Some new landscaping at a (sprinkler system) customer's house wound up having an evergreen tree up and die a year or so later, even though it did receive watering from the system. What I'm wondering is whether the tree could have been set a bit higher when it was planted. It went into fairly heavy trucked-in fill, and I could envision the roots being starved for air in that heavy soil, especially if the homeowner set the sprinklers to run every day. (The site itself is rather sandy, and a fixed number of zones have to cover lawn and beds simultaneously) I had always left a little bit of the root ball higher than grade, on my own home plantings in clay soil, just to ensure that the roots could breathe if the ground got saturated. Of course, unless you mulch heavily enough to cover up the hump, it doesn't look good.