Terry Horton wrote:
Plants are not just passive recipients of whatever is in solution
around them. They in effect chemically "mine" surrounding minerals,
and feed other organisms in return for a supply of water and minerals

Absolutely! I wonder if research has been done to model the mass transfer
mechanishm that occur in the soil... that would be an interesting project.
I would think that every time you water a plant, the mass transfer
drastically changes and a more homogeneous concentration profile is achieved,
albeit temporarily.

Are you seeing evidence of P deficiency?

No, because everything gets bone meal when planted and organic fertilizers
throughout the year.

--
Victor M. Martinez

http://www.che.utexas.edu/~martiv