Billy wrote:

the soil of the prairies was probably produced over
the period of time after the last ice-age. it isn't that
thick. if it could accumulate at a rate of an inch a
year it would be much deeper...

Best guess is 500 years/inch to produce prairie topsoil which was
approximately 10" thick when Europeans showed up..

There are two separate time spans here. One is the 13,000 years of
prarie since the last ice age. One is 5000 years to build 10 inches of
top soil.

Either the process eventually maxed out at 10 inches of top soil or
something very dramatic happened 5000 years ago to scour the top soil to
very thin. Let's check back in meteorology - Nope, nothing that
impressive that long ago. Conclusion, once the top soil reached 10
inches it maxed out and no longer grew.

So the article is about a guy who can grow an inch a year. Excellent.
Let's see how deep it is when it maxes out. Even better let's purchase
the stuff by the truckload and move it elsewhere so it never does max
out.