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DON’T OVER IRRIGATE Water experts believe half of the water applied to lawns is wasted. Most turf is watered using culinary water. This means watering turf is expensive and water conservation is essential.
IRRIGATE INFREQUENTLY Water is usually applied too often and left on too long so water runs off. Turf studies have shown that most lawns only need to be watered once every 4-7 days to stay healthy and green. Learn to water only when needed. If grass does not spring back after being stepped on, it’s time to water.
DETERMINE YOUR LAWN WATERING NEEDS
Use the Lawn Watering Schedule at the bottom of the page as a guide to determine how often to water your lawn. For example, if the average water depth was 2 inch after 15 minutes, turn your sprinklers on in the spring for 13 minutes every 4th day. During the hottest part of the summer, irrigate 26 minutes every 3rd day.
LAWN WATERING SCHEDULE
1. Scatter at least 5 cans with deep straight sides and flat bottoms on the lawn at least 4 feet from a sprinkler head. Get a gallon can from a restaurant or school lunchroom. (A size 303 vegetable can works better than a tuna fish can.)
2. Turn on the sprinklers for 15 minutes. If water begins to run off the lawn into the gutter, stop and let the water soak in, then continue irrigation until water has been applied for 15 minutes. 3. Measure the depth of water in each can with a ruler and determine the average water depth in inches. 4. Match you sprinkler output (average water depth in cans) with the water depth column in the table. 5. Read the number of minutes to water your lawn in the column below depending on the season of the year.
Water Depth in Cans After 15 Minutes 1/8" 3/16" 1/4" 5/16" 3/8" 2" 5/8" 3/4" 1"
Recommended Watering Time in Minutes by Season
Spring (Water every 4 days) 52 34 26 20 17 13 10 9 6
Summer (Water every 3 days) 104 69 52 41 35 26 21 17 13
Fall (Water every 3 days) 69 51 39 31 26 19 15 13 10
Table prepared by the Utah Division of Water Resources DON’T WATER EVERY DAY Watering every day creates a shallow root system. Watering infrequently develops deeper roots and healthier turf. Lawns do not require a full watering as frequently during the spring as during the summer.
DISTRIBUTION UNIFORMITY Observe how evenly or unevenly the system applies water to lawn, garden and shrub areas. Use the catch can method in the Lawn Watering Schedule to determine the water volume variability in the cans. Unfortunately, sprinkler systems do not apply water uniformly without proper maintenance. Make adjustments to avoid watering paved areas.
SOIL PENETRATION Don’t apply water faster than soil can absorb it. For best results, check how long it takes the sprinkler system to soak the entire root zone (12 inches deep) of each section. Set timer clocks to water each section for deep soaking. Sandy soils hold less water per foot of soil and are irrigated more frequently than clay soil.
EVAPOTRANSPIRATION (ET) Evapotranspiration (ET) is the amount of water lost from both plants (transpiration) and the surrounding soil (evaporation). The rate of water lost (evapotranspiration) from a landscape depends on the wind speed, temperature, relative humidity and solar radiation.
TURF WATER REQUIREMENT The amount of water the turf requires varies each week during the growing season. Turf needs about 26 inches of water during the season. Typically the evapotranspiration (ET) rate from April to mid October is about 26 inches total. During June, July and August, water use varies around 1.5 inches of water per week.
ACCURATE IRRIGATION WITH ET Replacing the water lost by the landscape, requires knowing the predicted water replacement value form evapotranspiration determination. The ET values for clay, loam and sandy soils and the recommended days between watering are available. During the growing season, Utah State University Extension Service provides a recorded message on the ET values for the previous week. This predicts the number of inches of water the lawn will need during the next two weeks. (The information is also given in gallons of water required per 100 square feet.) Check the website
KSL Greenhouse Tip Larry A. Sagers Regional Horticulturist Utah State University Thanksgiving Point Office
