By Heath Traver, CIC, CLIA
One of the great American pastimes is gathering together around the TV on game day to watch our favorite teams gear up and play football. There are a lot of factors that go into enabling these athletes to perform at such a high level and still remain as safe as possible. Yes, the equipment that they are wearing helps to protect them, but what is under their cleats is just as important. A field that is too dry (or too wet) can easily be the cause of serious injuries. Lower leg injuries have always been very common in the game, and now concussions are in the spotlight.
You rarely hear an announcer talking about the field’s playing surface unless there’s an issue. Many onlookers (if they are even thinking about the grass) rarely consider the effort that goes into keeping a field of that caliber in pristine shape. Most fail to realize the challenges that are faced by people in the sports turf world. They do not think about weather or other factors that would inhibit the field from being ready for game day, or the events that may have been held in between games.
Many things have to happen before a field is ready for the TV cameras. Of course, at the higher levels of play, teams have the resources to ensure that the field will be close to perfect. One of the biggest complaints that I hear while talking to people in the sports turf industry, is that their fields are being overplayed without the resources to be able to keep the fields up to the standard that is expected of them. Most of the professionals in our industry are asked to do more with fewer resources, and I expect that trend to continue.
A tool that can help a sports turf manager control the moisture content of a playing surface is irrigation. Sometimes Mother Nature does not provide us with the amount of water required to keep plant material healthy, and supplemental water must be applied. An irrigation system can come in many forms. There are portable types of irrigation, such as quick couplers, which are typically underground in a valve box and can be hooked into with a key. The key, which is attached to a garden hose, opens a valve, and water is allowed to pass through the hose, enabling the end user to put down water wherever needed.
Another type of portable irrigation system is a water reel. These reels can be moved from field to field, and automatically travel in a straight line while they apply water. Portable irrigation systems have less upfront costs, but are more labor intensive.
In-ground irrigation systems are more expensive up front, but are typically automatic. The ideal time for running a system will vary from field to field based on a variety of conditions. They are usually set to run overnight. Ideally, the field should have enough time for the surface to dry before anyone is using it, but not too early in the evening. If the field is allowed to be wet for a long time overnight, fungi and other types of diseases have a better chance of taking root.
How often and how much water is applied is also field-specific, and has always been a debated topic. Most professionals believe that a greater amount of water applied less frequently, promotes deeper root growth and encourages overall healthier turf. If the moisture in the soil profile is below the majority of the root system, the roots are forced to grow deeper into the soil in order to find the water.
It is very typical that a grass field will require an inch of water per week to remain healthy. This number may climb if the field is under heavy usage or if harsh climactic conditions exist. If we were to apply 1 inch of water per week to a typical football field, we would need approximately 60,000 gallons of water. If we multiply that number out using the typical 6-month growing season that we have in the Northeast for example, the turf will need approximately 1.5 million gallons of water in a season. These are very conservative numbers. Since we are dealing with a very large amount of water, it is critical that we are intelligent in the way we approach irrigation. This means only applying water when needed, and only applying the amount of water that is required by the soil to keep the turf healthy.
There are many ways to determine how much water needs to be applied. The first and simplest method is with the naked eye. Most sports turf professionals can look at the turf, and immediately tell if it is stressed. Some signs are that it may have a blue-green hue, or if a footprint fails to go away in a timely manner. These are indications that there is a lack of turgidity due to dry soil conditions. This is not the worst thing in the world, as many believe these conditions encourage the roots to grow deeper looking for water. However, if the soil is left dry for too long a period, the grass will eventually die. Secondly, soil probes can be used to determine how much moisture is in the soil, and how deep the water exists in the profile. These two methods for determining soil moisture content have less upfront costs, but are more labor-intensive.
There are also automatic methods for determining soil moisture. Rain sensors and soil sensors can also be used to monitor the moisture levels, and can shut off a system when the soil gets to a preset threshold due to a rain event. New irrigation systems also have the ability to utilize weather data to adjust how much irrigation water is applied. The system can use an onsite weather station, or use online sources to get evapotranspiration (ET) data, which is a combination of the water evaporating from the soil and the plant transpiring, or “sweating.” ET is affected by weather conditions (wind, solar radiation, temperature, humidity), and represents the amount of water that must be put back into the soil to keep the plant material healthy. The EPA estimates that these types of smart controllers provide water savings of about 30%.
Since we are dealing with millions of gallons of water, it is important that we irrigate as efficiently as possible. This all starts with the design and installation of the system. Proper design by a certified professional is the best way to ensure that the system has been designed with optimum uniformity based on available pressure and flow. The installation contractor also has an important role, and should install the system following the designer’s specifications. If the contractor decides to value engineer the project by eliminating heads, the system will probably end up with poor uniformity. When a system has poor uniformity, the end user will typically increase the zone runtimes to compensate for the weaknesses in the system, and the rest of the field will end up being overwatered. This is a very wasteful practice, and can be avoided with proper design and installation.
Another trend that is slowly being adopted by the sports turf industry is the use of sub-surface drip to irrigate turf. Since this is considered unproven technology, there has been resistance, but in parts of the country where water is less plentiful, this method of irrigating sports turf is slowly being adopted. The main things to consider when utilizing subsurface drip are that the drip will need to be deep enough to be clear of the aerator that will be used for regular maintenance, and that traditional overhead irrigation will need to be used in order to establish the seed or sod for a period of time until the roots find the water below.
Regardless of how we elect to manage moisture on a playing surface, the fact remains that moisture management is critical in ensuring that players are as safe as possible. This remains true at all levels of sports turf management, and is not going to change any time soon. Whether we are talking about million dollar athletes in high stakes games, or our children running around, keeping the playing surface as safe as possible will always be crucial. As always, it will be up to the sports turf professionals who are on the front lines of the ongoing battle, protecting those who have the privilege of playing on their turf.
Heath Traver, CID, CIC, CLIA is a specification manager for Rain Bird in the Northeast US, and is licensed to practice irrigation in New Jersey. Heath can be reached at firstname.lastname@example.org
High-end moisture control
One of the most important factors involved in keeping a grass field healthy is moisture control. Many stadiums employ a SubAir (or similar) system to control soil moisture content. These systems are essentially giant blowers that are hooked into the existing draining system below the playing surface. With the flip of a switch, the SubAir system’s vacuum mode can be activated. Negative pressure is created under the playing surface, and water and air are sucked through the soil, pulling through any unwanted moisture. Conversely, the SubAir can blow air into the drainage forcing air up through the soil profile. This can help aerate the soil with fresh oxygen, as well as help to control the temperature of the soil. It can be cooled when the temperature gets too hot, and it can also warm up the soil in order to “wake up” the grass earlier in the spring. This can be an excellent tool but comes with a hefty price tag.