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Re:Nitrates in soil making iron unavailable?

Pat Bowerman wrote Friday, Dec. 15:
.................. I believe that you were quoting Paul Krombholz,
>when you said that nitrates in the soil can make the iron unavailable.
>Could either of you explain this further? Should this be a concern to
>those adding plant tabs to the substrate?

I was thinking that nitrates in the soil would only temporarily delay the
reduction of iron.  I was arguing that adding nitrates to the soil wouldn't
be a very good way to make nitrate available to plants because most of the
nitrates would be used by bacteria as an alternative to oxygen after the
oxygen was used up.  The bacteria would convert the nitrates to atmospheric
nitrogen, N2, which is unavailable as a nitrogen source for plants.  I was
arguing that not only would most of the nitrate nitrogen be lost by this
denitrification process, but also, while the nitrates were present, the
redox potential of the soil would remain too high for the iron to be
reduced.   Judging by the 'greening up' response I see in nitrogen
deficient tanks, my aquatic plants respond rapidly to even one or two ppm
of nitrate nitrogen.  I see no need to supply it through the soil.

Paul Krombholz, in Jackson, Mississippi where we had 7 inches of snow
Sunday. We havn't had anything like that since the last big El Nino year,