Mineral carbon can be put there by biology?

Hey @DanT, @kanedan29 and @snapp, I talked to Tim LaSalle this week at a conference, and he was saying that there is some evidence that things like calcium carbonate can be produced by biological systems (specifically pooped out by earth worms), and by measuring only organic carbon we are potentially missing some of the most important long-term carbon storage that soil biology does.

He’s a smart guy (was head of Rodale, prof for 10 years, among other things) - you ever heard of that? Any thoughts? I’ll forward him this post, perhaps he can reply also with links.

It may be possible that CaCO3 can be produced by biological systems. However, in humid environments they are not going to remain in that form in the soil for very long. In dryland environments CaCO3 may indeed be an important component of total soil C.

From a practical standpoint, CaCO3, which is white, causes some real problems for NIR quantification of soil organic C. While measuring it may be important, I don’t think we could measure it the same way we measure organic C.

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Hey @gbathree, it is true that earthworms produce CaCO3, but I don’t know that I’d argue it’s a major source of soil C in most contexts. CaCO3 is generally pretty low in most soils unless it’s a soil whose parent material was limestone or something similar. I have a colleague who studies earthworms, so I’ve asked her for her thoughts. Also, CaCO3 is not necessarily all that stable a form of C. Easily mineralized by soil microbes in the right conditions.

I’ll echo what @DanT said. It presents real complications for VNIR methods. Some of our WY soils were CaCO3 rich and the model doesn’t predict all that well for them.

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