Water has many important roles within plants and if the water content in the tissue should drop below 60%, the turf is seriously weakened and can die or go dormant. Water is not only essential for growth but necessary for conditioning turf to handle and recover from stress caused by heavy use and harsh environmental conditions.
Supplemental water is necessary when natural rainfall is not sufficient to keep turf healthy after the soils have dried out. Temperature, sunlight, wind, humidity and natural rainfall are climatic factors that help determine the amount of irrigation that is needed.
Know your soil! soil texture (determined by the amount of sand, silt and clay in the soil) influences the amount of water that can be stored and available for plant use. For example, coarse textured soils such as sandy soils have poor water-holding capacity and will need to be watered more frequently than soils with more clay and organic matter which can hold more water. Soils can differ from field to field. (See Soils section for more information.)
Keys to proper watering
Irrigation should be supplied to replenish the amount of moisture lost. Monitor conditions and water only when needed. You can use a soil probe or moisture sensors to check the soil and see if it is wet to a depth just below the majority of the root system which is about 4-6″. Also, turf takes on a dull bluish-gray color and its leaves curl when under severe moisture stress. If you can see your foot prints after walking on the turf and the leaves won’t bounce back…begin irrigation. If the field is used before irrigation is applied damage will result.
How much?
Turf should receive about 1″ to as much as 2” of water per week during the growing season. A rain gauge is a very inexpensive management tool that can be used to monitor rainfall. If rainfall provides ½” you will have to provide the additional amount of water depending on your soil and grass and evapotranspiratioin amount, or ET.
Turfgrass managers use ET to help determine supplemental watering needs. ET is the abbreviation for evapotranspiration, which is the combination of water lost from the soil surface and the water used by plants through the process of transpiration. Find rainfall information and ET values at the Forecast website.
How often?
Deep and infrequent watering, once or twice a week, is preferred unless you are on sand that needs more frequent irrigation. Another time when more frequent watering will be necessary is at the time of establishment. At this time it will be critical to keep the seedbed moist to ensure germination and may require daily watering, even several times a day.
Caution:
Never apply more water than the soil can absorb. Water that does not infiltrate into the soil will be lost to evaporation or through runoff. There is an environmental risk to water quality when surface water runoff carries soil particles that contain adsorbed nutrients. When water bodies, such as lakes, estuaries, or slow-moving streams receive excess nutrients plant growth is greatly stimulated. When dead plant material decomposes the dissolved oxygen in the water is reduced and this can cause other aquatic organisms to die. Therefore, proper water management and nutrient management are critical for protecting both soil and water resources and aquatic life.
Best time of day to water
Water in the early morning when the wind is calm. This allows for adequate time for the turf blades to dry off before field use. Turf watered in the late afternoon or early evening remains wet longer allowing disease organisms time to penetrate turf tissue.
Be sure to finish watering at least 24 and preferably 48 hours before a game. Some managers water the field after the last practice or game if needed to help turf recover from the stress.
Watering during the growing season
Overwatering may lead to disease problems and thatch development. The better practice is to water deeply and less frequently which may be 1 to 3 times per week.
If the fields are not needed for summer sports and are in good shape, don’t worry about supplemental irrigation and let the turf go dormant. Keep in mind that Kentucky bluegrass can survive in a dormant state for several weeks as long as the crown is hydrated so water ¼” to ½” every 4 weeks. Avoid traffic and management practices such as coring, verticutting or scarifying that may stress out the turf even more.
If the fields are in poor shape, summer watering may help them recover and get ready for fall use.
In preparing turf for winter keep the field on the dry side. The slight moisture stress actually enhances hardiness and winter survival. Do not, however, allow the turf to become drought stressed.
Watering systems
Portable systems: Many school and community sports fields do not have in-ground irrigation systems and rely on rainfall or above ground portable systems to provide needed water. Water reels, for example, are portable traveling irrigation systems that can be moved from the field to field once they complete the irrigation cycle. All above ground portable systems will take time and labor to set up, move and monitor to ensure adequate and uniform coverage.
In ground systems: If you have an irrigation system check the heads to make sure they are level and running properly. Check the uniformity of your system by conducting a catchment test which will also let you know how long to run your system to provide the desired amount of water. Cans or collectors of the same size are spaced throughout the area being watered. After a period of 10, 20 or 30 minutes the amount collected is measured and noted to determine the amount of water applied and if there is even distribution so adjustments can be made.
Finally
Remember: All fields are not the same. Soil texture, upcoming games and predicted weather will all factor into how much you will water and when. Avoid watering in windy conditions (>5 mph) because you will not get very uniform coverage. Over time you can gain experience with each field so you can determine the watering rate and timing based on your fields’ characteristics.