Danielle Davis writes

How many years can you plant the same crop in the same spot before all
the nutrients are gone from the soil.

That depends on whether you replace them or not.

There is a trial set up by rothamsted in the 19C and still running where
no fertilisers have been applied and the field is/was sown to wheat.

At least that is what is claimed. Unfortunately rothamstead do not
publicly supply this data unless you have a contract with them, and then
claim copyright anyway.

A highly deplorable situation for what claims to be a scientific
establishment, at one time government owned.

The answer, by the way, appears to depend on soiltype and the amount of
nutrients coming in via rainfall and soil breakdown.

On this farm, when we came in the 1970's, soil index levels were very
low indeed and yields by our predecessors were close to 2.5T/Ha when
adjacent farms were obtaining twice this. However our predecessors did
apply limited amounts of fertiliser.

--
Oz
This post is worth absolutely nothing and is probably fallacious.
Note: soon (maybe already) only posts via despammed.com will be accepted.