For many years, Columbia and Richmond counties have been on a three-days-a-week watering schedule. People with odd-numbered addresses may water their yards on Wednesdays, Fridays and Sundays while those with even-numbered addresses may water on Tuesday, Thursday and Saturday. No watering is allowed on Monday.
That has changed since the Georgia Water Stewardship Act went into effect June 2. The act "allows daily outdoor watering for purposes of planting, growing, managing or maintaining ground cover, trees, shrubs, or other plants between the hours of 4 p.m. and 10 a.m. by anyone whose water is supplied by a water system permitted by the (Georgia) Environmental Protection Division."
When EPD mandates water restrictions, each municipal utility must do at least the minimum of what it says, but utilities have the option of mandating tighter restrictions. Columbia County is continuing with its previous watering policy, but Richmond County is following the new EPD guidelines. That means if you live in Richmond County, you may water every day if you wish, just not between the hours of 10 a.m. and 4 p.m. with a sprinkler. You may hand-water with a shutoff nozzle any time of the day, any day of the week.
How often should you water your lawn? When it needs it, not on a regular schedule. There are numerous factors that influence the amount and frequency of water needed for a lawn, including soil type, turfgrass variety, management level, rainfall, temperature, wind, humidity and competition from tree roots.
The biggest factor this summer has been the extreme heat. There is a big difference between 92 degrees and 102 degrees. Your lawn might need watering twice as often because it dries out so quickly.
Different soil types absorb and hold water at different rates. Clay soils absorb water slowly and stay moist longer than sandy soils, which absorb water faster but dry out quickly.
Our warm-season grasses vary in drought tolerance. The order of tolerance (from best to worse) is Bermuda, St. Augustine, centipede and zoysia. Bermuda, with its really deep root system, is far and away the most drought tolerant. Contrast that with zoysia, which has shallow roots and needs water more frequently.
The frequency of rain has a profound effect on watering. It's amazing what rainwater does for the lawn compared with irrigation water. Rainwater probably lasts three to four days longer. You can get a 1-inch rainfall, and even with the extreme heat, you probably won't need to water for at least a week, if not longer. Put out 1 inch of irrigation water, and it hardly lasts three days.
On the management level, the more you fertilize, the more water a lawn needs, because fertilizer are salts.
When it comes to watering the lawn, the starting point is 1 inch, once per week. You then make adjustments based on the previous factors. The most common mistake I see is light, frequent watering, which produces shallow, weak root systems. A shallow root system prevents the efficient use of plant nutrients and soil moisture. Roots only grow where the soil is moist -- they don't seek out water. Watering for 15-20 minutes at a time with a rotary sprinkler only wets the upper inch or two of the soil. This causes the grass to be much weaker and more susceptible to disease and insect damage.
The key to success is to condition the grass to get by on as little water as possible. The time to apply water is just before wilt occurs. Most grasses appear grayish and dull, the leaf blades fold or roll and footprints remain after walking over the area. If dry conditions continue, the grass will wilt. Water the lawn when the first symptoms of wilt begin to show.
Keep in mind that the length of time you run an irrigation zone is based on the irrigation heads -- gear-driven rotary heads and spray heads. Rotary heads put out a single stream or somewhat patterned spray as they rotate back and forth or 360 degrees, while spray heads put out a constant spray in one place. Spray heads put out a lot more water in a shorter period of time. Most rotary heads put out 0.4 inch per hour, so even with good overlap it might take more than an hour to put out an inch of water. Most spray heads will put out 1.5 inches per hour so you don't have to run them as long.
How do you know how much water to apply to your lawn? It should be enough to soak the soil to a depth of 6 to 8 inches. This is equivalent to 1 inch of rainfall on an average soil. For sandier soils, a half-inch of water might soak down that far, while it might take more than an inch in clay soils. Place some cans in various areas and see how long it takes to collect 1 inch of water. Then find out the depth of water penetration by using a soil probe or shovel and adjust your system accordingly.
Take note that you should not run sprinklers from 10 a.m. to 4 p.m. I would suggest not watering at least until 7 p.m. In the heat of the day, you are losing at least half, if not more, to evaporation.
CORRECTION: In last week's column, I incorrectly stated that the area of a circle is twice the radius times 3.14. The correct way is the radius squared, times 3.14 (pi r-squared). Thanks to those of you who pointed this out. Now my kids won't ask me to help them anymore with their math homework!
Reach Sid Mullis, the director of the University of Georgia Extension Service office for Richmond County, at (706) 821-2349 or smullis@uga.edu.
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