[Terrapreta] Black soil

[Kevin Chisholm]

Dear Richard

Richard Haard wrote:
> Kevin - i know you have been puzzling on this.

Yes indeed! Given that we have a Terra Preta Soil, did it originate from 
basically a "natural black earth" to which was added nutrients 
associated with human habitation (fish bones, food scraps, nightsoil, 
etc), or was the addition of charcoal essential to the formation of a 
Terra Preta Soil?
>
> Here is a very nice, basic piece from NRCS on soil color. It 
> specifically deals with soil colors of the prairie states, Iowa and 
> Kansas
>
> http://soils.usda.gov/education/resources/k_12/lessons/color/
>
> It seems there are a number of factors that effect soil color. First 
> the mineral composition can cause black soil colors. These are Iron 
> sulphides FeS, pyrite (FeS2), and manganese oxide. In addition, humus 
> gives soil the same munsell color as above (black). It is interesting 
> there is no mention of black carbon as a reason for soil color

If the soil pigmentation was primarily from Iron Sulphides and 
Manganese, the soil itself would probably be toxic to growth. Natural 
"black Earths", such as the Holland Marsh outside Toronto are probably 
organic matter per se, with their black color being due to organic matter.

Then we get close to teh question... is there "free carbon" in such 
natural black earths? If so, is it beneficial to growth?
>
> So far as the role of organic matter, not only is the organic matter 
> responsible for the color of some soils it is also the interaction of 
> the soluble organic pigments that move down in the soil with minerals. 
> Also interesting is Kansas (prairie) vs Wisconsin (forested) in the 
> latter example water soluble carbon leaves the surface and white 
> quartz remaining. We find all examples in Washington from the dark 
> soils of the Olympic rain shadow to the silica sand on the surface at 
> Snoqualamie Pass in the subalpine zone barely 70 miles away.
>
> Ain't nature great?

Mother Nature is fabulous!!
>
> ------------------------------------------
>
> Your point # 2
>
>> 2: Fully degraded organic matter that is basically only Carbon.
>
> Fully degraded organic matter is CO2 not C . Lets do some reading on 
> this but my thought is that the endpoint of organic matter 
> decomposition in soil are these humic acids that are very complex, 
> resistant molecules that serve use in soil just like clay colloids. 
> Eventually they do decay through metabolic action of microbes and 
> oxidation.

OK... by "fully degraded carbon," I had in mind natural organic 
materials that were stripped of their Oxygen and Hydrogen components, 
leaving "free carbon." Given that charcoal, also "free carbon" can last 
throusands of years in the soil, it would be reasonable to assume that 
"free carbon" released from decomposition of organic material would also 
be long lived.
>
> If carbon were the end product on this then in the desert where 
> virtually all detritus is consumed by oxidation then where are the 
> dark soils in these places? Hmm

OK... it may be as simple as the decomposition process that liberates 
"free carbon" must have anaerobic conditions. The bottom of a pond can 
be very anaerobic.
> There is some searching that can be done on this and what analytical 
> methods they use to isolate charcoal from organic matter.  I think Ron 
> Deluca's papers may have something.

Would you have a URL for Ron's papers?
>
> I think I mentioned to the list at some point, the farm where i work 
> was cleared from second growth forest about 1947 and the original 
> farmer, George Giardi, who was born here in 1901 used a boxcar of 
> dynamite to clear the stumps. Last winter walking around a section we 
> leveled with a bull dozer and looking at the ground with slight sheet 
> erosion and there were tiny pieces of charcoal everywhere that I was 
> picking up. I suspect most soils are like this.

Very interesting! Can you see any local differences where the charcoal 
is, and where it isn't similar to the stripes Nikolaus sees in his fields?

Best wishes,

Kevin
>
> Rich
> On Jun 3, 2008, at 1:35 PM, Kevin Chisholm wrote:
>
>> Dear Richard
>>
>> Richard Haard wrote:
>>> Kevin We have boggy soil out here in western Washington that is 
>>> black and is now drained and farmed for blueberries. I cannot see 
>>> how this could be charcoal causing this color but rather high om.
>>
>> That is exactly the point. I believe we can get "black carbon" from 
>> two sources:
>> 1: Charcoal/burned grass
>> 2: Fully degraded organic matter that is basically only Carbon.
>>
>> "Organic Matter" is C with significant H and O. That is biologically 
>> available. On the other hand, as far as I know, charcoal, char, soot, 
>> etc are incapable of entering into a biological reaction.
>>
>> The question is: Is there any effective difference between charcoal, 
>> char, soot, and "free carbon" that came from other organic matter 
>> sources?
>>>
>>> In Iowa I am always amazed by those soils. Having lived in Kansas 
>>> and watched annual burning of natural prairie in the Flint Hills I 
>>> cannot see how much charcoal can accumulate from this practice. Its 
>>> benefit is release of nutrients to grasses in early spring .
>>
>> These soils are high in "organic matter". They may also be high in 
>> "free carbon" from degradation of organic matter, either through 
>> pyrolytic action, or through biological action.
>>>
>>> I think we are looking at a climatic zone. The old soil terminology 
>>> for these soils are chernozem or chestnut soils. Chestnut is the 
>>> color, not black. It has reddish tone when you look at it. I do not 
>>> know what the 'modern terminology' is for this soil type,  however 
>>> on the west coast of Washington in rain shadow areas such as Olympia 
>>> and Whidbey Island there are more limited areas of these soils. 
>>> These black soils in the corn belt is a band literally from Iowa to 
>>> Illinois and their persistence under cultivation is interesting. 150 
>>> years of cultivation and still black??
>>
>> Is it possible that they have a lot of "free black carbon", and that 
>> claims of "soil degradation are because the associated organic matter 
>> is being depleted?
>>>
>>> If I come across anything I will forward to you guys. It should show 
>>> up in a literature search.
>>
>> Please do!! This is one fascinating puzzle.
>>
>> Best wishes,
>>
>> Kevin
>>>
>>> My sister in law, Sac City Iowa has these totally amazing summer 
>>> vegetable gardens with production that outshines anything I can do. 
>>> On Jun 3, 2008, at 11:37 AM, Philip Small wrote:
>>>
>>>> I do not have the reference at hand, but I have read that some soil 
>>>> scientists are persuaded that, to a significant degree, the black 
>>>> appearance of prairie soils is due to charcoal, and that 10 - 30% 
>>>> of the organic-C in these soils is in the form of charcoal. My 
>>>> thought is that it was probably a lower percent before tillage 
>>>> increased the rate at which org-C evolves to CO2, (pre-Columbian 
>>>> was 5-15% of the org-C maybe?) since char would be more persistent.
>>>>
>>>> On Tue, Jun 3, 2008 at 10:56 AM, Kevin Chisholm 
>>>> <kchisholm at ca.inter.net <mailto:kchisholm at ca.inter.net>> wrote:
>>>>
>>>>    Dear Rich
>>>>
>>>>    Richard Haard wrote:
>>>>    > Not all black soil soil is Terra Preta
>>>>    > <http://www.flickr.com/photos/rchaard/2548787688/>
>>>>
>>>>    Very interesting point! What are your thoughts on the difference
>>>>    between
>>>>    "Black Soil" and "Terra Preta"?
>>>>
>>>
>>> I had hoped to run tp thru my fingers earlier this year but did not 
>>> have a proper visa. Maybe next fall I can give first hand report.
>>>>
>>>>
>>>>
>>>>    When is a "dark earth" simply "Black Soil", and when is it Terra
>>>>    Preta?
>>>>
>>>>    Kevin
>>>>