Effect of nitrogen fertilization on flowering of strawberry (Fragaria × ananassa ‘Sonata’)

High yields are needed for profitability under shielded strawberry production. June bearing strawberry cultivars require a short day (SD) period in order to initiate generative growth. Nitrogen availability going into the SD-period, as well as during the period, can affect the process. To increase the knowledge about optimized nitrogen fertilizing, an experiment was set up under controlled conditions. Strawberry plants of the cultivar ‘Sonata’ were grown under combinations of different levels of nitrogen to evaluate its effect on timing on growth, flowering time and the number of flowers produced. The result showed that the time for opening of the first flower, the interaction between the pre-SD nitrogen level and the nitrogen level applied during the SD had the highest impact, and that low levels pre-SD flowered earlier. The number of flowers produced was affected by both pre-SD and SD nitrogen level as well as its interactions. Low nitrogen levels throughout had low yield potential while when low pre-SD nitrogen level was followed by high levels during SD, the yield increased.