Gypsum helps fertilizer enrich corn instead of algae

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Ohio State scientist Warren Dick, right, says a byproduct of coal-burning power plants called FGD gypsum, shown here in the foreground, can be used to improve farm soils, crop yields and Lake Erie. Photo: K.D. Chamberlain

Ohio State scientist Warren Dick, right, says a byproduct of coal-burning power plants called FGD gypsum, shown here in the foreground, can be used to improve farm soils, crop yields and Lake Erie. Photo: K.D. Chamberlain


An abundant byproduct from coal plants may help fight Lake Erie algae.

The stuff is technically called fluidized gas desulfurization gypsum. It is produced when lime reacts with sulfur dioxide in coal-burning power plants.

Gypsum has been mined for centuries, but the synthetic form is cheaply and abundantly produced in these plants.  It improves soil by preventing valuable phosphorus from washing off of fields and into lakes and rivers.

Applying gypsum to fields can reduce runoff by 40 percent to 70 percent, said Warren Dick, a soil biochemist at Ohio State University.

Soluble phosphorus is found in manure and other fertilizers commonly used at farms surrounding Lake Erie and the rivers and streams that drain into it. When rain washes those fertilizers into the water, they fuel Lake Erie’s toxic algae growth.

Such algae is toxic to fish and wildlife and can alter water chemistry, expanding Lake Erie’s dead zone, Echo recently reported.

Dick and a team of researchers are studying how gypsum application could prevent runoff into the Maumee River watershed, which flows through two thirds of Ohio’s farmland and eventually into the Maumee Bay of Lake Erie.

“There’s a growing interest now in farming with gypsum,” Dick said. “It’s been making a comeback in the last 15 years. But it’s not a new concept. The founding fathers were using gypsum as a fertilizer.”

water runoff, using  gypsum

Runoff from fields that have been fertilized with gypsum are visibly less polluted than those left untreated. Photo: Warren Dick.

Dick’s Maumee watershed study has been slow going, since last year’s drought made it difficult to gather enough viable water samples. His team applied one ton of gypsum per acre on farmland near the Maumee watershed.  There is a clear difference between water runoff from fields treated and untreated with gypsum.

“It’s a win-win,” he said. “One problem is phosphorus causing those algal blooms. But another problem is that phosphorus is a great fertilizer, and farmers want it to remain in the soil. Gypsum binds with that phosphorus and helps keep it where it belongs.”

When gypsum and phosphate bind together in the soil, they create calcium phosphate, a much less soluble form of phosphorus that is therefore less likely to run off, Dick said.

“The gypsum brings together fine soil particles, which then require more energy to erode,” he said. “It also keeps pores of soil from getting clogged, which means the soil can absorb that phosphate.

“It’s not sitting on the surface of the soil, ready to run off the next time it rains,” Dick said. “It stays in the field and remains available as a fertilizer.”


Samples of water runoff taken from farmland treated and untreated with gypsum. Photo: Warren Dick.

Gypsum application hasn’t been a part of Ohio farmers’ regular farming routine, said Joe Cornely, director of corporate communications for the Ohio Farm Bureau.

It’s still in the research phase, agreed Mark Burrs, public information officer for the Ohio Department of Natural Resources.

“Of course we support the continued study of gypsum and we think it’s a great idea,” he said. “But it hasn’t really gone beyond research.”

Dick said he hopes Ohio farmers will eventually be willing to put his work into practice.

“A lot of times to get farmers to do something good for the environment, you have to use a big stick or a big carrot,” Dick said. “In other words you have to promise more money or threaten the loss of it.

“I’ve seen a growing interest in this, without financial incentive,” he said. “It can really enhance soil quality on a farm.”

Dick’s Maumee watershed study is ongoing. In addition to the continued collection of water and soil samples, his team will soon compare crop yields from treated and untreated fields.



5 thoughts on “Gypsum helps fertilizer enrich corn instead of algae

  1. Bonnie,

    As I recall my general chemistry, the general rule is that salts of strong acids do not hydrolize to form the acid again. In other words sulfate plus water does not- under normal circumstances- produce sulfuric acid. Having said that, the salt of a strong acid, can produce a slightly acid environment in the presence of a weak base. In simple english, one could get some acid if the conditions are right, but it probably is not a huge deal because of all of the natural buffering likely to be going on in this situation.

    My gut says that both Harold (watch out for what else is in this stuff) and Brett (the phosphate may not be worth much to farmers) raise good points.

  2. Thanks Brett – a lot of that is helpful, but not an answer to my question as to the fate of the sulfur. Anybody? Mr. Dick?

  3. Arg, water being discharged from a subsoil drainage line is not “runoff.” Runoff is water moving across the soil surface that can cause erosion. It can carry soil particles with phosphorus attached into streams and lakes. Using gypsum could potentially reduce runoff (will not prevent) by improving soil flocculation and allowing water to infiltrate rather than run across the surface. Thats the story. Farmers may benefit from gypsum if their crops are in need of calcium and/or sulfur, two plant-essential nutrients. Creating calcium phosphate would likely happen irregardless of the addition of gypsum and is theoretically detrimental to farmers because plants cannot use calcium phosphate.

  4. #1 FGD = FLUE (“not fluidized”) gas desulfurization
    #2 FGD scrubs sulfur dioxide out of the flue gas which reacts with the lime to produce calcium sulfate (gypsum). If, in this application, the calcium sulfate reacts with phosphate to form calcium phosphate, what happens to the sulfate/sulfur? If it goes in the runoff water as sulfate (SO4) then it will end up as H2SO4, sulfuric acid, which can’t be good.

  5. But what else is in this coal-burning by-product? Like sewage sludge application to farmland, is this just another scheme to cheaply dispose of a partially contaminated waste?

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