Gypsum may improve soil, retain phosphorus

Using gypsum in agricultural production may have a double benefit – better soil structure to promote good crop yields and a reduction in the amount of phosphorus leaving fields.

Both aspects were reviewed Tuesday evening during an educational program at the Seneca County Fairgrounds Pavilion sponsored by the Sandusky River Watershed Coalition.

Gypsum, or calcium sulfate dihydrate, is not a new soil additive, but has been around since ancient times, said Warren Dick, environment and natural resources professor at Ohio State University’s Ohio Agricultural Research and Development Center, Wooster.

“It’s not new,” said Dick, who has been studying the use of gypsum to improve soil health. “It’s maybe rediscovered.”

Although Dick said gypsum has many benefits, better water quality is the reason its use is one of the cost-share programs being funded by USDA’s Natural Resources Conservation Service, said Mark Smith, NRCS state resource conservationist.

The use is one approach to reducing dissolved reactive phosphorus leaving fields.

“The purpose is to improve soil health by increasing infiltration and by improving the physical and chemical properties,” Smith said. “To improve the surface water quality by reducing dissolved reactive phosphorus concentrations in runoff.”

Smith said it’s one approach among many.

“There’s not one silver bullet,” he said. “It’s going to take every bullet in the gun and maybe even the whole cabinet to address the problems we have in Lake Erie and in other parts of the country and in the Gulf (of Mexico).”

Although improved water quality is one reason to use gypsum, Dick said another is to provide calcium and sulfur to crops, particularly corn and forages such as alfalfa, and also to help retain nitrogen in the soil.

“Calcium helps build humus in your soil,” Dick said. “We are beginning to understand more about these two nutrients and their role in improving plant growth and crop yields.”

Another benefit is to improve the physical properties of soil and allow water to better infiltrate from the surface to subsoil.

The calcium in gypsum has been known to bind with phosphorus to reduce the amount of the dissolved reactive phosphorus leaving fields and entering streams on their way to Lake Erie.

“Farmers who have been using gypsum for years are reducing their nitrogen rates because it’s more efficiently taken up,” he said.

Improved soil chemical properties is another plus to using gypsum, Dick said. The result is improved deep rooting of crops such as corn, soybeans and wheat, which leads to better use of water and nutrients in the soil.

“Gypsum will move down through the surface and improve the soil for rooting,” Dick said.

He said gypsum is getting a lot more notice throughout the United States.

“Almost every state in the country is starting to look at sulfur,” Dick said.

As air pollution has been reduced over the years, so was the free sulfur fields received in the form of “acid rain.”