[Terrapreta] The Science of Terra Preta Formation

[Michael Bailes]

On 09/04/2008, Gerald Van Koeverden <vnkvrdn at yahoo.ca> wrote:
>
>
> One thing we do know from the writings of the first European explorers in
> the Amazon, is that farmers did a lot of burning on the fields.  Note that,
> in the Mexican study quoted below, the subsequent increase in the amounts of
> N and P available to plants, was determined to come from the heating of the
> soil itself, not the ash of plants burned.
> Slash-and-burn clearing of forest typically results in an increase in soil
> nutrient availability.
>



Throughout the tropics, ash from consumed vegetation has been accepted as
> the primary nutrient source for this increase. In contrast, soil heating
> has been viewed as a secondarily important mechanism of nutrient release. Through
> the use of multiple burn plots and intensive pre-burn and post-burn
> sampling of mineral soil, this study quantified changes in total P and N,
> P fractions, and KCl-extractable N in soil during the slash-and-burn
> conversion of a Mexican dry forest to agriculture. Slash burning resulted
> in large transformations of non-plant-available P and N in soil into
> mineral forms readily available to plants. Anion-exchange resin, NaHCO3
> -extractable P, and KCl-extractable N in soil increased by 37 kg P ha-1and 82
> kg N ha-1. Organic and occluded P (sequentially extracted with NaOH,
> sonication + NaOH, and NaOH fusion) and organic N (total N minus
> KCl-extractable N) decreased after burning by 25 kg P ha-1 and 150 kg N ha
> -1. Immediately after burning, ash from consumed aboveground biomass c
>



ontained 11 kg P ha-1 and 27 kg N ha-1, of which 55 and 74%, respectively,
> were quickly transported off the site by wind. At this dry forest site,
> soil heating had a much larger influence on soil P and N availability than
> inputs of ash.
>
http://soil.scijournals.org/cgi/content/full/64/1/399
>


Gerrit very interesting study. Thanks for that.

I doubt wind would be a factor in a rainforest.

You have to now ask "Would the sterilisation of the soil by burning, result
in more available fertiliser than by encouraging microbial growth in soil
using TP methods?".(SOM, Char, pottery, fish, bones etc)
That is is next comparative study that they need to do.
m
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