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Choosing a coating that fits the crop

The arrival of photoselective coatings on the market has allowed more crop specific light to be offered to the plant. ReduHeat is the first photoselective coating that has been specially developed for horticulture. Many growers want to keep heat out of the greenhouse but aren’t prepared to sacrifice grow-light. This led to the development of ReduHeat, a coating that allows maximum transmission of light yet it reduces heat by reflecting infrared light.

Plant research increasingly focuses on the role of light colour in the plant. In recent years a lot has been discovered about the function of different receptors in the plant and their reaction to different light colours. Mardenkro used this knowledge to develop photoselective coatings, which they market under the name ReduFlex. One of these developments is ReduFlex Blue.

Properties of the coatings
A property of ReduHeat is its ability to reflect infra red light while transmitting grow-light. Infrared light is an important factor for warming the greenhouse and the crop. When using ReduHeat in warm periods of the year, a portion of the infrared light is reflected, so the temperature rises less rapidly. The table below shows the different shading percentages per product (excluding glass).

Figure 1: Net shading percentages

One of the properties of ReduFlex Blue is that relatively more blue light is reflected. The blue part of the light spectrum also affects the elongation of plants. By altering the relationship between blue and red light, more elongation of the crop occurs. The ratio of red and far red light also affects the elongation of the crop.

Which coating for which crop?
A crop that benefits from ReduFlex Blue is the rose (cut flower). During the summer months it can be difficult to achieve flower stems of the desired length. By using ReduFlex Blue it is possible to gain more length. An additional positive effect is that the flower stems are heavier and new shoots develop more easily. As well as roses, positive effects have also been seen in freesias harvested in the summer, with mostly heavier stems and better development of side shoots. ReduFlex Blue has also been used with carnations. This crop also responds by producing longer stems and more buds. Positive results from this coating have also been seen in orchid crops. This is mainly reflected in a more intense flower colour.

The PAR light transmission by ReduHeat is higher than that of ReduFlex Blue because the entire spectrum is transmitted. ReduHeat is often used with crops that can tolerate a lot of light, but where too much heat can lead to quality problems. Some examples are crops such as chrysanthemum and gerbera. The spectrum of both coatings is shown in the chart below.

The choice of coating is dependent on the crop, production schedule and the purpose for which it is applied. In addition, the technical equipment in the greenhouse, such as screen fabric type(s), is also important when deciding on the type and concentration of coating to use.

For more information
Mardenkro The Netherlands
Geerstraat 8
5111 PS Baarle-Nassau
The Netherlands
T: +31 (0)13 507 70 69
Email: [email protected]
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