>> Our Colorado soil is crazy hard clay, unfortunately.
Ouch! You've got a few years of hard work coming, unless you can get YARDS of leaves or manure or coffee grounds or fruit stand throw-outs.
But my theory is that heavy clay CAN be amended if you have enough organic matter and a little coarse stuff like crushed rock or sand including some very coarse sand. Plus I like pine bark fines and nuggets, because they last longer than wood products.
Maybe you'll have to combine a cover crop with some "lasagna" sheet composting, to give the first cover crop anything it can get it's rootlets into.
Sandy soil, now ... However much organic matter you add one year is likely to be 100% digested in a year or two, and then you're back to sand. I guess with both kinds of problems, you have to add compost or OM every year, but I hear that sand eats a LOT of compost. Clay-ey soil is less well aerated, so i think it tends to digest OM slower.
>> Thought the guys were going to break their Bobcat planting a tree up front, had 1 guy operating it and 5 on the back trying to keep it from going completely vertical while digging!
Hah! I bet six guys with picks could have done it faster than 6 guys with a Bobcat. Did they moisten the soil the day before? I used to make that mistake, trying to break up DRY clay. That's when I was glad I had lots of rocks, because they made the dry clay easier to break up.
But if I wet it down and gave it time to soak in, a pick-blow would sink in 4-8 inches instead of chipping off tiny clods.
