The healthiest lawns are produced when they are watered heavily at infrequent intervals. On an average, the lawn needs about one inch of water per week, either through rainfall or in combination with irrigation. This one-inch rule will normally soak the soil to a depth of 4 to 6 inches, allowing the water to reach deep into the root system.
No matter what kind of irrigation system or method you use, check and adjust it to the soil’s absorption rate. A good rule of thumb is to apply water at a rate equal to or slightly less than the soil’s ability to absorb it. Most irrigation systems apply water faster than is necessary, which wastes water through run-off. Also, don’t forget to check to see if the system is applying water uniformly.
The best way to check both of these functions is to set out a series of straight-sided, flat-bottomed cans for an in-ground system or a few cans for a movable sprinkler system. (Tuna fish cans are great for this!) Run the watering system for 30 minutes and measure the amount of water collected. You can determine the length of time needed to apply one inch of water with a little simple math. If you know the soil type, check the absorption chart below to figure out how long the system needs to run in order to soak the lawn to a desired depth of 4 to 6 inches. Remember to stop the watering for an interval if you begin to see run-off.
Hilly or sloping areas may require a soaker hose to reduce run-off and allow better water penetration into the soil. Soakers apply water slowly over a small area.
Let the lawn completely dry out between watering intervals. Most lawn grasses can tolerate dryer conditions over a reasonable period of time. Water only when a probe or screwdriver is difficult to push into the ground or it shows that the soil is dry 4 to 6 inches down.
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