The different tests not only provide knowledge about energy-efficient lighting systems, but also about light in relation to crop development and production. Striking in the exposure study were the results in sections with diffused glass.
Hybrid with diffuse
At Wageningen UR Greenhouse Horticulture and Green Q Improvement Centre a large trial with hybrid lighting with diffuse light is being conducted. This research is funded by the ‘Greenhouse as Energy Source’ program. Crops are lighted according to a model meticulously tailoring the number of lighting hours to the needs of the crop. The model takes into account the sunlight that has been given to the crops over the past three days, as well as the sunlight expected in the next three days (light integration). The test is economical with CO2.
"In the New Lighting we study how we can grow according to a fixed model and thereby save energy with less hours of exposure. This allows us to know how to bring about a profitable crop if the costs of lighting become higher, let’s say five years from now," says Piet Hein Baar from GreenQ. "We also want to find out how crop growth can be influenced by alternations in SON-T and/or LED lighting. We think more SON-T is useful when crops become too generative, and more LED when they are too vegetative. Experimenting with different variations and alternations allows us to be much more precise with light exposure, this in contrast to previous years, when the number of hours with both systems were similar."
Hybrid with far-red
At the Demokwekerij (the Demo Nursery) the effect of additional far red light in combination with hybrid lighting is studied comprehensively. Preliminary results were presented by Stefan Persoon of Inno-Agro. The study shows that additional far-red lightning stimulates growth and that a more open crop occurs, allowing more light to reach the lower leaves. The results of the research with the new energy saving LED lamps are as yet confidential, and available only to producers who funded the trial.
Discussion
During a discussion the concept of light integration was further explored. Researcher Tom Dueck entered the proposition that lamps in current tomato crops may burn longer than is strictly necessary. Hans Zwinkels disagreed and wondered whether fewer lighting hours were not at the expense of production at a time when the tomatoes are costly.
Presentations included:
Het Nieuwe Belichten bij tomaat, stand van zaken januari 2013 - Tom Dueck Wageningen UR Glastuinbouw
Lichtonderzoek Tomaat 2013 door TTO bij de Demokwekerij - Stefan Persoon Inno-Agro
Source: Energiek2020