Alarson,
I have never actually counted from my wild seng.
In Scotts book he says to seed at a 4-5 seeds per sq foot rate and expect 1-2 mature plants per sq ft at harvest time.
He also says that for every pound of seed you plant that you should harvest around 7 lbs of dry root.
A pound of seed is around 7000 seeds.
So for every 1000 seeds you plant you should harvest around 1 lb of dry seng roots.
If you start off with 4-5 per sq ft and end up with 1-2 per sq ft.
On the low end 5 seeds produce 1 mature root (20% survival to harvest).
On the high end 4 seeds produce 2 mature roots (50% survival to harvest).
Again 1000 seeds should yield around 1 pound of mature roots.
50% of 1000 seeds would be 500 roots.
20% of 1000 seeds would be 200 roots.
I expect the answer is going to be more like 250-300 roots per pound.
Now that could vary quite a bit depending on the size of the roots, excellent site (high calcium levels) vs poor site (low calcium levels).
TNhunter