CONCLUSIONS 43

In strawberries is it necessary to use supplemental lighting for 12 to 13 hours (Verheul et al., 2007). Longer lighting reduced the number of flowers. A day temperature of 18 °C and / or a night temperature of 12 °C was the best to get flowers and also at the shortest time.

At the nursery Kvistar were good results reached with minimal heating (day temperature of 16 °C and night temperature of 8 °C) in a plastic greenhouse in summer production. Under that conditions were 4 kg/m2 of strawberries possible and sold for 3.000 ISK / kg.

The positive influence of artificial lighting on plant growth, yield and quality of tomatoes (Demers et al., 1998a), cucumbers (Hao & Papadopoulos, 1999) and sweet pepper (Demers et al., 1998b) has been well studied. It is often assumed that an increment in light intensity results in the same yield increase. Indeed, yield of sweet pepper in the experimental greenhouse of the Agricultural University of Iceland at Reykir increased with light intensity (Stadler et al., 2010). However, with tomatoes, a higher light intensity resulted not (Stadler, 2012) or in only a slightly higher yield (Stadler, 2013a). Knowledge in growing berries at different light intensities is not yet available. Therefore, two light intensities will be tested to investigate if growing strawberries in winter is possible.

Incorporating lighting into a production strategy is an economic decision involving added costs versus potential returns. Therefore, the question arises whether these factors are leading to an appropriate yield of strawberries.

The objective of this study was to test if (1) the light intensity is affecting growth, yield and quality of strawberries, if (2) this parameter is converted efficiently into yield, and if (3) the profit margin can be improved by the chose of the light intensity. This study should enable to strengthen the knowledge on the best method of growing strawberries and give strawberry growers advice how to improve their production by modifying the efficiency of strawberry production.