How mowing affects turf

By Dr. Douglas Linde

Can you cut the soccer field lower for tomorrow’s game? The answer is “it depends.”

Mechanically, it is rather simple to lower the height of cut and mow the grass lower. However, under certain situations there can be some devastating consequences. For example, on Friday you lowered the mower from 2 to 1 inch and cut the Kentucky bluegrass/perennial ryegrass soccer field in preparation for a weekend youth tournament. Daytime temperatures have been consistently in the 90s, there are signs of drought stress and it’s been a month since the blades were last sharpened. The players and coaches that weekend had great comments about the playability. Over the next 2 weeks, you notice the turf is not recovering as you expect. The stand is thinning and plants are no longer actively growing. Teams continue to use the field and plants in the high use areas become desiccated and the leaves pulverized. The areas become bare. It finally rains, but it’s just before a game, and the foot traffic turns the bare areas into a muddy mess.

The purpose of this article is to explain how mowing affects turf and provide recommended mowing practices so that devastating consequences do not occur on your field.

Plant’s response to each mowing

Simply cutting a leaf blade is stressful for a grass plant. Botanically, mowing is harmful, but it’s needed for aesthetics and function. Although turf-type grasses adapt well to mowing, they still have to recover from a wound and a reduction in the plant’s energy-making factory, the leaves. Below are some of the plant’s physiological (not visible) responses to being cut.

  • Fluid exudes from cut leaf
  • Stored energy (carbohydrates) is used to help repair the wound
  • Carbohydrate production and storage reduced
  • Temporary increase in water loss from cut leaves
  • Root growth stops temporarily
  • Reduced water absorption by roots
  • Creates entry points for pathogens

Plant’s response to regular mowing

What makes a grass a turfgrass is that it persists under regular mowing which may range from daily to once per month. Regular mowing causes additional plant responses which are morphological (outwardly visible) and take more time for the plant to do. Here are these responses:

  • Dwarfism of plant
  • Increase tillering which increases density
  • Lowering of the budline (crowns)
  • Decrease in seedhead production

When grass leaves are cut, the most photosynthetically active portion of the leaf is removed and the total leaf surface area for photosynthesis is reduced. The plant uses stored energy to repair the wounds and to regrow the leaves that were lost. Under regular mowing at a consistent height of cut the plant will not only regrow the leaves but will also increase leaf surface area by growing more tillers (shoots). More tillers increases turf density which in most sports turf situations leads to improved playability and wear tolerance. Under regular mowing turf plants can adjust the size of their parts so critical parts like the crown are not cut. However, the amount of adjustment depends on species. The plants undergo a dwarfism in which plants maintained at a lower height of cut will have shorter shoots and roots. Less rooting is needed to support the smaller shoots.

Plant’s response to closer mowing

Turfgrass species have mowing tolerance ranges. Mowing above the tolerance range can lead to poor playability because the turf is too high. Mowing below the range for a particular species can provide the desired playability but can lead to devastating consequences. When mowing within the tolerance range the plants can easily adapt to height of cut changes, provide the desired playability, and undergo responses 1 through 5 listed below. These responses typically are not devastating to the plants. When mowing below the plant’s tolerance range, the plant not only undergoes responses 1 to 5 but can also undergo responses 6 to 9. These additional responses can lead to dead grass.

  • Increased shoot growth
  • Increased tillering and density
  • Increased succulence
  • Decreased root and stem growth
  • Decrease in carbohydrate production and storage
  • Scalping
  • Thinning
  • Less tolerant to environmental stress
  • Less tolerant to pests

Although closer mowing can improve playability, the smaller plants require a higher cultural intensity for them to persist. A shorter rootzone and greater competition make the plants less tolerant to other stresses caused by drought, heat, cold, pests, and traffic. Plus, the shorter root zone means there is less soil from which the plant can withdraw water and nutrients. Mowing, irrigation, fertilization, and pest management all need to be more frequent and more precise. Therefore, the turf manager needs a larger operating budget and more expertise. For example, the shorter the grass is maintained, the more frequent it should be mowed. Research has shown that the turf plant is least impacted by mowing when less than 30-40% of the leaf area is removed at one time. This is the basis for the classic one-third rule for mowing frequency which is to never remove more than one-third of the leaf at one mowing.

Removing more than one-third can lead to scalping which exacerbates the stress created by removing leaf tissue and the plant uses more stored energy and takes more time to recover. Mowing frequency should depend on growth rate not day of the week. When following the one-third rule for an actively growing turf, a 1-inch turf should be mowed at least 3 times per week whereas a 3-inch turf can be mowed only once per week. Just labor alone, there is a big cost difference between heights.

Turf’s response to the mower

In addition to cutting the leaves, the mower can impact turf quality and playability through additional stresses. These stresses include things such as hydraulic leaks, tire wear, excessive clippings, improper mower setup, poor after-cut appearance due to mowing too fast and/or dull mower blades, mowing wilted or frosted turf, mowing saturated turf, mowing when too hot, spread disease and weeds, double/triple cutting, mowing thatchy turf, etc. A dense, actively growing turf can often tolerate these mower stresses. Be aware of these stresses and train your staff on how to limit them.

So, can you cut the soccer field lower for tomorrow’s game? It depends. A one-time drop in height that’s within the plant’s tolerance range should not lead to devastating consequences if the turf stand is healthy and there are few additional stresses present. Drop below the tolerance range and add some other stresses, you risk serious consequences.

Douglas Linde, PhD, is Professor of Turf Management, Delaware Valley University, Doylestown, PA.


Recommended mowing practices

  • Regularly sharpen and adjust mower
  • Operate mower properly
  • Match speed with conditions for a quality cut
  • Set cutting height within plant’s tolerance range
  • Follow the “one-third” rule
  • Limit double/triple cutting
  • Avoid mowing when: disease is active; when turf is drought and/or heat stressed; or when turf is saturated and heat stressed
  • Raise cutting height during environmental stress periods
  • Reduce thatch
  • Alternate mowing pattern
  • Mow grass when dry, if possible