Winterkill on Annual Bluegrass: Don’t Skip the K

We lost the ice cover on our Poa annua trials two weekends ago (March 7-8th) and initially the turf looked okay. But now… it doesn’t. And it will probably get worse, if we are reading the symptoms correctly.

Blotchy, tan-colored plots and borders around this potassium trial are suffering from winterkill. Photo taken 15 March 2015. Healthier looking turf has received K fertilization; dying turf has not.

Blotchy, tan-colored plots and borders around this potassium trial are suffering from winterkill. Green, healthier looking turf received K fertilization; dying turf did not. (15 March 2015)

Last Friday (March 13), my graduate student, Chas Schmid, informed me that I needed to look at his potassium trial on our Poa annua turf. There was a huge difference between no-K and K fertilized plots. The no-K plots have steadily lost green color and become very blotchy. Plants taken from those plots are water-soaked and feel mushy when squeezed (How is that for a scientific description?). Dr. Lindsey Hoffman has a lot of experience with winterkill on Poa annua in Massachusetts and she is convinced that many of the plants are dead. And it smells like it – silage on a dairy farm!

Take home for me – don’t let your Poa annua turf become potassium deficient! Chas’ data for suppressing anthracnose severity indicates that a soil test (Mehlich 3) ≥50 ppm K and a tissue level of ≥2% K in the clippings are indicators that the K level is good. And winterkill in March 2015 hasn’t changed my mind about that data!

Looks like this might be the end of this Poa annua field. Dr. William Meyer said, “Good riddance.”

Traffic Alert: Damage Threat is High

Damage to landscapes from traffic can be severe during winter and especially now during the thaw. Soil conditions currently range from being frozen to partially thawed/frozen to thawed.

Partially frozen soil will be thawed and very wet at the surface while being frozen at some depth below. Under this condition, soil and turf will be extremely vulnerable to shearing and rutting damage. Traffic, even light foot traffic, must be withheld when this condition exists otherwise severe rutting (soil displacement) will occur.

Severe rut in partially thawed soil.

Severe rut caused by a wheeled vehicle driving on partially thawed soil.

Soil temperature has been “stuck” at freezing for some time now. Today is the first time this year that I have noticed the 2-inch deep bare soil temperature was above 33 °F (> 35 °F at the time of writing this post) at the New Brunswick Rutgers Gardens weather station. Interestingly, the 2-inch soil temperature under sod at this station remains only tenths of a degree above 32 °F, illustrating the insulating effect that vegetative cover has on soil.

Keep in mind that just because a soil has thawed doesn’t mean it is out of danger from traffic. At this time of year, soil will be very loose from frost heaving and very wet or saturated. Soil on very well drained sites will firm up sooner than poorly drained sites but all sites will be very susceptible to damage from traffic for some time after a thaw. Care should be taken to avoid traffic of any kind when the soil and turf is vulnerable.

Allow soil to thaw completely and drain to at least field capacity (preferably drier) before allowing traffic on the landscape. Draining and drying will help to re-settle areas that frost heaved. Light-weight rolling may be need on soil that experienced extensive frost heaving and remains too loose after draining and drying.

Winter Thaw about to Begin

If the 10-day forecasts are correct, the winter thaw we’ve all been waiting for is about to begin this weekend.

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Winter thaws are when most of the phosphorus enters our lakes and streams from “nonpoint” or “runoff” pollution.

 

 

 

 

 

 

 

As managers of landscapes, we need to keep in mind that: [Read more…]

Soils Are Cooling – That’s Good and Bad

Recently, surface soil temperatures have been dropping below 70° F at night. While this is a good temperature range for growth of cool season grasses, it is a signal that much cooler soils are not far away. Grow of new seedings, overseedings, and turfs needing recovery will slow dramatically once soil temperatures break below the 60° F threshold. We have reached the time (October 1) where we no longer recommend seeding of most grasses except perennial ryegrass. Perennial ryegrass can be seeded as late as October 15 and still have high probability of develop a stand of turf.

If you need more growth out of your turf, this means there is little the time for action. Waiting another two weeks could be too late for any substantial growth through the rest of this year. In New Brunswick, the rain total for September has been very modest (1.23 inches) and there may be a need to irrigate to get recovery or better establishment of seedings before it is too cool.

Fertilization is another factor to evaluate. A turf that is healthy and vigorous probably doesn’t need fertilization but a thinning stand of grass with a sickly yellow-green color is likely to need some nitrogen fertilization. You need to soil test to figure out whether other nutrients such as phosphate and potash are needed.

Now is a good time to fertilize if the turf conditions warrant it. An application of 0.5 to 0.9 lb. of nitrogen per 1,000 sq. ft. is probably all that is needed for many turfs at this time of year. If the turf continues to struggle nutritionally (sickly yellow-green color), another application of 0.5 to 0.9 lb. of nitrogen per 1,000 sq. ft toward the end of October would be useful. At high rates (above 0.7 lb. of N), use a fertilizer product that contains slowly available nitrogen. Note that state law requires lawn fertilizers sold at retail (to homeowners) to contain slow release nitrogen. Also recall that state law prohibits nitrogen and phosphate fertilization by homeowners after November 15. Professional are prohibited from N and P fertilization after December 1.

Cool weather is about to limit the establishment of new seedings. In this photo, poor seed to soil contact will also inhibit the establishment of new turf.

Cool weather is about to limit the establishment of new seedings. In this photo, poor seed to soil contact will also inhibit the establishment of new turf.

 

The 2014 Rutgers Turfgrass Research Field Days Sets Attendance Record!!

The annual event, held on July 29-30, highlighted ongoing turfgrass research at Rutgers and was attended by over 800 industry professionals! Read the full story here.

Localized Drought Stress is Here

As stated in an early post, summer stress is developing throughout the state. Summer stress isn’t widespread or severe but it is developing, particularly wilt stress, within very localized areas of many landscapes. Landscapes that receive little to no irrigation are especially prone to wilt and drought stress right now.

It is important to scout and assess the severity of any wilt stress in moderate-to-high value areas of the landscape. Hours are important, don’t put off the scouting of wilt stress. Assuming the grass or other plants will tolerate wilt stress without confirming the severity of the situation can lead to severe drought stress and stand loss at this time of year.

Symptoms of subtle wilt stress on June 22. Healthy turf will likely to tolerate this level of wilt stress.

Symptoms of subtle wilt stress on June 22. Healthy turf will likely to tolerate this level of wilt stress.

 

 

 

 

 

 

Grasses such as the fine fescues and annual bluegrass will be [Read more…]

Crabgrass Emerging

Crabgrass has been emerging for several weeks now, depending on the exposure. Warmer and more open turfs will likely have more advanced (larger) plants while cooler and denser turfs will have smaller plants.

Relatively small crabgrass plants  (most pre-tillering stage) emerging from a footpath on June 11th.

Relatively small crabgrass plants (most pre-tillering stage) emerging from a footpath on June 11th.

 

Management options for this weed at this point in the season range from doing nothing to [Read more…]

Tis the Season for Summer Stress

Optimum growth of cool season grasses occurs within the temperature range of 60 to 75 °F. Yesterday, the New Brunswick weather station indicated that soil temperature at 2 inches exceeded 75 °F for more than 12 hours and peaked at 82 °F.

This doesn’t mean that grasses will soon be dead. But it is a signal to be watchful for summer stress problems.

Summer stress is often a combination of multiple stresses. Localized drought, ponding of water, diseases, insect pests, poor culture (mowing, fertilization, and irrigation) and other stresses combined with high temperature stress can challenge the health and persistence of cool season turfs from now through the end of summer. It is important to avoid situations that compound too many stress at the same time.

For example, now is the time [Read more…]

Right On Cue: Dollar Spot Disease

Exactly like Dr. Bruce Clarke teaches, Memorial Day arrives and so does dollar spot disease.

Symptoms appear as round, brown to straw-colored spots approximately the size of a silver dollar. On short cut turf, the spots with advanced damage can become somewhat sunken. At taller cutting heights (greater than 1 inch), the damaged spots are larger and more diffuse.

Highly susceptible grasses will be the first to exhibit symptoms including annual bluegrass, creeping bentgrass (depending on cultivar), and perennial ryegrass. Tall fescue and most Kentucky bluegrasses will be more tolerant of this disease.

Cultural techniques that can suppress dollar spot disease include disruption of dew and guttation water in the morning and increasing N fertility (if it is low). Mowing early in the morning (disruption of dew) should also be helpful.

Creeping bentgrass entries in Dr. Stacy Bonos' evaluation trials that are highly susceptible to dollar spot disease appear in the image foreground.

Creeping bentgrass entries in one of Dr. Stacy Bonos’ evaluation trials that are highly susceptible to dollar spot disease (image foreground).

Update: Green-up of Turf

Most landscape lawns, sports turfs, and golf course surfaces should have reached full green-up but there will be some exceptions. The major exception to this is zoysiagrass turf. Zoysiagrass will not begin green-up until mid- to late-May. Although not as slow to green-up as zoysiagrass, fine fescue will be slower than perennial ryegrass and tall fescue. Many of the Kentucky bluegrass varieties that are commonly used for sod production will be slow to green-up in the spring.

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Dormant zoysiagrass with patches of perennial ryegrass in a home lawn.

 

 

 

 

 

 

 

Lawns that are predominately fine fescue lawn should not be aggressively fertilized with nitrogen; do not apply more than 0.5 lb. of N per 1,000 sq. ft. unless the fertilizer contains 30% or more slow release nitrogen. Even with slow release N, applications to fine fescue should not exceed the 0.75 to 0.9 lb per 1000 square feet range during the spring. Over-fertilizing fine fescues could lead to serious summer stress problems including poor heat and drought tolerance.

A predominately hard fescue lawn that has not reached full green-up in late April. Avoid overfertilizing fine fescues to force green-up. Serious summer stress problems could develop.

A predominately hard fescue lawn that has not reached full green-up in late April. Avoid over-fertilizing fine fescues to force green-up. Serious summer stress problems could develop.

Slow green-up of Kentucky bluegrass can be overcome to some extent with N fertilization. Fertilization in the spring will not cause the same summer stress problems with Kentucky bluegrass compared to fine fescues. But care should be taken to avoid over-fertilization. Over-fertilization problems on Kentucky bluegrass are more likely to be evident over multiple growing seasons rather than a single season. Excessive thatch build-up is the major problem of over-fertilizing Kentucky bluegrass, which typically expresses as a severely drought-sensitive turf (roots are growing in thatch, not soil). The total amount of N applied to Kentucky bluegrass during the spring should be within the range of 0.5 to 1.9 lbs. per 1000 square feet. Application rates above 0.7 lb. per 1000 square feet should include slow release nitrogen to limit surge growth and protect against N leaching.

Rectangular plots with a tinge of tan-color are varieties of Kentucky bluegrass exhibiting slow spring green-up (photo taken 18 Apr. 2014).

Rectangular plots with a tinge of tan-color are varieties of Kentucky bluegrass exhibiting slow spring green-up (photo taken 18 Apr. 2014).