[Terrapreta] viable idea?

[Richard Haard]

This report (summary statement below ) from May 15, 2007 Scientific  
American sums up the opinion that Larry and I share. We both think  
that dumping charcoal on soil does not make terra preta. Our interest  
is to work on enrichment culturing  beginning this spring, sort of  
like to highly aerobic system used to make compost tea only tailored  
to getting charcoal and charcoal/substrate\ acclimated to enhance the  
naturally occurring biota .

Special Report: Inspired by Ancient Amazonians, a Plan to Convert  
Trash into Environmental Treasure

But is it Viable?


As with all new technologies, many questions about the ultimate  
utility of agrichar have yet to be answered. "As of now agrichar is  
not a uniform product," explains John Kimble, a retired USDA soil  
scientist. "And there's no easy way for farmers to apply it with  
existing equipment. They also need to know there is a large enough  
source of the material. Farmers are driven by profit, as is everyone,  
and they need to be shown that it will improve their bottom line."

Complicating debates about the costs of agrichar is the paucity of  
data on the subject. "No one is sure what types of biomass should be  
used as raw material," Kimble notes, "or exactly what production  
methods work best, so calculating the costs is really an exercise in  
speculation."

In addition, scientists are finding it hard to replicate the original  
terra preta soils. "The secret of the terra preta is not only applying  
charcoal and chicken manure—there must be something else," says Bruno  
Glaser, a soil scientist at Bayreuth University in Germany. Field  
trials in Amazonia using charcoal with compost or chicken manure find  
that crop yields decline after the third or fourth harvest. "If you  
use terra preta you have sustaining yields more or less constantly  
year after year," he says.

"I'm skeptical about adding just a pure carbon source," says Stanley  
Buol, a professor emeritus from the Department of Soil Science at  
North Carolina State University's College of Agriculture and Life  
Sciences who spent 35 years studying Amazonian soils. "It will be  
black and look good," but will it contain enough inorganic ions, such  
as phosphorus and nitrogen, essential to plant growth?"

Many of the interactions between the char, the soil and the  
microorganisms that develop with time and lend the soil its richness  
and stability are still poorly understood. Glaser believes that the  
key to making agrichar behave liketerra preta lies in the biological  
behavior of the original Amazonian dark earths—a difference he  
attributes to their age. "You would need 50 or 100 years to get a  
similar combination between the stable charcoal and the ingredients,"  
he cautions.

"I think [research into the biological behavior of terra preta] is  
where the new frontier will be," Lehmann counters. If he is right, and  
scientists can perfect a modern-day recipe for agrichar, then its fans  
will not need Richard Branson's $25 million to jump-start their  
initiative—the annual demand for fertilizers exceeds 150 million tons  
worldwide.
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