In its second year, a trial from Grodan and Signify demonstrated it’s possible to produce high-quality cherry tomatoes with significantly less heat input than previously thought, without compromising on quality and taste. Building on these results and a commitment to low-energy growing, the partners are extending this year the trial at Botany to larger tomatoes on the vine.
As part of the trial, the Axia Macxize XR variety was transplanted 24th of September in week 39, where light levels are increased to 350 µmol/m2/s, compared to versus 300 µmol/m2/s in the last season.
The trial is in partnership with Ridder for its climate computer and screens, Wireless Value for sensoring, and Normec Groen Agro Control for advice on nutrient and water strategy. Seed supplier Axia will be a new addition to the existing group of research partners.
Exploring further energy efficiencies
The trial will test two different growing scenarios—multi-channel LED toplighting compared to a combination of LED toplighting and interlighting, keeping the total daily light integral (DLI) the same while optimising spectrum and light intensity. For this, Signify will install its four-channel Philips GreenPower toplighting force in the entire greenhouse and Philips GreenPower LED interlighting in one half of the greenhouse to provide extra light directly within the canopy.
“We expect the combination of toplighting and interlighting to result in a better light use efficiency (LUE) by improving the distribution of both light and temperature in the crop,” comments Marcel Raats, plant specialist for Philips Horticulture LED Solutions at Signify. “Our goals this year are to gain a better understanding of the radiation balance at the top of the plants, and to finetune screen steering to further optimise the energy input together with Ridder.”
Continued focus on precision irrigation
“As in the previous two years, we will use Grodan’s stone wool growing media to precisely manage the water and nutrient uptake, enabling us to create a strong, generative plant balance aligned with the low heat input. In collaboration with Normec Groen Agro Control, we will also explore the possibility of improving the nutrient uptake to avoid green spots and blotchy ripening using an adjusted drip composition compared to the standard used in practice. This facilitates sufficient nutrient uptake and good fruit quality, while maintaining production levels,” states Andrew Lee, Knowledge Manager at Grodan.
Both the vertical plant temperature and the fruit temperature will be closely monitored. The data will inform a better crop balance and steerability in the development speed – all the way from the young fruits in the head of the plant to the maturing fruits in the lower part of the canopy.
Building on proven results
The research partners have already proven that low-energy tomato cultivation can be accomplished, with last year’s results yielding 18.24 kg/m² with a Brix level of 9.32 and an average fruit weight of 12.20 g.
The partnership continues to refine its approach with a combination of active dehumidification, screens with higher insulation value, closing the screens for more hours in the day, and minimising the rail pipe operation. By dynamically adjusting LED light spectra i.e., switching off less efficient colors when conditions allowed, electricity costs were reduced by a further 2% this year.
From an irrigation perspective, controlling the leaf area index (LAI) with low-nitrate feed strategies optimised the canopy development, while fine-tuning the K, Mg, and Ca ratios led to enhanced nutrient uptake and fruit quality. The dedicated dehumidification system was key in maintaining ultra-stable greenhouse climate conditions to support consistent crop growth, setting the tone for the future cultivation of high-quality tomatoes, using less energy.
