INCREASING SEEDLING DENSITY, AGE, AND NITROGEN-FERTILIZATION INCREASES ONION YIELD

Three onion (Allium cepa L.) cultivar transplants were grown in the greenhouse in 200-cell plastic trays with one, two, or three plants per cell; at 75, 150, or 225 ppm N; and for 8, 10, or 12 weeks. Increasing the number of plants per cell resulted in smaller seedlings at transplanting and reduced time to maturity in the field by 1 week. Two and three plants per cell yielded more bulbs greater-than-or-equal-to 76 mm in diameter, but one plant per cell had the highest percentage of bulbs greater-than-or-equal-to 102 mm in diameter. Older seedlings and higher N applications produced larger plants at transplant and larger bulbs at harvest. Increasing N applications reduced maturation time slightly. Bulb fresh weight at harvest and yield of bulbs greater-than-or-equal-to 76 mm in diameter were highest with 10- and 12-week-old transplants, and at 150 and 225 ppm N.