In recent years, we’re produced a number of No-Till Farmer articles on the benefits of utilizing gypsum to improve plant nutrition and soil structure. Now, new research from Ohio State University indicates gypsum may play a key role in controlling the harmful algal blooms that are a growing concern in Lake Erie, the Chesapeake Bay, the Mississippi River and the Gulf of Mexico.
Blamed on fertilizer and nutrient runoff, dead-zone problems in the Gulf of Mexico can create an oxygen-free zone that in some years can be as large as 8,000 square miles where fish can’t survive.
Coal Plant Byproduct
Warren Dick has found that an abundant byproduct from coal-burning power plants could help control these harmful algal blooms. The soil biochemist has found that appling fluidized gas desulfurization (FGD) gypsum to corn and soybean fields can reduce the amount of soluble phosphorus being washed away from the soil by heavy rains and into waterways.
Dick says the product comes from the air-emission scrubbers at coal-burning power plants. These scrubbers remove sulfur dioxide from the plants’ exhaust emissions, creating a gypsum byproduct that would otherwise be lost to acid rain. The powdery product resembles flour and costs $35 to $50 per ton spread on the field, with a typical application of 1 or 2 tons per acre every second or third year.
Dick says excess soluble phosphorus is the primary cause of the toxic algal blooms that have plagued a number of bodies of water in recent years. The phosphorus comes from fertilizer and manure runoff from farms, sewer overflow from storms, discharge water from wastewater treatment plants and leaking septic systems.
“Gypsum can cut the amount of soluble phosphorus running off soils by 40% to 70%,” he says. When spread, it binds in the soil with phosphorus to produce calcium phosphate. This keeps soluble phosphorus from running off soils and getting into bodies of water.”
Gypsum also interacts with nitrogen, which improves efficiency. “It improves the soil structure and improves aeration and water infiltration, which reduces runoff,” says Dick. “It allows water to move into the soil, but doesn’t keep the soil waterlogged so air can move into the soil and allow the crops to grow well.”
Dick has documented a nearly 7% increase in corn yields and an 18% jump in alfalfa tonnage from using gypsum. Gypsum can increase no-till corn yields by about 5 bushels an acre and lead to a quick payback with an application every 2 or 3 years.
Gypsum also provides sulfur. “If you harvest huge amounts of alfalfa, corn or soybeans, you’re removing a lot of sulfur. If you never put anything back, eventually you’ll run deficits,” Dick says.
Especially with heavy clay soils, using gypsum in a no-till system can reduce soil erosion, boost carbon sequestration in the soil and help farmers spend fewer dollars on tillage equipment and fuel.