The world of commercial strawberry cultivation is at a crossroads. Internal and external factors are driving forward-looking growers like Genson to rethink their production practices, including the substrate they use. In this context, a few years ago, Genson asked an independent expert, Elke Schellekens of Floraison, to conduct a series of trials testing different substrates, including Grodan stone wool. The trials are still ongoing, but Elke took some time out of his busy schedule to reflect with the people at Grodan who participated in the trials on the progress to date.
Genson Group is a major plant propagator/grower and market leader in the Dutch strawberry market, with customers including the country’s largest supermarket chain. Elke Schellekens is a research and development expert in berry and flower mapping. She studies new varieties and the best way to grow them. If a customer wants to know anything from optimal feeding times, whether or not to cut the leaves, to the best tray plants to use, Elke will do the hands-on research to find the answer.
Problematic old substrates
Over the past 30 years or so, strawberry growers have made huge improvements in production, first using peat substrates and then coco. But the use of such substrates is becoming more and more difficult. Firstly because the legislation is getting tougher to deal with their environmental impact, for example through the extraction of peat. But also because responsible producers themselves want to find more sustainable solutions. Genson has therefore set up trials to find out which other substrates, including stone wool but also, for example, wood fiber substrates, could offer the solution for the future.
“The stone wool trials are now in their third year,” says Elke, “We have had good results. There are obviously still things we need to refine, but the results so far from the substrates tested suggest that stone wool has great potential.
Why is that? “When running a trial, we continually adjust parameters, such as the feeding schedule and water levels, to determine how to optimize a plant’s fruit production. With rockwool you can do this very quickly and precisely. It is also an ecological solution.
“Rockwool has key characteristics that help improve production,” adds Maarten Coelen, Business Support Export Market at Grodan, who also has over a decade of experience as a strawberry farm owner. “Primarily, its manageability, its hygiene and the fact that rockwool doesn’t buffer anything, so what you give to a plant is directly available to it. And in terms of sustainability, stone wool uses relatively little water and recycling that water is relatively easy. In addition, there are various end-of-life solutions for stone wool, and in the Netherlands 100% of used stone wool is already recycled.
Propagation and steerability
Another key aspect of the trial process involves propagation, and here Elke’s expertise in flower mapping comes into play. “Flower mapping,” she explains, “is microscopic research where you look at things like how far along a developing cluster has already formed inside the plant, how many flowers it has, if it is a more generative plant or more vegetative. And during the propagation stage, you can “direct” the plant, for example by feeding it, to obtain more or less flowers and thus develop a plant with the properties that the grower wants. »
When discussing what makes rockwool such a strong candidate, one word that keeps coming up is “orientability.” Maneuverability is the degree to which you can precisely change settings. For example, water content levels in the substrate in response to climatic conditions. Or the level and composition of nutrition. There is no nutrient binding in rockwool, which makes it very orientable. This is important because if certain nutrients bind in the substrate, as is the case in other traditionally used substrates, it is very difficult to see how much is bound or released and at what point in the process this is happening. So you can’t properly measure the effect of the changes you introduce during testing.
Another key aspect of these trials is the sensors. “The first year was also a trial for the sensors,” confirms Elke. “They are essential for monitoring areas such as water content and EC levels. You must also use a drip system to bring water into the slab. Basically, using sensors and rockwool just requires a whole different way of thinking about culture. »
New thinking
“Exactly!” enthuses Thomas Peters, Business Development Manager at Grodan. “The strawberry world needs to change, which industry leaders are very aware of. And we believe stone wool can play a role in that change.
The pressures for change also come from outside the industry. In the near future, all farms will have to have closed water systems. While land restrictions and growing consumer demand for local production suggest indoor growing will be more important in tomorrow’s strawberry growing landscape. All the additional reasons why a new growing medium is needed for strawberries, and rockwool increasingly seems capable of ticking all the key boxes.
Promising results
But the main thing is the production results. “The results of the trials for Class I and Class II fruits are very promising,” says Elke. “We also look at things like bruise, texture, taste, and softness (brix), and rockwool scores well in all of these areas.” In trials, the Favori variety showed very positive results, for example producing more than 10 kg of salable fruit per running meter (6.1 kg Class I).
But like any good scientist, Elke is rightly cautious. “I believe stone wool has the potential to achieve what is needed, especially when it comes to sustainability aspects. But a lot of research is still needed. Not only in propagation and production, but also in the technical aspect of things. For example, we currently use the tiles in traditional gutters, but it’s probably not ideal for commercial production using stone wool. And having confirmed the considerable advantages of rockwool as a substrate, we still have to identify the optimal way to grow on it. »
Communication is key
Elke is also very positive about her experience working with her Grodan counterparts. “The first year, everything about working with rockwool was new to us: from how you treat it before planting, to the feeding schedule, which is different from other substrates, and throughout of the process. Grodan did a great job walking us through it all. Good communication is key during testing, and communication with the Grodan guys has been very good so far. We are now talking about where the focus and goals should be in the future.
Speaking of moving forward, what does Elke think about the future of the trial? “There are things to work on, but it’s basically a great research program, and everything looks positive: the berries, the higher production quantities…” And finally, the fact that with Elke on the trails, this most delicate of fruits is in very good hands.
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