The Impact of Nitrogen and Sulfur Fertilization on Yield, Quality, and Flavor of Field Grown Vidalia Onion

Vidalia onions (Allium cepa) are marketed based on their characteristic sweet and mild flavor. Previous greenhouse-based research has concluded that both nitrogen and sulfur fertility have a significant impact on onion flavor potential. However, there is a lack of field-based information regarding the impact fertilizer application on quality and flavor in Vidalia onion.  Therefore in the 2014 growing season, Vidalia onions were grown under five fertility programs representing high and low applications of nitrogen and sulfur fertility as well as the impact of elevated soluble calcium on onion quality and flavor characteristics.  Onions, ‘Sapelo Sweet’ and ‘Goldeneye’ were transplanted on 21 November 2013 at the Vidalia onion and vegetable research center in Reidsville, GA. Levels of nitrogen and sulfur fertilizer ranged from 106 to 252 kg·ha^-1 and 40 to 134 kg·ha^-1, respectively.  An additional 280 kg·ha^-1 of calcium was supplied using calcium chloride for a high-calcium treatment.  Onions were grown to maturity and harvested in April 2014 with yield and grade determined.  Quality characteristics measured included methyl flavor volatiles, pungency, bolting, doubles, storage quality, firmness, and disease susceptibility.