How to make trees drought resistant?

Here are a couple of pics from Carpenter ranch. While the recent drought did not affect us in any way, we are always watching out for new ways of optimizing irrigation water use. I came across this research findings in a recent article by Doll, who is a Univ of California nut crop advisor.

• Wait for trees to stress before watering: In other words, don't water your trees right when they need it. I know this sounds strange. Apparently, the goal here is to hold off on water so you can stress the trees a little more. This results in less vegetative growth (so no new branches or leaves) and fewer stomatal openings (fewer pores on the leaves - less water escapes thru these pores - more water is retained in the tree).   

• Cut back on nitrogen to avoid growth flushes: If you are reducing the water by 50%, you should reduce nitrogen application by 25%. Applying too much nitrogen will flush growth, increasing vegetation, which will require more water.