Regardless of the sport played on your field, or the level of quality your field is currently at, there is one constant: mowing. I am sure some of you have someone that mows your field for you, such as a school or city park groundskeeper. Good for you, now you have time to do other things on your field! You still need to hear what's coming up, because I am sure there have been times you wish you had just mowed yourself. But for those of you that find yourself sitting on a mower a few times a week listening to the latest Jon Gordon podcast, I have some things to consider each and every time you to mow.
When to mow
This may sound intuitive, but do not mow when the field is too wet. The ground is already saturated with water and driving heavy equipment over the field will only cause uneven surfaces on your field (affecting playability) and create compaction, which limits air movement to the turf roots and results in stressed or even dead turf.
Mow after the dew lifts from the field in the morning. Most of the time, a dewy morning does not necessarily mean that the soil is wet, but just the leaves. When mowing wet leaves, the quality of cut is diminished and you will likely end up with huge clumps of wet grass clippings all over your field. Then you are forced to mow the field a second time to disperse the clippings when you could have just waited for the field to dry before mowing.
What to mow with
The most popular type of mowing equipment for sports fields at the high school level is a rotary mower. Whether it's a tractor or a zero-turn mower, the cutting style is the same. The motion of the mower blades forces grass blades to stand up before cutting them. Rotary mowers are fairly affordable and the cutting unit is easy to maintain compared to a reel mower. At some high schools, but definitely at college and professional facilities, reel mowers are the preferred cutting unit as they provide the most superior quality of cut by using a scissor-like action to cut the grass. Regardless of the mower you are using, turf tires are a must have to ensure as little damage is done as possible when driving across your field.
Reel mowers also have rollers on the back of each cutting unit, which creates the striping effect we all marvel at. Essentially, the rollers lay the turf down in different directions so that the light-colored stripes are mowed away from you and the dark stripes are mowed toward you. If you're unfamiliar with a reel mower, I want you to think about the old school mowers that didn't have a motor on it. All of the power was being supplied by you. The way the grass is being cut has not changed, but the machine has.
Reel mowers come in many different shapes and sizes. The reel mower in the image below has three wheels and three cutting units, which are hydraulically lifted. Mowers with three cutting units are commonly referred to as triplexes. For larger areas, it is common to see mowers with four wheels and five cutting units (five-plex). Toro makes a three-wheel five-plex unit. If you're feeling ambitious and want to have skinny passes on your infield or sidelines, walk-behind units are available as well.
Reel mowers provide a great quality of cut, but can be expensive to acquire and maintain. You may be able to find a used machine in good condition to fit your budget. A local golf course may be able to lead you in the right direction in finding units. Reel mowers require extra attention to maintain the reels. Instead of easily sharpening or replacing rotary mower blades, reel mowers require backlapping regularly and grinding (which requires special equipment). A good cross-over that incorporates the rotary decks and blades, but also independent, hydraulically-lifted cutting units and roller (for striping) is a Toro Groundsmaster.
Check your blades
We want clean edges on the blades of grass after they have been cut, and that is directly related to the sharpness of your mower blades. The easiest way to check the sharpness of your mower blades is to get off the mower and look at the grass you just mowed over. Check out the image below from a University of Arkansas Division of Agriculture Cooperative Extension Service fact sheet on mowing to see the difference that a sharp mower blade makes.
Mowing height
For those of you in the southern United States, bermudagrass will be the turf most commonly used on sports fields. However, during the fall and spring many coaches will overseed their fields with a ryegrass (hopefully perennial, not annual...we will cover overseeding in another post) so the field is green while play is occurring. It is recommended that perennial ryegrass (PRG) sports fields be mowed at 1-1.5". When the summer comes around, 1" is the recommended mowing height for common bermudagrass sports fields. If you happen to have hybrid bermudagrass on your field (you likely know who you are), I prefer 0.75" but you can go up to 1". Hybrids also tend to work the best when cut with reel mowers.
This is a good spot to discuss mowing height vs mower setting. Just because the dial on the rotary mower reads '1' or '1.5' does not necessarily mean that you are mowing at 1 or 1.5". I recommend mowing a pass at a desired setting then measuring the height of the turf with a ruler starting from the base of the soil. There have been many times that I have used a mower that cut at 1.5" on the 2.5 setting.
While these mowing heights are recommended, they're not suited for every coach's time availability. With that being said, lower mowing heights require a greater level of responsibility: they require mowings more frequently. We want to follow the rule of thirds when mowing. The rule of thirds simply states that no more than 1/3 of the leaf blade should be removed during any mowing event. For example, if you want your field mowed at 1", then you should mow again before the turf reaches a height of 1.5". You will likely find that a 1" height of cut will result in mowing 2-3 times per week. The rule of thirds prevents scalping, which essentially means that you cut too much leaf tissue off. You see straw-colored turf where you had just cut instead of green turf. The rule of thirds also prevents excess clippings from bunching up all over your field. We have all seen the rows of clippings parallel to your mowing pass that ejected from the mowing deck...
The take home message about mowing height is that if you cannot keep up with the mowing frequency required to maintain your field at 1", then bump the height up.
To calculate how tall your turf can get before requiring mowing, just take your mowing height you want and multiply it by 1.5. Example: You want to mow at 1" x 1.5 = 1.5" height that your turf can get to before mowing.
Now, I know you're wondering about what to do when you have not been able to get out and mow for a week because your field has been soaked from rain. Let's say your field has gotten up to 2" over the week and you want to follow the rule of thirds because you know what you're doing, take 2" and multiply it by 0.67. That equals 1.34", but to make things easy we can round up to 1.5". If your ideal mowing height is 1", then you only require one more mowing to reach 1" since 1.5 x 0.67 = 1".
The take-home message about mowing height is that if you cannot keep up with the mowing frequency required to maintain your field at 1", then bump your height up. Sure your field may not play as fast as you would prefer if you raise the mowing height, but safety and playability can be affected even greater by rows and clumps of grass clippings all over the field. Your surface will provide consistency that would not happen if you have a lower mowing height and fail to mow frequently enough. Compare some of the different mowing heights and their estimated mowing frequencies from the table below so you can select a mowing height that works best for you.
Final considerations
Change directions each time you mow. Mowing the same pattern every time will create tire tracks and ultimately an uneven playing surface.
Before mowing, pull back the edges of your mound and plate tarps to ensure that you can reach the edges of those areas and to eliminate the chance of shredding a tarp.
When mowing edges with a rotary mower that ejects clippings to one side, ensure that you are blowing the clippings away from the skinned surface and not onto the skin. You may have to go multiple passes along the edge in order to reach a point where you can comfortably mow in the opposite direction.
If you are turning on the skin, there are a few items to consider: 1) only turn on the skin when it is completely dry. If it is wet, make a three-point turn on the grass (do not make sharp turns). 2) Turn your blades off or raise your reels when turning on the skin to ensure that infield conditioner is not being displaced and potentially building up in your edges.
Keep raking!