Lemnis Oreon has been actively involved with research into the effects of LED lighting on various crops since 2005. “We have always attached a great deal of importance to the working relationships between growers, researchers and manufacturers, in order to arrive at improvements in greenhouse horticulture together. These research projects have always been carried out with Dutch research facilities, like the WUR and the Demokwekerij up to 2015. Last year was the first time that research was also supported in Belgium at the Testing Station for Vegetable Cultivation in Sint Katelijne Waver. The results show that increasing the light level with LED top lighting definitely resulted in a clear increase in production. Meanwhile at the research facility Hoogstraten, research was also conducted into SON-T top lighting and LED interlighting.”
by Michiel de Jong, Sales Manager Lemnis Oreon
Various different light levels were suspended above the tomatoes in three compartments in Sint Katelijne Waver. The variety was Foundation, the plant date was 21st October 2015 and the results were measured to 23rd February 2016:
A) 169 uMol SON-T (4 x 1000 W per grid). 3.75 stems per m2
B) 211 uMol SON-T (5 x 1000 W per grid). 3.75 stems per m2
C) 240 uMol SON-T (4 x 1000 W + 2 x Oreon Grow Light per grid). 4.38 stems per m2
Contrary to expectations, the production levels in B, with 18% higher light level SON-T lights, appeared lower than in A. The reason for this is sought in a lower measured temperature at the top, (next to a cold glass wall) as well as in the higher RV. A total of ~131 W/m2 was installed with five SON-T lights per grid. Higher production levels of 17% were clearly achieved in compartment C with 29% more light. There was a total of 135W/m2. The energy consumption of the installed ~70 uMol/m2 of the Oreon LED’s (developed as top lighting) are ~45% more efficient than the 1000W SON-T lights.
In addition to the production figures, researchers have also noticed that the climate in the hybrid section feels better and that the plants are highly generative. The Oreon Grow Light is water cooled and in this test the heat generated by the lights is being used by having an extra tube underneath the gutters. This ensures virtually all energy is properly utilised, but still the grower stays in control over light and heat separately. This was only the first year crops were grown under this hybrid top lighting. “Some learning points will undoubtedly come out of the evaluation, which can serve to further improve next year’s result.”
The results were mixed in Hoogstraten. Hybrid lighting with 114 uMol/SON-T top lighting and 55 uMol LED inter lighting resulted in lower production figures then with 169 SON-T. Adding one string inter lighting with 169 uMol SON-T did result in a 12% higher production, but that being with 33% more installed light. And 114 uMol SON-T with two strings of LED (110 uMol) interlighting only resulted in an additional production level of 4-7%. “Even though you can never make like for like comparisons, we can certainly draw the cautious conclusion that increasing the light level in winter with LED toplighting can be more effective than with inter lighting. As long as the plants aren’t yet light saturated in the higher canopy levels, there’s no ratio to put inter lighting in. Getting the light into the canopy is what matters. The Oreon Grow Lights have therefore specially designed optics.”
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