WHAT WENT WRONG? — PROBLEMS WITH ATHLETIC FIELDS (A PACIFIC NORTHWEST PERSPECTIVE)
Assoc. Prof. Hort.
Oregon State University
Once upon a time a school district decided to replace their mudhole sportsfield. They consulted several experts and contracted with a reputable engineer and experienced construction company. The site was excavated and drainage trenches were dug with a laser trencher. Trench spoils were removed from the site and drain tubing was installed. A uniform fine grade of drainage gravel was used to cover drainlines and form a base layer. A rootzone mixture of sand and organic matter was placed on the drainage layer. The field was equipped with a multirow automated irrigation system. Final grading was done with a laser grader and the field was seeded to a blend of perennial ryegrasses. Seeded in the spring, the field was ready for limited use that fall and heavy use the following spring. The field performed beyond expectations and the maintenance supervisor was a happy man. He decided to retire quickly before something went wrong!
What went wrong? That’s the question I ask myself when I look at athletic fields with problems. Unfortunately I rarely see fields like the ones in the fairy tale above. In fact, it’s amazing how many problems athletic fields can have. Problems can develop at the design stage, during construction, from improper maintenance, and from user abuse. In most cases one of several basic principles of athletic field construction and maintenance are violated. The following examples will demonstrate some of the ways that things can go wrong on an athletic field.
Several years ago an architect designed a field by installing drain tubing, a layer of drainage rock, a geotextile filter fabric, and a 16 in. layer of topsoil. To further insure good drainage the field was crowned so that the center of the field was 30 in. higher than the edges.
The field was seeded with perennial ryegrass and Kentucky bluegrass which produced excellent turf. Midway through the first season of use, the field was a mushy quagmire. The youth soccer league even refused to play on the field!
So, what went wrong? In a word, everything. From the drainage installation which used 2 in. drain rock to the geotextile fabric which restricted internal water movement, to the topsoil which puddled up quickly when the fall rains came, this field was meant to fail. The crown was not effective due to excessive footprinting and surface puddling. This is an extreme example of failure by design and an expensive one at that. The architect violated the cardinal rule that athletic fields must be free draining at all times. Proper drainage can only occur if water can move into and through the rootzone.
Sometimes people do everything correctly in constructing new fields and make a crucial mistake when the field is almost finished. For example, a small playfield in Oregon was constructed recently with full under drainage and a top mix of nearly 12 in. of top quality sand. It should have been a perfect field but during the first summer it became chlorotic and would not take water. By the end of the summer the field was thin and weak and so hard it couldn’t be aerated. What could have caused this problem? The cause was a 2 in. layer of bark dust that was applied as a surface mulch prior to seeding the field. The designer had studied proper construction techniques prior to drawing up his plans but added this layer because it seemed like it would make it easier to grow grass if there was some organic matter present. The solution to this problem involved repeated applications of wetting agents and numerous corings during winter and through the following year to break up the surface. Fertilizer levels also were increased to offset the effects of the bark in the rootzone.
The most common error I see in sand fields that fail to drain is surface sealing. In some cases this is due to accumulation of organic debris and in some cases thatch build up. In such cases, field drainage decreases slowly over a long period of time before failing. A common observation is that the field worked great for the first 10-15 years but in recent years it gradually started to puddle up.
Sometimes young fields seal up within a year or two of construction. This is generally due to the use of field grown sod to speed up establishment. The sod was always washed to remove soil but as soon as we dig up the surface we invariably find a 1/2 in. layer of soil. It’s hard to believe that such a small amount of soil could cause so much trouble but it effectively seals the surface every time.
The best solution to surface sealing is to remove the surface layer whether it is soil or thatch or just organic glup. The field should then be brought back to grade with quality sand and be reseeded. After that, regular thatch control, periodic coring, and weekly spiking during the season should prevent sealing indefinitely. Of these practices spiking may be the most important and the least disruptive. Spiking involves running vertically oriented V-shaped blades mounted on circular metal disks over the turf. Blades make a small slit in the turf surface and typically penetrate 4-5 in. deep. These slits help maintain infiltration rates and get water past thatch or any layers that may be present. The effects don’t last long so it is important to spike weekly or twice weekly during wet weather. Most people think they can eliminate the problem by coring frequently and topdressing with sand. I have never seen this approach work for any period of time. As soon as the rains come the holes seal over and the quagmire returns.
Occasionally fields appear to have very simple problems but upon examination we find much more serious trouble. I remember visiting with a school with a relatively new sand field. They called because the turf had worn out halfway through the season. On the phone it sounded like a simple case of too much use. After all they used the field for physical education classes, band practice, and played an average of three varsity games on the field each week. They also told me the field didn’t seem to drain as well as it was supposed to. That turned out to be an understatement. This field had everything wrong with it. Drain tubes were installed without trenching. When the topmix was put in place and graded many of the drain tubes collapsed. The topmix which was supposed to be 12 in. deep was as thin as 8 in. in some areas. To top it off, they planted sod grown in soil. The solution to this one was total reconstruction, and that’s what they ended up doing.
Not all problems are related to design and construction. Often the problems I hear about are due to inappropriate maintenance. Not too long ago I visited a school on the Oregon coast. They had a sand field which they weren’t happy with and wanted advice on what to do to improve it. I was shocked when I saw this field. It was one of the nicest fields I have ever seen.
Why were they unhappy? For one thing the grass grew too fast. For another it required too
much fertilizer. They explained to me their old field only needed fertilizer once per year while this one received four applications last year and was still light green. Whenever they fertilized the grass grew too fast! During my discussions with them it was apparent they didn’t understand why the field was built out of sand, what the maintenance needs of a sand field were, or anything else. With proper care this could have been one of the finest fields in the state but will likely fail due to gross ignorance on the caretaker’s part.
I’m often asked how many games can be played on an athletic field. That’s a hard question to answer because of all the variables that need to be considered. A soil field in the western portions of the Pacific Northwest may be mush after only ten uses in the fall but might tolerate fifty contests of spring and summer soccer with proper maintenance. A good sand field may tolerate forty football uses in the fall plus a hundred uses from spring through summer for soccer. Poorly maintained fields will provide good surface conditions for only a few uses. All fields will hold up better and last longer if they receive proper maintenance for the entire year. Proper maintenance includes regular mowing year around, irrigation as needed during summer, fertilization adequate to maintain turf density, coring three or more times per year to maintain good conditions for infiltration of water and aeration in the rootzone, spiking regularly in season, and overseeding throughout the year to insure turf cover in heavy wear areas. It also involves timely dethatching to remove accumulated surface debris. To achieve maximum smoothness, topdressing with sand three or more times per year may be necessary.
What goes wrong with maintenance of athletic fields? The most common problems are neglect in the off-season, over irrigation, inadequate nitrogen fertilization during summer months, failure to overseed regularly, failure to core and spike regularly, and failure to dethatch on a timely basis.
Where I grew up they used to let the football field grow up and go to seed in the summer. Each fall it was mowed down a few weeks prior to the beginning of football. No wonder the field was thin and weak during the season. The best way to strengthen turf is to mow consistently year around at an appropriate height for the grasses being grown (1-2 in. for perennial ryegrass and Kentucky bluegrass in the Pacific Northwest). I cringe when I see fields mowed at 4 in. all summer suddenly cut down to 1-1/2 in. at the start of the season. This scalping defoliates the grass, may cause depletion of reserve carbohydrates, often restricts root growth, and reduces turf density just before the period of major use.
I often get calls from people complaining that the grass on their field has very poor roots and tears out easily. The first thing I ask is whether they have an automated irrigation system. Usually the answer is yes. When I ask how often it runs, the answer is usually every night. This often occurs from April to October when fall rains come. This approach yields pretty turf that is lush and often dense but has a shallow root system, poor wear tolerance, and excess surface moisture. With use the surface quickly seals and we’re back to the mudhole syndrome.
There is no simple recipe for irrigating athletic turf. Without some means of measuring soil moisture tension or plant water use the best you can do is guess. The old argument of whether to irrigate once a day or once a week isn’t appropriate on sand fields. With sand based turf irrigation will generally need to be frequent but the goal is to put down only what the turf needs and no more. To make irrigation decisions either check fields regularly with a soil probe or fit your irrigation system with one of the newer devices for measuring soil moisture tension so the system will apply only the amount of water turf needs when it needs it.
What happens if fields are subjected to heavy use? Often the turf wears out! Does that mean the field is no good? No, it just means the turf wore out. What will happen if the field isn’t overseeded? Annual bluegrass and other colonizing grasses will quickly invade and dominate the turf. This scenario occurs on many fields every year. Since the grasses we plant initially don’t reseed themselves we need to do it for them or the fields will soon be dominated by annual bluegrass, bentgrass, or roughstalk bluegrass. Overseeding should be done every fall in areas west of the Cascades, Oregon and Washington, and as needed after that to maintain desirable grasses. Perennial ryegrass is the only grass we can overseed with predictable results. Overseeding must be viewed as a regular maintenance practice just like mowing.
Often when I visit fields with problems, I see serious compaction. When I ask to see the aerifier, either they don’t have one or it’s broken. The aerifier is an important component of any maintenance program but is often the least used piece of equipment in the maintenance shed. Fields cored spring, summer, and early fall will generally improve dramatically and often drain much better than non-aerated fields. Problems with localized dry spots often disappear and fields may require less irrigation during summer than they did before aeration.
The final category of problems I’d like to discuss is user abuse. The most common example is over use. Soil fields or even well maintained sand fields will fail quickly if used too heavily. Each field has a carrying capacity unique to that site. Determine that capacity by starting out with a conservative guess as to how much the field can handle. Keep records of use and compare the use records to field performance. Increase or decrease use as appropriate to provide good turf for most of the playing season.
I’ve never visited a school or park district yet where any kinds of use records are kept and used to determine how much traffic individual fields can handle. We tried it on a new soil soccer field and found that as laid out the field could handle only about twenty uses before it became unplayable in goal areas. Had the field been set up with portable goals, we estimated it could have tolerated up to 40 uses and still have been in better condition than it was with fixed goals.
The other major user abuse involves practice sessions concentrated in the center of the playfield. It’s not clear why the center of the game field is the only possible place where conditioning drills and other forms of practice can be performed. Maybe the solution to this problem lies in improved communications between coaches and maintenance personnel. We need to foster the concept of developing special zones for the various types of drills so wear and tear can be distributed throughout the total turf area available instead of the center of the game field.
This list of problems experienced on sports fields could go on and on. Those I’ve discussed so far rank among the most common types. The chief weapon we have to combat these problems is intelligent maintenance and a common sense approach towards use of fields.