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Gypsum could help keep farm water clean


October 6, 2014
By Ohio State University

Oct. 6, 2014, Wooster, OH — Gypsum, which has roots in the past as a farm soil treatment, may also have a bright future as a protector of water.

Warren Dick, a scientist in Ohio State University’s College of Food, Agricultural, and Environmental Sciences, is two years into a three-year study of gypsum’s benefits on farms, including to soil quality, crop yields and reducing phosphorus runoff.

So far, he said, farm fields in his study treated with gypsum are seeing an average 55-percent reduction in soluble phosphorus runoff, based on tests of water samples collected from the fields’ drainage tiles.

“There’s no one technology that’s going to solve the issue of phosphorus runoff,” said Dick, a soil and environmental chemistry professor in the college’s School of Environment and Natural Resources. “But I think gypsum is going to become one of the tools in the toolbox, something farmers will use with other approaches as part of their total management package.”

Experts say soluble phosphorus runoff from farms is a cause of the harmful algal blooms plaguing Lake Erie and other lakes in recent years. In August, for instance, a toxic bloom in western Lake Erie led to a two-day drinking water ban in Toledo.

Soluble phosphorus is the form of phosphorus most readily taken up by crops and other plants. It’s also the form of concern in Lake Erie — algae thrive on it, too.

Dick’s research is taking place on farms in the Maumee River watershed as well as around Grand Lake St. Marys, which also has suffered from the blooms. The Maumee watershed, located in northwest Ohio, is home to Toledo and is Lake Erie’s largest tributary.

Gypsum, also called calcium sulfate, is a powdery white material. Farmers can use regular spreaders to apply it.

When spread on a field, gypsum binds with the soluble phosphorus in the soil, said Dick, who is also a scientist with CFAES’s research arm, the Ohio Agricultural Research and Development Center. This keeps the phosphorus from running off yet keeps it available to plants.

He said the effect lasts for at least 20 months after treatment, based on his findings so far.

“So you have the best of both worlds,” he said. “The phosphorus stays in the soil and field where you want it, but it’s there for the corn and soybeans and other crops when they need it.”

In an added environmental twist, the gypsum used in Dick’s study doesn’t come from mining, gypsum’s traditional source, but is a byproduct of scrubbing sulfur dioxide from the gas emissions from coal-burning power plants. The process creates millions of tons of gypsum annually. Some of it goes to make drywall. But much of it, for now, lacks a use and ends up in landfills.

The Ohio Coal Development Office and the Electric Power Research Institute, a nonprofit organization funded by the electric power industry, are helping fund the study.