Its hard to know what to believe. I talk to one guy and he says, they don't like to be babied with fertilizer or water, it makes them grow too fast and weak. Another guy says the best osage is along the creeks, plenty of water, grows quick.
I think the seed stock is just as important as the growing conditions. There won't really be a way of telling how good the trees will be for bows until you grow and harvest it, and make a bow.
I have one osage in my yard, planted from a seedling that was given to me at an archery shoot. I planted it around 2008-9, staked it to help it grow straight. Its about 3 &1/2"- 4" in dia at the base, around 2&1/2" 6-7ft up the trunk. Never watered, except for the rain. Rocky, sandy soil, good drainage. Not in any hurry to want to get bows out of this one, thin rings no doubt, but hopefully they will be solid, dense ones.
I harvested some billets last year from a 40 year old black locust growing, about 10ft away. The wood from it looks excellent, large to medium rings. Dark, solid earlywood, not pithy. Looks like it should make nice bows.
I'd say my osage is quite slowly grown, you could probably get one one the same size in half the time.