Grodan provides more certainty about quality

Dutch tomato producer Solyco has been working with Grodan’s new Elite stone wool slab since the start of this crop cycle. According to Jack van Schie, head grower at one of the company’s three locations, the combination of this slab with both the Plantop block and the GroSens sensors gives him more certainty that he will achieve the high quality that customers expect.   

[Text] Jack van Schie is head grower at Solyco’s greenhouse in Berkel en Rodenrijs, where two varieties of tomatoes are produced: the medium-truss variety Radiance on 4ha and – for the first time this season – the small-truss variety Roterno on 3ha, both under HPS lighting. The family company has two other locations: the main 4ha plum tomato production facility in Bergschenhoek which is managed by the owner Gertjan van der Spek, and a 6ha facility managed by Albert Thunnissen in Bleiswijk, where large truss tomatoes are grown under a hybrid lighting system.

Jack has been with the company for four years, since the Berkel en Rodenrijs facility was built in 2017. The greenhouse has two permanent employees plus a flexible team of around 40 seasonal workers. The company has been sourcing substrate blocks and slabs from Grodan since before Jack joined the company. “But I used to grow tomatoes myself and I’ve been using Grodan products since the mid-1980s,” he says. “Both of our varieties are sold to major retailers so it’s important for us to achieve both a high level of quality and uniformity as well as a high yield, all year round.” The company sources the young plants from a local plant raiser when they are approximately 60cm tall and the first truss is already flowering. “Then we transfer them straight into 10x15cm Grodan Plantop blocks to provide sufficient stability,” he continues. “For us, it’s important for a block to be robust and also homogeneous with very even distribution. Above all, it needs to work well with the slab beneath it so that the uptake of water and nutrients is efficient and effective. You don’t want the block to dry out or turn yellow.”

New Elite slab
To ensure an optimal combination of block and slab, Solyco has chosen to use Grodan’s new Elite slab for the first time this season. Jack explains: “Our owner Gertjan is keen to keep moving with the times so he is always open to trying new things that will improve our crop performance. The hybrid lighting system in Bleiswijk is one example of that, and the Elite slab is another. So at the start of this season, all three locations switched from the 7.5cm Vital slab to the 10cm Elite slab across all 17ha.” Solyco has also purchased GroSens sensors in a shift to a more data-driven approach to growing. “When we plant the crop, we put two sensors in the slab and one in the block. Then after a couple of days, we move that sensor into the slab too, initially in the top layer. The dual-layer design helps to spread the water more evenly horizontally across the slab and allows it to seep downwards gradually. So we use the sensors to monitor both the top and the bottom layer of the slab for the first few weeks and then move all three sensors to the bottom layer,” he adds.

Evenly distributed roots
The tomatoes were planted on 1 August 2020 and Jack is happy with the crop performance so far: “The roots are now much more evenly distributed all through the slab rather than being concentrated at the bottom. I tend to steer the crop generatively to stimulate production and fruit setting, and that’s no problem at all with this slab. And Elite is more ‘forgiving’; even if you happen to give the plants a bit too much water, the slab seems to let go of the excess more easily which prevents root damage.”

Now that spring has arrived, Solyco is heading into the most challenging time of the year, when sudden fluctuations in the radiation and humidity levels can put a lot of pressure on a plant’s ability to maintain its moisture balance. “Strong roots are essential to keep the plant replenished with the moisture it loses through evaporation. Otherwise it will take it from the fruits, and we will be left with an unsaleable product,” comments Jack. “So I check the root growth regularly, and this season I’m pleased to see that there seem to be more side roots and root hairs than in previous years, which is a very good sign in terms of plant health and vitality.”

Easier to steer
Jack is also experiencing the benefits of the GroSens sensors: “It’s easier to steer both the moisture level and the EC, plus it enables us to monitor that our employees have taken care of the drainage properly, so it gives us a better picture of the overall greenhouse operation.” At Solyco they combine the GroSens data with the other greenhouse data from the climate computer to help them make comparisons per day, per week or per month in the online dashboard. “I also have access to the My Root Zone app on my phone and I check that every day. It’s interesting to have so much data at your fingertips,” states Jack.

Since switching to the new slab, he has changed his irrigation strategy a little he says: “Using the sensors together with the slab has allowed me to experiment with how much water I give and for how long. I can now precisely monitor how much the plant has absorbed from the slab overnight and keep adjusting things until I find the ideal balance.”

Advice and support
The Grodan team have provided valuable support throughout the whole process. “Things were pretty tense at the start of August because we were not only planting a new variety on a new slab using a new sensor system, but it was also extremely hot,” Jack recalls. “We had regular contact with Grodan, and we were even welcome to call them for advice when we were working at night or at the weekend to make sure that the plants rooted well. Now, we speak every couple of months and in the meantime they keep an eye on our data in the computer remotely and provide us feedback if necessary.”

“It’s a little early to say what the effect will be on total production at the end of the season, but so far I can see that it’s a strong crop with a healthy growth rate and the fruits are all nice and uniform – and the data is extra confirmation of that. So I’m happy with how the new slab works in combination with the Grodan block and the sensors. Above all, this set-up gives you more certainty because stronger roots mean healthier plants and therefore better-quality tomatoes – and that’s essential for us and for our customers,” he concludes.