Sulfur Levels in Soil and the Effect on Vidalia Onions.

Vidalia onions are the uniquely sweet onion varieties grown in a specific region of South Georgia.  Over the past decade, growers in the area began noting a change in onion flavor.  These observations led the Vidalia Onion Committee to partner with the University of Georgia to commission a study to investigate the cause.   In 2014-2016, field trials were performed to examine the relationship between soil sulfur concentrations and the spiciness of the onion, gauged by measuring its lachrymatory factor (LF).  A significant correlation between soil sulfur levels and the LF of onions was observed.  Our results showed sulfur accumulating in the claypan layer at a depth between 12-24 inches.  Our results show that current sulfur application rates may need to be reduced in order to maintain the unique sweet flavor of Vidalia onions.  Furthermore, soil sampling techniques should be modified to account for the potentially large pool of available sulfur at deeper soil depths.