AMES, Iowa (AP) — An agronomy professor at Iowa State University is developing a way to determine how much soil is lost from farm fields from sudden heavy rain. Downpours can create what is called ephemeral gullies — temporary washouts that carry valuable topsoil from fields. Agronomy professor Richard Cruse is leading a U.S. Department of Agriculture National Integrated Water Quality Program project to study the issue and develop better ways to control such erosion.

Global studies show that the world’s cropland is losing topsoil faster than new soil is forming, reducing cropland’s fertility. Such erosion also increases the amount of phosphorous and nitrate carried into streams, lakes, and rivers. Cruse says the land’s ability to retain water also decreases as more sediment is washed down a river leading to even more erosion.