Best Watering Strategy
With southern lawns, the choice of grass type is perhaps most important when it comes to watering. If it seems you are watering too often to keep the lawn from going brown, re-evaluate your choice of grass. For instance, if you have a centipedegrass lawn, you may want to change over to more drought-resistant hybrid Bermuda or zoysia grass. Regardless, if you mow it to the correct height, and the soil contains sufficient organic matter, the roots will grow deep enough to access water deeper in the soil.
When you must water your lawn, water deeply and infrequently. Light daily sprinklings keep grass green but they also encourage roots to stay near the soil surface to get water. Because the roots have not penetrated into the soil very far, the grass dries out quickly as the moisture near the surface of the soil is rapidly depleted by evaporation. Also, roots of grass growing in compacted soil stay near the surface need frequent watering too, until the soil is improved.
When to Water
Water when the grass indicates that it needs it. Water in the morning, so it starts the day with moisture and has plenty of time to dry off before nightfall to avoid problems with fungal disease. Turfgrass signals moisture stress in two obvious ways. As it loses moisture from its cells it changes color, acquiring a drab bluish tinge. This is most obvious when you look out over the lawn in the afternoon when the dew has dried off.
The other obvious sign is failure of the grass to rebound when you walk on it and crush its foliage under your feet. Well-irrigated grass blades recover their shape quickly and your footprints will disappear within several minutes. Grass blades that are depleted of moisture will lie flat on the ground for up to half an hour. They need watering to restore fluid to their cells.
How Much to Water
Bahia, Bermuda and zoysia grasses are the most drought resistant. However, Southern turfgrasses generally need about 1 inch of water a week during the spring and fall and 2 or more a week during the summer to remain green in the heat. In healthy soil the more drought resistant grasses can manage for a week or two with no ill effects. Grass with shallow root systems typically needs watering once or twice a week during droughty summer months.
Water the grass down 6 to 8 inches. Adjust your watering time for the type of soil you have. To reach 6 to 8 inches deep deliver one half inch of water to sandy soil, 1 inch to loam soil and 1 1/2 inches to clay soil. To determine how much time your sprinkler takes to deliver one inch, set out 4 or 5 empty tunafish or cat food cans at various points in its watering pattern. Time how long it takes to fill these 1inch deep cans. If you have poor soil, then it is better to water only 1/2 inch at a time and do it every few days.
Considering In-ground Systems
While in-ground pop-up watering systems are seldom needed in the home landscape in the North, there are some conditions down South where such a system may be worth investigating. An in-ground pop-up sprinkler system is expensive to install and should be done by a professional company. The major attraction of such a system is that you can set it to water automatically whenever water is needed. These systems of course save you a lot of time and if used properly can protect your lawn from moisture stress.
Unfortunately, these in-ground systems are seldom used properly. Because the system is so easy to set, the usual mistake is to water much too often. Except for tropical areas in the Deep South, most southern lawns really don’t need frequent watering except possibly in the most intensely hot summer months, so compare costs and benefits of hand watering versus automatic watering. There is no question that if you have a larger than average lawn that is exposed to full sun and you are very serious about having a nice green lawn all summer, then an in-ground sprinkler system is an attractive option.