By Charles Wortmann
Approximately 100 trials have been conducted since 2000 to evaluate sulfur (S) use in corn, sorghum, and soybean. The trial results have validated
- the UNL recommendations of applying S to sandy soils in consideration of soil test results; and
- the probability of profit gain due to increased yield from S application to medium and fine textured soil is very low.
Deposition of atmospheric sulfur and sulfur application in fertilizers such as single super phosphate is much less than it was three to four decades ago. This implies that S availability needs to be monitored.
- The probability of response to S has been determined in recent years to be high enough for some parts of Iowa to justify routine application.
- Soil test results for sulfur availability continue to be of little or no value and response is best monitored with on-farm trials comparing yield with and without sulfur applied.
- Applying S often does result in greener crops while not increasing grain yield. This can be important to farmer satisfaction and impressing neighbors and land managers.
Sulfur is abundantly available and fertilizer sulfur use can be of modest cost without much environmental concern. Sulfur applied as sulfate does not affect soil pH, but applied as elemental S, it can contribute to soil acidification. Gypsum is often abundantly available and can be a good sulfur source. Flue gas desulfurization gypsum, a by-product of coal-fired electrical power generation, is a potential sulfur source with a liming effect.