Plant Population, Transplant Size, and Variety Effect on Transplanted Short-day Onion Production

Onions (Allium cepa) produced in southeastern Georgia's Vidalia-growing region are primarily grown from on-farm-produced bareroot transplants, which are usually sown the end of September. These transplants are pulled midwinter (November-January) and are reset to their final spacing. This study was to evaluate transplant size and spacing effects on yield and quality of onions. Large transplants (260-280 g per 20 plants) generally produced the highest yield. Medium transplant size in the range of 130 to 150 g per 20 plants produced satisfactory yield while maintaining low numbers of seedstems (flowering) and doubled bulbs, which are undesirable characteristics. Smaller transplant size (40-60 g per 20 plants) have reduced yields and lower numbers of seedstems and double bulbs. Increasing plant population from 31,680 to 110,880 plants/acre can increase yield. In addition, plant populations of 110,880 plants/acre can increase yields compared with 63,360 plants/acre (industry standard), but only when environmental conditions favor low seedstem numbers. Seedstems can be high because of specific varieties, high plant population, or more importantly, in years with environmental conditions that are conducive to their formation. 'Sweet Vidalia' was the only variety that had consistently reduced quality and high numbers of seedstems. 'Sweet Vidalia' has a propensity for high seedstem numbers, which may have influenced results with this variety. A complete fertilization program that included 133 or 183 lb/acre nitrogen did not affect onion yield, regardless of variety or population density.