CASSODAY, Kan. (AP) — Ranchers in the Flint Hills say they are planning to start controlled burns on the prairie this spring.

The burns on the tallgrass prairie rarely happened the last two years because drought conditions made it too dangerous.

Ranchers say that delay has left a lot of grass on the prairie, and they intend to burn it this spring. The burns release nutrients, which provide more nutritious grasses for the grazing cattle. They also help brush and weed control.

The increased burning is raising concerns that it could affect air quality in downwind cities. The Wichita Eagle reports  the state is providing two smoke modeling tools to help ranchers determine how burning might affect air quality in downwind.