Might have gotten a quicker response up in the arborist or homeowner section. Here's my opinion. Water , then let dry. Usually once per week is sufficient although if sandy soil then maybe more often. I believe that underground sprinkling systems have caused many problems for trees since they are usually set to run every day or every other day. Have seen more root rot type problems since underground sprinkling systems have become more widespread. I'm from Michigan so it might be different in Arizona.