By: Evan Ware, Extension Agent, Agriculture and Natural Resources, Mississippi State University Extension (email@example.com) www.mobilecountymastergardeners.org
NOTE: Mobile County Master Gardener Alice Marty reads far and wide for good gardening information to share with all of us. She found this helpful piece written by a former agent at Mobile County Extension.
Home gardeners with irrigation systems often ask how long and how frequently it should run. The answer is a little more complicated than it may seem and depends on many factors. Of course, plant type and plant age (lawn or trees/shrubs, newly planted or established) is important to consider. You will also need to know how much water your system applies to each zone when it runs – your water pressure, sprinkler head type, and distance away from the water source are all factors that can affect this number. We typically get so much rain in south Mississippi (similar to Mobile) that frequent irrigation is not needed for the average home landscape. Watering your landscape when it doesn’t need it not only wastes water but can also lead to plant disease issues. However, we do sometimes have periods of drought, or may need to water new sod or plantings regularly while they establish.
The only way to know how long to run your individual irrigation system is to calibrate it. Follow these steps to calibrate:
· Calibrate on a day when wind conditions are calm.
· Set several flat bottomed, straight sided containers (all of equal size) equally spaced within a watering zone. Tuna cans or coffee cans work well.
· Turn on the sprinkler system for 15 minutes.
· Add all the water collected from each can into one container of the same size that you used. Measure the depth of the water in the container to the nearest 1/8”. Try to be as accurate as possible.
· Divide the measurement (in inches) by the number of collection containers to determine the average depth of water applied in that zone in 15 minutes. Multiply this depth by 4 to get an approximate rate in inches/hour.
· Adjust as needed.
Once you know how many inches/hour your irrigation system applies, make adjustments to your system. Don’t run the system any longer than needed, and don’t apply more than ½-inch of water per application. Use this recommendation as a guideline. Depending on your soil type, you may need to adjust this number. If you have sandy soils, you may need to add up to ¾ inch of water per hour since sandy soils don’t hold water as long. Remember to keep an eye on the weather and don’t let your system run when we get enough rain. Rain shutoff devices or soil moisture sensors can be installed to help make sure you’re not watering when it is not needed. Calibrating your irrigation system is an important step to save water and money and to decrease the likelihood of garden disease issues.
Also, remember to schedule your irrigation system to run in the morning when you can see it, to avoid any problems you might be missing. Irrigation heads get bent and broken over time. It's important to do seasonal checkups on your irrigation system to make sure that it is working properly.