by Charlene Burgi
Over the years, many questions have popped up regarding the best way to irrigate. Some customers asked if it was best to irrigate a little every day, or every two days, etc. Others asked if it was best to irrigate in the morning, afternoon, or evening. Some wanted to know what irrigation method is best for hillside planting.
And, over the years, many of you have heard me say to irrigate effectively as well as efficiently. To irrigate efficiently is to apply water to the root zone of the plant and replace just the amount of water lost due to evapotranspiration (ET). ET is the loss of water through transpiration from plants (we perspire, plants transpire) and through evaporation from soil. MMWD uses data from its weather stations to calculate the rate of ET and generate the Weekly Watering Schedule. Replacing just the amount of water lost keeps the plant and surrounding areas in balance, but this alone is not necessarily effective.
For example, suppose the ET loss for the week is one inch. A person could water a tiny bit daily, replacing just 1/7th inch of water each day to total one inch for the week. However, that tiny bit of water would barely wet the surface of the ground and evaporate quickly. Much better would be to apply a half inch twice a week or one inch of water weekly to get down to the root system of the plant. Water at that depth will take longer to evaporate—especially if there is a thick layer of mulch on top of the soil. That would be effective as well as efficient.
Another means of being more effective is to avoid irrigating when it’s windy or during the heat of the day. Typically, there is little wind during the evenings or early morning. If you set your controller to turn on after sunset or before sunrise, you’ll save water and comply with MMWD’s new daytime irrigation prohibition. Since your irrigation system will be in action while you sleep, do a quick monthly system check—running each station for a minute—to look for blown emitters or misaligned nozzles. During the month between system checks, simply look around in the morning. Do you see a puddle? Are the sidewalks wet? Are you finding dry spots or wilting plants? These are signs that adjustments or repairs may be needed.
Watering hillside plantings is a challenge in anyone’s book. There are steps that can be taken to make this irrigation challenge both effective and efficient. First, use very low-flow methods of irrigating such as drip emitters or MP rotators for overhead irrigation. Next, use multiple start and stop times on your controller. Some controllers call this the cycle/ soak program. Water for a brief time before you see any sign of runoff. At that time, program the controller to turn off. Let that water soak into the hillside for 20-30 minutes before setting the controller to start again. Continue the cycle/ soak until the water penetrates to the depth of the root system—but not until you find water run down the street!
Be water smart. A few moments to adjust your controller will yield water savings and happy plants. And please take a few minutes to become familiar with the current water conservation regulations.