Fertilizing Cool-Season Horse Pastures

By Krista Lea

Good pasture management begins with maintaining good soil fertility to promote the growth of desirable grasses, such as Kentucky bluegrass, orchardgrass, perennial ryegrass, and novel tall fescue. Now is an excellent time to review your soil fertility records and make plans for grazing this season.

Soil sampling can be conducted throughout most of the year, but early spring and fall are most common times to do so. Sample only the top four inches of the pasture, and divide large pastures into “sub-pastures” for sampling based on the varying topography.

Phosphorous (P), potassium (K), and lime

• P and K promote plant growth and longevity, but plants don’t use lime directly. Rather, lime adjusts soil’s pH, making other nutrients more available for the plants to use.
• Soil tests can help determine whether you need to apply P, K, or lime (and other nutrients), and applications might not be needed annually. High-traffic areas might not require P or K as it is recycled in animal manure.
• P, K, and lime can be applied at any time of the year, as long as the weather is cooperative.

Nitrogen applications

• A spring nitrogen application is generally not needed for cool season horse pastures because grass growth is naturally rapid in the spring. However, farms that have high stocking rates and intensive grazing can benefit from light nitrogen applications in early spring.
• In the fall, apply nitrogen in two applications (30-60 pounds per acre each time) to prolong fall pasture growth and prepare plants for overwintering. Well-fertilized pastures will survive winter better and will green up sooner in the spring.
• Only fertilize in the summer if harvesting hay or managing warm season grasses, such as bermudagrass. Be sure to apply it on cool days or use nonvolatilizing nitrogen sources such as ammonium nitrate.

While it’s not required to restrict grazing access to recently fertilized pastures, good horsemanship and pasture management suggests giving fields a week of rest or a good rain before returning animals to the pasture. For more information, see Soil Sampling and Nutrient Management (AGR-200) at uky.edu/ag/forage.