At Gitzels, they are always looking for improvements and new developments. That is in the company's DNA, says Mike Gitzels, responsible for Innovation & Development within the nursery in Wervershoof. Together with growers and suppliers, they are working hard on greenhouse climate issues, biostimulants, fertilization, biological cultivation, and crop protection. Matthijs Woestenburg (R&D) has been part of the Gitzels team since 2016. Every day he deals with the essential question: how can we do things a little better, says Mike.

"By focusing on research and development, we want to improve plant quality. We started with the organic cultivation of open ground vegetable plants (cabbage plants) and learned a lot about the climate and screens.

Playing with screens to keep the plant active also during the night for a heavier crop

The new 2.8 ha greenhouse is currently being built behind the 7.5 ha existing company in Wervershoof. Gitzels has a 2 ha greenhouse in Hem, but these stands will be demolished at the end of the year, and the released hectares will be set up as a habitat for meadow birds. In the new greenhouse, organic cultivation will fully equip the 6000 m2. The rest of the greenhouse is prepared for organic cultivation. Svensson's PARperfect screen solution will fully equip the greenhouse.

"We chose to set up the entire greenhouse with double screens," says Mike.

"The high diffusivity of PARperfect ensures even distribution of natural light over the plants. By closing the upper climate screen more or less, the crop always receives the correct radiation. Cabbage is a 'cold' crop; PARperfect is ideal for crops that need protection from the bright sun in summer. We want to play with that more in this greenhouse."

Gitzels has a single screen in the existing greenhouse in Wervershoof, which is mainly used to prevent energy radiation and to control the temperature. Sensors are used to observe how small plants develop. There are many small plants in the greenhouse, 950 per square meter, says Mike.

"The microclimate in the greenhouse is, therefore, of great importance. We used to look at the ambient temperature of the greenhouse and heat the temperature on it. However, we have noticed that the plant temperature experiences very differently. The challenge is to keep the plant going day and night. We have learned that by playing with the screen, we can also keep the plant active at night. You get heavier plants from that."

Optimal light and water consumption

The plant nursery strives to deliver plants continuously in order to use the greenhouses as effectively as possible. Cabbage cultivation peaks in April, when everyone wants to have their cabbage plants, they know at Gitzels. Crops such as cauliflower, pointed cabbage, and broccoli is grown more evenly over the season by open-field vegetable growers. That means that there are many young plants in the greenhouse that receive a lot of radiation in the summer, says Mike.

"By playing with screens, we want to find out how much light a plant can absorb. With the PARperfect screen solution, we want to determine the optimal light consumption of the plant per period, with optimal watering. All this with the intention of making plant material more consistent and stable, so that we can supply our customers with plants that grow even better."

"With PARperfect, light level differences are a thing of the past."

Infinitely variable control of the screen level

PARperfect is Svensson's new screen solution, says Svensson consultant Bart Bakker. With PARperfect, the screen level in the greenhouse can be infinitely controlled, from 20 to 100 percent, just like a light dimmer, he explains. A combination of at least two screens is assumed. The bottom screen is the Harmony PARperfect climate screen.

"The position of the screens is continuously adjusted based on the intensity of solar radiation. The screens keep the light level at crop level constant, regardless of the season or time of day. Thanks to the PARperfect climate screen's very high diffusion, the light distribution at the crop level is optimal. Every plant gets the same amount of light."

According to Bart Bakker, PARperfect offers several advantages: each plant receives precisely the right light level under all circumstances, and a higher PAR sum of natural light is possible. Direct sunlight on the crop is excluded, which prevents crop damage. This can result in more uniformity, acceleration of cultivation, better production quality, and fewer hours of assimilation lighting and, through that, lower costs.

"What we want to achieve in the Gitzels greenhouse is that the plant grows optimally with a certain light sum. You are going to imitate them without having to force."

Mike Gitzels continues: "We expect that with PARperfect, it will be even easier to guarantee the consistent quality of the plant material and to grow a heavier young plant. The uniformity increases due to diffusion, and we can optimize the balance in the greenhouse. We want to control light, humidity, and energy in the new greenhouse and look for the plant's optimal conditions. By measuring at the plant level, you learn to understand the plant better."

Fully automatic planting

The plant nursery sees several challenges for the coming years, in which the new greenhouse can play a role. Gitzels sees it as its task to serve the customer optimally concerning plant material.

"Growers want a plant that is healthy, stable, and sturdy, and that is growing well. For example, we see that the development of fully automatic planting on land is on the rise: fully automatic planting machines already plant around 20 percent of our plants. The grower prefers to have a uniform plant of 12-15 cm." The nursery will also integrate the good aspects of organic cultivation into conventional cultivation, such as substrate, fertilizers, and biology. Finally, Gitzels is working on a platform for local plant growers to gather and exchange knowledge.

"We have experienced that there is a lot less research in open-field vegetable crops, especially in cabbage crops. By sharing knowledge and experiences, we hope to accelerate innovations and developments."

Article published in Kas Magazine 2020-03