EFFECTS OF NITROGEN-FERTILIZATION AND HPS SUPPLEMENTARY LIGHTING ON VEGETABLE TRANSPLANT PRODUCTION .2. YIELD

Transplants of celery (Apium graveolens L.), lettuce (Lactuca sativa L.), broccoli (Brassica oleracea italica L.), and tomato (Lycopersicon esculentum Mill.) grown in multicellular trays under natural light or with supplementary lighting of 100-mu-mol.s-1.m-2 (PAR) in factorial combination with four rates of N fertilization (100, 200, 300, and 400 mg.liter-1) were tested for productivity under field conditions. Celery was seeded once, lettuce twice, and broccoli and tomato three times. Broccoli and tomato were transplanted at two sites, celery and lettuce at one. Supplementary lighting had no effect on yields of celery, lettuce, and broccoli, but significantly increased yields of early seeded tomato. High rates of N fertilization (300 and 400 mg.liter-1) applied at the transplant stage improved yields for all the species.