Watering your mature, healthy lawn every day, or even every other day, is the definition of overwatering. This is wrong no matter what other people tell you or what your neighbors do! What is wrong with watering like this?
Overwatering drowns the plant's roots
Grass plants do not need, and cannot use, this much water! The soil underneath your sod is composed of sand, silt, and clay particles - as well as porous spaces. When it rains, water fills those porous spaces by pushing out the air. Daily watering keeps those pores filled with water instead of oxygen, which is vital to plant growth. Without oxygen, the roots of the sod will suffocate and die, leaving the plant with a very shallow root system.
Shallowly rooted plants are easily stressed
When the roots of the turf plant die due to lack of oxygen, the plant is put under stress. This, in turn, makes them more susceptible to disease and insect damage. Minor disease and insect problems can become major lawn disasters when a lawn is shallowly rooted. Even though the roots are not easily visible, they alone determine the health and beauty of the plant.
Overwatered lawns have more weeds
To compound the problem, the weeds that overwatered lawns often have are the kinds that are more difficult to control. This is especially noticeable on a lawn that has been overwatered for more than two years.
Overwatering wastes time and money and contributes to pollution
Ground water is a natural resource. Wasting water on plants that do not need it just doesn't make sense. Pumping this unneeded water also wastes electricity. Established lawns do not dry in drought - they go dormant and start growing again after a rain. Your lawn will not die if you underwater it. Fertilizer that is applied to overwatered lawns is washed past the roots before it can be absorbed by the plant. Ultimately, this results in nitrate pollution of the groundwater.
Excessive fertilizer applications are needed
Since the fertilizer that you have applied is washed through the root zone before absorption, the lawn will lose color faster. The natural response, of course, is to then apply more fertilizer. In reality, one application that is absorbed, and not washed out, is all that is needed.
How to properly water a lawn
Homeowners want to believe they can have a beautiful lawn all year long by setting their sprinkler system once in the Spring. This is simply not possible because the only settings on a system are how often and how long a zone is watered. What really determines if grass needs water is how dry the soil is. Soil moisture is determined by air temperature, humidity, wind speed, rainfall frequency and amount, soil type, and overall grass condition. These are complex and interrelated factors and the type of equipment needed to take all these factors in account is not available to homeowners today. Until this technology comes along at an affordable price, homeowners will have to take a hands-on approach to lawn watering if they truly want to have a nice looking lawn.
The proper way to water a lawn is very simple: thoroughly but infrequently. When the soil is dry to a depth of five inches, water the lawn long enough to wet the soil five inches deep. When a homeowner has a new lawn and or a new automatic sprinkler system, he or she should take the time to become acquainted with both. The important area to explore is how much water does the sprinkler apply in, say, 30 minutes and how deep in the soil will this water go down? A garden trowel can be used to dig in the soil to see how dry it is. A screwdriver can be used to poke in the soil. By digging and poking, you can soon learn to equate how much effort it takes to poke the screwdriver in the soil with how dry the soil is. This saves you from constantly digging up your yard. Twelve hours after watering is long enough to see how deep in the soil the water traveled. Each zone should be checked the same way because there are usually differences in the amount of water each zone needs and how much water each sprinkler applies. A lawn can be watered any time of day but it is best to avoid watering in the late afternoon or evening. Early morning is a good time to water.
How do you know when to water?
Walking in your yard and looking for visual signs that it needs water is also important. St. augustine grass will get a bluish color, the leaves will look narrow, and your footprints on the grass will remain for a long time when the grass is dry. Ideally, the lawn should be watered the day before the visual symptoms occur.
Watering correctly seems complex, but all it takes is a little practice. Remember, your lawn will not die if you underwater it. There is a larger penalty to pay for overwatering than under watering!
Luc Limbourg is a graduate of ArtCenter College of Design, the owner of Green Team landscapes, an FNGLA certified horticulturalist, landscape designer and exam judge.