Vicpiz,
There are always new ideas coming out about how to plant new trees and what kind of soil to use. The most common that I've heard lately is not to ammend the soil too much. The line-of-thinking here is that the tree will prosper in its compost-rich soil, growing quickly, and just plain lovin' it. But then, once those roots hit outside the radius of ammended soil, they reach the local soil and they say, "Whoa...I think I'll hang out in this good soil!" and they grow no further. And then the roots become root-bound (all intertwined) and the plant's health begins to decline.
So, with all that in mind, here's what I do:
I always ammend the soil with some quality compost 1st. In order to avoid the above problem, I try to do a pretty large area if possible. And continue adding a compost mulch around the tree annually, gradually increasing the diameter. Otherwise, just dont make the soil too much better than your local soil.
Oh yeah, and when planting, dont forget to create a berm. The top of the root ball should be a little above ground level...maybe a couple of inches. Then form a small slope that drains water away from the stem but collects it at about 1'- 2' away from the stem. This is done by forming a small, circular moat, with walled-up dirt to hold in the water. A little mulch added goes a long way in that:
1) holds moisture longer
2) keeps soil temperature at a nice warm level
3) biodegrades to add nutrients to the soil.
Now, when watering, fill up the little 'bowl' that we created, let it soak in, and then fill it again...and maybe one more time - depending on how dry it is.
The great thing about this system is that it helps prevent stem rot (water drains away from stem), it promotes outward root growth (the water is channelled up to 2' away from stem, drawing the roots out there), and you can systematically water your plant...let's see, I fill the 'bowl' three times twice a week.
