Adjust Automatic Sprinkler Systems
The hot weather in late August and early September made it necessary to increase the amount of irrigation needed to keep lawns green. Almost overnight plant water needs are decreasing as weather cools and days become shorter. As daytime highs drop consistently into the 70’s, you can reduce irrigation frequency.
The best way to decrease irrigation is to lengthen the interval between irrigations. Daily irrigation is always too frequent at any time of year unless you are starting new plants or a new lawn. Daily irrigation causes plants to have shallow roots because the soil is always dry except the top fraction of an inch. Keeping the top of soil moist also encourages weed seed germination. If you have been watering on a 2 day interval, the best adjustment would be to change the interval to 3 days. If your interval is 3 days, adjust it to 4 days.
In general, enough water should be applied in each irrigation to reach a depth of 6 inches. This varies from about ½ to ¾ inch of water. The length of time needed to apply this much water depends on several factors including the type of sprinkler heads, pipe size and water pressure.
An easy way to check water output with your specific sprinkler system is to place shallow cans such as tuna fish cans on the lawn or ground and turn the water on for a specific amount of time such as 30 minutes. Measure the amount of water accumulated and then calculate how long it will take to apply ½ inch.
By placing several cans at different distances from sprinkler heads, you will also discover how uniformly your system applies water. You will probably find that some areas receive twice as much water as others. If differences are too great you may want to contact a sprinkler contractor to adjust or update your system.
The best time of day to irrigate is between midnight and 7 am. Water loss due to evaporation is much less when the sun is not shining. Plant diseases are less when plant leaves are not wet for more than 6 hours. Sunlight right after irrigation allows leaves to dry out quickly.