Gypsum performed best in a USDA study that examined the ability of soil additives to control phosphorus runoff from farm fields into waterways.

During the study, Agricultural Research Service scientists examined how well gypsum, alum and ground-up wastepaper curbed phosphorus leaching from farmland near Kurten, Texas.

The results show gypsum, a soft mineral, was the only one of three soil additives that reduced soluble phosphorus in a field that contained more than 10 times the amount of phosphorus normally present in soils.

Commonly found in sedimentary environments, gypsum also is a byproduct of coal-burning operations.