[Greenbuilding] Fence posts--gravel or concrete

[Benjamin Pratt]

I promised to help my friend put in a fence this summer. I was
recommending that he use gravel, or class 5 crushed gravel, to set
them in, rather than concrete. From my experience, concrete breaks
apart anyway when the post swells. I also think the posts would rot
more slowly in gravel, especially if there is a lot of gravel in the
hole underneath the posts. But he is skeptical. Do you agree with me?
Also, how deep should he put them in?  This is in minneapolis, MN.

-Ben

PS. No , he will not consider using a GFX  ;-)