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Organic substrate slab ready for upscaling after successful testing

Over the past two years, the necessary tests have been carried out with organic substrate slabs from Klasmann-Deilmann. Both research centers and practical growers have already been introduced to the Growbag, consisting of a mix of special wood fibers and coco coir on a small scale. Next season, growers at home and abroad will take the step towards half or even whole hectares for cucumber and tomato crops in particular. As product manager, Jan Vanoverschelde closely follows the developments.

From his experience as an account manager in ornamental plant cultivation and his experience in the substrate industry, the product manager is well acquainted with how the sector is looking for renewable raw materials. Spurred on by a large, four-year Flemish research project aimed at sustainability in fruit vegetable cultivation, many trials have been carried out with the Growbag in Flanders over the past two years.

In the process, Jan has gradually become the product manager for what has become "a new segment" for the substrate producer. "I am confident that this product will grow in the coming years. From our international sales organizations, we get almost purely positive feedback."

Jan at the start-up of a trial of the Growbag in tomato cultivation in October 2022 at Agrotopia in Roeselare

In the first tests, in 2021, growing on slabs with organic substrate was still a bit uncomfortable. "In West Flanders, growers in cucumber cultivation started using our slabs. The comparison with coco coir substrate slabs was made in particular. The Growbag proved to have the advantage of retaining less water compared to coco coir."

Initially, these were still small trials. "Sometimes growers really only had a few Growbags between their regular substrate slabs, so results were immediately spotted. It also still sometimes happened that the mat was not properly stable. We quickly learned from that. The machines for filling are now set so that the slabs are filled optimally."

Tests continued to follow, including in tomatoes, both exposed and unexposed. Here, in addition to the comparison with coco, comparisons with growing on perlite or rockwool are often made. "Perlite is very draining rockwool, on the other hand, is quite wet. With the Growbag, we are somewhere in between. Our organic mat is also more steerable and airy than coco coir substrate slabs." In comparison trials, the organic substrate was often not steerable. "Yet we were able to keep up well. We are still fine-tuning steering on the Growbag, but it requires only minor adjustments compared to common systems."

With the Growbag, you can plant directly on the mat, and pre-rinsing the mat is not necessary. By planting directly on the mat, the crop automatically grows generatively and roots well, Jan saw in trials.

Raw materials
The Growbag owes its good steerability to the choice of raw materials, they stress from Klasmann-Deilmann. "The Growbag consists mainly of our special wood fiber mix with Greenfibre. We have 20 years of experience in ornamental plant cultivation with this. We produce it locally in the Netherlands and Germany. It is softwood chips that are expanded. This keeps the product stable over time. A constant quality is also important for controllability."

A limited part of the mixture in the Growbag consists of coir. "This product has a good buffering effect. Because we only use a small amount of this, we can guarantee availability well here too." Peat is no longer used in many cases. "For strawberry cultivation in southern Europe, we do still work with a small percentage of peat in the Growbag. This is because the water buffer of peat is known to growers, and we want to make the transition without peat in steps. We see that the air/water ratio in our standard composition is also very good. Peat is also more difficult to rehydrate if it gets drier."

Rooting in view. Jan: "Physically, our standard composition based on Greenfibre and a proportion of coco coir appears to buffer just as well as a composition where you replace the same proportion of coco coir with peat.

Organic minded
Klasmann-Deilmann offered the product for field trials to growers this year, mainly in Europe. "Trials were largely done in France, Italy, and Poland, but also in Germany, Austria, Switzerland, and the UK. And, of course, in the Netherlands and Belgium. Certain countries, like France, are more into it. They are more organic-minded there, but you also see it coming more and more in other countries."

Undeniably, the ubiquitous emphasis on sustainability is helping in the transition to other substrates, such as the Growbag. This is also reflected in the covenant concluded between the Dutch government and industry at the end of 2022. With the aim of reducing the environmental impact of substrates by promoting the use of renewable raw materials. The objective is to ultimately achieve a climate-neutral European chain for substrates by 2050 (with intermediate steps in 2025 and 2030) in which at least 90% of the substrates consist of renewable raw materials, without negative environmental impact, and with CO2 neutrality. So, it is also up to the industry to develop these renewable raw materials and create sufficient availability.

Yet at the moment - although the demand will come - sustainability is not always the main reason to take the step to growing on organic substrate, Jan notes. "Growers are concerned about availability, the cultivation having to be good, and, of course, yield and costs. Partly thanks to the fact that our product is easily compostable after cultivation, we are competitive here too."

The bag containing the organic substrate is not yet compostable, and neither is, incidentally, the plastic film around the plant blocks, Jan stresses. "Of course, we are looking at this. The challenge now is that the product must remain sturdy and stable, even with growers who sometimes grow on the same slab for two seasons. With the current set-up, this has now been proven in practice."

Being able to plant directly on the mat saves labor.

Nevertheless, Klasmann-Deilmann continues to look critically at the composition of the Growbag also for other crops. Especially in cucumber and tomato cultivation, growers are starting to grow on the Growbag. Aubergine and pepper are less represented, although Jan points, among others, to a pepper grower who will start growing on Growbags on a large scale next season. "Here, we too, are learning about the effects of growing on organic substrate on crop resilience. This grower sees positive effects of better microbial balance."

The substrate producer also soon learned of the customized requirements of the market. "We started with a mat of one-metre length, 2 to 5 planting holes, and the choice of with or without drainage. Now, we also offer the 80-centimetre length, which is much in demand in France to match their drip systems and plant spacing. We also offer customized perforations of planting holes and spacing. We have also developed special perforations for strawberries. And that's not all. We will have to expand the options further if this segment is going to grow. We are ready for it."

Growbag, with perforations below

For more information:
Jan Vanoverschelde
Klasmann Deilmann Benelux B.V.
[email protected]

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