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Photo courtesy of Weber Basin Water Conservancy District

What are the water needs of your lawn?

By Weber Basin Water Conservancy District | Posted - May 9th, 2019 @ 8:00am



We live in a climate that requires us to irrigate landscapes because natural precipitation doesn’t typically provide enough moisture through the summer. As the weather warms, we start thinking about irrigating our lawns. Despite irrigation water being made available as early as April, we typically have had good spring rains and sometimes even spring snow that provides plenty of soil moisture for our landscapes.

To encourage proper lawn root development and summertime health, the best practice is to wait to water for as long as possible in the spring. This typically means that our landscapes will not require any irrigation well into May. This practice allows the roots to grow deeper with the water that is already in the soil and will help keep our lawns healthy in the heat of the summer.

When irrigation is needed, the adage “more is not always better” rings true. There is a misconception that lawn in our climate needs to be watered every day. Lawns do not need water every day but knowing how often and for how long water is needed is a challenge for most.

Try to envision your soil as a reservoir from which plants can draw water (using their root systems). Water leaves that reservoir by traveling down through the soil and going below root depth, through evaporation, and by plant transpiration. The rate at which all this loss occurs depends on several factors, but early in the season and later in the fall the rate at which water is lost is much less than in the hot summer. Knowing how much water your soil holds or needs allows you to know how long to irrigate. Once you know how long to irrigate, you will only adjust the frequency of irrigation as the seasons change.

How long should you be watering your lawn?

A general guideline for irrigation cycles is to apply a half-inch of water each time you irrigate. For the average soil that is enough to fill the root zone (the top 4-8 inches of soil where most of the roots are) without overwatering. To know how long it takes to apply a half inch, put out an empty soup can in the middle of the area being irrigated and then measure the depth of the water in the can after you irrigate.

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Adjust irrigation time up or down to get about a half inch. If your sprinkler system is not applying water evenly, the measurement in your can could be off compared to the rest of your yard. For a more accurate reading, use multiple cans spread out and take the average amount of water collected after irrigation.

Better yet, take advantage of the district’s free water check program for those within Weber, Davis, Morgan and Summit Counties. They are performed by Weber Basin staff at your individual property. Call 801-771-1677 to schedule an appointment. For those living outside of these four counties visit slowtheflow.org to sign up.

Another option to get a more exact measurement of irrigation rates and uniformity would be a catch cup test. Follow this link to learn how to do it yourself from the Center for Water Efficient Landscaping: http://www.cwel.usu.edu/watercheck

How long it may take to apply a half inch depends on the type of sprinkler heads you have. There are two general types of heads; rotors (includes impact heads) and fixed pop up spray heads. Rotor heads have a stream of water that moves back and forth over the area being irrigated. Spray heads pop up and spray a fixed fan pattern over the area. These usually put out water at a faster rate than rotors for the area being covered. On average it may take 10-20 minutes for spray heads to put out half an inch of water and 30-60 minutes for rotors.

For those with heavy clay soils or who are trying to irrigate hills, try the cycle and soak method. To do this take the total amount of time you need to water to put down a half inch, and break that into two or three shorter periods, then allow 30 minutes to one hour between each short cycle so that water can move into the soil without runoff. You still apply the total amount needed, but you have put it into shorter cycles with soak time in-between.

How often should you be watering your lawn?

This question is almost as complicated as how long to water, it depends on your soil type, plant material being watered, and the weather conditions.

How does soil factor into how often I water? Varied soil textures hold onto water differently. One particle of sand is about 500 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, decreasing drainage and increasing 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 loamy soils, which means a good mix of clay, sand and organic matter will water somewhere in between.

Weather conditions also play a significant role in how often we may need to water. The warmer it is the more frequent the irrigation will be, however, there is no need to water every day in most situations. 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.

Graphic courtesy of Weber Basin Water Conservancy District

The exception to this may exist in very sandy, or rocky soils where short, but very frequent irrigation may be needed. The schedule below provided some general guidelines for how often you may need to water your lawn.

If you are finding it difficult to adjust your irrigation timer as frequently as needed, you might want to consider purchasing a smart controller that will connect to a local weather station close to your home and adjust the frequency of irrigation for you as the weather conditions change.

There are rebates available for Water Sense approved controllers. Visit http://weberbasin.com/index.php/rebates/rebates for more information.

These are general guidelines to try and help you have a healthy lawn and reduce excessive irrigation. Your soil, irrigation system, and landscape are unique to you. If you follow these guidelines and your lawn has a hard time staying green, make adjustments to your schedule in small increments to find the right time and right frequency.

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If you have been watering every day your roots are going to be shallow. It will take some time to train them grow deep and a little bit of stress on your lawn will encourage this. Try tapering off slowly. After a little while of watering as infrequently as possible your roots will be deep and your grass more drought tolerant.

It’s also a good idea to check your irrigation system regularly for broken, tilted, or heads that have been turned incorrectly. Sometimes the yellowing and dry spots in our grass are because of poor uniformity or inefficiencies in our system caused by a minor adjustment that is needed to the heads, not because you are not watering long enough.

If you have one or two spots that are always a problem, 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. Look for ways to improve sprinkler coverage in those areas.

A healthy lawn does require that we pay attention to irrigation, proper fertilization, and proper mowing practices. When lawn growth slows down in the summer or the dark green turns a little lighter, know that this is normal for cool-season grasses and doesn’t mean the lawn is dying. Other lawn stresses could be bugs, fungus, or simply a lack of water due to poor sprinkler system performance.

Because we live in an arid area that requires irrigation, we encourage you follow these guidelines for proper landscape irrigation. You can also consider some great alternatives to lawn that require much less water but still provide the attractive landscape you want. Visit www.weberbasin.com/conservation for classes and other resources to help you achieve water savings in your home and in your yard.

Weber Basin Water Conservancy District

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