Moss that grows in a lawn is a common problem that indicates less than adequate conditions of the lawn. To completely eradicate moss, these conditions must be identified and changed. If you remove the moss without pinpointing the underlying cause, it will grow back, even if the area is reseeded with grass seed.
Poor Soil Quality
The presence of moss in a lawn is an indicator that the soil is too acidic. A soil test should be conducted to verify a high pH. Lime is often used to cut down on the acidity, according to the Oregon State University Extension, although correcting for acidity alone will not get rid of moss. After correcting the pH, destroy the moss by spraying the area with ferrous ammonium sulfate and iron sulfate.
Another problem contributing to moss is poor soil nutrition. One remedy is to ensure the lawn receives regular fertilization, especially adequate amounts of nitrogen, specifically in the spring and late fall. Ensure the lawn is aerated regularly as well to cut down on soil compaction.
Soil with poor drainage contributes to moss, which thrives in wet conditions, according to "Jerry Baker's Green Grass Magic." Poorly draining lawns can be fixed by ensuring the lawn is graded away from any structures, and by installing a gravel-filled drainage system with underground flexible drainpipes to move the water from the lawn.
Too Much Shade
Moss thrives in shady areas. One way to correct this problem is to remove or prune trees and shrubs that block sunlight. It is possible, however, to leave trees and shrubs where they are and change other conditions, such as poor drainage and acidity to solve a moss problem. If moss is eliminated in the area, then shade-loving grasses can be planted in the spot without removing trees.