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The Landscape Alerts
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.
Printer-friendly versionIrrigating During Cold Weather Can Cause Problems!
Landscape sprinkler systems normally deliver water in the form of fine spray droplets. In winter months, when temperatures are at or below freezing, part-circle heads which are not aligned properly can create icy conditions on roads and sidewalks. Frozen irrigation water on roads and walks can be difficult to navigate safely creating dangerous conditions for travelers. This is not only a safety issue. It could also be a liability issue for the property owner who may be held responsible for damages or injuries.
Irrigation is most efficient when irrigation equipment is installed properly and regularly inspected. We achieve irrigation efficiency when most of the water is applied to the landscape and is available to plant roots. A system that is not properly maintained may result in sprinkler heads that are misaligned or need adjusting especially if water is being applied to roads or sidewalks.
Problems can be avoided with a few simple steps:
- Adjust sprinkler systems so that water is distributed to the landscape and not to roads and walks. This is especially true of busy, public roads. Wet or icy conditions on roads or water hitting a windshield can cause accidents. Irrigation directed at roads and walks is a safety problem and a waste of water!
- Monitor irrigation systems routinely for leaks throughout the year. Underground leaks may actually show up better in the winter because they create icy spots in the lawn or landscape. Sprinklers heads should also be checked regularly for adjustment or alignment problems.
- Irrigate depending on plant needs, soil moisture, and current weather conditions. Plant water needs are less during cooler temperatures as compared to summer conditions, even for plants such as pansies and cool-season turfgrasses. Devices such as soil moisture sensors are useful in determining irrigation needs.
- It may be necessary to completely drain/winterize an irrigation system if a landscape is composed of deciduous or dormant plant material or in areas that have regular freezing weather. Freezing water in pipes expands and can cause damage which can be very expensive to repair.
- Plants or sod that were planted in late fall and have not had time to establish a root system may need to be irrigated prior to freezing conditions to avoid drying out during cold, dry weather. Irrigation should be applied before soil freezes since the water cannot move through a frozen soil profile. Water is more likely to puddle on the surface when the soil is frozen.
Regularly evaluating the distribution and coverage of your sprinkler system and following good irrigation practices and scheduling should have several advantages:
- An efficient system can result in water conservation which is a cost-effective and environmentally sound way to reduce our demand for water and save energy.
- Plant health and appearance is improved.
- Chemical applications may be reduced.
- Less water is loss due to surface water runoff and deep percolation.
Save money and water, and reduce hazards by making sure the water is falling where you want, when you want, and in the proper quantity.