When moss grows among lawn grass, it makes the lawn look uneven and unkempt. Controlling the moss is easier than you may think. Several products are at your disposal for ridding your entire lawn of this nuisance plant. You can easily apply these products without worry that you will kill your grass. For moss to stay away, however, you must take additional measures to improve the quality of your lawn.
Put on rubber gloves and a pair of safety glasses. Pour spray-on moss killer (or a fertilizer containing moss killer) in a garden sprayer. Follow the label directions carefully -- most come in concentrated formulas that must be diluted with water. Apply this first in early spring, if moss has already developed in your lawn.
Spray every area of the lawn upon which moss is growing (unless using it with fertilizer -- in that case, spray the whole lawn and not just patches).
Rake the lawn the following day, when the product has dried. The purpose of this is not only to rake out dead moss, but to help dethatch your lawn. According to gardening.wsu.edu, raking the soil and getting rid of thatch keeps moss from returning.
Bring a soil sample to your local extension office (some gardening centers also offer testing for a small fee) to have it tested. Bryophytes.science.oregonstate.edu advises that lawns with a nutritional imbalance provide a better environment for moss growth. By bringing your lawn back into balance -- through amending the soil -- you may prevent future moss growth. The products you should use depend on how poor the soil is and what kind of grass you have.