Controlling Crabgrass with Corn?

Three years ago, I set up two scientific weed control trials, in a home lawn and bare soil, using an organic herbicide made from corn gluten (available commercially from a lawn and garden store), versus corn gluten feed additive obtained from a local feed mill. The reason for doing this was cost. I could buy the corn gluten from the mill for $7.00 per 100 lbs. and the organic herbicide, made from corn gluten, cost $35.00 per 50 lbs. or 10 times as much.

A university researcher, from Iowa, I think, discovered that weed growth was inhibited where corn kernals were lying in the soil in the year following the corn crop. It was deduced that a chemical substance was being leached from the corn into the soil and this was inhibiting weed seed germination. Tests have shown this to be true.

All treatments were replicated 4 times in a randomized complete block design, in plots that measured 10 x 10 feet. I applied the corn gluten herbicides at a rate of 2 lbs. per acre through a shaker jar to evenly distribute the rate over the plot. Untreated check plots were included as part of the randomized trial.

Weeds in the trials were crabgrass and oxalis, in the turf, and common ragweed, and barnyardgrass in the bare soil site. Literature researched on this topic indicated to apply the corn gluten early to give it time to weather into the soil and leach the natural chemical substances that provide control of germinating weeds.

The turf application was made in April and weed control was evaluated at 50 days post treatment. Bare soil was treated in May and evaluated 50 days later in July. Evaluations were made by visual estimation compared to the untreated check plots.

Results show that the corn gluten herbicide was significantly more effective than the corn gluten meal in both trials. The corn gluten herbicide provided significant control compared to the untreated check. Control in turf was 50% and nearly 100% in the bare soil study.

Why the difference in weed control between corn gluten herbicide and corn gluten meal? I speculate it is in the formulation of the product. The corn gluten meal was very coarse-ground whereas the corn gluten based herbicide was very fine and uniform. Thus, there was more particulate surface area to weather and leach into the soil. Coverage was more uniform with the commercial corn gluten herbicide because it had uniform size and dispersed better from the shaker jar.

I did not grind up the corn gluten meal to test my hypothesis. I believe using corn gluten based herbicides can be an alternative to chemical herbicides. Give it time to work, so start early in the spring before crabgrass germinates (before forsynthia petal fall). Corn prices have risen in the past year or two so check with your feed mill before trying corn gluten meal.

A plus to the turf trial, I could see the effect the following season as enhanced green turf. The corn acted as a fertilizer the following year.