Extension

Mingying Xiang, PhD, Professor of Turfgrass Science / Turf Extension Specialist

Late August is an important transition period for turfgrass fertilization in Oklahoma. Warm-season grasses are approaching the end of their fertilization season, while cool-season grasses will soon begin recovering from summer stress.

Warm-season Grasses

For bermudagrass, zoysiagrass and buffalograss, apply the final nitrogen treatment between late August and early September. Complete all nitrogen applications by September 15. Fertilizing later may promote tender growth, reduce winter hardiness and increase disease risk.

Do not fertilize severely drought-stressed or dormant turf. Quick-release fertilizer should be watered in promptly to reduce the risk of turf burn.

Cool-season Grasses

Tall fescue, Kentucky bluegrass and perennial ryegrass benefit most from fall fertilization. Wait until temperatures moderate and the turf resumes active growth, generally from mid-September through early October.

Apply approximately 2 to 2.5 pounds of actual nitrogen per 1,000 square feet during the fall, either as a slow-release application or divided into multiple lighter applications.

Test Before Applying Phosphorus or Potassium

Use a soil test to determine whether phosphorus, potassium or lime is needed. Applying nutrients that are already present in adequate amounts will not improve turf quality and may waste money.

A well-timed fertilization program, combined with proper mowing and irrigation, will help turf recover from summer stress and prepare for the coming season.

For more information, see HLA-6420 - Lawn Management in Oklahoma.