If it ever stops raining:Learn when to water

March 24, 2005
Victoria County Master Gardener Intern

It's the oldest saying in the world: "The grass is greener on the other side." Is this true in your neighborhood? There are so many characteristics that could cause a neighbor's turf to be greener than yours. And by the way, greener may not be better! A really dark green turfgrass may be one heading for failure. If it is a dark green, there are too many nutrients applied, which predisposes the turfgrass to a high level of disease. While that is a whole other topic for another article, my goal today is to tell how to water your turf so it can receive your approval of a green, healthy lawn.

You might ask, "Why talk about watering grass now when we have received so much rain?" Well, remember it WILL get dry in a short few months and there are other reasons, too, that I will mention shortly. First, let us stand back and observe our lawn - and see what it is telling us. If signs of folded leaves, footprints that don't spring back when walking across the grass, wilting grass or an overall change in color of the canopy from green to a bluish or brown hue exist, your lawn is screaming "drought stress." On the contrary, your grass can be sitting in water (walking in it will cause a sloshing sound), and it can also wilt from being waterlogged. If this occurs, quit watering and look into ways to improve drainage.

Now that sounds simple, even elementary, but it is unbelievable how many yards have had sprinklers running through the wettest past six months in our history! Excessive water affects grass just like excessive nutrients affect grass (since water is a nutrient) and this, too, can lead to failure with disease problems when the weather warms up. Waterlogged soils kill deep roots and only shallow roots remain alive, if the grass survives.

While we can't easily change our soil type, an ideal turfgrass soil has equal parts of air space, soil and water. If there is truly air space in the soil, then it usually does not get waterlogged. But if you are blessed with the heavy, black clay soil, your turf may suffer from waterlogging due to very little air space in clay soils and recent persistent rains. The best advice is to drain the soil internally by putting in drainage tiles. This allows for a more ideal soil profile, one that produces root growth throughout the entire profile instead of just in the top few inches.

So now let's say everything is getting back to normal, things are drier and grass leaves are starting to curl. When should you water? David Chalmers, Texas Cooperative Extension turfgrass specialist, says that the best time to water is in the early morning. The wind is usually calm and the temperature is low, so less water is lost to evaporation and the grass is already wet with dew so you are not extending the wetting period. The worst time to water is in the late evening because the grass stays wet all night and into the dew-covered morning, making it more susceptible to disease. Also, the evaporation rates are higher in the evening.

Next we need to consider the duration of watering. There are various methods to use. If you like to manage your lawn correctly, then you need to apply enough water so the soil is moistened to a depth of 4-6 inches. Chalmers shared a method to measure this with our master gardener training class last fall. His method consists of sporadically placing five cans in your yard (tuna cans work great). Turn on the irrigation system or sprinklers and water for 30 minutes. Use a ruler and measure the amount of water in each can and record the information. Calculate the average depth of water. His example used was: 0.5 +0.4 + 0.6 + 0.4 + 0.6 = 2.5 inches. 2.5 inches divided by 5 (cans) equals 0.5 inches of water in 30 minutes.

Next he said to take a garden spade and push it into the ground opening a hole 6 inches deep for a cutaway view. You are looking to see the depth the water soaked into the soil. Once you know this, you can determine if you need to add time to the 30 minutes or decrease time to achieve the 4-6 inch soaking. The goal of this is to eliminate runoff and waste of water, yet still provide a deep watering for a healthy root system.

With many irrigation systems, timers can be set to have a greater efficiency in watering, especially if there is loss from runoff. Set the timer to have several cycles for short periods of watering, still totaling the full time length, to help eliminate runoff. Water 15 minutes, wait one hour, and water the second 15 minutes. This allows the water to soak in instead of running off.

There is one more approach Chalmers discussed with the class. Again, his goal was to maintain a healthy, water-efficient canopy of green grass. He stressed that those who live in Texas need to be more responsible with their use of water, and be "water wise." One way to be water wise and help gauge when to water is to find out the total water loss from the turf soil system through evapotranspiration, or ET. While this can be a complicated process, the potential ET estimated by many weather sites assists you in calculating when to water. With further research and experimentation with this process - and data more readily available for our area - more information on this type of water management will be provided to you in a future article.

So, if you are not into digging into your lawn to see if it is dry 6 inches deep, just let the lawn dry out and water only when the conditions are starting to look dry, but not stressed, as described above. Keep in mind, you still need to gauge runoff and the length of watering time because you don't want to over-water. This, too, provides a more efficient use of water and a healthier lawn.

With this knowledge, you can successfully water your turf when it begins to show signs of drought stress. You can also help Texas conserve water, save on your water bills and achieve a beautiful carpet of green grass.

While turfgrasses and their care will be not emphasized on the upcoming Annual Garden Tour, each yard does have a kept and managed lawn in its landscape design with planted beds and containers. Be sure to mark your calendars for April 30 and May 1. Tickets will be available at various outlets the first week of April. A new feature this year will be two educational workshops available each day of the tour. If you are interested in bonsai or container gardening, consider signing up on a first-come, first-reserved basis. Look for more AGT information in each upcoming issue of this column.