When Grass Needs to be Watered
The only way to keep grass green during dry periods is to water it. Most lawns use 1 inch of water per week. Heavy claylike soils hold 2 to 3 inches in the root zone, enough to last a lawn for 2 weeks following a good soaking. Sandy soils hold only 1/2 inch or less so they need watering more frequently.
On the heavier clay and silt soils, watering should be fairly slow and prolonged. It may take more than an hour of sprinkling to soak 2 inches of water deeply without any running off. On sandy soils such as occur near the beaches, water would be wasted if more than about 1/2 inch were applied, and this soaks in about as fast as you can water. Because it drains so quickly, it should be watered every 3 or 4 days during drought periods.
Well-established lawns can usually become completely brown from drought yet come back green when conditions again turn favorable. So most watering is for appearance's sake rather than for the health of the grass. As a matter of fact, watering sometimes helps the weeds more than the grass, encouraging annual bluegrass, nutgrass and other water-loving weed species.
If you are interested in installing an irrigation system, select one that applies water evenly at the right rate. In most cases it is advisable to have them installed by a professional to be sure of proper coverage, correct pipe size and adequate water pressure.