Gypsum for Phosphorus Runoff Reduction

Part of our work to find ways to limit agriculture’s impact on water quality involves an unlikely product: gypsum.

Used commercially to make wall board, gypsum is also spread on farmland to improve soil productivity (particularly sulfur-deficient soils).

Sand County Foundation is partnering with industry and academia to test the potential of Flue-Gas Desulfurization (FGD) Gypsum to do more than just improve soil. We’re evaluating its ability to reduce farm run-off and improve water quality.

FGD Gypsum comes from an unusual source. It’s a byproduct of scrubbing the exhaust systems of coal-fired electric power plants. This gypsum is nearly identical to mined gypsum, and is believed to bind with phosphorus, a common fertilizer applied to farm fields.

Wisconsin is the ideal place to test how spreading FGD Gypsum on fields can reduce phosphorus run-off. The state is home to more than 1.25 million dairy cows producing manure that is rich in phosphorus. Even when properly applied to cropland, manure and phosphorus can reach surface waters during snowmelt and heavy rains.

The goal is to keep phosphorus (beneficial for growing corn, soybeans and alfalfa) on farmland and out of the water where it can lead to harmful algae growth.

Our work takes place on farms on three paired test sites in the Milwaukee River watershed.

Sand County Foundation manages field research activities as part of a project team that includes Electric Power Research Institute, Milwaukee Metropolitan Sewerage District, We Energies, University of Wisconsin's College of Agricultural and Life Sciences' Department of Soil Science, Gypsoil and Water Resources Monitoring Group, LLC.

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