Many of you likely watched at least some of the summer Olympics. I watched all I could. There were a number of commercials advertising automobiles with many touting fuel efficiency. With the price of gasoline, most everyone likes to get the most miles per gallon. However, shouldn’t we try to efficiently use everything including the water for our lawn?

    Depending on the type of sprinkler, only 50 to 70 percent of the water leaving the source is actually delivered to the lawn. Sprinkler efficiency is affected by the type of sprinkler, water pressure and droplet size, environmental conditions during watering and other factors. All too often I see lawns being sprinkler irrigated on a hot, windy afternoon. These conditions result in the least efficient use of water. If your water is metered and you’re paying by the gallon, then this is especially costly.

    It’ll take a little time, but you can fairly easily determine how inefficient it is to water during hot, windy conditions. Place several equal-size cans on the lawn and run your sprinkler in the cool part of the early morning with no wind for a set amount of time, say 20 minutes. Pour all the water collected into one can and measure the water depth in inches. Divide the inches measured by the number of cans to determine average inches applied. Then, exactly repeat the procedure in mid afternoon with wind.

    The best time to water a lawn is in the very early morning because there is less evaporation and generally no wind. An ideal time to irrigate is 10:00 p.m. to 6:00 a.m. With an automatic sprinkler system, it’s simple to accommodate these times. If you don’t have an automatic system, begin watering as early in the morning as possible, but stop by about 10:00 a.m. when the temperatures start to rise.

    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 days unless you have sandy soil in which you should apply about one-half inch every two days.

    A simple way to determine if a lawn has enough water is to push a long screwdriver or rod into the soil. If it goes in easily to a depth of 8 to 10 inches, then the lawn is adequately watered. This method doesn’t work well on sandy soils, however. Occasionally, it’s better to dig a hole in the lawn and feel the moisture content of the soil at a depth of about six inches. This will work on all soil types. Detailed information about watering lawns can be found at http://www.cals.uidaho.edu/edComm/pdf/CIS/CIS1157.pdf

    Happy Gardening!

William H. Bohl is Extension Educator with University of Idaho located in Blackfoot, 785-8060 or wbohl@uidaho.edu.