Long season for organic raspberries

Between 2008 and 2011, a trial with growing organic raspberries in tunnels was conducted at Rånna experimental station in southwestern Sweden. Different varieties and fertilizer rations were tested. Among autumn raspberries the variety Polka is the most popular as it has both good yields and flavourful berries with good durability. Glen Ample was the variety of summer raspberries that gave best yield and managed overwintering best.

High nitrogen ration gave leaf damages
Cultivation directly in soil gave generally higher yields compared to growing in pots. There was little difference in yield for the two nitrogen rations in the experiment. At the higher nitrogen ration leaf damage was observed in June 2011, probably caused by high nutrient availability. Conclusions from the project was that the 9-12 and 12-17 grams of organic nitrogen per plant and the season can be recommended as optimal doses for organic cultivation of autumn and summer raspberries.

Smaller raspberry aphid attacked both summer and autumn raspberries, so there was a need for control with starch-based preparations alternated with soap throughout the growing season. The summer raspberries were also attacked by dryberry mite. Further development of pest management strategies for organic raspberries in the tunnel is necessary.

Cultivation in tunnel is profitable despite large investments
Growers and advisors involved in the projects’ reference group have ensured that the experimental orchard is very close to practical farming conditions. Experiences from the project thus provide a basis for advising, directly applicable in practice. Tunnel cultivation requires investment in tunnels, horticultural fabrics for covering and more. But calculations from the Board of Agriculture show that at the yield levels achieved in the experiment the tunnel cultivation is nevertheless profitable.