We like green lawns in Utah and as the weather starts to warm up we need to start thinking about irrigating. Two frequent questions to consider are how often and how long do we run our irrigation systems to keep our grass green without wasting water? Here are some general guidelines to help you figure that out:
As a rule of thumb, put down half an inch of water each time you irrigate. For the average soil that is enough to wet the root zone (the top foot or so of soil where most of the roots are) without wasting (soak depth will depend on your soil type).
How long do I have to run my sprinklers to get half an inch? That depends on the type of sprinkler heads you have. Rotor heads are ones that have one stream of water that moves back and forth. These types of heads put out water at a slower rate than spray heads. Spray heads are those that pop up and the water is sprayed in a fixed pattern of quarter, half or full circle shapes.
So how do I know how much my heads are putting out? For sprays, an average application rate is .45 to .6 gallons per minute per head. For rotors, an average application rate is 4-5 gallons per minute per head. To find out exactly how much your individual system puts out do a catch cup test.
Follow this link to learn how to do this yourself from the Center for Water Efficient Landscaping: http://www.cwel.usu.edu/watercheck
Weber Basin offers a service where they will send a team of individuals to your home to do an audit on your system and help you figure out an individualized irrigation schedule for your yard. Call 801-771-1677 to schedule an appointment.
This question is almost as complicated as how long, it depends on your soil and what the weather is like.
How does soil factor into how often I water? It all depends on the surface area of your soils. That sounds complicated? Let us break it down. One particle of sand is about five hundred times larger than one particle of clay. This means that one cup of clay has much more surface area than once cup of sand. The more surface area a soil has the more water clings to it and it decreases drainage and increase water holding ability.
What does this mean for your watering schedule? If you have a clay soil you will need to water much less often than those that have sandy soils. Those that have soils somewhere in between will water somewhere in between.
The weather also plays a huge factor in how often we water. There is NO NEED water every day. Doing so encourages grass roots to remain shallow and encourages thatch. Both of which complicate irrigation and make lawn dry up when it’s too hot. Try this instead:
Have a hard time getting out to the garage to adjust your timer every time it rains or the temperature changes? Consider purchasing a smart controller that will connect to local weather stations and adjust for changes in the weather for you. Visit http://weberbasin.com/index.php/rebates/rebates for more information.
Keep an eye on your grass. These are simply guidelines that have been generalized. Your soil, irrigation system, and landscape are unique to you. If you follow these guidelines and your lawn has a hard time staying green, feel free to adjust your schedule. That being said, if you have been watering every day your roots are going to be shallow, it will take some time to train your lawn to grow deeper roots, a little bit of stress on your lawn will encourage deep roots. Try tapering off slowly. After a little while of watering as infrequently as possible your roots will be deep and your grass drought tolerant.
It’s also a good idea to check your irrigation system regularly for breaks or turned heads. Sometimes the yellowing in our grass is because of inefficiencies in our system, not because we need to water more. If you do have one or two spots that don’t seem to want to green up with the rest of the lawn consider watering these spots individually one or two more times a week with a hose rather than running your whole zone longer or more frequently.