Since inception in 1975, Greenhorizons has been seeking the most effective methods for installing, rejuvenating, and maintaining high performance turf. Thanks to some European ingenuity in the mid 90’s, we were able to incorporate an incredibly valuable tool into our arsenal of turf care equipment: the fraise mower.
We had always been working to solve the problem posed by excess organic matter that accumulated in the turf’s thatch layer over time.
Thatch is a layer of grass shoots, stems, and roots (stolons and rhizomes) that are either alive and well, or are dead and will be broken down into nutrients for the plant! Thatch build up occurs when the turf produces organic debris faster than it can be broken down. This is a common occurrence on high performance turf pitches.
Thatch provides many benefits to turfgrass including insulation, protection from physical damage, and promoting lateral growth. It’s also a nice cushion for any players that happen to fall on the pitch!
Unfortunately, it’s not all sunshine and rainbows when it comes to thatch… Thick thatch can cause extensive root damage because of how quickly it heats up and dries out. It can also hold too much water during rainy periods resulting in root rot. Even large populations of disease-causing organisms can be found in thick thatch layers. Ultimately you want a thatch layer that’s not too thick, not too thin, but just right!
Traditionally, sports turf managers have controlled thatch using core aeration. This helps to correct soil compaction and improve air circulation in the soil. Improved air circulation promotes microbial activity and healthy microbes in the soil are essential to turfgrass performance. These microorganisms process soil nutrients so that they’re readily available for the plant to absorb. Topdressing with a sand-heavy soil after aeration will help decompose the thatch layer, and also help with water percolation preventing root rot.
Since the introduction of fraize mowing, core aeration isn’t the only way to manage thatch… If the thatch layer is out of control, and you’ve concluded that the field in question requires intensive renovation, go on and put that fraize mower to work. Be aware however that fraize mowing is a very aggressive process and it must be part of a comprehensive renovation strategy. Several parameters need to be established beforehand such as depths, expectations, field conditions, and field downtime. An initial discussion is crucial to ensure that fraize mowing is truly the right solution, and that it is going to be performed properly.
The concept of fraize mowing is simple: remove the top layer of organic matter including thatch, weeds and invasive grasses, while leaving the main root structure and crown intact. In conjunction with an overseeding process, this main root structure will regrow. There are several different types of fraize mowers that each have their own unique applications. From straight bar, to carbide tip round shank, to a 90-degree tiller blade; as a sports turf manager, you have options. With each implement, you also control depth. Whether you are planning on simply re-growing, overseeding, slit seeding, drop seeding and top dressing, coring and overseeding, or sodding, you can find the perfect fraize mower and depth combo to achieve the best results.
If you decide to fraize mow a field, be prepared to move lots of organic debris! Even light fraize mowing will remove hundreds of yards of material that will need to be pulled off the field using trailers, wagons, or trucks. A close dump site is essential and a plan for how to compost the material for later use will help immensely.
Since fraize mowing removes so much organic debris, it is an excellent cultural practice from an Integrated Pest Management perspective. Instead of using chemical solutions to combat broad leaf weeds and Poa Annua, fraize mowing can pull away any seeds and stands that would have out competed your desired cultivar. As previously mentioned, fraize mowing will also reduce the amount of thatch in your field, which can be home to disease-causing microorganisms! It is an excellent cultural alternative to the many chemical solutions used to treat diseases.
The fraize mowing process will also remove small divots and undulations from the field. You will be extremely pleased to see the flat field that results from proper fraize mowing. In extreme cases when there are large divots and holes, the field will need to be terra planed.
Terra planing is a deeper, more aggressive form of mowing. This is almost strictly used when fresh sod is to be laid, or if the field is too uneven to simply be seeded. Typical terra planing depth is 1.5-2 inches. Sod will root and interface with the existing root structure much better if the surface has been terra planed. If the field is to be overseeded, terra planing is not recommended because the establishment time from seed to usable-field will be very long.
If you choose to lightly fraize mow a field, the post-mow process is typically topdress, groom, an aggressive starter fertilizer application, seed and water. This must be commenced immediately so that the stolons and rhizomes are allowed to regrow.
Here at Greenhorizons, we find that a medium fraize mowing depth in a reasonably even field, followed by mechanical slit seeding provides excellent results. When slit seeding, depth is crucial! Be careful not to plant the seeds in the left-over organic matter, but right down into the soil. Direct seed-soil contact is critical to the success of the project.
A method that has also worked extremely well for Greenhorizons, is to terra plane the center 15,000 to 20,000 square feet of the field and re-sod that area. Then, fraize mow the outer edges of the field at a light to medium depth and topdress or slit seed that area. This will provide a usable field in approximately 6 weeks depending on the initial conditions of the field.
The ideal time to fraize mow for us is the first two weeks of September. This gives the field time to recover for the rest of the fall and early spring before programming is started in late May/June of the following year. Keep in mind though that it is highly recommended to complete your fraize mowing project before the irrigation system is winterized. Some days in September and October can be very windy and dry!
Once a field has been fraize mowed, be sure to have all your tools and materials ready to go immediately following completion. Whether you’re seeding, topdressing, or coring, having your equipment prepped and ready to go is key. Additionally, having water access and irrigating as soon as possible will prevent the field from desiccating.
Remember that you need to give the field time to recover after fraize mowing! Improper field management following this process can result in a field in worse condition than before. Be sure to have plenty of time allocated to the project in anticipation of potential hang-ups. You need to be very detail oriented when fraize mowing so as to complete the project properly and in a timely manner.
A word of caution, especially when it comes to soccer fields, never renovate only the goal mouth’s and centres. Although this is what typically wears out first, the ability to keep these smaller areas intensively maintained is very difficult. Choose a reasonable width for the centre and fraize mow from end to end. This can typically be irrigated with a zone or two, and can be mowed separately from the rest of the field allowing the renovated area time to establish without traffic.
In summary, fraize mowing can be an excellent tool in the turf manager’s bag of tricks, but it must be part of an overall rejuvenation plan. If you plan on fraize mowing, remember these key points: establish a complete renovation plan before starting; consult with a company who has rejuvenation experience; ensure water is readily available for a speedy recovery; and make sure you have the equipment to haul a large amount of organic material and enough space to compost it.