Irrigation Basics

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How much and how often should you water your grass?

Sounds like a pretty basic question, but the answer isn't a simple one.

Irrigation and watering needs are dependant on many factors — the kind of grass you have, your soil profile, mowing height, and the kind of irrigation system or sprinkler system you have. Plus, of course, what Mother Nature doles out.

My basic irrigation schedule takes into consideration temperatures and rainfall:

Normally, turf and landscapes in this area do fine with 1-1½ inches per seven-day week when daytime temperatures are in the 70s and 80s.

As daytime highs hit 88-92, you can probably up that to 1-1½ inches every four to five days.

When temperatures exceed 93 degrees consistently (normally July-August), you should probably water every two to three days.

The kind of grass you have is also very important. St. Augustine needs the most water, Bermuda the next most, and Zoysia far less than the previous two.

Your soil, however, is ultimately the most critical factor. Clay or sandy soils not very well enriched with organic matter definitely need more water because they dry out quicker.

Water early in the morning. That's when water pressure is best, there's less wind to evaporate the moisture, and the turf will have a store of water for the warm day ahead. If you have an automatic sprinkler, schedule it to run between 3 and 8 a.m. If you don't have an automatic system, start the sprinkler when you first get up. If you water at night, you run the risk of suffering fungal diseases like brownpatch.

How do you determine how much time it takes for your system to put out an inch of water? Place an empty tuna or cat food can at the farthest point the spray pattern reaches. When it fills up, that's how long it takes. Depending on the system, the time can range from 15-45 minutes.

If it seems some of your neighbors don't run their sprinklers as much as you, it could be they have more organic matter in their soil. Rich, organic soil doesn't happen overnight, though ... enriched topsoil or soil activators need to be added consistently each year.

Finally, if you aren't mowing as tall as your lawnmower will allow, make the change today. Tall grass in good soil develops deeper roots which draw a larger volume of deep moisture, requiring less supplemental irrigation. Plus, lawns mowed tall provide shade for the soil surface.

There is one caveat to all of the above, however. Newly sodded lawns need to be watered on a daily basis during the heat of the summer. Keep the "mud" wet under the root zone so it will break down and allow the roots to establish in the soil below. Don't drown the new sod ... just keep it moist enough to soften the soil and help the roots grow down.

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