Safe Lawn is an organic herbicide made from corn gluten meal. Applied in spring and fall, it works as preemergent weed control by preventing germinating weed seed from developing root systems. Safe Lawn does not kill existing weeds but can reduce their population over time. This product is sold as a natural alternative to chemical herbicides because it doesn't contain any ingredients that can harm animals or people.
Corn Gluten Meal
Safe Lawn is made with 100 percent corn gluten meal. Corn gluten meal is a by-product of wet milling corn, which is the process used to make corn syrup and cornstarch. This waste product is also used in animal and fish foods because it is high in protein. According to the Northwest Coalition for Alternatives To Pesticides, corn gluten meal does not directly kill weeds, but it makes newly germinated roots more prone to dehydration. In order for it to be effective as an herbicide, corn gluten meal has to be applied before weeds germinate and then deeply watered in. The topsoil must be allowed to dry completely so the seeds that germinated from the watering die from lack of moisture. The Safe Lawn product label claims that corn gluten meal prevents germination of grasses like crabgrass, Bermuda grass and foxtail as well as common weeds like clover, dandelions and smart weed.
Corn gluten meal is 9 to 10 percent nitrogen, making it an effective weed and feed product. Since grass is primarily foliage, it is a heavy nitrogen feeder. Nitrogen contributes to healthy photosynthesis and vigorous foliar growth. Researchers at Oregon State University were unable to replicate the original Iowa State University experiments that showed corn gluten meal to be an effective herbicide, and they found that Safe Lawn did not significantly control weed populations over two years. They did find, however, that the high nitrogen content in corn gluten meal contributed to healthy, lush grass growth which perhaps helped the grass compete with the weeds. Even though the heavy dose of slow-release nitrogen contained in Safe Lawn is good for the grass, the nitrogen still converts to nitrates that can leach into the groundwater. The Oregon State University Extension Service also warns that corn gluten meal can attract rodents and suggests that other organic methods of weed control be used.
Corn gluten meal contains 60 percent protein. In a 1994 study published in the "Journal of Plant Growth Regulation," researchers discovered that it is corn gluten hydrolysate, a protein in corn gluten meal, that is toxic to newly germinated root systems. Other research is underway at Iowa State University Department of Horticulture to isolate herbicidal proteins in corn gluten meal and make them available to the public in spray form. Although corn gluten meal is perfectly safe for people and animals, the NCAP points out that this herbicide can cause allergic reactions in people who are hypersensitive to corn if they inhale dust from the product or get in on their skin. According to the magazine "Gluten Free Living," corn gluten meal does not contain proteins that affect people with sensitivity to the gluten in other grains.