When it comes to effective weed management, the time of the treatment is of the utmost importance. It should be applied between the end of March and the middle of April, at least three to five weeks before the seeds of the crabgrass begin to germinate. It should be uniformly distributed on the grass at a rate of 20 pounds per 1,000 square feet, and then a gentle misting of water should be used to work it into the soil.