In mid-September last year, new tomatoes were planted for the Hybrid Lighting Tomato project at Delphy Improvement Center. In this project, the vine tomato Merlice is grown under a combination of LED and Son-T lighting. The goal is to harvest more than 55 kg / m² by the end of week 18. They have now been harvesting for 13 weeks and with that they are halfway to week 18 . High time for an update on the state of affairs.
After five years in a row with 100% LED lighting, Signify has opted for a hybrid solution that includes Son-T lamps. More and more companies are looking for higher light levels but with Son-T lamps the limitation is in the heat generation. In this test, a 180 μmol/m²/s Son-T installation was taken as the basis, namely ± 105 Watt/m². By leaving half of the Son-T installation intact with 90 μmol/m²/s, 54 Watts/m² remained to be used for LED lighting. This is divided into 90 μmol/m²/s toplight and 55 μmol/m²/s interlight. In total, this provides a light level of 235 μmol/m²/s where 255 μmol/m²/s would have been possible.
Together with Delphy Improvement Center, De Ruiter Seeds, Saint-Gobain Cultilene and Gremon systems, they are looking for the right cultivation strategy to achieve the objectives. Every week, they come together for this, and they are supported by three dedicated growers in order to keep the connection with the market.
On September 12, the 3.3 st/m² section was planted with a plant that was topped on the third leaf. While in the past it was chosen for a plant topped on the second leaf, we now wanted to start the winter range immediately. This saves yet another five weeks of a higher stem density harvesting compared to do it directly after planting a stem to keep. The 3-header with which it started was of a fine quality with 3 strong equal heads. A week after planting, the first bunch was blooming. In week 49, they arrived at 3.9 st/m² with which the season is to complete.
Halfway through November, the crop was on the heavy side and did not show the strength they were aiming for. The objective of getting through the winter without the need of spray treatments had to be put aside, as a somewhat weak bunch had to be checked. In order to see the effects of the interlight on a weak bunch, they decided not to tie the bunch in one path.
After a thorough climate evaluation, they decided to stop watering in advance and the crop immediately arrived at the right balance. Since then, they have been looking critically at the settings and accompanying graphs. Fine-tuning is done every week. In the past 8 weeks, only minor changes were made with regards to the cliimate strategy.
With an average weekly production of just over 2 kg/m² and a total production of over 25 kg/m2, they are on course to exceed the goal of more than 55 kg/m² in week 18. A final production of around 107 kg/m2 is also in sight. The somewhat weaker bunch has now also been harvested, it nonetheless met the quality standards with an average fruit weight of 155 grams. Here again, they clearly saw the added value of interlight on a weak truss set.
Now that spring times are approaching, the additional benefits of this lighting installation can be further exploited. "If the outside temperatures went up, we would have to be able to continue 100% lighting with this installation in order to reach the maximum light sum for the crop. Only above 450 Watt we will switch off the Son-T and only illuminate with the LED."
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