A
consultant friend of mine used a CO2 / humic acid extractant that he developed.
The thought was to get a more accurate read relevant to biological methods of
producing crops. Testing calcareous soils common in the SW US seem to require a
different approach although this sort of method may be relevant for other soils.
The important question is -- Do the numbers you generate relate to the
response you see in the field? If they don't, it doesn't have much
value.
Another tack is to do bio-assays such as culturing
azotobacter or pot tests. Of course, this does not generate the crisp and exact
numbers that has become the norm for assessing soil.
John Cowan
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