Dryject Aerification Demo

Every year aerification is scheduled for early spring in order to get this process out of the way before the golf season is in full swing.  However, one of the drawbacks to aerifying this time of year is that the greens aren't growing quickly and the holes take longer to heal.  This shouldn't come as a shock to people--after all, how many times has your lawn been cut in March?  And with temperatures well below average for most of this month, patience will be needed as the greens recover.

Aerification can have a couple of different goals.  When we use solid tines in the spring, no material is removed from the green, so we are focusing on diluting the organic matter by creating channels of sand.  The solid tines are great at creating a smooth hole that readily accepts a large quantity of sand.  Typically we will apply over 80 tons of sand to the greens in the spring.

We are always looking to improve our management of the course, in order to provide quality conditions in the long run, with a minimal amount of disruption.  One potential improvement for us may be the use of the Dryject aerification system.  Like our solid tining, the Dryject machine does not pull a core, but incorporates a large volume of sand into the soil profile.  The key difference with the Dryject is that there is little surface disturbance.

The Dryject machine in action.



This Wednesday we had the local Dryject contractor use this system on the back of #9 green (which we had not aerified with the solid tines).  The Dryject uses our irrigation water with a high pressure pump to blast a small hole at the surface which then vacuums sand into it.  In a few trial areas, green sand was injected into the ground, and it's truly amazing how much sand is pulled below, with such a small hole on the surface.



This profile sample shows how much sand is injected below the surface.
 

If you have the opportunity, putt a few balls on this area of #9 over the next couple of weeks, and let us know what you think.  The difference in healing time and putting quality will help in determining if we should use the Dryject process on all of the greens next spring.

Conventional solid tine holes in the foreground, and Dryject area in background.

Seedhead Suppression

As we discussed last week, one of Poa's survival mechanisms is its ability to produce huge quantities of seed.  When this seeding takes place in the spring, it's one of the times that this turf can be frustrating for golfers.  The grass becomes bumpy, and it's not uncommon to see a ball heading toward the cup like a heat-seeking missile suddenly diverted by some Poa plant's chaff, just as a missile would be by...chaff.

What can be done to reduce the seeding and its bumpiness?  One of the best ways we can limit Poa seedhead production is by applying growth regulators.  Timing is critical with this application--there is a narrow window, and spraying a few days too early or too late will lead to limited control of Poa. 

How do we know when to spray?  When you compare March 2012 to March 2013, clearly there is a huge difference in spring temperatures from year to year, so this isn't an application whose date can be written on the calendar ahead of time.  As with many things on the course, we get down on our hands and knees and scout for signs of seedhead development.  However, in addition to this, one of our primary tools is a count of degree days.

Our application is based on a degree day model using 32 degrees Fahrenheit as a base.  Beginning on January 1, we take each day's average temperature and subtract 32.  For example, if the high temperature is 50 degrees and the low temperature is 24 degrees, we have a mean temperature of 37.  We subtract 32 from this, resulting in a degree day count of 5.  Our target for making the seedhead suppression spray is a year to date total of 450 degree days.

So, how good is the seedhead control?  The picture above (from 2012), clearly shows that there is a significant difference from the treated area to the untreated check plot.  However, even with optimal timing, this spray will never give 100% control. 

As mentioned last week, there are hundreds of different bio-types of Poa, and this genetic diversity will often lead to the plants seeding at different times throughout the spring.

The other challenge in timing the spray are the numerous micro-climates around the golf course.  That is, each green is going to vary slightly from every other green in terms of sunlight and temperature, meaning that a warmer green's Poa may be ready to go to seed a week or more before a cooler green's will.

The Q and A on P-O-A

The word Poa probably brings an image to mind. To many golfers it’s the grass that makes the greens bumpy every spring. To golf course superintendents, it can be the unreliable turf that has to be nursed through the summer heat.

Bad stuff, right? But wait a minute. Isn’t Poa the turf on some of the most famous putting surfaces in the world, such as Pine Valley, Oakmont, and Pebble Beach? At Laurel Creek, #17 has the highest percentage of Poa, yet many players say it’s one of the smoothest greens we have. Clearly this must be a wonderful variety of grass!

Confusing? Perhaps a closer look at this grass will shed some light on the different perspectives. There are many types of Poa Annua, also known as Annual Bluegrass. In fact, over 500 different cultivars of Poa have been identified. So, one might say that there is “good” Poa and “bad” Poa.

Although it is all referred to as Annual Bluegrass, many of the better performing bio-types are now considered perennial in nature. This perennial Poa has extremely high shoot density, and produces little seed. Just like a tightly woven fabric, the finer the leaf blade and the greater the number of shoots per square inch, the smoother and faster the greens.

Okay, you say, I’m sold on Poa—why wouldn’t everybody want it at their course? Well, the downside to Poa is that there is also the true annual type, which tends to be the first to show up at golf courses. This type of Poa seeds in the spring, providing bumpy conditions. Once the seeding is finished, Poa is susceptible to several insects and turf diseases that Bentgrass is not, and Poa has a relatively short root system, making it prone to wilting in the summer.

So if Poa has all of these problems, how does it out compete Bentgrass in the first place? Remember those seedheads that your ball bounces across in the spring? Poa’s survival mechanism is its ability to produce voluminous quantities of seed. After a few years, the soil contains what is referred to as a seed bank of Poa which can germinate after the late summer aerification. The only certain way to remove this seed bank of Poa is to apply a soil fumigant to sterilize both the green’s surface and the soil beneath. This process was undertaken at Tavistock during their renovation.

Can Poa be stopped from encroaching on Bentgrass? Going back to June, 2000, our USGA Turf Advisory Service Report answered this question by referring to it as, “…the inevitable onslaught of Poa Annua.” At this time, the USGA’s recommendation is for us to manage Poa on our 24 year old greens, rather than trying to eliminate it. This involves the application of different plant growth regulators to minimize seedhead development and help to match the growth rates of the Poa and Bentgrass.

Because of the desirable traits of the perennial types of Poa, such as a high shoot density and lack of seedheads, Dr. David Huff of Penn State has undertaken a breeding program to develop cultivars that could be used on golf course putting greens. However, in an ironic twist, the best performing Poa doesn’t seem to produce enough seed for commercial production.

Well, regardless of what you call it—Poa Annua, Annual Bluegrass, or just plain Poa, given the number of varieties and their different characteristics, this is clearly one plant that can’t be pigeon-holed into the strict categories of preferred or unwelcome.

During much of the year, Poa can provide a smooth putting surface.

A Better Type of Sod

The Clubhouse grounds were originally sodded to Kentucky Bluegrass.  Unfortunately, this turf is susceptible to Summer Patch disease, and perennially fungicide treatments are necessary.  In an effort to improve conditions, we have replaced some of the Bluegrass sod in front of the Clubhouse with Tall Fescue sod.

Why switch to Tall Fescue?  Years ago, Tall Fescue was known as a clumpy, coarse-leafed grass that wasn't aesthetically pleasing.  However, times have changed, and today's improved varieties of Tall Fescue look great and have many advantages over Bluegrass sod:

• Better traffic tolerance
• Better resistance to drought stress
• Not susceptible to diseases and insects that attack Bluegrass



Sod is stripped surrounding the Bentgrass in front of the Clubhouse.

Tall Fescue sod does a great job of framing the Bentgrass.