Moss tends to thrive in damp, shaded areas. In addition, acidic soils and overgrazing of competitive grasses increases the chances of moss growth.
While there are chemicals such as ferrous ammonium sulfate or ferrous sulfate that can be applied to reduce and eliminate moss growth in pastures, they are expensive and may only temporarily solve the problem unless other pasture management techniques are implemented.
If the soil is extremely damp, you may want to try implementing a drainage system in that location. In addition, planting a grass that is tolerant to moist soil will help compete with the moss.
A soil test will help determine whether you need to apply fertilizer or lime to the soil. Moss tends to thrive in infertile and acidic soil. By improving the soil quality, you will help the grasses compete with and crowd out the moss.
Finally, ensuring that the pasture is not overgrazed will go a long way to preventing moss growth. The pasture forage should never be grazed below 3 to 4 inches. In addition, large livestock should be isolated from wet pastures so that they don't compact the ground. Practicing a rotational grazing system will help to prevent overgrazing.
If the pasture is extremely poor, it may be necessary to renovate it by working the soil, applying the proper nutrients (from the soil analysis recommendations), and reseeding. Consider contacting your local Cooperative Extension office for more advice on performing a soil test and the best seed mix for your area. To find your county Extension office, go to:
For more information on pasture management for horses, take the eXtension HorseQuest Learning Lesson Equine Pasture Management
Also, watch the Web cast by Dr. David Freeman titled Pasture Management for Horse Acreages