Effect of planting dates, chilling periods and N/P foliar spray on flowering traits of strawberry (Fragaria × ananassa) cv. Robygem in a hydroponic system.

This study was conducted in an unheated greenhouse during the 2022 and 2023 growing seasons at the Malta Forest Nursery of the General Directorate of Forests and Rangeland / Duhok city, Duhok governorate, Kurdistan region- Iraq, at an elevation of “526” meters above sea level. The research aimed to investigate the effects of planting dates (15th September, 1st October and 15th October), chilling periods (0, 10 and 20 days) and foliar applications of nitrogen and phosphorus (0 and 100/100), as well as their bilateral and triple interactions on the flowering characteristics of the strawberry plant cv. Rubygem in hydroponic system. The lowest number of days to flowering obtained on 15th October for two growing season 57.708 and 60.792 days respectively. Whereas longest period to flowering was obtained on 15th September in both seasons 72.333 and 73.542 days respectively. Planting date 1st October resulted in a significant increase in number of flowers per plant which reached 18.042 and 16.167, The setting % of flowers, length of flowering period for two growing season 73 and 70.625 days. Chilling periods of 20 days significantly increase the number of flowers per plants, length of flowering period and vitality of pollen. In both growing seasons spraying plants with N/P 100/100 ratio increase the number of flowers per plants 18.222-16.083, setting % of flowers, length of flowering period for both years 73.472 and 71.028 days and vitality of pollen. Both bilateral and triple interaction between the three factors significantly effect on most traits in both growing seasons.