At a test on September 2nd, 2019--an untreated lawn was heavily infested with crabgrass. One sqft plots were treated with Drive, and then immediately seeded with annual rye. One teaspoon per sqft--about 10 pounds per thousand sqft--and 2,3 or 4 teaspoons. Day temperatures were about 75 F. and the plot was not irrigated--although some rain occurred. The crabgrass faded out and the annual rye took hold most densely where the seed rate was very high.