Wageningen University is currently running a test involving three separate greenhouses. One has diffuse glass and hybrid lighting, one has clear glass and hybrid lighting and a reference greenhouse just has SON-T lighting. The three nurseries, all growing tomatoes, will be closely monitored in the next couple of months. The test, conducted in light of the New Lighting-Project, will determine whether cultivation is still possible with a 40% reduction of energy and a maximum of 30 kg/m2 CO2. The experiment is expected to last at least another six months.
Jan Janse, researcher at the University, explains: “Normally the crops receive about 18 hours of light a day, at least during the winter months. We give them 16. Using a model we will calculate what the plant needs and what the irradiance is. We then decide what the number of light hours should be. Here we apply a three-day light integration.”
So far, the New Lighting-Project has gone well: growth was sustained with considerably less energy than usual. And the three greenhouses didn’t reveal any major differences. “But we aren’t there yet,” Janse warns. “We are very much dependent on weather conditions. The real winter cold is still to come. It’s too early to tell. The benefits of hazed glass probably won’t divulge themselves until spring.”
In order for growers to reach similar results, Janse says they need to look at the plant’s need and the daily irradiance. “Don´t just flick on the lights, but study, calculate, use models.” The use of CO2 is also part of the test, reducing the amount with 50%. Janse claims the resulting amount used – 30 kilos CO2 – is feasible for the average grower: “But then the dosed amount of CO2 needs to correlate with the amount of insolation and ventilation. And the mind-set is important: a grower put some effort into it.”
Jan Janse, researcher at the University, explains: “Normally the crops receive about 18 hours of light a day, at least during the winter months. We give them 16. Using a model we will calculate what the plant needs and what the irradiance is. We then decide what the number of light hours should be. Here we apply a three-day light integration.”
Jan Janse in greenhouse three, the one without LED interlighting
So far, the New Lighting-Project has gone well: growth was sustained with considerably less energy than usual. And the three greenhouses didn’t reveal any major differences. “But we aren’t there yet,” Janse warns. “We are very much dependent on weather conditions. The real winter cold is still to come. It’s too early to tell. The benefits of hazed glass probably won’t divulge themselves until spring.”
Left: greenhouse without interlighting, right: 90 µmol/m².s LED interlighting between tomato plants
In order for growers to reach similar results, Janse says they need to look at the plant’s need and the daily irradiance. “Don´t just flick on the lights, but study, calculate, use models.” The use of CO2 is also part of the test, reducing the amount with 50%. Janse claims the resulting amount used – 30 kilos CO2 – is feasible for the average grower: “But then the dosed amount of CO2 needs to correlate with the amount of insolation and ventilation. And the mind-set is important: a grower put some effort into it.”
Nursery number 1 and 3 use LED interlighting