Short answer: A little bit. It simply affects young seedlings from developing root systems (SOMETIMES). As a Fertilizer it will add nitrogen to the lawn to green it up. It is not considered a slow release fertilizer, it greens up fast and fades away fast too. As a Crabgrass Management tool, it needs to be a registered product for this purpose. It must be applied at double the rate to get any benefit for crabgrass prevention. Dr. Christian’s studies and others, show it takes 2-3 years of applications to get to about 50-60% control of crabgrass. THAT’S REALLY LOW, and not normally noticeable since crabgrass plants can easily put out hundreds of seeds per individual plant, every year! You can read more about corn gluten here.