Properly Time Turf Preemergence Herbicide and Fertilizer Applications

Often one of our biggest problems in the spring is fertilizing turf too early. Early application of fertilizer can lead to early green up. Though this may please the client, turf that greens up early can be more susceptible to damage by late cold weather. Early fertilization may predispose the turf to disease problems. Also, nitrogen applied too early may not be taken up by plant roots which are still dormant. This nitrogen can be lost by leaching and runoff.

Properly time preemergence herbicide applications for best weed control: Preemergence herbicides should be applied before weeds emerge. Suggested dates of application of preemergence herbicides for crabgrass and other annual grasses are February 15 to March 5 in South Georgia and March 1 to March 20 in North Georgia. These dates typically correspond to the time when soil temperatures begin to reach 55 F, the temperature at which crabgrass will germinate.

Time turf fertilization based on soil temperatures: The recommendation for warm-season turfgrasses is to withhold the first spring nitrogen application until the soil temperatures at the 4-inch depth are consistently 65 F and rising. Nitrogen application is typically 30 to 45 days after the application time for preemergence herbicide for summer annual grassy weed control (e.g. crabgrass) products. See www.georgiaweather.net for soil temperatures in your area.

Advertisements in the spring encourage use of herbicide-fertilizer combination products (i.e. weed-n-feed) that typically have a high nitrogen content. Since herbicide application and fertilization should not be applied at the same time, the use of these products means one of the two components will not be used at the optimal time.

Good options for applying preemergence herbicides and fertilizers include:

• Apply the preemergence herbicide alone and apply fertilizer later as a second application.
• Use combination fertilizer products that do not contain nitrogen. Potassium is a good fertilizer carrier for late winter or early spring application. Products that combine potassium fertilizer (like a 0-0-7 analysis) are better choices than combination products containing nitrogen.

Warm-season turfgrass calendars found on the Georgia Turfgrass website can serve as good guides for properly timing your turf activities.

• Turf Lawn Calendars (See right sidebar)
• Bermudagrass
  
• Centipedegrass
  
• St. Augustinegrass
  
• Zoysiagrass
  

Please share this information with others in the landscape & turf industry. For more information:

Call your local Extension Agent at (800) ASK-UGA1 or locate your local Extension Office.