The final meeting of the Strawberry Under Control II project was held on 9 October 2024. The final report will be published in mid-January 2025. A fossil-free year-round cultivation of strawberries is the dot on the horizon. Govert Trouwborst of Plant Lighting and Vera Theelen of Delphy ISFC give an update on Greenhouse as a Source of Energy.
Two intermediate goals have been formulated for this project: firstly, halving the input of gas and electricity per square meter: from 15 to 7.5m3 and from 200kWh/m2 to 100kWh respectively; and secondly, year-round cluster-inducing cultivation in balance whereby a harvest of over 500g/m2/week can be achieved in winter.
To achieve these intermediate goals, cultivation was completely different from what is currently common practice with multiple plantings of chilled June vines and associated peak production. Fresh June carriers Inspire and Fandango were grown. The learning point of season '22/'23 was that dormancy in winter should be avoided. Therefore, three strategies in three trellises in a 600m2 greenhouse were tried in season '23/'24 to stay further away from deep dormancy.
Energy and cultivation results
The savings in electricity to over 100kWh/m2 is largely due to the switch from SON-T to LED. Additional kWh have been saved by saving on far-red and dimming lamps during the day. Heat demand was minimized by using a transparent energy cloth and a light emission screen. As a result, gas consumption was around 7m3/m2. In terms of production, this trial did not pick the kilos planned in advance. Thus, several varieties went into dormancy anyway and an imbalance developed in the plant. This resulted in significantly reduced truss induction.
In conclusion
From an energy point of view, this was a successful trial: gas and electricity inputs were halved. Botanically, it was concluded that the cultivation concept is not yet ready for practice. Key areas of concern are:
- Variety choice: Inspire cultivation is less risky with respect to deep dormancy than Fandango. This seems to be related to the cold requirement, "low chill" versus "medium chill", respectively.
- Initial production was induced on the tray field outside. A brake on the continuation in winter production around week 2 is most likely the negative influence of the September climate in the greenhouse just after planting on the bunch induction that should then take place.
- Because of the higher temperatures, truss induction in summer is also a point of attention, which can be adjusted with day length. To make this cultivation practice-ready, it is necessary to re-examine all cultivation-technical aspects. It is also important to map out how new varieties should be grown, with which cultivation concept they fit best and whether it is possible to develop new varieties that keep inducing trusses more easily and avoid the deep dormancy.
This project was carried out by Delphy ISFC and Plant Lighting and funded and coordinated by Kas als Energiebron, an innovation program of LVVN and Glastuinbouw Nederland. Made possible in part by the Strawberry Research Foundation, Signify, Plant Sciences, and Fresh Forward. The trial was followed and supervised by growers.
Source: Greenhouse as a Source of Energy