Q: The soils in my horse pasture have a very high level of clay. Areas that my horses use a lot get very compacted. If I want to reseed a compacted area what steps would I take so the grass will grow?
A: Compacted soil resists absorption of water, restricts movement of air around the roots, and produces a physical barrier to the development of roots. Research from Montana State University suggests soils were not compacted by horse hooves when horses were grazed for short periods of time. Longer term changes in soil compaction may result from repeated or continuous grazing. If you are experiencing compaction from horses, it should only be surface compaction and if your pasture if getting sufficient rest, the compaction should be minimal.
On average, pasture areas need 30 days of rest between grazing periods of approximately 7 days. The rest period allows the pasture to rest and regrow. The rest period can also be beneficial to horse owners. It allows time to mow, fertilize (if needed), drag and chemically control weeds (if necessary).
If resting the pasture area doesn't seem to help, aerification should. Aerification relieves soil compaction and increases water and oxygen infiltration into the soil. Aerification is best done in the cooler weather of late summer (August 15 to September 15). Aerification is done with an aerifier. An aerifier is a machine which removes plugs of soil, leaving holes about a half-inch in diameter and up to 3 inches deep. The cores of soil are typically left on the soil surface to gradually break down and filter back into the grass. If you have a large pasture, aerification might not be practical. An aerifier can be rented or hired through a lawn service.
When trying to establish a pasture in a compacted area, first take a soils test. Fertilize the area as needed, aerate, then drag your seed (or use a slit seeder) into the ground. If severe compaction is observed, tillage (such as plowing or disking) may be needed. Remember that unless you change your practices (like giving the pasture rest), compaction will continue to occur.
By Krishona Martinson, PhD, University of Minnesota