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Spring Maintenance Techniques for a Healthy Lawn
submitted by Sarah Browning, UNL Extension Educator
For cool season grasses like Kentucky bluegrass and Tall fescue, spring is an excellent time of year. They are growing actively and are usually free of insect and disease damage, although this year many lawns are showing dieback from last summer's extremely dry conditions.
Kentucky bluegrass and tall fescue lawns should both receive their first fertilization of the year between April 20th and May 10th. This application is usually a combination fertilizer and pre-emergent herbicide. Choose a product containing a good amount of slow release nitrogen sources, like urea formaldehyde, sulfur-coated urea and IBDU whenever possible. These fertilizer ingredients are listed in the active ingredient statement, under nitrogen source.
Apply 0.5-1.0 lbs. Nitrogen/1,000 sq.ft. Following the manufacturer's label directions for application, will usually result in 1.0 lbs. of Nitrogen/1,000 sq.ft. Use this guideline to adjust your application, if you decide to use a lower rate. Lower rates of spring fertilizer applications aid in reduced summer disease problems, and also lower your lawn's water needs.
Spring is also an excellent time to control weed problems before they get a firm foothold in your lawn. Annual weeds like foxtail, crabgrass and spurge can be controlled with a pre-emergent herbicide that kills the weed seed as it begins to germinate.
Crabgrass, a very common weed, germinates when soil temperatures consistently reach 55 degrees Fahrenheit, and is usually considered the "standard" by which we decide when to apply pre-emergent herbicides. A few hours or even a single day of warmth, even with temperatures up into the 70's, is not enough to induce germination, several days of 55 F degrees soil temperature is required. For this reason, April 20th to May 5th is the target date for pre-emergent application by do-it-yourself homeowners in eastern Nebraska. However, this spring's cooler temperatures have also resulted in cooler soil temperatures, and we are currently about 5 degrees behind normal for this time of year. To check this week's soil temperatures, go to the Backyard Farmer website, byf.unl.edu, and under the Local Conditions section, click on "soil temperatures."
But remember, if you are reseeding or overseeding your lawn this spring, the only pre-emergent herbicide that can be used with new seedings is siduron, commonly sold as Tupersan. This herbicide will provide good control of annual grassy weeds like crabgrass and foxtail, yet still allow the grass seed to germinate.
If you have not reseeded your lawn this spring, several pre-emergent herbicide products will give good weed control. Look for these chemical names under the active ingredient on the fertilizer bag: pendimethalin, balan (Benefin), betasan (Bensulide), prodiamine (Barricade) or Team- a combination of trifluralin and benefin. Remember, pre-emergence herbicides should be watered in immediately after application with at least 0.5 inches of water.
There is a direct relationship between mowing height, and potential turfgrass rooting depth. So choosing a taller mowing height also enables your lawn to develop a deeper root system. Recommended mowing height for Kentucky bluegrass is 2.5 to 3.5 inches, and 3.0-3.5 inches tall fescue. Choose a mowing height and stay with it all summer.
Lawns with deeper root systems are able to draw water from a larger soil area; tolerate hot, dry conditions better; and are not as susceptible to drought injury as lawns mowed at a shorter height. Choosing a taller mowing height also provides the benefit of reducing crabgrass germination, even with no application of pre-emergent herbicide.
Bagging vs. Mulching- Ideally, mowing is done frequently enough that clippings can be left on the lawn. Clippings returned to the turf can contribute up to 1 lb. Nitrogen/1,000 sq.ft. over the course of a summer, and will not contribute to the development of thatch. However, if more than one-third of the grass height must be removed at one time, there will be a lot of clippings, so the clippings should be bagged and removed. Heavy clippings, if left on the lawn, will cause damage through light exclusion, resulting in yellowing and thinning of the turf. Heavy clippings left on the lawn can also encourage disease problems.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office
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