Gypsum is a naturally occurring mineral that has been used in the United States since Benjamin Franklin first applied ground raw gypsum, called land plaster, on his soils.
Today, as Franklin did then, farmers use gypsum to improve soil tilth, water infiltration and nitrogen uptake in their fields.
According to the American Coal Ash Association, a utility industry group, U.S. farmers used 279,000 tons of gypsum in 2008. That’s more than three times the amount they used in 2002.
“With gypsum, the soil structure becomes more sponge-like so even tight clay soils readily absorb water and move it down through the soil profile rather than allowing it to pond or run off,” says Ron Chamberlain, director of gypsum programs for Beneficial Reuse Management (BRM). The company sells a synthetic gypsum product, Gypsoil, for agricultural use.
Synthetic gypsum is a common byproduct of fossil-fueled power plants that work to remove sulfur dioxide from flue gases in their effort to curb pollution and comply with clean air regulations. In recent years, synthetic gypsum has gained ground with farmers, because of its availability and lower price.
“Gypsum is a big benefit to corn as the plants’ roots are able to work their way deeper into the ground,” says Brad Brown, who farms about 1,200 acres of corn and soybeans near Center Point, Ind., and uses synthetic gypsum.
“It keeps the pores of soil open so we get more oxygen to the roots of the crop,” he adds.
Brown says his soybean crops also benefit from gypsum.
“We are seeing a reduction in mold problems because the water is able to move into the soil,” he says.
USDA/ARS National Soil Eroision Lab at Purdue University research indicates that gypsum also offsets the impact of aluminum toxicity in low pH soils, helps curb phosphorus runoff and increases iron uptake by reducing the detrimental effects of bicarbonates.
Some seed companies, such as Beck’s Hybrids, are conducting field research to determine whether the various soil benefits from gypsum also support increased crop yields. To date, the data shows mixed results.
Brown has used gypsum for eight years. While he says he saw some benefit from gypsum his first year of use, the soil quality benefits have improved steadily over time. A side payoff, he notes, is that his fields containing gypsum are easier to harvest in wet conditions.
“It helps keep these heavy soils from coating the tires of our combine and other equipment as much because they aren’t as sticky,” he says. “That’s a great thing when you’re harvesting in wet, muddy conditions like we were last year.”
Brown says he applies gypsum annually at a rate of 1 ton/acre to select fields post-harvest. He uses a lime spreader to make the application.
“It’s the very last thing we do each year in the fall,” he says.
The gypsum he purchases from a local power plant, contains roughly 16 percent sulfur and 22 percent calcium. The moisture content is roughly 6 percent.
“It has the consistency of baking soda,” Brown says.
Cost-wise, Brown says he pays between $9 and $14/ton for the product.
“What we pay depends on the year and how much the power plants have available,” he explains, adding that the construction industry also uses the product to make wallboard.
To keep costs down, Brown loads and transports the gypsum to his farm. He uses a polyurethane liner in the semi-truck to help contain the product and make it easier and faster.
Because the country remains reliant on coal-fired plants, farmers can expect to have access to a large, steady supply in the years ahead.
The federal government encourages farmers’ use of synthetic gypsum to minimize a build-up of the product around plants. A handful of environmental groups are at odds with this decision.
“The power plants used to just throw away the gypsum,” Brown says. “Now that we know it’s useful to our soils, it can be a good deal for everyone.”