Dutch strawberry cultivation under light is focused on June bearers. This is mostly a single crop or a continuous crop. The disadvantage of this is the relatively long lead time to harvest, followed by a relatively short harvest time due to one large peak in production. To make cultivation under light fossil-free and more efficient, it is desirable for a plant to have continuous fruiting, as in tomato cultivation, in order to keep harvesting continuous and largely avoid harvest peaks and troughs, writes Henny van Gurp on Kas als Energiebron. There he points out the "multiple advantages".
Spectrum choice
One project examined the fossil-free cultivation design. There were two greenhouses of 200m2 each, each with its own daylength strategy during the winter period with lighting. Cultivation was done with the low-chill varieties Fandango and Inspire. In the run-up to the lit season, in both greenhouses, the natural day was extended to 12 hours with cyclic lighting (12-hour greenhouse) or pure far-red or red depending on elongation (18-hour greenhouse). In the lit period from week 47, a "short" 12-hour day was maintained in one greenhouse. In the other greenhouse, lighting could continue until 18 hours with red light as after-lighting.
Previous research has shown that with this spectrum, a long day's lighting can be maintained without stopping cluster induction. The light sums were kept the same, so the instantaneous LED intensity was much higher in the 12-hour greenhouse. After winter, the day length was shortened to 12.5 hours in both greenhouses to maintain a cluster-inducing day length in order to have fruiting in late spring and summer. Eight weeks before the end of the trial, a natural day length was maintained because then further bunch induction would no longer make sense.
The project had two main objectives: (1) Halving the input of gas and electricity per square meter from 15 to 7.5m3 and from 200kWh/m2 to 100kWh, respectively, and (2) year-round truss-inducing cultivation in equilibrium where a harvest of over 500g/m2/week can be achieved in winter.
Read more at Kas als Energiebron here (in Dutch).