[Terrapreta] Guidelines for Using Terra Preta

[Richard Haard]

Tom, Larry and temperate zone list readers.

I have to admit that I am not reading all of the threads that come  
across this list but my comments below on Toms posting are addressed  
to those interested in the so - called terra preta phenomenon in  
soils in temperate North America.

I think it is way too early to state with confidence that the effect  
of charcoal in soil , in the temperate north has any effect other  
than a soil conditioner that sequesters, nicely, some carbon. My own  
idea of what we were doing here on this list is to encourage  
temperate NA readers to try the material and to study and discuss the  
scientific research on the  topic that is occurring in the global arena.

On Apr 21, 2007, at 2:41 PM, Tom Miles wrote:

> Much of our discussion in the past few months has been to clarify  
> what terra preta is and how it functions. There are clearly many  
> misconceptions about charcoal, the qualities of charcoal, how it is  
> made, how it can be used, and how it functions in different soils  
> with different plants.  A useful product of this discussion and the  
> ongoing research and field trials would be draft guidelines for the  
> use of terra preta. I’m thinking of the kind of general information  
> published by our extensions services. Eventually these will be  
> developed by many organizations, including the IAI, but it would be  
> useful to start drafting something here.
>

My own view from here in the northwestern corner of the US where I  
have been farming the same tract of soil for 20 years is that I may  
have 'terra preta' already, even before I apply charcoal on to my soil.

  If you look at the recent comment by Christoph Steiner on the  
characteristics of the soils in the humid tropics of Brazil -

On Apr 16, 2007, at 10:13 PM, Christoph Steiner wrote:
> Dear All,
>
> Most soils in the Amazon Basin have very low contents of inorganic
> nutrients. These are deeply weathered soils and the predominant  
> minerals
> are iron and aluminum. Therefore most nutrients in Terra Preta have
> organic origin. Terra Preta fertility is linked to an anthropogenic
> accumulation of phosphorus and calcium associated with bone  
> apatite, thus
> increasing the pH. Increased pH alters the availability of nutrients.
> Phosphorus, which is considered to be the primary limiting nutrient to
> plant production on the highly weathered soils of the humid  
> tropics, could
> become available through fine root endomycorrhizal associations and
> through heterotrophic phosphate solubilising microorganisms, which are
> supposed to be stimulated by soil charcoal additions.

I actually felt differently about my own farming effects on our farm  
soil before I started conducting soil analysis at our field and  
comparing the results to analysis of the new field on the same soil  
type that has never been intensively farmed. Our farming practice of  
raising bare root plant crops on our sandy loam soil could not be  
harder on soil organic matter because we harvest everything, roots  
and tops leaving, sometimes, the leaves of deciduous species behind  
to be recycled. Yet our soil organic matter is holding at 4 to 5% in  
comparison to 5 to  6% on the new soils.

I farm in a climatic zone where like the moist tropics precipitation  
exceeds evaporation and rainfall leaches the soil carrying away the  
soluble elements not captured by the microbes and plants into the  
water table.

My soils are the product of glacial deposition and sediments carried  
by the great Frasier river system of British Colmbia, that formed our  
land during the post glacial period 10 to 15,000 years ago. In  
contrast to the moist tropics these soils carry large natural  
supplies of phosphorus, potassium and calcium in addition, our  
neighboring dairy farmers over the years have been spreading liquid  
manure to further cause accumulation of nutrition and OM.

My farm's limiting factors are some trace elements which can be  
easily controlled, water during our  normal summer  drought period  
which is a problem in our well drained soil, and soil nitrogen which  
is always in on the low end of the spectrum in both our heavily  
farmed field and our new field.

What then would I look for in my soils that would indicate a positive  
effect from the application of charcoal? In my case retention of soil  
nitrogen and improving soil water holding capacity.

  Less than 3 miles away from our fields are very rich glacial till  
soils that we had farmed for 7
years  during our B&B ornamental growing period. These soils have  
bottomless nutrition and superior water holding capacity, they never  
need to be fertilized and never need irrigation but they are useless  
for bare root plant production because they are a mucky mess during  
the wet winter months when we harvest. Across the temperate United  
States we have a matrix of soil types in diverse climatic zones and  
diverse geological origins that are equally different from soils and  
climates of the moist tropics where terra preta has been described.

Is is not premature to write down guidelines for 'using'  - Tom wrote  
- 'terra preta' , I would write charcoal in soil?

Where is the data that it works up here? Perhaps the Montana paper  
that described better nitrogen retention in forest soils where fire  
sources inorganic carbon is encouraging but for those of us who are  
trying charcoal out in soils in this venue what results and what  
evidence should convince us that - yes we are having a 'terra preta'  
effect in our farmed soils? Measuring the crop yields and looking for  
improvement in controlled studies with charcoal would be another  
useful indication but I have yet to see any conclusive evidence that  
shows crop yields, up here, are better when charcoal is applied. Yes  
some interesting indications that call for more studies but not any  
reason to stir up farmers and their technical support organizations  
to recommend the use if charcoal in soil much less to call it 'terra  
preta'.

To me this is still an interesting research topic and is not ready  
for dissemination as proven agricultural methodology in the temperate  
zone

Rich Haard, Propagation Manager, Fourth Corner Nurseries
Bellingham, Washington



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