Turf - Late Fall Fertilization

Late November is the best timing for the last fall fertilizer application to turf. The following is an article on the subject from Penn State University.

One of the best ways to maintain a healthy, weed-free lawn, is to provide timely fertilizer applications so the grass can compete with weeds and recover from stress. In our area, the best times to fertilize are late spring (around the beginning of May), late summer-early fall (early September), October, and late fall (late November). Let's take a look at late fall fertilization and why you should make it a part of your lawn maintenance program.

When should late fall fertilizer be applied? Most experts agree that late fall fertilization should take place when foliar growth stops (or slows to the point that turf no longer needs to be mowed), grass is still green, and before the soil freezes. This period usually occurs around Thanksgiving. Application timing may vary from year to year depending on weather conditions.

Why fertilize in late fall? Fall is the time of year when cool-season turf grasses recover from summer stress-related conditions, such as drought, heat, and disease. The cooler temperatures and moist conditions are conducive to good turf growth and provided that plants are properly fertilized in late summer (early September) turf begins to accumulate carbohydrate reserves in stems, rhizomes, and stolons. Carbohydrate reserves help turf resist winter injury and disease and serve as a source of energy for root and shoot growth the following spring.

What are the benefits of late fall fertilizer?

Late fall fertilization helps maintain turf color into early winter without increasing the chance of winter injury and disease.

Fertilizer applied in late fall can also enhance spring green-up without the excessive stimulation of growth that accompanies early spring fertilization. The green-up from a late fall fertilizer application will often last into mid-spring, eliminating the need for early spring feeding. When compared to early spring applications of nitrogen, late fall fertilization increased rooting in spring.

Timing is everything! Studies show that late fall fertilizer does not increase winter injury, snow mold, or annual bluegrass encroachment. However, fertilizer applications made in mid-fall (mid October to early November) while turf is actively growing, may increase potential for winter injury and disease (especially snow mold).

How much fertilizer should be used? For Kentucky bluegrass/perennial ryegrass/ fine fescue lawns and grounds, use 1 pound of soluble nitrogen per 1000 square feet, or 1-1/2 to 2 pounds of slow release nitrogen per 1000 square feet. Controlled release sources like sulfur coated urea and IBDU are good. Nitrogen can be applied alone, or as a part of a complete fertilizer. To avoid potential leaching and runoff problems, use slow release nitrogen on sandy soils. Don't apply any fertilizer to frozen soils.

Most late fall fertilization programs include moderate amounts of nitrogen, phosphorus, and potassium. Both phosphorus and potassium can benefit turf when applied in late fall, but there is no benefit to applying excessive amounts. Application rates should be based on a soil test. Phosphorus is important in root growth and maturation of turfgrasses. Potassium is used by turf in relatively large amounts. It enhances rooting, cold hardiness, disease resistance and wear tolerance.

Adapted from "Late Fall Fertilization: A Prescription for Turf Recovery," by Dr. Pete Landschoot, Department of Agronomy, Penn State University, The Keynoter, Volume 23, No.4.