Turfgrasses, like all plants, require water for growth and survival. Without significant rainfall, home lawns must be supplied water though irrigation. The most efficient way to irrigate or water a lawn is to apply water only when the lawn starts to show signs of drought stress from the lack of moisture. There are several ways to help determine when this time has come.
One of the first signs of drought stress is the color of the turfgrass turns from green to a bluish-gray to even a white cast. Another indication is the "footprints" on the turfgrass. If you walk across your lawn late in the afternoon, look behind you and see if your steps have left any footprints. If so, the lawn may need watering. When your feet compress the leaf blades of the turfgrass, the low water levels in the plant tissues prevent the leaf blades from recovering, or "springing" back up, after being pushed down. If the footprints remain for an extended period of time, water the lawn to prevent the turfgrass from turning brown and becoming dormant.
The visual condition of the turfgrass blades can also be used to evaluate drought stress. Turfgrass blades respond to drought stress by folding, rolling, and/or wilting. Another means of evaluating drought stress on a lawn is the "screwdriver" test. To do this test, push a screwdriver down through the lawn and into the soil. If the soil is very dry, it will be difficult to push the screwdriver down into the ground. Use this screwdriver test to confirm the results of the other visual indicators above to help determine when a lawn should be watered.
If your lawn exhibits the visual symptoms of drought stress, apply about ½ to 1 inch of water, which will moisten the soil to a depth of 4 to 6 inches, depending on the soil type and degree of soil compaction. Then, after watering, use the screwdriver test to determine the depth of water penetration. This will prove valuable in the future in determining how much water should be applied.
Unless the lawn has received a significant amount of rain lately, as a general rule, apply about one inch of water per week. Increase the amount to 1½ during severe dry periods. And it is also best to divide the irrigation time into two ½ inch applications per week. Frequent watering only encourages shallow rooting of the turfgrass plants, making the lawn less drought-tolerant. When watering, avoid applying water to the point of runoff. Allow the water to soak into the lawn and soil. If needed, apply less water and allow it to soak in before continuing with the watering process. The best time of the day to irrigate or water is early in the morning because it minimizes the potential for water loss through evaporation. Watering at night is not a good practice because it can promote various lawn fungal diseases and lead to damaged lawns
Automated irrigation systems are nice but can have flaws. Check to be sure your system is working properly and is applying the correct amount of water of one inch per week. Irrigation systems should be set or manually turned on twice per week in the early morning hours to meet this need. However, if significant rainfall has fallen for the week, then turn off those automated timed irrigation systems so water is not wasted.
Once you have watered the lawn, do not water again until you observe similar drought stress symptoms. Never water a lawn every day except during the establishment phase or renovation. Properly watering equals a happy and healthy lawn. Be good stewards of our drinking water and demand others to do the same.
Shane Harris is a Regional Extension Agent for the Alabama Cooperative Extension System serving East Central Alabama.