Nitrogen fertilization of Florida-grown tomato transplants: Seasonal variation in greenhouse and field performance

Fall-grown tomato (Lycopersicon esculentum Mill.) transplants were larger than spring-grown transplants when fertilized in the greenhouse with NH3NO3 at 0, 15, 30, 45, 60, or 75 mg . L-1 N in a standard 1/4 strength Hoagland's solution. All transplant growth characteristics measured (stem length, leaf area and number, root and shoot dry mass) increased linearly with increasing N in both seasons. However, in the fall, when greenhouse temperatures and light levels were higher, stem length, leaf area, root : shoot ratio, and the ratio of shoot dry weight : leaf area responded quadratically, In the spring, total fruit yield and production of extra-large fruit increased with increasing transplant N fertilization, but the opposite trend occurred in the fall. These differing seasonal responses suggest fundamental differences in tomato transplant growth that must be addressed by modifications in N fertilization between spring and fall.