How Corn Gluten Meal Works
Corn Gluten Meal (CGM) is a by-product of the corn wet milling process that contains the protein fragment of the corn. Patented in 1991 by researchers at Iowa State University, Corn gluten meal is considered a non-toxic natural alternative to synthetic pre-emergence herbicides. But the chief question is, does it really work? And if so, how?
Corn gluten meal inhibits the formation of roots of germinating plants primarily by desiccation. CGM will not kill existing weeds. As a matter of fact, CGM contains 10% nitrogen by weight. Meaning, if you apply it to an existing stand of weeds you'll just be encouraging their growth. CGM should be applied before any germination of weed seeds. You will also need a bit of luck on your side as corn gluten meal needs a dry period after the weeds have germinated to thoroughly kill the germinating weed. If there is an extended period of moisture in the soil after germination, the weeds will continue to form roots and grow on.