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Clean water for improved hydroponic lettuce cultivation

Cultivation advisor Ron Peters is a jack-of-all-trades. He assists growers with virus issues in fruit vegetables, where his hygiene advice for tomatoes, for example, often aims to keep ToBRFV at bay. However, he also sees opportunities in hydroponic lettuce cultivation. Currently, he is helping a German-speaking grower master the cultivation of lettuce and spinach in water, with special attention to water quality. "Water quality is crucial in lettuce cultivation."

Hydroponic lettuce at Future Growing in Klazienaveen

The grower Ron is working with started with hydroponic lettuce cultivation a few years ago. Not yet on a commercial scale, but with the intention of growing into a new business in the future. They're not ready to publicize their project yet, but they're happy to share some details.

"When Ron told us about how he treats water, we finally saw an opportunity to enter this type of cultivation. We had thought about hydroponic lettuce before but hadn't taken the step. Ron is a fan of keeping it simple with a DWC system, and to test this, he looked for a partner company to share and test his ideas."

Water disinfection
Currently, the trial covers three thousand square meters and started in mid-2022. Especially the cultivation of spinach in water proved to be a challenge. "It went well for a few cycles, but then the growers encountered problems," Ron knows. Root exudates were a cause. A known problem in water spinach cultivation that growers were aware of from the beginning. "Together with Ron, we're now figuring out how to remove these root exudates from the water. Luckily, we're on the right track."

At the start of the cultivation, the pond, where various types of lettuce and baby leaves are grown on floaters, was filled with water from a source. "We still use that water as the base and top up what evaporates with rainwater."

Ron: "What we have now learned is that it is not only the root exudates that determine success. The floats and the climate are also essential to achieve a good result."

To optimize the cultivation, new shading cloths were installed, and lighting was added in the rented section of the older greenhouse to make cultivation cycles possible even in winter. Additionally, a system was installed in the greenhouse to water from above after sowing. "Indeed, as if it's raining from above," the grower confirms. "When the seeds start to germinate, the roots don't immediately reach the water. That's why you need to irrigate from above at the start."

The vegetable growers had no experience with water cultivation of leafy vegetables. Starting something new always brings challenges sooner or later. This trial is no exception. Especially the issues with root exudates in spinach raised doubts, even about whether the trial should continue. The grower looks forward to new varieties but also knows that they are not yet available.

NFT-system at Klazienaveen. "Are we going to be successful again keeping the water free of exudates?"

Scaling up
Every two weeks, they take a water sample from the pond where the floaters with lettuce and spinach are located. "Based on the results, we know how to adjust the nutrient recipe. Unlike in the cultivation of fruit vegetables, we don't have a drain. That takes some getting used to." Taking a water sample is manual labor, but that's also true for the rest of the cultivation. "At this stage, we're not really focusing on automation. That's something we'll look into before we consider scaling up."

Next year, the company hopes to be further along. They express hope that the water system, which is now stable and reliable, will remain so in twelve months. "If so, then we can move on to the next phase, scaling up the different cultivations." Meanwhile, they are also exploring the market potential for a step into the commercial cultivation of leafy vegetables and continue to monitor cultivation developments with Ron.

"Well, it looks very promising." On the website of Future Growing a livestream of the cultivation can be watched.

For more information:
Ron Peters
Future Growing
Gantel 12
7891XA Klazienaveen
The Netherlands
+31 (0)6 2505 2941
[email protected]