If your grass is in really rough shape, it may be easier to kill it and start over than to try to rehabilitate the lawn. Before you get to that fresh start, it will take a bit of effort to eliminate the old grass. Grass can be killed in an number of different ways, both chemical and orgainic. Whichever way you choose, once the old grass is gone, you can create a healthy, thick lawn with proper mowing habits, watering and fertilization.
Apply a herbicide containing glyphosate using a low-pressure sprayer. Only apply the herbicide when there is no rain forecast for the next eight hours.
Cut a border between any grass you want to keep and the grass you want to kill. Push a spade into the ground, severing the underground roots between the two areas. This will keep the grass killer from spreading through roots from the grass you are eliminating to the good grass, according to Colorado State University Extension.
Lay down newspaper for a more environmentally-friendly way to kill grass. Put at least 10 sheets of newspaper down on top of the grass you want to get rid of. Overlap the pieces to make it even thicker.
Layer 4 inches of wood chips on top of the newspaper. This will weigh down the paper. Moisten the chips to keep them in place. The newspaper will decompose and become a mulch of sorts, according to CSU Extension. Use this method in the fall and your grass will be dead by spring.
Grow New Grass
Level the planting area. Fill in any dips with topsoil and rake until smooth.
Apply a starter fertilizer that is high in phosphorus. Read the packaging to determine the rate to set the broadcast spreader.
Fill a mechanical spreader with grass seed. Determine how much seed by referencing the package. Use a hand spreader if you're seeding a small area. Apply an even amount to avoid overcrowding or gaps.
Put a sprinkler on the oscillating setting. Water the seed a few times daily to keep it moist for two weeks. Don't oversaturate the ground, advises Greenview, a Pennsylvania-based grass seed company. After the seed sprouts, reduce watering to once a day.
Mow the grass when the blades are 3 inches tall. Cut them to a height from 2 1/2 to 4 inches, depending on the variety of grass you are growing. According to the Texas A&M University Turfgrass Program, grass cut the appropriate height will grow more densely, providing shade at the roots and preventing weed seeds from germinating.