Here is an article I read in the Dallas Morning News:
Do you know how much water your lawn needs?
Most people don't. If you turn on your sprinklers two or more times a week, you might be overwatering.
Watering too much isn't just wasteful. Deep and infrequent watering is better for the health of your grass. Such a schedule helps grow deep roots, which makes grass less susceptible to freeze damage and disease. A general rule is to give your lawn one inch of water per week. A more precise rule is to water enough so that the soil is moist to a depth of 6 inches.
How do you determine how long to run the irrigation system? The Texas A&M turfgrass program recommends these steps:
- Set out five or six open-top cans, such as old tuna or cat-food cans, randomly on the lawn. You need at least five because sprinkler heads don't spray uniformly; some areas of your lawn get more water than others.
- Run the sprinkler or sprinkler system for 30 minutes.
- Measure the depth of water in each can.
- Add the water depth in each can and divide by the number of cans. This gives the average depth of water. For example, three of the five cans measure 0.5 inches of water, one measures 0.6 inches and the last 0.4 inches. Add up the five (2.5 inches), divide by five (you used five cans), and you get 0.5 inches of water in 30 minutes.
- Once you know the depth of the wet soil and how long your sprinkler system ran, just do the math to figure out how long the system needs to run to put out an inch of water. (In our example, the sprinklers put out a half-inch of water in 30 minutes, so an inch of water would be an hour.)
Clay soil such as ours, which doesn't drain well, presents special problems. If water is running off your lawn after 20 minutes or so, split the time you water. Water, let the soil dry for 30 minutes or an hour, then resume watering until you reach the ideal time.
After the initial 20 minutes of watering a lawn planted in native clay, push a garden spade into the ground. "It will push through the wet soil easily, but will become difficult when it reaches dry soil," the turfgrass site says. Measure the depth of the wet soil. If, for example, the depth is 2 inches, you triple the watering time to wet the soil to the desired 6 inches deep.
You can follow the general rule to give your lawn one inch of water per week, or you can go one better: Irrigate only when the grass needs it.
How do you know when your lawn needs watering? Symptoms of grass that needs watering, according to the Aggie turf experts, "include grass leaves turning a dull, bluish color, leaf blades rolling or folding and footprints persisting for an extended period of time after walking across the lawn."
MORE WATERING TIPS
- While established lawns need deep and infrequent watering, newly planted turf needs light and frequent watering. Reduce the frequency and increase the amount of water when the new plantings take root.
- Add in rainfall when calculating how much water the turf needs that week.
- Water in the morning to minimize evaporation.
- Trees suck up moisture, so grass near trees will need more water than other areas.
- Make sure sprinkler heads are in good condition and that they water the lawn, not the sidewalk.
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