Corn gluten meal is a powdery byproduct of the corn milling process. Originally used as a supplement in hog feed, corn gluten meal has become a common organic alternative to synthetic chemical herbicides. It can be effective as a pre-emergent herbicide used to control crabgrass and other lawn weeds, and it also has nutritional properties. Corn gluten meal is about 10 percent nitrogen by weight, meaning 100 pounds of corn gluten meal contains 10 pounds of nitrogen. This organic source of nitrogen is slowly released over a three- to four-month period.

How Corn Gluten meal Works

Corn gluten meal does not prevent weed seeds from germinating, but it does inhibit those seeds from forming roots after germination This means that applications must be very carefully timed. When the application of corn gluten meal is timed correctly, crabgrass seeds germinating will form shoots but not roots, and will therefore die, provided there is a short dry period after seed germination. However, if conditions are too wet immediately after seed germination, the weed can recover and establish a root.

Application Timing

Corn gluten meal is useful only as a pre-emergent herbicide; it provides no post-emergent weed control. If crabgrass and other weed seeds have already germinated and taken root, a late application of corn gluten will only serve as fertilizer for the weeds. Further, applications of corn gluten meal need to be precisely timed around rainfall or watering. After application, corn gluten meal needs to be watered in, either by rainfall or by artificial watering, within five days of application. Rainfall of about 1/4 inch, or a comparable artificial watering, is ideal. After this, a dry period of one or two days is required to prevent weed seedlings that have germinated from growing roots.