There are several sulfur sources producers can use to meet crop demand including elemental sulfur, fertilizers such as ammonium thiosulfate and gypsum.
“Elemental sulfur is used, but it is very acid forming so it isn’t ideal for every situation,” Dick says.
At 16% sulfur by volume, gypsum is a budget-friendly option. That is particularly true for growers who use Flue Gas Desulfurization (FGD) gypsum, a synthetic form that’s produced by the pollution control systems used to reduce emissions. Mined gypsum is significantly more expensive than FGD gypsum.
“The cost of a pound of sulfur in FGD gypsum is significantly lower than sulfur in other forms,” Chamberlain says. “It also provides sulfur in a plant-available form and moves sulfur through the soil profile so it’s where it needs to be in the form it needs to be in for plants to use it.” Gypsum provides the added benefit of 17-20% calcium and is often used in potato production and other calcium-loving specialty crops.
Extensive studies have shown all of the various gypsum sources are safe for land application, says Dick.
For Center Point, IN, producer Brad Brown, gypsum provides the double benefit of building soil structure and replenishing sulfur.
“We didn’t know about sulfur when we first started using gypsum in 1986 to loosen our soil for better drainage and rooting,” Brown says. “Getting sulfur with our gypsum was a win-win, it really helps our corn and it’s in the cheapest form we can get. Our yields are more even from acre to acre and year to year. The sulfur seems to excite the corn for good early season growth.”
Brown applies gypsum every other year. Initially he applied 1 ton/acre but has dropped to 1,400 lbs. every other year applied in the fall ahead of corn.
“As the soil structure builds we’re able to cut back on the rate but we will keep applying it to maintain the sulfur supply for our corn. We shoot for 200+ bu./acre,” says Brown.
Wisconsin farmer Ken Ihlenfeld agrees gypsum is becoming a valued tool in his cropping operation. “We were attributing sulfur deficiency symptoms to disease, but now that we know what it is we’re able to correct the situation and our yields improved after only one application,” Ihlenfeld says. “Gypsum is a win-win for us because it boost yields by correcting the sulfur deficiency and the calcium helps loosen up our compacted soils.
1. Dealing With Sulfur Deficiency in Iowa Corn Production. Sawyer et al. 2009 Integrated Crop Management Conference - Iowa State University. 2009. P. 117-123. http://www.agronext.iastate.edu/soilfertility/info/Sulfur_ICM_Proc_2009.pdf
2. Sulfur: A Missing Link Between Soils, Crops, and Nutrition. Franzen and Grant. 2008. P. 105-115.
3.Fertility Needs of No-Till Corn, Soybean and Wheat, Raymond C. Ward, Ward Laboratories, Inc. Kearney, NE