Effective water resource management is quickly becoming the most important environmental issue of many municipalities throughout the country.
It is no secret that turf grass, a living organism, needs water to survive, but are we managing our turf areas wisely to ensure we are providing enough water without wasting this precious resource?
There is no set answer to the question: “How much water does turf grass need?” Due to many variables — like turfgrass species or cultivar, soil texture, soil structure and environmental conditions — it is extremely difficult to accurately determine. However, there are things you can do to mitigate water usage and still maintain quality turfgrass.
Quantity & Quality
Water resource management takes two forms — water quantity and water quality. Here, we’ll focus primarily on water quantity. In other words, how can we maintain our sports turf and other turf grass areas to high standards and still reduce the amount of water we currently use?
First, we’ll look at the turf grass plant and its need for water, then we’ll look at managing that need most effectively and efficiently.
The living portions of a turf grass plant can be up to 80 percent water. Water is used by the plant to transport nutrients and organic compounds, to maintain turgidity (stiffness), is a requirement in and is a part of many metabolic processes within the plant, and — through the process of transpiration — helps the turf grass plant control temperature. In fact, turf grass uses more water to control temperature than any other function.
Transpiration is the process by which turf grass roots take up water from the soil, then deposit it into the atmosphere through stomata (tiny openings in the leaf tissue that open and close) as a vapor.
It is this process of changing water from a liquid to a gas, that energy is used with the result being cooler temperatures, i.e. evaporative cooling. Together, evaporation and transpiration provide us with a measurement called evapotranspiration (ET).
Some of the factors that increase ET are temperature, humidity, wind and turf grass vigor. To answer the question posed earlier, turf grass ideally needs the amount of water that is lost through ET. The difficulty is that ET can be drastically different from one point to another, even just a few feet away.
On the good side, turf grass has adapted to deal with fluctuations in water amounts. Stomata will close to slow the release of water into the atmosphere, wilting will begin to change the orientation of the leaf blades to the sun, and as the water supply lessens the plant will go into dormancy, conserving water for the crown of the plant which must be kept alive for re-growth.
There is also strong evidence that stressing a plant through a lack of water will aid in deeper roots as they grow to seek a water source.
A moderate amount of stress from a lack of water is good for the grass. Deep and infrequent watering will produce deeper roots and use less water. The whole idea is that grass with a deep root system will be healthier and require less water than one with a shallow root system.
Soils also play an important part in water use and conservation. Most new golf course tees and greens as well as many sports fields are being constructed with a sand-based root zone that has large pore spaces to increase drainage, minimize compaction and promote deep rooting.
When constructed properly, water will quickly drain through the upper surface, then form what is called a perched water table deeper in the soil profile. This water table then provides a water reservoir deep in the root zone to encourage deep rooting.
Conversely, soils with high percentages of silt and clay have smaller pore spaces, making it more difficult for roots to penetrate. They also have a tendency to puddle water at or near the surface, which leads to shallow rooting. The small pore spaces also limit water infiltration into the soil.
A sustained program of core aerification and top dressing with sand can increase rooting depth, water percolation and a medium for gas exchange, all of which produce a stronger plant.
I highly recommend having both your existing soil and your proposed topdressing sand analyzed for compatibility prior to starting a program.
I highly recommend having both your existing soil and your proposed topdressing sand analyzed for compatibility prior to starting a program. There are many quality soil testing labs in the country. Contact your extension representative or land grant university for a lab in your area.
Deep rooting is the key to sound water use when managing turfgrass. During peak root growth times — spring and fall for cool season turfgrass and during the summer for warm season grasses — it is imperative you do all you can to encourage deep roots. This means core aerification to reduce compaction and encourage deep rooting. On cool season turf it means reducing your nitrogen fertilizer during the heat stress of summer to reduce leaf growth. On Bermuda grass it means increasing nitrogen to encourage root growth, especially when you are attempting to rejuvenate it.
Most turf managers irrigate too often. The key to healthy turfgrass is to water when the plant needs it, not because it’s convenient for you to set your clocks to turn on every other day.
And, when you do water, do so deep enough to wet the entire root zone. In other words watering deep and infrequently will produce a turfgrass stand with deep roots, less incidence of disease and less water use.
Visually, bluegrass and ryegrass will turn a dull blue-green just before wilting. It is then that the roots can no longer provide enough water for the plant’s needs and it is then that you must water to avoid wilt and possible dormancy.
Another task that can reduce the amount of water and produce a much healthier turfgrass is an annual irrigation audit. An irrigation audit is a thorough check of your irrigation system prior to its use for the season.
While a full irrigation audit can be complicated and should be conducted by or with the advice of a qualified irrigation consultant, some of the items that will be checked are:
• Water pressure and volume
• System leaks
• Pump station function
• Sprinkler head function
• Proper water distribution
Irrigation timing is a factor that can also affect water use. However, what is ideal for the plant is not always ideal for the turf manager.
Having the ability to irrigate in the early morning is ideal because you can apply the water, have it soak in, then allow the leaf surface to dry quickly with the break of dawn and rise of temperatures.
With multiple fields this is not always possible. However, if you can water when the grass would be wet anyway because of dew you will diminish the incidence of diseases. You may find water scheduling one of the most challenging aspects of your job.
Manufacturers of irrigation systems have long been concerned with water usage. They have come through in a major way to help you in your pursuit of water conservancy.
Various nozzle trajectories, precipitation rates and droplet sizes will allow you to water in windy conditions with little loss.
Radio or hard wire central irrigation controllers provide the flexibility needed to adjust times with the stroke of a few keys, a hand held radio, a PDA or even your home computer or telephone. Information from satellite controllers can be sent back to the central to alert you to any problems that may have taken place during the previous watering cycle.
Rain sensors can turn off an irrigation system automatically and integrated weather stations that calculate ET can program your daily water requirements into the controller for you.
As most municipal and sports park facilities are substantial distances apart it is imperative that you consider a centralized controller that can communicate to each location from one central office. This presents the best opportunity manage your watering needs.
There are many things you can do to mitigate water usage in turfgrass areas and still maintain quality grass. Evaluate your system for maximum effectiveness, develop turf maintenance practices that encourage deep rooting, perform an irrigation audit every year and if possible invest in technology that will minimize water waste.
Dale Getz is a Certified Sport Field Manager (CSFM) for The Toro Company. Getz has 18 years of experience in turf management, including 12 years as the athletic facilities manager at the University of Notre Dame.