Comparison of direct-seeded, bareroot, and various tray seedling densities on growth dynamics and yield of long-day onion
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Root, bulb and shoot growth of transplanted onions produced from seedlings on 228-cell flats were determined. Treatments were one (TC1), two (TC2) or three (TC3) seedlings/cell, and single plants separated at transplanting from those grown with two (TC2-1) or three (TC3-1) seedlings/cell. Controls were direct seeding (DS) and bareroot transplants (BR). Transplants were established with the following inrow spacings: 5 cm (BR, TC1, TC2-1 and TC3-1), 10 cm (TC2) and 15 cm (TC3). During early to mid-development root number and root dry weight were higher for TC1 as compared with BR. Transplant leaf mass peaked between 64 and 80 days after transplanting (DAT). Initially, DS had a rapid bulbing rate, while transplants exhibited a faster rate 60 DAT. Before final maturity, TC1 had a higher bulb size than DS and TC3. Total yields were similar, but yields by size class differed significantly between treatments. DS and TC3 had an increase in the small bulb size (35-50 mm diameter). All containerized transplants, except for TC3, had an increase in the large bulb size (60-70 mm). TC1 had 36% of the total marketable yield in the jumbo size (> 70 mm) compared with 16% for direct seeding and 24% for bareroot transplants.