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LED is being applied on an increasingly large scale in greenhouses, for vegetable as well as floriculture crops. Although many crops have already been proven to grow well under 100% LED lighting, a hybrid solution is sometimes chosen as a first step.

When making the (partial) transition to LED the choice can be made for significant energy savings on the one hand, or for raising the light intensity on the other. In both cases, next to selecting the right LED spectrum, you should keep the total cultivation setup in mind to make the transition successful. This includes factors such as plant density, irrigation, and plant variety amongst others. HPS lighting creates radiation heat which LED lighting mostly lacks. The LED modules which are being applied most at the moment have an efficiency of 3,2 to 3,7 ┬Ámol light per joule electricity-input, and for HPS, with an efficiency of 1,8 ┬Ámol/J, this is 40 to 50% less. Besides the factor of energy savings, this big difference has the advantage that the climate can be controlled better by steering the warmth and light separately. However, consequently, you as a grower should constantly be mindful to realize the right climate- and cultivation conditions for the way in which the LED lighting is being applied. Naturally, there are big differences between cultivations, but there are several common factors as well. In this article, lighting experts with signify share what they have learned from experience.

Tip 1: Optimum use of your lighting with dimmable LEDs
Obviously, you will choose an LED spectrum with proven results for your crop. For many crops, the light recipe has been developed, and we can select from a database of over 150 proven recipes. When HPS lighting is being replaced (partly) by LED, the total light level in the greenhouse usually increases significantly. In that case, especially, it is useful to be able to dim the intensity of the LED lighting: with a dimmable installation, you can respond to both the needs of the crop, weather conditions, and the energy market, without making concessions to the uniformity of the light. An additional benefit of dimmable LEDs is that they become approximately 10% more efficient when dimmed. This decreases the energy usage per light unit.

Tip 2: Crop activity is the key
Dividing the assimilates created by photosynthesis is an important consideration. It is a pitfall to have the plant absorb all the lighting with an artificial lighting installation, but neglect to create circumstances for the plant to distribute the assimilates to the parts of the plant where we would like them to go, which are often the fruits and/or the flowers. Without taking the appropriate actions the crop could have too little evaporation, the plant temperature could stay too low, or absorb insufficient fertilizers.

Erik Stappers with Signify

Due to the absence of radiation heat, in some cultivations with LED screening is used more intensively and the windows stay closed more often to keep the heat inside the greenhouse. This can lead to a climate that is too passive, where the plant has problems evaporating. There are several options to keep the plant active. Key is the drainage of fluid around the plant. You can also consider extra air movement by fans for example, or by adding a (minimal) heating pipe in combination with a gap in the screen, and possibly leaving the windows slightly open. Active dehumidification by air handling units, for example, is also a perfect option in combination with LED lighting. In that way, you …….

Source: https://www.hortidaily.com/article/9390496/5-tips-for-growing-with-leds/

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