NITROGEN-FERTILIZATION OF FLORIDA-GROWN TOMATO TRANSPLANTS - SEASONAL-VARIATION IN GREENHOUSE AND FIELD PERFORMANCE

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