Is It Time to Irrigate?

Last Friday I noticed a few wilted areas in my lawn. So I decided it was time to irrigate on Saturday. Then I woke up to drizzle. The all day drizzle was enough to produce a surprising amount of moisture: about 3/10ths of an inch. Some areas received more than ½ inch. That is enough to put off irrigation for another 3 or 4 days.

We are very close to the point where the evaporation and transpiration will be higher than the moisture provided by the light rains this time of year. Many have already turned on their automatic sprinkler systems. I see many systems which are set to come on every day or every two days. What is the best time interval for irrigation?

Enough water should be applied to reach the full depth of the root system. Now is the time to 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 3 or 4 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.