Water needs vary considerably among the turfgrasses. Consider this when establishing a lawn, for it may significantly reduce irrigation needs during the summer. Of the common turfgrasses tall fescue requires the most water and buffalo-grass the least. St. Augustine, hybrid bermuda grass and common bermuda grass have intermediate water needs. Lightly water newly seeded or sprigged lawns at frequent intervals. Keep the seed or sprigs moist but not saturated during this initial growth period. This may require watering four or five times on hot, windy days. The first 10 days to 2 weeks are especially critical. If young plants dry out, they may die. After a couple of weeks root system development should be well under way and the watering frequency can be slowly reduced. At about 1 month after seedling or sprigging the lawn it should be treated as an established lawn. Purple or red colored bermuda grass may indicate seedlings are overwatered. If this occurs, reduce watering and plants usually recover.
Water newly sodded lawns much like established lawns except more frequently. After the sod is applied, soak it with enough water so that the soil under the sod is wet to a depth of 2 to 3 inches. Each time the sod begins to dry out, resoak it. Roots develop fairly rapidly and within 2 weeks or so the sod can be treated like an established lawn. Ideally, a lawn should be watered just before it begins to wilt. Most grasses take on a dull purplish cast and leaf blades begin to fold or roll. Grass under drought stress also shows evidence of tracks after someone walks across the lawn. These are the first signs of wilt. With careful observation and experience, one can determine the correct number of days between waterings. Common bermuda grass lawns can go 5 to 7 days or longer between waterings without loss of quality. Early morning is considered the best time to water. The wind is usually calm and the temperature is low so less water is lost to evaporation. The worst time to water is late evening because the lawn stays wet all night, making it more susceptible to disease.
When watering a lawn, wet the soil to a depth of 4 to 6 inches. Soil type affects the amount of water needed to wet soil to the desired depth. It takes about 1/2 inch of water to achieve the desired wetting depth if the soil is high in sand, and about 3/4 inch of water if the soil is a loam. For soils high in clay, an inch of water is usually necessary to wet the soil to the desired depth. If waterings are too light or too frequent the lawn may become weak and shallow-rooted, which in turn makes it more susceptible to stress injury.
Use the following steps to determine the amount of water your sprinkler or sprinkler system puts out and check its distribution pattern at the same time.
- Determine the rate at which your sprinkler applies water to the lawn.
o Set out three to five empty cans in a straight line going away from the sprinkler. Set the last can near the edge of the sprinkler’s coverage.
o Run the sprinkler for a set time such as 1/2 hour.
o Measure the amount of water in each can.
o Each can will contain a different amount of water. Usually, the can closest to the sprinkle will have the most water. The sprinkler pattern must overlap to get an even wetness of the soil. Use this information to find out how long it takes your sprinkler to apply 1 inch of water. For example, if you find that most cans contain about 1/4 inch of water after the sprinkler runs 1/2 hour, it would take 4 x 1/2 or 2 hours to apply 1 inch.
- Run the sprinkler or sprinkler system long enough to apply at least 1 inch of water or until runoff occurs. If runoff occurs first:
o Stop sprinkler and note running time.
o Allow water to soak in for 1/2 hour.
o Start sprinkler.
o If runoff occurs, repeat above steps until at least 1 inch of water has been applied and allowed to soak into the soil.
- Do not water again until the lawn has completely dried out. (This usually takes 5 or 6 days.)
o Apply enough water to wet the soil to a depth of 4 to 6 inches.
o Avoid frequent light applications of water.
o Water in early daylight hours.
o Select a turfgrass with a low water requirement.
o Avoid using soluble nitrogen fertilizers. (They promote high growth rates which, in turn, increase water requirements of the plant.)
Many soils will not take an inch of water before runoff occurs. If this is a problem with your lawn, try using a wetting agent, also called a surfactant, which reduces the surface tension of water making it “wetter.” This “wetter” water runs into the soil at a faster rate and goes deeper than water in a non-treated soil. There are a number of wetting agents available; apply them according to directions on their labels. If this does not solve to runoff problem, it may be necessary to apply 1/2 inch one day and 2 inches the next day.
