Nitrogen fertigation requirements of drip-irrigated strawberries

Strawberries (Fragaria xananassa (Duch.) were grown in two seasons at Dover, Fla., with polyethylene mulch and drip irrigation. Nitrogen was injected weekly at 0.28 (50), 0.56 (100), 0.84 (150), 1.12 (200), and 1.40 (250) kg N/ha per day (kg . ha(-1) for season) for 'Oso Grande' and ''Sweet Charlie' in 1991-92 season and for 'Oso Grande' and 'Seascape' In 1992-1993 season. Nitrogen fertilization in 1991-1992, over the range of 0.28 to 1.40 kg N/ha per day, had no significant effect on early (November to January) strawberry yields. March (the largest production month) yield and total-season yield increased with increasing N fertilization to 0.76 and 0.54 kg N/ha per day, respectively, Nitrogen fertilization did not affect yields of strawberry in 1992-93. Fruit firmness and average fruit weight were not affected by N fertilization from 0.28 to 1.40 kg N/ha per day. Nitrogen fertilization increased whole leaf N, leaf blade N, and petiole sap nitrate-N concentrations linearly for most sampling dates in both years. Early yields were greater for 'Sweet Charlie' than 'Oso Grande', Yields were greater for 'Oso Grande' during March, and total-season yields were similar for both cultivars in 1991-92, (Oso Grande' had greater early, March, and total yields than 'Seascape' in 1992-93.