Covering a production area of almost 24 acres, the RedStar tomato nursery in the Netherlands has been up and running for over a year now. The company is currently making preparations for phases 2 and 3 of construction. The nursery’s revolutionary greenhouse design and eco-friendly growing methods require a high degree of co-operation, communication and information exchange. Closely monitoring the plants to fine-tune the climate and irrigation volume is key to maximizing production.

We've achieved what we set out to do
The RedStar nursery is currently around 24 acres in size. Its rural and open surroundings provide enough space for two more phases of construction. All the buildings, the boiler house and technical facilities were designed with this in mind. Bram Hendrickx, General Manager of RedStar: ‘We’ve been operating for over a year now and our team is getting into its stride. Although we’ve achieved what we set out to do in the first year, we won’t be able to gauge the success of the project until the third phase is complete. The different phases will enhance one another. The possibilities and potential of this greenhouse are enormous.’

Harvesting energy
Bram Hendrickx continues: ‘We chose the Ultra-Clima® greenhouse concept with an eye to the future. Current greenhouse structures won’t remain viable in the long term. We need to grow cleaner and more sustainable crops and lower our energy and water consumption. This means we need to ask questions such as: how can we utilize solar energy or the heat radiated by the lamps? The Ultra-Clima® greenhouse allows us to ‘harvest’ energy as it were. This is in line with current developments that are forcing us to find new and better growing methods.’ The greenhouse structure is much lighter and has fewer air vents. The number of Ultra-Clima® greenhouses is steadily growing worldwide and with it the experience gained with this method of cultivation. The RedStar greenhouse is unique, however, in that it’s the only facility equipped with a supplementary lighting system.

No two days are the same
Bram Hendrickx said the following about climate control in the greenhouse: ‘Our greenhouse works with overpressure and air tubes. Air is drawn into the greenhouse, conditioned in the mixing chamber and then distributed throughout the structure via tubes under the crop gutters. Some of the air is then recovered and returned to the mixing chamber. This allows us to create the best possible climate in which the plants can thrive. We use a large number of fans, resulting in multiple air streams. There are many factors that can affect the climate in the greenhouse. You have to be careful, as one minute you may be heating particular sections while the next you may be cooling them. In addition, the weather in the Netherlands can change from day to day. It may be bright and sunny today and wet and rainy tomorrow. No two days are the same. Luckily, we have a process computer that controls the greenhouse climate, so we can focus on the plants.’

This greenhouse requires an extremely flexible computer
‘The plants tell us what climate they need’, according to Bram Hendrickx. He continues: ‘Choosing the right climate computer is essential. It must be flexible enough to respond to those constant changes. That’s why we went for the HortiMaX MultiMa. Not only were we at RedStar already familiar with this computer, but, HortiMaX was also very flexible in meeting all our needs for this project.’ It’s not just a standard computer. Bram continues: ‘A huge number of modifications were made to the standard MultiMa. They listened carefully to our wishes and those of the greenhouse supplier. If I look at the MultiMa now compared to what we started with, there’s a world of difference. Together with HortiMaX, we also keep on optimizing the control process.’

Irrigation based on plant needs
The conventional method of irrigation is also not suitable for RedStar’s needs. Bram Hendrickx: ‘Irrigation based on time or radiation doesn’t really work here. Because of the lamps and the constant air current, the water uptake of the plants is completely different than it would be in a conventional greenhouse. The plants not only tell us what climate they need, but also how much water they require. We determine this by continuously monitoring the weight of the substrate, the drain water quantity and weight of the plants. This gives us a very reliable picture of the substrate’s water content and the condition of the crop. Irrigation is triggered automatically based on the measured undersaturation level of the grow slabs. We use a HortiMaX ProDrain for this purpose.’

Learning as we grow
Bram Hendrickx: ‘I have a lot of respect for the people who developed this climate computer. Theoretical knowledge and models are fine, but how the system works in practice is what really counts. This is where it happens and you need to be sensitive to that. That’s why we’re regularly in touch with HortiMaX to make adjustments to the process. They offer practical support that helps us grow our crops in this advanced greenhouse environment. There’s still much to learn. I believe that that is generally the case for most companies. We learn as we grow in practice – that wouldn’t be possible with just theory.’

Knowledge and co-operation: the soft performance indicators
A company in development, a new greenhouse concept and a new growing method – each of these factors sets different requirements on the climate. Bram: ‘It’s a learning process, especially in the first year when everything still needs to be fine-tuned. You may think that you’ve programmed the settings correctly, but in practice it appears otherwise. We did that well as a team, but it’s just the start of the process. We programmed the most essential parameters to the right values, which we could tell by measuring production. This is one of those hard performance indicators (or KPIs). But there’s more to it than that. Together with HortiMaX, we’re still working on perfecting climate control. We don’t know what every function does yet. This requires communication and information to be passed on. It’s a pity there are only 24 hours in a day...’

Upcoming events


20-22 February
Gorinchem, The Netherlands

Shouguang Veg. Expo
20-22 March
Shouguang, China

9-11 May 2018, Booth #1342
Ernest N. Morial Convention Center, New Orleans, LA

Hortiflorexpo IPM
9-12 May
Beijing, China

12-14 June
Amsterdam RAI, The Netherlands

Cultivate '18
14-17 July
Columbus, OH, USA

Canadian Greenhouse Conference
3+4 October
Niagra Falls, Canada

Expo AgroAlimentaria
13-16 November
Irapuato Mexico