Influence of air humidity enrichment under high tunnel conditions on some quantitative and qualitative parameters of strawberry fruit

Everbearing strawberry (Fragaria × ananassa Duch.) cultivation involves a long-lasting harvest curve, even in mountain environments. This characteristic, in addition with protected cultivation, increases the risk that plants can be subjected to adverse thermo-hygrometric conditions, influencing both production and fruit quality. During summer 2012, an air humidity enrichment experiment was conducted in order to evaluate the influence of microclimatic conditions on quantitative and qualitative parameters of everbearing strawberry fruit, cultivar 'Capri'. An over-head irrigation fogging system was set in the high tunnels of a soilless strawberry orchard (1100 m a.s.l.) located in Trentino, Italy. Three relative humidity (RH) treatments were defined: 60%; 70% and control at environmental RH. The RH treatments succeeded in increasing the RH, except during windy or very dry days. Water sprinkling determined a decrease in mean hourly temperature: the 60 and 70% RH treatment reached an average temperature 3 and 5% lower than control, with peaks of 5 and 10%. However, no significant increase was observed in the production (marketable and discard yield) and in the fruit parameters (weight, firmness, shape coefficient, weight lost, total soluble solids, titratable acidity), while fruit colour (Chroma index) and misshapen fruit percentage increased significantly in the treatments. In conclusion, although the treatments modified the high tunnel microclimate and the plants perceived this modification, it is difficult to have consistent results using this approach under high tunnel conditions.