Energy-efficient raspberry cultivation in the winter?

CO2 dosing of raspberry crops in the winter has almost zero effect on production and quality. That is according to the Netherlands' Fruit Growers Organization (NFO). More light does mean more production. But there are vast differences per variety and plant.

This is evident from a study done by Wageningen University's Glasshouse Horticulture and Flower Bulbs Research Unit. The trial was done to see if, in the future, fossil-free cultivation is possible. That is with limited or no CO2 dosing. And if so, with minimal heating.

In the Lagorai and Kwanza raspberry experiments, scientists applied two doses of CO2 and two light intensity variations. Neither level of CO2 dosing affected production and quality much, if at all. Therefore, in winter, with relatively little sunlight and growing lights, CO2 levels and doses do not need to be as high.

More light equals more production
Both light intensity trials used LED lighting for about 1,850 hours. That was throughout the entire cultivation period. The trial showed that heat consumption was high. At high and low light, it averaged 12.8 and 16.9 m3/m2, respectively. These lights were mainly needed for dehumidification. That prevents settling and fungal growth issues.

This heat consumption would have to be greatly reduced in fossil-free farming. The total PAR light differed by 15% in the treatments. Harvesting more fruits increased Class 1 fruit production by 11.5%. More light increased the photosynthesis rate, but that fell during cultivation.

These two varieties' eventual production differences proved to be quite considerable. That was partly due to non-uniform plant material. Class 1 fruit average production was 2.0 and 3.5 kg/m2 for Kwanza and Lagorai, respectively.

You can read the extended trial report (in Dutch) on

Source: NFO

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