Pretransplant Watermelon Nutrition with Various Nitrate: Ammonium Ratios and Supplemental Calcium

Watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai 'Crimson Sweet'] was seeded in a commercial peat medium in multicell containers. Five NO 3 :NH 4 ratios and five levels of supplemental Ca were combined factorially in a 100N-31P-265K mg-liter -1 pretransplant nutrition regime. The medium was amended with CaCO 3 in 1989; the medium was not amended in 1990. Dry-matter accumulation had decreased with increasing NH 4 -N3 weeks after seeding both years. In 1989, increasing NH 4 -N also had decreased seedling growth by the last sampling date due to decreased NH 4 + uptake []