How to Water Your Lawn Efficiently

Water deeply to encourage deep root growth. Frequent shallow waterings encourage weed germination, and they also cause the grass plants' roots to grow shallow, leaving the plant more susceptible to drought and to certain diseases. Watering only when your grass really needs it encourages the roots to grow deeper, but only if you apply enough water each time to penetrate the root zone. The most accurate way to determine the depth of the root zone is to dig a small hole and measure how far the roots go down. Alternatively, you can follow these general approximations: if you have a bluegrass lawn, each watering should moisten the soil to 6-8 inches, while for most other grasses, the water should penetrate 8-12 inches. You can determine how long to leave the sprinkler(s) on by using one of the following methods.

Turn on your sprinkler for 15 minutes. After 18-24 hours, find out how deep the water soaked in by digging a small hole in the watered area or using a probe (a probe will push easily through damp ground). You can also push a shovel into the ground and use it as a lever to spread the soil apart enough so that you can see several inches below the surface. Once you see how deep the water went in 15 minutes, you can calculate how long you need to leave your sprinkler on. For example, if the soil is damp to 4 inches below the surface and your goal is to moisten the soil to a depth of 8 inches, you'll need to leave the sprinkler on for 30 minutes (2 X 15 minutes) each time you water.

Estimate how much water you'll need based on your soil type. In general, 1" of water will penetrate sandy soils to 12", loamy soils to 6-8", and clay soils to 4-5". Using these estimates isn't quite as accurate as digging, but it's pretty close, especially if you have a good knowledge of your soil composition. To figure out how long you need to keep your sprinkler or sprinkler system on, calibrate your sprinklers.

Water early in the morning. When you use sprinklers, some water evaporates before it hits the ground. On a hot, windy day, the amount of water that never reaches your grass can actually be quite substantial. To reduce loss to evaporation, water sometime between 4 A.M. and 9 A.M., when the air is still cool and the wind is usually at its calmest.

Aim your sprinklers to water the lawn, not the sidewalk or street. Slight adjustments to your sprinklers can save a lot of water. Ideally, you shouldn't water your sidewalk, patio, street, or driveway at all.

Avoid creating runoff. Even with sprinklers correctly targeted at the lawn, many people water until (or even after) water begins to run off the grass and into the street or driveway. This can waste a lot of water, and it isn't doing your lawn any good. If water starts to run off your lawn before you've been able to give it a deep watering, turn off the water for 15-20 minutes to let the ground absorb the water, and then continue watering as needed (rotating a sprinkler between one area and another will also do the trick). Some soil types absorb water more slowly than others, but runoff can also be caused by excessive thatch buildup, which can promote disease--and which is sometimes caused by routine overwatering.