In a current study we found that soil fertility indicators (namely base saturation, exchangeable calcium, and resin extractable phosphorus) were shifted towards a drier end of the spectrum as compared to a very well studied, but much older, nearby system. These soil fertility indicators have proven to be a reliable method for mapping the extent of intensified agriculture of the region. We are trying to explain the shift towards the dry in this new system. One aspect we are convinced is playing a role is a kinetic limitation of weathering due to low surface area in these very young soils, but as I've been reading I feel that the very high carbon levels (20-30%) may also be interacting with soil minerals to repress the formation of secondary minerals (namely imogolite and allophane) and potentially reduce the retention capacity of the soils. Any thoughts on this?
Thanks for the response Mattias. I did know that it is complicated. :) But I'll check out that paper and see if it can shed some more light on it. What's funny is the very best resource I have found so far is a book from the 1980 (Soils of Variable Charge), that has been my bible in trying to discuss what's going on in our system.
Yes it's mostly all organic carbon. In some cases it seems very well integrated into the soils, so I've been assuming a lot of Al- and Fe- humus complexes. There are more analyses I'd like to do to try and figure some of it out, but unfortunately I'm out of time and money on this project.
Thanks for this new citation...definitely looks very helpful and I look forward to checking it out.
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