Brown patches of dead grass are very unattractive in any landscape, especially if you're trying to improve your gardens. The best way to ensure a vibrant, lush lawn is to dig up the old grass and replant grass seed. Because you're already growing grass in that area, you know the soil is suitable and doesn't need to be amended with compost or sand. It's a matter of digging up the lawn and spreading a new layer of seed. There are several ways to kill the grass--some more environmentally friendly than others.
Use an herbicide with glyphosate as its main ingredient. Push a spade into the ground, cutting a border between the grass you want to keep and the grass you are digging up. Cutting the underground roots between the two will prevent the grass killer from spreading.
Apply the solution with a fine mist spray. Set it to the lowest pressure so the grass killer goes exactly where you want it. Apply it when you know it's not going to rain for eight hours.
Layer newspaper on top of old lawn to kill it in an environmentally conscious way. Lay at least 10 sheets of newspaper on the ground. Make the layers thicker by overlapping the papers.
Put 4 inches of wood chips on top of the newsprint to hold the paper down. Spray them with the hose. The wood chips will kill the grass within a few weeks and the newsprint will break down and become a mulch.
Mow the grass really short if you want to dig up the roots. Put the mower on its lowest setting and bag all the clippings.
Loosen the soil 4 to 6 inches deep with a rototiller. Make sure to dislodge the roots from the compacted ground.
Run a rake over the lawn, picking up the roots and removed grass. Eliminate all other debris, including stones and weeds.
Fill dips and low lying areas in with topsoil. Slope the yard downhill slightly from the house, garage or other structures. This will ensure there isn't pooling water near foundations.
Spread a starter seed fertilizer high in phosphorus. Set the broadcast spreader to the rate specified on the package.
Put the grass seed in a mechanical or hand spreader. Figure out how much seed to use by referencing the package. Spread an even amount to avoid gaps.
Water the new grass seed a few times daily to keep it moist. Do this for the first two weeks. Once it sprouts, reduce watering to once daily.