Question: I dug a hole to plant a new tree and found that the soil was very dry below 3 inches. I am concerned about whether my trees and shrubs are getting enough water with my current irrigation schedule. My sprinklers are set to water 10 minutes every morning. That schedule is keeping my lawn green. If I water longer than 15 minutes, water starts to run off in some sloping areas. What would you suggest?
Answer: You might want to dig in several areas to find if the soil is consistently dry below 3 inches. Then increase the amount of water you are applying. You can program your sprinkler clock to run 2 or more times in succession on the same day. I would suggest that you try running through two 15 minute cycles on Monday, Wednesday and Friday. Turn the sprinklers off on other days (Tuesday, Thursday, Saturday, Sunday). This will give you almost 50 % more water than your present schedule. The 30 minute schedule should reach at least twice as deep (perhaps 6 inches). This will also allow the soil to dry out on top between irrigations. This will reduce the sprouting of weeds in both lawn and beds. Check your soil with a shovel after a week or two on this schedule. This will tell you if water is reaching the greater depth.
We have reached the peak of water use by plants and use will go down from now on as the days get shorter and temperatures decrease. As you gradually reduce irrigation amount, increase the interval between irrigations instead of reducing the length of irrigation time. Go to one irrigation every three days and then a four day interval.
In areas with trees and shrubs, you can increase the length of irrigation time about once a month to get water to the deeper roots. If this is not practical, you could water trees and shrubs separately once a month. Drip and ooze tubes apply water at very slow rates. They can be snaked through a group of shrubs and turned on for several hours (perhaps overnight). A line can be placed around a single tree at the outer drip line. Check with a shovel to see if water has reached 10 or 12 inches deep.