Does Irrigated Corn Require Multiple Applications of Sulfur?

Sulfur is applied to irrigated corn (Zea mays L.) grown on sandy soils. The objective of this study was to evaluate the sprinkler‐irrigated corn response to S. Treatments were a factorial combination of 0, 14, 28, and 42 kg S ha⁻¹ as (NH₄)₂SO₄ applied on the soil surface at four locations at planting and in season (V5). Tissue samples were collected at V8 and R2 and evaluated along with corn grain yield and soil pore water SO₄²––S concentration measured at 60 cm with suction tube lysimeters. Application of S increased V8 plant mass, V8 whole plant S concentration and S uptake, and R2 leaf S concentration but did not increase corn grain yield. Decreased V8 plant mass was a result of S deficiency and was only corrected when some S was applied at planting. A total of 28 kg S ha⁻¹ was sufficient to ensure adequate plant growth and S uptake whether S was applied at planting, in‐season, or as a combination of the two timings. Concentrations of S were elevated in soil pore water from at planting and in‐season S application indicating a portion of the S applied were still available for most—and at the end of—the growing season. Sulfur fertilizer is crucial early in the growing season for irrigated corn to ensure optimal corn growth. Rate of application is more important than time of S application in irrigated corn production. Incidental applications of S may reduce the need of S fertilizer for irrigated corn. CORE IDEAS: Application of sulfur at planting is required to maximize early irrigated corn plant mass. Delaying sulfur application to the V5 growth stage results in luxury uptake of S in corn. Rate of sulfur applied is of greater importance than timing and number of applications. Sulfur applied at planting will not fully leach from the root zone the year of application. Sulfur fertilizer may not be required to achieve maximum grain yield for irrigated corn.