Use water efficiently to irrigate lawns

Happy Gardening
by William H. Bohl

I’m an avid bicycle rider, and love riding with no wind and a temperature of 65 to 75 degrees. Although I’m able to ride in those conditions, oftentimes it’s too hot, too cold, too windy or some combination thereof.
Homeowners with automatic lawn-sprinkler systems are more often able to irrigate in the very early morning when there is usually little to no wind and cool temperatures, which are ideal conditions for using water efficiently. However, homeowners who irrigate their lawns with hose-end sprinklers generally don’t irrigate in the very early morning, so tend to irrigate during the daytime hours, which tends to be a less efficient use of water.

Depending on the type of sprinkler and numerous other factors such as water pressure, wind, temperature, etc., only 50 to 70 percent of the water leaving the source is actually delivered to a lawn. All too often I see lawns being sprinkler irrigated on a hot and windy afternoon resulting in the least efficient use of water. If your water is metered and you’re paying by the gallon, this is especially costly.

It’ll take a little time, but you can easily determine how inefficient it is to water during hot and windy conditions. Place several equal-size cans on the lawn and run your sprinkler in the cool early morning hours with no wind for a set amount of time, say 20 minutes. Pour all the water collected into one can and measure the depth in inches. Divide the inches collected by the number of cans to determine the average inches applied. Then, repeat the procedure in mid afternoon with wind.
An ideal time to irrigate is 10 p.m. to 6 a.m. If you can’t irrigate at this time, some experts suggest watering from 6 a.m. to 10 a.m. before temperatures rise and the wind may begin. There is some debate about watering a lawn beginning at 6 a.m. because of the possibility of diseases. However, it’s likely that lawn diseases will only increase if a lawn is continually over-irrigated. In our dry climate lawns usually dry rather quickly, so from a water-use efficiency standpoint, water anytime from 10 p.m. to 10 a.m.

A common lawn watering error, especially with automatic systems, is to apply too little water too frequently. At this time of year, you should apply about one inch of water every four to five days unless you have sandy soil in which you should apply about one-half inch every two to three days. Detailed information about applying the correct amount of water to a lawn can be found at http://www.cals.uidaho.edu/edComm/pdf/CIS/CIS1157.pdf.

Happy Gardening!

Bohl is Extension Educator with University of Idaho located in Blackfoot. He may be contacted at 785-8060 or wbohl@uidaho.edu.

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