During the hot, dry summer, we need to pay attention to our lawns. Although most grasses can survive short periods of drought, it stresses and weakens them, making them more susceptible to other environmental problems.
Timely and adequate watering will help maintain a quality lawn. How much and how often you water depends on your soil type, and the amount of shade the lawn receives. Sandy, porous soils require more frequent watering; clay soil retains moisture longer as do sections of lawns receiving more shade.
Lawns need about 1 inch of water per week to maintain peak performance. The best scheme to develop a deep root system that can take advantage of a larger reservoir of water is to water deeply and as infrequently as possible. That may mean watering every 3 to 7 days in the summer, depending on soil type, temperature, rainfall, etc.
Although you should water as infrequently as possible, you should also water at the first sign of wilting grass. Ideally, your irrigation scheme should wet the soil 6 inches deep. This may be difficult on clay soils or on sloping sites. Do not waste water by allowing runoff to occur. In these cases, either turn the sprinkler off or move the sprinkler to a new location to allow the water to soak into the soil. After the surface has dried, move the sprinkler back and apply more water to further wet the root zone.
How do you know how long to water? Set out 5-6 open-top cans randomly on the lawn (tuna and cat food cans work best because they have short sides). Turn the sprinkler system on for 30 minutes. Measure and record the depth of water caught in each individual can.
Calculate the average depth of water from all of the cans. For example, you used five cans in your yard and the depth of water collected was 0.5″, 0.4″, 0.6″, 0.4″, 0.6″. Add the depths together and then divide by the number of cans you used (5 in this case). 0.5″ + 0.4″ + 0.6″ + 0.4″ + 0.6″ = 2.5″ / 5 cans = 0.5″ of water in 30 minutes.
Use a garden spade to determine how deep the soil was wet during the 30 minute watering. Push the spade into the soil. It will push through the wet soil easily, but will become difficult when it reaches dry soil. Measure the depth of the wet soil.
When you know how much water was applied in a 30 minute cycle and how deep that volume of water wet the soil, it is easy to determine how long the sprinkler head must run to adequately wet the soil to a depth of 6 inches. For example, the irrigation system put out ½ inch of water in 30 minutes, and wet the soil to a depth of 3 inches. Therefore, 1 inch of water will need to be applied to wet the soil to a depth of 6 inches, giving a run time of 1 hour.
For more information on conducting an audit of your irrigation system to make sure it is operating at peak performance, see the online publication on Irrigation Auditing at http://earthkind.tamu.edu in the Publications section.
After you have adequately wet the soil, do not irrigate again until the grass needs it. Drought stress symptoms will develop when the lawn needs watering. Symptoms include grass leaves turning a dull, bluish color, leaf blades rolling or folding, and footprints persisting for an extended period of time after walking across the lawn.
If you have spots in the lawn where the grass is turning yellow, wilted or stunted, be sure to differentiate between lack of water and chinch bugs. Make sure your sprinklers are all operating efficiently. Heads can get partially plugged or misaligned, or sprays can be obstructed, causing a non-uniform pattern of water distribution. Dig in the affected spot with a shovel to be sure the soil is moist several inches deep.
Chinch bugs are mainly pests of St. Augustine grass, especially during periods of hot, dry weather. Adult chinch bugs are black, about 3/16 inch long, and have either fully developed or very short wings which, when held in place across the back appear as white spots. Immature chinch bugs range from 1/16 to 3/16 inch long and are either dark grey or orange-pink and have a white band across their abdomens.
Chinch bug infestations are usually spotty and often are restricted to just a part of a lawn. Usually hot, sunny areas or dry areas next to concrete walks, drives and the hot side of brick homes are the first to be attacked. These insects injure grass by sucking sap from grass stems and by injecting a toxic substance that prevents the plant from transporting water.
Infested spots at first appear dry and wilted, or stunted with some yellow and brown leaves. The usual assumption is that the grass needs water. However, chinch bug damaged grass does not respond to irrigation; instead the grass turns yellow and dies.
Check suspected areas for chinch bugs during the heat of the day by carefully observing the greener, outer edge of affected patches of grass for the rapid movements of these small insects. In large infestations, you can often see them quickly darting back and forth, up and down on the blades of grass.
One way to drive them out of the thatch so they can be more easily seen is to flood the area with water or with a dilute liquid dishwashing soap solution (1 oz. per gallon of water to 2 square feet of sod) where the damaged and healthy grass meet. Some folks cut the bottom from a coffee can, force it into the soil and fill it with water. Chinch bugs, if present, will float to the top. Check several areas to be sure. If found, treat the area with an insecticide labeled for chinch bugs. Insecticides containing bifenthrin, cyfluthrin lambda-cyhalothrin, or permethrin are suggested products for treating chinch bugs. Read the label for specific instructions and follow the directions for application.
For more information on chinch bugs, see the AgriLife Extension publication on chinch bugs.