepper varieties. “We need more vigorous plants because we want to retain four equal stems per plant. We have to convert that vigour into production, and that’s easier to realise with a higher block.”
More uniform batches
According to Van Herk, the uniformity of the plants in higher blocks is a major advantage in a four-stem system like that used by Gubbels. “The greater the number of stems, the greater the risk of plants lagging behind. The capillary wool ensures an efficient distribution of water inside the block, which in turn ensures a more uniform development of the plants. That’s what makes GRODAN’s Plantop Delta blocks more advantageous than standard blocks, especially after the longest day.”
On top of the envisaged greater production, the plants are also expected to be less affected by Fusarium in autumn.