August 14, 2002

LINCOLN, Neb. — Homeowners can renovate drought-damaged lawns and fertilize cool-season turf grasses this fall to ensure healthy lawns next spring, a University of Nebraska horticulturist said.

Fertilizing during fall's cooler temperatures stimulates root growth and encourages rapid carbohydrate production, said Anne Streich, horticulturist in NU's Institute of Agriculture and Natural Resources. It also increases shoot density, improves turf color and thickens lawns to reduce weed encroachment.

"The cooler soil temperatures allow the cool-season turf grasses to utilize nutrients better and establish a decent food reserve," Streich said. "As a result, lawns fertilized in the fall will green up earlier next spring than those that weren't."

Streich cautions homeowners to apply fertilizer only to green, actively growing cool-season lawns in the fall. Wait to fertilize dormant lawns until grass greens up with cooler temperatures and increased moisture, she said.

Lawns thinned by drought may need to be overseeded before applying fertilizer. Overseed when air temperatures are 60 to 75 degrees during mid-August through mid-September, Streich said.

"It's important not to seed too late, since newly planted or overseeded lawns need a month of good growing conditions to survive the winter," she said.

It's also important to get good seed-to-soil contact to prevent the seed from germinating in the thatch and dying, she said. Power raking or aerating lawns create spaces for seeds to contact the soil, she said.

Overseeded lawns need to be irrigated two to three times a day with an eighth inch of water to moisten soil and prevent seeds from drying out, she said. Overseeded lawns also can use fall fertilization with reduced nitrogen during the first application, she said.

For green, actively growing lawns, Streich recommends two fertilizer applications when temperatures are cooler, since applications to turf already stressed by warm weather can magnify problems.

The first fall application helps lawns recover from summer stresses and should be in mid-August to mid-September when air temperatures are 60 to 75 degrees, she said.

"Some root recovery will happen during this early fall application," she said. "It's important not to apply too much nitrogen at this time because all the other benefits will be erased by excessive leaf growth."

Most cool-season grasses, such as Kentucky bluegrass and tall fescue, need 0.75 to 1 pound of nitrogen per 1,000 square feet for the first fall fertilization, she said.

The final application should be timed with the last mowing in mid-October to mid-November when top growth ceases but the grass is still green. Apply 1.5 pounds of nitrogen per 1,000 square feet for the last fall fertilization, she said.

Streich recommends using granular products with a mix of slow- and fast-release fertilizers for uniform growth. Homeowners can split the application and apply each half with a drop spreader, crossing the lawn in perpendicular directions for an even application, she said.

"If you accidentally miss 6 inches, you won't have streaks in your lawn since you'll be coming back across," she said.

During the fall, lawns need to be watered deeply and infrequently, Streich said. Watering about 1 inch per week, including natural precipitation, will promote deeper root systems, she said.

Local NU Cooperative Extension offices, nurseries and garden centers can provide more information on fertilizing cool-season grasses.

For more information on overseeding cool-season grasses, consult NU Cooperative Extension NebGuide G81-558-A, Tall Fescue Lawn Calendar, or NebGuide G80-517, Kentucky Bluegrass Lawn Calendar, available on the Web. Both publications also are available at local extension offices.

08/14/02-SH

Anne Streich
Agronomy and Horticulture
Extension Horticulturalist
(402) 472-1640

Sandi Alswager Karstens
IANR News and Photography
(402) 472-3030

Department: Agronomy & Horticulture