Sulfur is critical to the taste and pungency of the bulb. Supplies need to be tailored to suit the desired market requirement. Sulfur can also improve skin strength and color, and has a marked effect on the pungency of the onion through increasing the pyruvic acid content of the bulb. Therefore, it is important to use the right soil and an appropriate rate and timing of sulfur that satisfies market demands.
Sulfur also has a marked effect on bulb sugar content, so soil type and use of sulfur as part of a nutritional program have to be carefully considered in order to meet market requirements. For example, sweet onions benefit from being grown in low sulfur soils and should have low S-fertilizer regimes with most of the S applied early season to minimize uptake into the onion bulb.