September 16, 2010

University of Arkansas, Division of Agriculture

Turfgrass Science Program (http://turf.uark.edu) – Turf Tips

 

Renovating Cool-Season Turf


The intense heat and humidity of this summer has wreaked havoc on cool-season turf in Arkansas.  In fact, it looks as though a bomb went off in the middle of our bluegrass and fescue variety trials in Fayetteville (Fig. 1).  So, for those of you managing cool-season turf areas, it is likely that you will need to repair damaged areas, or perhaps completely re-establish, depending on how much damage was experienced.  Now is an ideal time to renovate cool-season turf areas since nighttime temperatures have dropped consistently below 70 degrees and cooler fall temperatures are approaching.  Hopefully, this turf tip will help guide you through the renovation process.


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Figure 1.  Cool-season cultivar trials following the stressful growing conditions of Summer 2010.  Photo taken September 16, 2010.


WEED CONTROL.  Weeds should be controlled prior to seeding as they may prevent turf seed from germinating and will compete for light, water, and nutrients with turf seedlings, resulting in a poor turf stand.  If very little desirable turf is present, a nonselective herbicide (glyphosate) should be used.  Broadleaf herbicides containing 2,4-D should be avoided as they typically have a 7 to 30 day restriction for seeding tall fescue.  For maximum weed control, site preparation activities such as scalping, power raking, etc… should be delayed 3 to 5 days following herbicide application.


SOIL PREPARTION.  Now is a good time to address any drainage issues, especially low lying areas that stay wet.  Bring in topsoil to fill holes, smooth the surface, and provide gentle slopes away from structures to maximize surface drainage.  Also, if the soil is compacted, core aerification should be done.  This is best done following a soaking rain or irrigation so that the aerification tines penetrate into the compacted soil.  Multiple aerification passes are recommended in highly compacted sites.  Core aerification will not only relieve compaction but open up the soil to capture seed and provide good seed to soil contact.  Seed to soil contact is extremely important for successful seed germination.  This can also be enhanced by scalping, verticutting, or power raking the site.


STARTER FERTILIZER.  A starter fertilizer should be applied at a rate of 1 pound nitrogen per 1000 ft2 just prior to seeding.  Ideally, a soil test should be performed prior to seeding to correct other nutrient deficiencies and soil pH, but it may not be feasible to get test results back before it is time to seed.  However, go ahead and send soil samples off for testing now, so that any soil problems can be addressed later this fall or next spring.  To quickly calculate how much starter fertilizer you will need at your site to apply 1 lb N / 1000 ft2, divide the square footage of the site by ten times the nitrogen content of the fertilizer.  For example, if the site is 5000 ft2 and the starter fertilizer is a 20-27-5 grade, then you would need 25 pounds of starter fertilizer [5000 / (10 X 20)].


SEED SELECTION.  Once the site is prepped for seeding, you will need to decide exactly what to plant.  New grasses appear on the market about as fast as new models of your favorite car. Companies are constantly tweaking and releasing “new and improved” cultivars of grasses. Unfortunately, this makes it both difficult for the consumer to find the grass that they were familiar with last year or even for researchers to make recommendations, since the cultivars change more quickly than the trials that we plant. However, it is important to look at the cultivars that are locally-available and then, once this is determined, information on those cultivars is generally available online.

Over the past decade, the UofA turfgrass program has been a testing site for the National Turfgrass Evaluation Program (NTEP) tall fescue trials. One trial, planted in 2001, had 160 tall fescue cultivars and a more recent trial, planted in 2006, had 113 entries. Each year, we report the data that we collect at our location to the NTEP and that data is available to the general public at their website (www.ntep.org ). The Fayetteville location can be viewed separately from other locations if desired (http://www.ntep.org/data/tf06/tf06_10-8/tf06ar109t.txt ), but it can also be helpful to look at similar locations such as Stillwater OK, Columbia MO, Knoxville TN, etc., to see how specific cultivars are performing across the region.

Many of the tall fescue cultivars that we have tested over the last decade produce a very high turfgrass quality when conditions are favorable for tall fescue. However, when brown patch pressure is high, there are cultivars that have performed near the top of the trials and would be good choices for Arkansas lawns since brown patch is one of the major weaknesses of tall fescue. The following is a list of some of the top-performing cultivars at our location with regard to brown patch resistance.


It should be noted that although Ky-31 has very good resistance to brown patch, it is a forage-type cultivar and should only be used in very low-maintenance turf situations, since it will have poor turfgrass quality compared to other cultivars. It is also important to recognize that tall fescue is often sold as blends of 3 or more cultivars so it is best to find a blend that has several favorable cultivars.

We have also conducted several drought tolerance trials with tall fescue, comparing cultivar performance during the summer in the complete absence of irrigation and rainfall.  Cultivars that have performed well in these trials should be considered for sites without automatic irrigation systems (Richardson et al., 2010 ; Karcher et al., 2009 ; Karcher et al., 2008 ).

Another seeding option to consider is Kentucky bluegrass.  Kentucky bluegrass has performed consistently well at our research facility in Fayetteville during the past 10 years and some cultivars (particularly Midnight and Mallard) even fared well through the 2010 growing season (Fig. 2).  Mixing Kentucky bluegrass seed with fescue will provide more recuperative potential to the turf, due to the rhizomatous growth habit of Kentucky bluegrass.  Also, a fescue / bluegrass mixture will be less susceptible to brown patch during the summer than a 100% fescue turf.  A Kentucky bluegrass / tall fescue seed mixture should be composed of 10 to 15% Kentucky bluegrass (by weight).  Such a mixture will have nearly equal numbers of tall fescue and Kentucky bluegrass seeds (bluegrass seeds are much smaller than fescue seeds).



Figure 2.  Blocks of Kentucky bluegrass cultivars (‘Midnight’ A. and ‘Mallard’ B.) that performed well in Fayetteville through the summer of 2010.  Photos taken September 16, 2010.


SEEDING.  Plant tall fescue seed at a rate of 8 to 10 pounds of seed per 1000 ft2.  Applying the seed at a half rate and then going over the site in two directions will improve the uniformity of seed distribution and is preferable to making a single pass at a full rate.  Rotary spreaders, drop spreaders, and slit seeders can all be used for seeding.  Slit seeders are ideal since they plant the seed into the soil and maximize the seed to soil contact.  A drop spreader is preferable to a rotary spreader since the seed distribution pattern is typically more uniform with a drop spreader and rotary spreaders will often throw seed where it is not wanted (i.e. landscape beds).  On larger sites it may be best to seed the perimeter with a drop spreader and the interior with a rotary spreader.
Immediately following seeding, lightly rake (a leaf rake works well) the surface to bury the seed slightly, which will improve seed to soil contact. This is very important for keeping the seed moist and ensuring successful germination.  Using a mulch or cover (straw, hydromulch, or a germination blanket) will help improve moisture retention, buffer soil temperatures, prevent soil erosion and seed washouts, and ultimately improve overall establishment.  If straw is used, it should be applied lightly so that it does not smother the seedlings.  A good rule of thumb is that a typical square bale should cover 500 ft2.

The seed bed should be watered lightly and frequently to keep the surface inch of the soil consistently moist.  Following germination, irrigation should be applied less frequently, but at heavier amounts so that the soil is wetted to the depth of the developing root zone.


POST-ESTABLISHMENT CARE.  Mowing the new turf will promote tillering and decrease the time until it reaches full coverage.  Mowing should begin once the seedlings have begun to tiller and have reached 4 to 5 inches in height.  Make sure that mower blades are sharp so that seedlings are not ripped out of the soil and that the soil surface is dry enough to support the mower without rutting.

Finally, additional nitrogen fertilizer should be applied later in the fall (late October to mid-November) at 1 to 1.5 lb N / 1000 ft2.  This application will result in better winter color and provide a “jump start” of growth as soon as soil temperatures begin to warm next spring.  Once the site has been successfully established, be sure to follow recommended mowing, fertility, irrigation, and other cultural and pest management practices for tall fescue (see Lawn Care Calendar: Tall Fescue , FSA6118 ) to prevent renovation from becoming a regular necessity!


OTHER RESOURCES

Soil testing
Test Your Soil for Plant Food and Lime Needs
The Soil Test Report
Understanding the Numbers on Your Soil Test Report
Liming Your Lawn

Seed selection
Turfgrass Quality Ratings of Tall Fescue Cultivars in the 2006 National Tall Fescue Test at Fayetteville, AR
Drought Tolerance of Kentucky and Hybrid Bluegrass Cultivars
Drought Tolerance of Tall Fescue and Bluegrass Cultivars
Drought Tolerance of Tall Fescue and Bluegrass Cultivars – 2nd Year Data

Tall fescue management
Lawn Care Calendar: Tall Fescue

 

Doug Karcher and Mike Richardson

 

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