Is Sulfur Limiting Corn Yields In Illinois?.

The last statewide survey to determine corn response to sulfur (S) in Illinois, USA was conducted over three decades ago where only 5 out of 82 sites showed a mean 0.7 Mg ha^-1 corn grain yield increase with S application. Since that earlier study a combination of increasing S uptake by higher-yielding crops and a reduction of S inputs from the atmosphere and in the inputs used in farming today might be causing insufficient S supply for corn. Our objective was to quantify the likelihood of corn response to S in relation to soil characteristics and location within Illinois. Small plots (3 x 9 m) received ammonium sulfate (NH₄)₂SO₄ (21-0-0-24); two forms of MicroEssentials^TM S (ME S)— ME S15 (13-33-0-15) and ME S10 (12-40-0-10); calcium sulfate (gypsum) CaSO₄·2 H₂O [0-0-0-22(Ca)-17(S)]; and elemental S (0-0-0-90). Sources were applied at a rate of 26 kg S ha^-1, except for ME S15 that was applied at 0, 13, 26, 39, 52 kg S ha^-1 in a randomized complete block design with 4 replications at six locations in Illinois in 2009 and 2010. In addition, strip trials with 0 and 34 kg S ha^-1 replicated four to seven times were established in 18 on-farm fields throughout the state. Plant-tissue samples were analyzed for S and grain yield data were collected. No response to S source was observed in the small-plot sites. While ear-leaf S content was above the sufficiency level (1.5 g kg^‑1), S content increased with each successive S rate to 39 kg S ha^-1. Grain yield increased in three out of 12 site-years, on a silty-loam soil in east-central Illinois and on a fine sandy-loam soil in northern Illinois, with an application of 26 kg S ha^-1 that produced a mean yield increase of 1.6 Mg ha^-1 relative to the unfertilized treatment and maximized grain yield at 13.1 Mg ha^-1. Two out of 18 on-farm sites showed an increase in yield with S application. A 34 kg S ha^-1 application on a sandy-loam soil in central Illinois produced a 3.2 Mg ha^-1 increase above the 10.5 Mg ha^-1 yield produced in the unfertilized strip, and a silt-loam soil in east-central Illinois produced a 1.3 Mg ha^-1 increase over the unfertilized strip. These data indicate that the frequency of S deficiency and magnitude of yield response to S application seem to have increased since the earlier study.