What the research measured
The cited Iowa and Indiana studies reported sulfur responses in roughly half of tested corn fields, compared with about 5% of sites in the cited Illinois research. Soil properties, manure history, and trial design differ across these datasets; the percentages describe the studies, not all fields in each state.
About 150 Iowa trials, 55 Indiana field-scale trials and 40 (plus 81 historical) Illinois trials, two sets published in peer-reviewed journals in 2025,.5 independent sources.What it is. Ammonium sulfate, ammonium thiosulfate and gypsum supply plant-available sulfate to corn, a nutrient that used to arrive free from the air in power-plant fallout and now largely does not: Midwest wet sulfate deposition fell 72% between 2000–02 and 2020–22.
Study conditions and limitations
- Response concentrates on coarse, low-organic-matter, eroded or side-slope soils and fields without manure; Minnesota rates the probability high at 0–2% organic matter, moderate at 2–4%, low above 4%.
- Rates: about 15 lb S/ac on fine-textured and 25 lb S/ac on coarse soils (Iowa State, Purdue); sandy soils usually need S every year.
- Starter-only S at 5 lb or less paid in just 1 of 9 Indiana trials; the lowest sidedress rate tested (5–30 lb S/ac) captured the full response.
- Soil sulfate tests and ear-leaf S were unreliable predictors in the Illinois trials; Purdue uses tissue S below 0.15% with an N:S ratio above 20:1 as the deficiency signal.
- Elemental S reduced yield at 1 of 18 Illinois sites; sulfate sources are needed for current-season supply, and ammonium sulfate’s 21% N belongs in the N budget.
Read the sources · 5
- Corn response to sulfur fertilizer rate and source in Illinois ↗
Forty Illinois trials (2009–11) found a significant yield increase from S at only 2 of 40 sites, where gains were large (+14.7% and +30.5%), while 34 kg S/ha reduced yield at two fine-textured sites. The 1977–79 Illinois survey found 5 of 81 trials responsive. Soil sulfate and ear-leaf S tests did not predict response.
- Long-term field study on corn response to sulfur fertilization in Iowa, USA ↗
Twelve central-Iowa experiments comparing ammonium sulfate, thiosulfate and gypsum at 34 kg S/ha: only 17% of trials yielded more than the control even though S raised early-season plant S in half of them. Economic return averaged up to $27.6/ha at favorable prices.
- Corn Response To Sulfur Fertilizer In Indiana: Research Update ↗
In 55 field-scale strip trials (2017–22), sidedress S increased corn yield in 26 of 55; where it responded the gain ranged 3–34 bu/ac and averaged 11. Starter-only S had no effect in 8 of 9 trials, and a 2% organic matter loamy sand responded in 5 of 6 years, averaging 20 bu/ac.
- Crop Sulfur Fertilization This Spring ↗
Of about 150 Iowa corn trials, approximately 50% showed a statistically significant yield increase from S. Iowa research supports about 15 lb S/ac on fine-textured soils and 25 lb S/ac on coarse soils.
- Progress Report: Atmospheric Deposition ↗
Wet sulfate deposition in the Midwest fell 72% between 2000–02 and 2020–22, from 5.3 to 1.5 kg S/ha per year: the reason free atmospheric sulfur no longer covers crop removal on many Corn Belt fields.
Before you buy, ask
- What did my soil test show, and did the cited studies respond at similar levels?
- What rate, source, and timing were tested, and what did the untreated check receive?
- How does the price per pound of nutrient compare with the sources I already use?
Record
- Sources checked
- September 26, 2026. Every figure shown is printed on the linked page; unit conversions are noted on the chart.
- Company response
- None yet. Makers and suppliers of this product can send corrections, additional trials, or a statement; it is published here, labelled, and never edits the research summary. Send a correction →