In dry, disturbed soil throughout the West, a weedy invader from Eurasia has gained a tenacious foothold. Kochia scoparia, also called poor man’s alfalfa, has slender, gray-green leaves that turn an ornamental orange in autumn. Despite control efforts, this weed springs back relentlessly thanks to its bountiful seed bank.
At Pecos National Historical Park in northern New Mexico, a 50-acre mantle of kochia drapes excavated archaeological sites. The National Park Service has teamed up with University of Nevada researchers Scott Abella, Lindsay Chiquoine, and Matt Rader to investigate better ways to control it.
Seeing that kochia is becoming resistant to herbicides, the team’s approach is to boost its natural competitors. After a patch of kochia is weedwacked, native grass and wildflower seeds are planted inside a ball of soil to see whether they germinate better than scattering bare seeds that are vulnerable to animals and weather.
The researchers are also trying to boost microbes in the soil. Microbes compete with plants for nutrients, like nitrogen. Adding simple table sugar to the soil provides carbon to grow more microbes, which might then starve kochia of nitrogen and encourage natives.
Abella’s team next will apply what it’s learned at Pecos to kochia infestations at Tuzigoot National Monument in Arizona.