Keeping your lawn lush and green is not always as easy as it looks. Any number of problems, including moss, will affect the health of the grass negatively. The conditions that moss requires to thrive are opposite that of grass. You can get rid of moss and reinvigorate the lawn by reversing the soil conditions.
Moss thrives in moist, shady areas and prefers compacted, acidic soil. According to Clemson University Cooperative Extension Service, it is not true that moss kills grass. Moss grows where there is no grass. When a lawn is sparse and struggling, moss is more likely to flourish. The first step in ridding an area of moss is to loosen compacted soil. Clemson suggests, in determining if the ground is truly compacted, that a soil probe should be used to remove sample plugs of soil. A metal pipe with a 1/2- to 3/4-inch-diameter can be used. Clemson also said that the probe should be able to go into the soil 4 to 6 inches without much effort. Check the samples for small, white grass roots. If the soil is compacted, the grass roots will be shallow.
Rake the mossy area vigorously and remove as much as possible. If the ground is compacted, aerate the soil. The Clemson Extension Service said an inexpensive spading fork or manual sod- coring tool can aerate soil effectively. If the area is large, rent a power-driven core aerator from a lawn and garden center or hire a lawn care service to aerate the soil.
University of Illinois Extension's Lawn Talk (see "References" below) says if moss is growing, you can assume the lawn lacks essential nutrients. Take a small sampling of soil to the local county extension office and get a pH test. If the soil lacks necessary nutrients, the extension office or other lawn and garden store specialist can offer advice in the most effective fertilizer for the conditions, depending on what region you live in.
After the moss is gone, apply ground limestone to counteract the acidic conditions in the soil that can inhibit grass growth. Grass grows best in soil with a pH value between 6.5 and 7.0. Ask the extension agent or store specialist how much lime to use on a lawn the size of yours.
Reseed the bare area. Do this well after liming the area to prevent killing the young seedlings. Sow a generous amount of grass seed over the bare area. Cover the seeds with about 1/4 inch of loose soil; water regularly until the seedlings take root. If an area gets less than four hours of sun a day, grass is not likely to do well, so a shade tolerant ground cover might work better.
Once the problem of compacted, acidic, nutrient poor soil is addressed, the lawn will be healthier. This coupled with more sun and less moisture should eliminate moss problems completely.