Remove unnecessary shrubby undergrowth as well. When moss occurs in a sunny location, consider fertilization practices. Even low-maintenance lawns need one or two fertilizer applications a year to grow well. In some cases the soil may be compacted and need aeration as well. Soil testing will provide the soil pH. Grass grows optimally at a pH of 6.8 to 7.2 which is close to neutral.
Many people automatically assume the soil is acidic when moss occurs and want to add lime.
Iowa generally has alkaline soils and liming can make matters worse. A soil test will eliminate the guesswork. Materials, such as copper sulfate, do eliminate moss in lawns. Use these products according to the label directions. However, copper sulfate only cures the symptom, the moss.