Best Way to Irrigate
July and August are the highest water use times of the year. We have a combination of warmer days, hotter temperatures and little if any rainfall. All this adds up to a higher evapotranspiration rate. Evapotranspiration is a combination of evaporation of moisture from the soil and transpiration from plant leaves. Leaves transpire water vapor from their leaf pores for cooling.
The best way to irrigate you lawn and other landscape areas is to apply enough water to reach the full depth of the root system. You can develop a deep root system by allowing the soil to dry between irrigations. It requires at least 1/3 inch of moisture to reach six inches deep. A 10 minute irrigation will only wet the top inch or two of soil. It is better to water for 20 or 30 minutes and then wait 2 or 3 days between irrigations.
You can determine how long it takes to deliver 1/3 to 1/2 inch of water using your sprinklers by placing shallow cans such as tuna fish cans on the lawn. Water for a specific interval such as 30 minutes and then measure the accumulated water with a ruler.
When you place a can in brown spots and another in nearby green areas, you will probably find that they are not receiving the same amount of water. You may be able to adjust your sprinklers so the water distribution is more uniform.
Raising the mowing height will also help in keeping your lawn green. Years ago I observed two different experiments on lawn mowing height. Both showed that the amount and depth of grass roots is in direct proportion to their leaf surface area. Lawns mowed at 2 inches will have twice the root system as lawns mowed at 1 inch. The greater root system makes the grass more efficient in extracting water from the soil.
Sometimes brown areas are patches of native grasses which turn brown in summer regardless of how much water they receive. Most of our Northwest lawns are a mixture of grasses, including some native grasses which have invaded by seeds blowing in. The only way to eliminate these brown patches is to resod or reseed those areas.
