Ross Kurcab is a Certified Sports Field Manager (CSFM) and a professional sports field consultant with 30 years’ experience as a head turf manager in professional football. He graduated from Colorado State University’s Turfgrass Management program and now operates and owns Championship Sports Turf Systems.
Fraze mowing is gaining popularity in the US and it can be a very effective cultural practice on your natural grass fields when done correctly. Simply put, fraze mowing involves the mechanical removal of the top layer of thatch and organic matter accumulation by use of a rotary spindle using specialized tines or blades. Depending on how deep you go, you can also remove some of the surface soil. We have been using these types of machines for years to remove a deeper top layer (.5-2”) of grass and soil for re-sod operations, but the newer tines and axles allow a less invasive top layer removal that leaves some plant material behind on the surface. With fraze mowing, we are looking at a shallow depth that will leave roots, stolons, rhizomes and some crowns intact for turfgrass re-growth. The debris that is removed typically is run up a conveyor belt into a collection unit for disposal, composting or other uses. You’ll want to plan ahead for what you will do with your spoils.
The benefits of fraze mowing may include stimulated growth as above-ground stolons are severed on Bermudagrass fields, generating new shoots and roots. In bluegrass and even ryegrass fields, the shallow root “pruning” may stimulate compensatory root growth in live plants left behind after fraze mowing. Another benefit is the physical removal of any undue thatch and the removal of unwanted organic matter accumulation on the surface of your soil. This will open up your surface which can result in improved infiltration (water into the soil profile) and better soil oxygen if the surface was really “sealed off”. That may be the first thing you notice after fraze mowing. The field usually accepts water much better after fraze mowing.
There is also a smoothing effect on your playing surface for minor undulations. If your field is bumpy, fraze mowing can really help. However, the smoothing affect is limited to minor undulations and divot-depth disturbances, not major undulations of more than an inch or so, depending on how deep you go.
Fields infested with weeds may also benefit from fraze mowing. However, some perennial weeds will be more stubborn and may actually be stimulated by fraze mowing. The procedure should be a carefully managed part of a more comprehensive weed management program based in the principles of Integrated Pest Management (IPM). Fraze mowing does a good job of removing Poa annua plants from your field, depending on the level of depth and aggressiveness to your treatment. In my experience, if you don’t do anything to correct the factors that lead to a Poa annua invasion in the first place, it will often find its way back in a year or two. In highly managed and closely mowed cool-season turfgrass, Poa annua must be continually managed and never allowed a “foothold” on your field. Fraze mowing may be a valuable part of your overall Poa annua management plan.
For many years, we in the US have been limited to the types of tines, rotors and their respective applications with the “L” shaped blades typical of the early Field TopMaker type units. This technology quickly gained popularity in the late 90’s-early 2000’s for removing worn grass areas prior to re-sod operations. They are still in use today and can even be used at a very shallow depth to effectively fraze mow a turf. However, the newer Universe rotors and tines are specifically designed to fraze mow and leave more viable plant material behind.
In ryegrass overseeded Bermudagrass fields, fraze mowing can be of great aid in removing and stressing the ryegrass and stimulating Bermudagrass growth in spring/summer transitions. Removing some of the verdure will expose more of the soil surface to the suns warming rays which may stimulate the Bermudagrass. Cutting some of the above-ground stolons will also stimulate the Bermudagrass. The same concept will also work well in Kentucky bluegrass fields that may have been overseeded for some time with perennial ryegrass to the extent that the PR population is more than the turf manager desires.
Surface black layer, crusting and algae can pretty much be removed by fraze mowing. Again, get to work on the conditions that may have led to these maladies in the first place or they may return in time.
Fraze mowing may be a much less expensive alternative to complete re-surfacing by sod or other more invasive full surface renovation treatments, but it can’t cure all. It is a fairly invasive treatment that will require some time without play for healing and reestablishing the turf stand. The no-play period will vary between a couple of weeks in lighter, less invasive fraze mowing’s and up to a month or even two in some more aggressive cases that rely more on seeding for reestablishment rather than regrowth as the predominate reestablishment mechanism.
Seeding the field after fraze mowing is typical, but depending on how deep and aggressively you choose to fraze mow, you may hasten the recovery process through some re-growth. Your re-growth potential is also greatly determined by the grass species, and more importantly its growth habit. Spreading grasses like Bermudagrass and Kentucky bluegrass can regrow from buds in cut rhizomes (KB) and both rhizomes and stolons (Bermudagrass). Bunch grasses like perennial ryegrass will struggle to regrow relative to spreading grasses after fraze mowing unless you just “tickle” the surface with your depth setting. With a ryegrass field, you will need to depend more heavily on post fraze-mow seeding in most cases for re-establishment of the turf. Having said that, the process was started and perfected over in Europe several years ago where the pitches are predominately perennial ryegrass. Having managed a 100% ryegrass field, I believe it’s a good idea to periodically fraze mow and remove all the dead “tiller muck” after the season and reseed, even annually on intensively managed fields.
Fraze mowing is a great cultural practice for the field manager’s toolbox of treatments that can be performed on a seasonal or yearly basis and can deliver significant benefits all year on your playing surface. I don’t see it solely as a corrective treatment, rather as a preventative and rejuvenation cultural practice. I believe it works best when done more frequently and less aggressively, depending on the circumstances. Fraze mowing is the opposite of what were taught about irrigation. With fraze mowing, light and frequent is best in my opinion. That said, it is a surface conditioning treatment, and it will not address issues deeper in the soil profile like subsurface layering or hard pans, for example. Fraze mowing is also fairly invasive to your playing surface and may require a longer ‘healing’ period for the field than some other cultural practices more commonly done like solid tine aeration. As a surface conditioning and periodic rejuvenation process for your field, I believe this will become a staple in North American athletic field management. It may act as a far less expensive alternative to re-sod operations in certain situations. Most importantly, it gives us a tool and a new focus on how we manage the soil surface of our fields. By keeping a “clean surface” we may increase grass plant health. Any time we do that we can look to better performing fields capable of taking more wear and tear. We are learning what the Europeans have known for years. Periodically cleaning the rubbish off your turfgrass surface is a sound management practice.
Spring can be a very good time to perform some cultural treatments on your sports fields, depending of course, on your schedule of play. But from a strictly turfgrass seasonal physiology point of view, spring offers the cooler temperature ranges that can provide for better growth and recovery from the invasive nature of some of these corrective cultural practices. During the heat of summer, cool season grasses stress and slow their growth naturally and as such intensive summertime cultural practices can be harder to recover from than spring. By the cooler days of fall, we are back to a good cultural practices window again on cool season grasses.
Perhaps the most basic and effective of these cultural practices is core aerification. Your father’s core aeration has stood the test of time, and now we have so many different tines, depths, and fracturing/heaving mechanisms available to us to dial in on the exact type of application will fit our needs. Heck, we can now even inject air directly into the rootzone and create new drainage channels with a high pressure blast of air and very little if any surface disruption. The key is to identify what issue in the soil you are trying to correct or improve upon and employ the type of soil aeration that best attacks that issue. In some cases you may want to look at more than one single type of cultural practice. For example, you may verticut and vacuum the field before or after coring or other aeration treatment, then finish with some overseeding and topdressing.
In most cases, you don’t need to remove any cores left behind. After they dry, a mowing or two will often break them up and incorporate into the soil. Any thatch buttons left behind can be raked or vacuumed to remove.
Whatever you choose, now is a good time to plan things out so you take advantage of the tight field use and weather windows you have to do the work and allow for adequate field recovery. Do you have enough irrigation flags to locate and avoid damaging any irrigation heads, valve boxes or other in-field components? Tines wear out, faster in an abrasive sand-based soil. Have a generous supply, you will use them eventually. Is the equipment you need in good working order? Some of the treatments you may want to employ are best contracted out to a qualified firm to perform. Now is a good time to get your project on their calendar with a poor weather contingency, if you haven’t already.
Spring overseeding cool season grasses is generally not recommended as the ideal time in the textbooks due to the potential of weed competition and other factors. Sometimes, that may be your only good window to establish mature grass cover via overseeding. Maybe you are hosting an important tournament early this summer and you need to fill in thin and worn turf. The use of Radiant Evergreen vented covers is especially effective during the cold/cool spring months in getting the field back to play quickly after any springtime renovation treatments and cultural practices.
In the warm season zones, where Bermudagrass is the predominate sports field turfgrass species used, spring is not the preferred time for invasive cultural practices that require some recovery for the field. This is because warm season (C-4) grasses are not growing very actively, or much at all in the earlier spring months, depending on your particular climate. Except perhaps the Deep South and years when we experience unusually warm spring weather, you’ll want to wait until later spring or early summer to perform the more invasive cultural practices that require regrowth/ healing time. Many of the same cultural practices and treatments that I have described for the cool season grass fields can be effectively employed to overcome soil challenges in Bermudagrass fields just as well as in cool season grass fields. It’s just that you want to perform these procedures when the temperature ranges at the most conducive time of year possible for active growth and therefore faster recovery and less down-time for the field. You can’t always time your cultural practices at the agronomically best times, but many of these procedures require some re-growth and field rest time. That non-use period on your field will generally be shortened by doing these practices at the optimal time of year for your particular grass and climate.
Carefully timed fraze mowing (described above) can be a good way to stimulate spring Bermudagrass growth and can be an important part of transitioning-out fall seeded ryegrass.
Even before your Bermudagrass breaks its winter dormancy, there is important work to do in the spring. Depending on where you live, your first order of business may be to assess how the turfgrass came through the winter and estimate the re-growth potential. This can be done by cutting out a few cores from representative areas or areas of concern and bringing the turf plugs indoors. Identify and place them in a bright warm sunny window or better under a warm grow-light to get an idea on your re-growth potential after a cold winter.
If you overseeded ryegrass or any other cool season grass into your fields last fall for winter cover and color, you will need a plan to transition out some or all of the ryegrass this spring and summer. In the old days, the ryegrasses were so poorly tolerant of heat that we could just wait for the hot temperatures of summer to cook them out of the stand and transition back to Bermudagrass. Nowadays, the ryegrasses are bred to be more heat tolerant and chemical removal is often indicated. The University of Tennessee has a good paper on this process. This is an older article, but a good one about using some cultural practices to help transition out the ryegrass in the spring and summer.
As with cool season fields, the use of the right kind of evergreen vented field cover can warm the soil and significantly hasten the late spring or summer green up of your Bermudagrass fields. You might also consider using a green dye type of colorant on the dormant Bermudagrass to trap heat from the sun and hasten green–up. It can also make your brown, dormant Bermudagrass field look green and “game-ready” for recruiting season without having to pump up your winter ryegrass just to look good to recruits. Anything you can do to safely darken the color of the dormant-brown turf or lighter colored exposed soils may help significantly warm up the grass and break dormancy sooner.
A great YouTube video from a baseball/softball infield maintenance seminar featuring Grant Trenbeath, head groundskeeper for the Arizona Diamondbacks at Chase Field in Phoenix. There is a wealth of info here in his 28 minute on-field demonstration.