Gypsum, which has roots in the past as a farm soil treatment, also may have a bright future, and not just as a booster of crops but also 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% 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. The practice was demonstrated and discussed at CFAES’s 2014 Farm Science Review trade show in September.
A September 2014 workshop involving CFAES scientists, called Healthy Soils for Healthy Waters, which spent its third day at Farm Science Review, also featured gypsum among on-farm solutions for phosphorus runoff. Details on that event are at go.osu.edu/qUz.
When spread on a field, gypsum binds with the soluble phosphorus in the soil, said Dick, who also is 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.”
He said gypsum also provides two yield- and soil-friendly nutrients:
Sulfur, an essential crop nutrient increasingly in short supply in some soils, especially ones used to grow corn.
Calcium, also an essential crop nutrient, which can also prevent soil surface crusting, loosen the soil, and improve air and water infiltration.
Previous research by Dick on gypsum has found it can increase yields of both corn and alfalfa, sometimes by up to 50% or more.
Gypsum’s use to improve and enrich the soil dates back to the Greeks and Romans. Benjamin Franklin was an early U.S. proponent.
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.