Feature Article - January 2022
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Fields of Green

Smart Strategies & New Ideas in Sports Field Maintenance

By Dave Ramont

Climate makes a big difference as far as which type of turfgrass grows best and how to maintain it, as each variety has its own requirements. For instance, Bermuda grass performs well in the southern United States, while Kentucky bluegrass is more common in northern areas. "At Iowa State we really push Kentucky bluegrass," said Tvrdik. "It's a dark, dense grass that stripes up nice and recovers well in our climate. And with new cultivars of bluegrass coming out, we are able to push it harder and expect more out of it than what we could in the past."

Keeping that grass mowed is obviously a critical task, and in many cases, athletic fields should be mowed at least twice per week, starting in early spring. No more than one-third of the leaf blade should be removed during mowing, which explains the need for frequent mowing. Some NFL teams mow three to five times per week, but of course most athletic fields don't have the maintenance budget for that. Therefore it's important to research how high the grass can get without causing damage to it when it's cut. Mower heights must also be considered, as this can affect turf roots, turf density and wear tolerance.

"When determining height of cut (HOC), there are a few items to consider: grass type, climate/season, sport and amount/level of usage," said Bergdoll. "Certain grasses perform better when cut at (certain) heights, and then you have to consider ball roll and playability." A higher cut of grass might slow ball roll while a lower cut will increase the speed. "These considerations should be taken when determining the grass type when planting a field."

When it comes to mowing equipment, there are many options and considerations, and while today's zero-turn mowers cover a lot of ground, Bergdoll explained that they might not be the best option for higher-profile athletic fields. Some manufacturers build mowers specifically for sports fields, which might be designed to stand grass up for a better cut and offer a wider width of cut, more cutting units or blades and rollers for striping. "Whatever piece of equipment is used, ideally you assign a specific unit for fields and/or certain grass types to decrease the chances of contaminating the athletic fields with weeds or other grass species," said Bergdoll, adding that blade sharpening is also important. "Sharp blades produce a clean cut that not only looks better but is better for the health of the plant itself."

Tvrdik explained that there are two basic types of blades for grass cutting: conventional blades and reel blades. "We use the conventional style like what's on your mower at home due to the ease of being able to sharpen them when needed. Reel blades are more commonly used on very short grass like a putting green. Since we cut most of our grass at one and one-quarter inches, we're able to get away without having reel mowers."

As far as fertilization, Tvrdik said they perform annual soil tests on all their fields to put together a fertilizer program that caters to what the grass needs. "We shoot to apply between four to seven pounds of nitrogen a year depending on what the soil test results are. We also spoon feed our turf; every two weeks we're applying small amounts of micro/macro nutrients to the turf to make sure it stays happy and healthy. We apply fungicides throughout the season to prevent any diseases from attacking the turf."

Tvrdik also said they core aerate their fields five to six times a year to prevent organic buildup in the sand-based root zone. "This also allows for great drainage and promotes a strong and healthy root system so our athletes have good footing. After we core aerate, we cover the field in sand to allow air and water movement through the profile."

Tvrdik also stressed the importance of drainage for keeping fields playable during inclement weather. "All our game fields are built on a USGA sand profile, which means we have 12 inches of sand on top of two to four inches of an intermediate layer, which sits on top of 12 to 14 inches of pea gravel with drainage pipes running throughout the field. Our football fields are all crowned to have water shed off them to keep the center of the field as dry as possible. Most native soil fields will retain water for hours after a heavy rain where having a sand-based system will allow for quick drainage."

Bergdoll agreed that poorly drained fields have a negative impact on use and increased maintenance input. "Ideally having some type of internal drainage system is preferred, but at the very least having the field graded properly to ensure surface runoff is very important."

On the flipside, Bergdoll said some of their fields have irrigation systems, and stressed that water and moisture management are key pieces of maintaining natural grass surfaces. "However, breeders continue to develop new varieties of turfgrasses that require less water, and we try to incorporate those when appropriate to help reduce that input and be more sustainable."

Tvrdik reported that all their fields have subsurface irrigation. "We monitor moisture levels at two- to three-inch depths to make sure we aren't overwatering or underwatering. The moisture-level reading is crucial in telling us how much water to apply or how long to hold off. All our scheduled irrigation times are based off of moisture-level readings."