Within the EU-FP7 project EUROBERRY Wageningen UR Greenhouse Horticulture has to propose means for season extension of strawberry cultivation in simple tunnels. In particular, we have evaluated the chances of delaying both frost for the autumn season and excessive temperatures in the spring season, by modifying the properties of the cover. After adaptation and validation of the glasshouse climate model KASPRO to fit this purpose, we have evaluated several options for a farmer cooperative producing small fruits in the Italian Alps, at 600 to 800 m.a.s.l.
In the research to prolonging the autumn season, we have estimated that an energy screen, with the dual effect of preventing radiative losses and limiting air exchange (thus keeping inside the heat released by the soil at night) could delay freezing by even six weeks.
The options extending the spring season by whitewash is the only acceptable option as far as the cover properties are concerned.
Better options, since assimilation would not be limited, would be forced ventilation to increase air exchange (reaching 35°C inside the tunnel could be delayed by some six weeks) or high pressure fog inside the tunnels (total prevention of 35°C).
The feasibility and possible implementation of (some of) these methods will be investigated in the next phase of the project.