UNIVERSITY of Illinois Extension horticulture educator Kelly Allsup said it is becoming increasingly popular to use corn gluten meal as an organic weed preventer and nitrogen source.
Typically sold as a feed ingredient, homeowners and horticulturalists have discovered that the product is fairly effective at controlling weeds in lawns and as a fertilizer for established grass. Allsup said the success of using corn gluten meal depends on a number of environmental factors centered on application timing.
The application must be done before weeds germinate, since plants that have already germinated will not be controlled. Similarly, Allsup said the product must contain at least 60% protein to be effective, and applying it soon after a rainfall will reduce its effectiveness.
Iowa State University scientist Nick Christians, speaking at a symposium in Memphis, Tenn., last year, told horticulture experts that he discovered corn gluten meal as a growth regulator through a series of experiments in the late 1980s examining the effects of five corn derivatives on the survival of potted creeping bent grass.
In subsequent field tests, he found that applying 20 lb. of corn gluten meal per 1,000 sq. ft. in the spring, with a second application in late summer, controlled 60% of weeds in the first year, 80% in the second and 90% in the third.
Christians said his research showed that corn gluten meal is an effective pre-emergent herbicide that suppresses other grasses and broadleaf weeds, including lambsquarter, dandelion, foxtail, purslane and redroot pigweed. Growers can use it for controlling weeds in backyard gardens as well.