We asked experts from several leading equipment manufacturers: How does height of cut factor into healthy turfgrass on athletic fields?
JOSH FRIELL, PH.D.
Senior Principal Research Scientist/Toro
It’s well known that following proper mowing practices encourages stronger rooting and denser turf growth. Typical recommended mowing heights range from 0.75 to 1.75 inches for bermudagrass to 1.5 to 3 inches for cool-season turfgrasses, like Kentucky bluegrass or perennial ryegrass. These ranges are just starting points and should be adjusted based on growing conditions, maintenance practices and specific field requirements. At times, it may be tempting to mow at lower heights of cut to increase the speed of the field, but it’s important to remember that doing so removes an excessive amount of photosynthetic tissue and can lead to decreased traffic tolerance, lower recuperative ability after play and, ultimately, results in a thin, weak canopy. Moreover, lower heights of cut also require more intensive maintenance and more frequent mowing when following the one-third rule, which states that not more than one-third of the leaf tissue should be removed at one time to avoid negative effects like unsightly scalping and decreased stress tolerance.
General Manager/MTD Specialty Turf Products
At a fundamental level, the amount of surface area potential for photosynthesis has a direct correlation on root depth — the shorter the height of cut, the shallower the roots and, conversely, a higher height of cut facilitates deeper rooting. As athletic fields are often subject to lateral forces through the action of player inertia, it’s vital that strong rooting is in place to offer a good level of shear strength and the resultant integrity of the sward. Preservation of sward integrity is vital to the playability of the field and in maintaining a healthy plant. A shallow-rooted plant will unanchor easily from the rootzone, which places it under more stress and makes it subject to pathogen attack. This is further compounded, as any shallow-rooted sward will require more frequent irrigation, again, making the grass more prone to disease.
Engineering-General Manager/Progressive Turf Equipment
Far be it from me to tell a professional sports turf manager what height of cut to use to maintain the health of their turf. There are just so many variables to consider; from the grass species, field usage, the growing cycle, or even the amount of shade the stands create, among many others. So instead, Progressive took a different approach: We made the height of cut very easy to adjust on all of our roller mowers, so if it needs to be changed, it can be done quickly and accurately. Further, we made the cost of operating and maintaining the mowers as low as possible with features such as maintenance free blade spindles and roller end bearings, and 100 hour PTO shaft greasing intervals. These are the areas that we can add true value for the sports turf Manager and why we see our 12’ and 15.5’ tri-deck roller mowers gaining in popularity.
In order to maintain healthy turf, it’s important to mow at the correct height and frequency with the correct type of mowing equipment. However, it’s also important to bear in mind that there are so many other factors to consider when selecting the correct height of cut, such as the sport, type of grass species, time of year, plant health, recent fertilizer or chemical applications, as well as other renovation activities. Each turfgrass species has a mowing tolerance range, which indicates the lowest and highest heights tolerated by a species. Failure to mow inside of the tolerance range will no doubt put stress on the plant and lead to weak turf. Generally, higher heights of cut are easier to maintain and are associated with deeper roots. Demands for ball roll, playability and aesthetics, on the other hand, can drive the need for lower heights of cut.
Senior Turf Product Manager/Kubota
Height of cut should always start at the recommended turf type maintenance height; that height will yield the best overall results. Slightly increasing the cut height will drive the roots deeper, giving them improved nutrient and water access. This is typically done when the field isn’t in high demand. A constant cut height will increase the density of the turf, and any cut height changes should be done over time, at 0.25 inches per week, or per mowing. By following this method, you’ll avoid cutting too much of the blade, weakening the turf. Returning some grass clippings to the turf is also very important to maintaining healthy turf, as these clippings provide food for the turf growth. But excess clippings can smother the turf and cause heat stress to build under the clippings, which can also lead to disease growth.
Product Manager/ John Deere Golf
Cutting too high or too low can lead to a big difference in turf quality and appearance. There are two ways to measure height of cut — bench setting and effective HOC. Bench setting is what you set the height of cut to in the shop using a gauge. Effective height of cut is the actual height of cut on the turf, best measured with a prism. Those two are very rarely the same. Typically, effective height of cut is lower than bench set height of cut. Weight of the cutting unit, roller types, bedknife attitude, cutting unit attachments and turf conditions all play a role in how much they vary. Knowing the best height of cut for maintenance of your turf is also important for determining the number of blades you need on your reel. Too many blades on a reel with a higher height of cut can fan the grass over and make it difficult to achieve the cut you want. At heights above 1.5 inches, a rotary mower may be more appropriate. As a general rule, especially at lower height, you want your frequency of clip with a reel to be equal to your height of cut. This helps determine your optimum blade selection, reel speed and mowing speed.