[Terrapreta] Black soil

[MFH]

Thanks Richard, useful material.

 

Seems only iron and humus relate to black soil. 

 

Let me compare with the soils in the Gazelle Peninsular of PNG. The last
major eruption (neglecting for the time being the 1994+ eruption) was in
1937. These were eruptions where vast volumes of gas and pumice are released
in clouds that can rise thousands of metres, with the pumice eventually
falling back to earth under the spreading cloud of debris. Basically, the
'37 eruption covered a substantial area of fertile land with inert pumice to
depths up to 5m. Most of the damage to houses and trees occurs because the
pumice gets wet with rain, sets like concrete, more falls and gets wet, and
eventually this is too much for a roof and the building collapses. It sticks
on the leaves and branches of trees and palms, and these collapse leaving a
central trunk.

 

There were no deliberate attempts at rehabilitation of the soil. But it
rained, and the winds blew some organic debris over the landscape, birds
poo'd, and some dropped seeds that germinated. In about 10 years there was a
reasonable vegetation cover and the beginning of a humus layer.

 

10 years later this was supporting food gardens and copra and cocoa
plantations. By 30 years there was a 200mm layer of dark brown fertile soil
overlaying the almost-white and very porous pumice, and topped with a humus
layer around 100-125mm. 

 

The best of these soils is about this colour. There's no char and there's no
evidence of Fe beyond minimal. Its reasonable to assume that the colour and
vitality of the soil has come from the self-accumulation of organic matter,
aided by average rainfalls of 2500mm and a temperature range throughout the
year between 20 and 35C. In a cocoa plantation where machinery isn't used
between the rows, its normally possible to dig into the soil by hand to a
depth of 200mm. It feels right, smells right and is laden with organic
matter and worms. 

 

40 years ago there was a very distinct line between the topsoil and the
pumice. Over time this has broadened as the pumice starts to weather and
break down.

 

The colour is about like the following, which will probably show differently
on different computer screens. Its not black - more like a well-worn pair of
brown leather shoes that have been polished every day with dark tan boot
polish.



 

There's no evidence of char. These fertile soils have been created without
much help from Man over a relatively short time period. Certainly the
climate has helped, but to me the most critical factors are (a) they were
protected from exposure to the sun as soon as the initial "weeds" grew, and
(b) were equally protected from direct exposure to rain. 

 

There must be areas of the Amazon with a similar climate, and with similar
inert base soils. It seems that the Amazonians chose to improve their soils
by adding char whereas the PNG's basically let nature take its course.
Irrespective they both had an apparent understanding of the benefits of
living soil, a fact that seems to have escaped many industrial farmers.

 

Max H

 

 

-----Original Message-----
From: terrapreta-bounces at bioenergylists.org
[mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of Richard Haard
Sent: Wednesday, 4 June 2008 9:29 AM
To: Kevin Chisholm
Cc: Philip Small; Terrapreta
Subject: Re: [Terrapreta] Black soil

 

Kevin - i know you have been puzzling on this.

 

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

 

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?

 

------------------------------------------

 

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.

 

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

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.

 

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.

 

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

>>> 

>>> 

>>> 

>>>    _______________________________________________

>>>    Terrapreta mailing list

>>>    Terrapreta at bioenergylists.org <mailto:Terrapreta at bioenergylists.org 

>>> >

>>>
http://tech.groups.yahoo.com/group/biochar/

>>>    http://terrapreta.bioenergylists.org

>>>    http://info.bioenergylists.org

>>> 

>>> 

>>> 

>>> 

>>> -- 

>>> Philip Small, RPSS

>>> Land Profile, Inc. * PO Box 2175 * Spokane, WA 99210

>>> 509-844-2944 cell * 509-838-4996 fax * 509-838-9860 office

>>> Profile: http://www.linkedin.com/in/philipsmall

>> 

> 

> 

> 

 

 

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