Seed slitters, also known as slit seeders, are the most effective tools for re-seeding heavily damaged or neglected lawns. Without the help of a seed slitter, planting areas must be tilled, killing the existing grass. But a seed slitter deposits grass seed in shallow slits in the soil increasing soil-seed contact without destroying the existing lawn. Seed slitters do, however, damage the existing grass' root system. To ensure that the grass recovers quickly, wait until the beginning of the grass' growing season to reseed.
Remove any rocks, branches and debris from the lawn.
Dig up all weeds by hand and be sure to remove their root systems. You will not be able to treat the weeds or tread on the lawn while the new seed is germinating.
Cut the top third of the grass the day before you re-seed.
Water the lawn deeply the day before you use the seed slitter. One to two inches of water will hydrate the grass' roots and help it recover from the seed slitter's blades more quickly.
Fill the seed slitter's hopper or box with seed. Your seed slitter's manual manual will contain the recommended application rates for most types of grass seed.
Set the seed slitter's grass seed hole size (if present on your machine) to the appropriate size for the type of grass seed you are using (dictated by the manual).
Set the slit depth adjustment (if present) on your seed slitter to make 1/4 inch slits in your lawn.
Locate the seed rate adjustment lever (refer to the manual for its location) and set it to broadcast seed at half of the rate recommended for your lawn. The seed application rate can be found in the "seed rate chart" in your seed slitter's owner's manual.
Engage the seed slitter's engine and make your first pass over the lawn, moving in straight rows as you would with a lawn mower. Start the seed slitter at its lowest speed and shift up gradually until you reach a comfortable speed (ideally between 3 and 5 mph). Lift the seed slitter's tines out of the soil while turning at the end of each row.
Make a second pass over the lawn, at a 45 degree angle to the first, to broadcast the other half of the seed.
Push a lawn roller over the lawn immediately after the seed slitter. This will seal the holes made by the seed slitter.