In greenhouse horticulture, a uniform climate is crucial to grow a uniform crop. Especially in propagation of young plants, there is a need for year-round uniform growing conditions (light intensity and quality, temperature, humidity, etc.). In some cases, this requirements go beyond the control options in a greenhouse. However, this may be realized under daylight less conditions, in a vertical farm or climate chamber.
Cultivation in a vertical farm requires high amounts of electricity for cooling and lighting, thereby posing a major cost factor. Costs could be reduced when lighting could be applied based on the pattern of electricity prices over the day and season, rather than in a traditional day/night rhythm. The question thereby is how this would affect the growth and development of the crop. In other words: how flexible are plants?
In order to answer this question, a number of trials were carried out in 2019 and 2020 as part of a project on “daylight less cultivation”, funded by the Club of 100 of the business unit Greenhouse Horticulture of Wageningen University and Research, a group of horticultural supply companies. In this project, young tomato and lisianthus plants were grown under 4 lighting treatments in climate chambers in Wageningen. These treatments differed in the period of the day when lights were on, where lights were switched off or light intensity was reduced during the hours of the day when electricity prices were highest. Our results showed that the tomato and lisianthus crops were quite flexible, although responses differed per crop and cultivar. These results offer new perspectives for the use of dynamic light regimes.
We will further develop this principle in the new Vertical Farm facility of the business unit of Greenhouse Horticulture of Wageningen University and Research in Bleiswijk, The Netherlands. We will apply the principles of a dynamic lighting regime, where we do not light during the hours with the highest electricity prices, in a fruit-bearing cucumber crop. With this we will examine to which extent the principles and results we have obtained in young plants can also be applied in a generative high-wire crop.