Nitrogen (N) fertilizer recommendations exist for controlled environment strawberry (Fragaria ×ananassa) fruit production. However, optimal N fertilizer concentrations may differ for strawberry mother plants, given that vegetative growth rather than reproductive growth is preferred. Our objective was to evaluate the impact of N fertilizer concentration on strawberry daughter plant yield and quality. Strawberry ‘Albion’ and ‘Monterey’ were grown in a greenhouse in 19.1-cm diameter pots filled with a soilless substrate (50 perlite : 25 coco coir : 25 peat). Plants were fertigated with a modified strawberry nutrient solution (Yamazaki) to provide 50, 100, 150, 200, 250, or 300 mg·L-1 N. After 12 weeks of treatment, cultivar but not N concentration impacted total stolon number and total daughter plant number. ‘Monterey’ produced 129% more stolons and 72% more daughter plants than ‘Albion’. Likewise, cultivar but not N concentration impacted branch architecture and where daughter plant formation occurred. The percentage of plants that produced primary, secondary, tertiary, and quaternary stolons was 100%, 97%, 61%, and 7% for ‘Monterey’ and 100%, 82%, 12%, and 0% for ‘Albion’. The distribution of daughter plants produced on primary, secondary, and tertiary stolons was 75%, 24%, and 1% for ‘Albion’, whereas it was 56%, 40%, and 4% for ‘Monterey’. Daughter plant quality exhibited quadratic responses to an increase in N concentration. Calculated maximum values were at 149 mg·L-1 N for daughter plant crown diameter, 172 mg·L-1 N for daughter plant fresh weight, and 187 mg·L-1 N for chlorophyll content index. Daughter plant foliar %N increased linearly as N fertilizer concentration increased from 50 to 300 mg·L-1 N, from 1.76% to 2.86% in ‘Albion’ and from 1.48% to 3.33% in ‘Monterey’. Mother plants also responded quadratically to N fertilizer concentration. Mother plant height, width, crown diameter, fresh weight, and a qualitative root rating assessment were greatest at calculated N concentrations of 154 to 169 ppm N. Necrosis of leaf margins began to appear in mother plants supplied 200 to 300 mg·L-1 N due to high nutrient solution electrical conductivities (ECs). In summary, although N concentration did not impact daughter plant yield, an N fertilizer concentration of 150 mg·L-1 N would optimize daughter and mother plant quality without inducing EC stress.
