Tip 1: Optimise screening strategy

During summer, a high level of radiation has alarge effect on crops. When plants start to feel stressed, it is necessary to reduce the energy supply by closing the climate screen.
There are three ways to do this:

• The easiest way is to close the screen, based on a set level of radiation. However, this measure is often taken very ‘prudently’ which unnecessary limits growth;
• The second method is to adjust the set point to thelevel of greenhouse humidity. In most cases this is done based on Relative Humidity (RH). This means that the screen closes when the RH is too low combined with a certain level of radiation. In the case that the RH level is correct, the screen remains open;
• Plant stress is measurable with a plant temperature meter. In the case that the plant temperature exceeds the greenhouse temperature, it is a sign that plants can’t cool down, because plants cool down due to evaporation, this means the risk of water stress increases.

With this knowledge, growers can increase the light level when the greenhouse climate is correct. On days that plants struggle more to retain the photosynthetic process, reduce the light level. This can increase crop growth.

Tip 2: Optimise greenhouse temperature control

The temperature control has a large influence on the speed of growth. High temperatures can cause an unbalanced plant and even water stress. During summer, growers face a dilemma: do they need to reduce temperature by ventilation, or do they need to close vents to maintain the right level of humidity and reduce CO2 loss?
Research shows that water stress in the late afternoon is caused by a low level of humidity. This means that a high temperature has less influence. On the contrary, a high temperature combined with a high level of radiation increases photosynthesis. This benefit only applies when the stomata of the plants are opened for uptake of CO2.
To create a win-win situationfor the plant, Hoogendoorn advises growers to increase the set point of the ventilation. This prevents a low level of humidity: the temperature increase is much less as expected.

Curious how to increase crop quality and yields? Increase your knowledge!
With over 49 years of experience in hortcultural automation, Hoogendoorn has much in-house knowledge. Via (customised) training knowledge is shared about safe, efficient, and environmentally friendly production with advisors, students, customers and partners.

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