Frequently Asked Questions
by Allan Balliett in Acres USA, February 2007
Why did production of terra preta stop after European contact?
Although decimation of Amazonian population and collapse of elaborate social systems that supported terra preta creation (to make all that pottery and all that charcoal, and incorporate it up to two feet in the ground really does take a village) was a contributing factor, it was undoubtedly the introduction of the steel axe by the Spanish that—in combination with the impact of contact—led to slash-and-burn by small bands replacing slash-and-char by large groups. When clearing land with a stone axe, a conservation of all biomass and an intensification of soil production becomes a necessity. Steel axes—and, later, chainsaws—contributed to exploiting the very short-term benefits of ash.
Remember that traditional methods can die out in a single generation, and in Amazonian social structure, the elders were responsible for all technical knowledge. It makes sense that the elders were hardest hit by epidemics, and loss of their cultural knowledge combined with social disruption led to the replacement of a deeply effective technology with a less-effective mimicry.
Did natives use special microbial brews to innoculate the soil to create terra preta?
There is no proof that a "mother" culture was used for starting terra preta. Current research indicates that the incorporation of charcoal of certain qualities (created in relatively low heat, for example) in combination with appropriate initial fertilization (often, in university tests, with conventional fertilizers that are damaging to soil life) will produce a substantial increase in yields. It is assumed that the char provides such an effective habitat for microbes that effective communities will rapidly develop within most soils. What we don't know yet is whether the simulated terra preta will have the ability to maintain its fertility for as long as the ancient form.
Has terra preta been discovered outside of the Amazon?
Yes, high-carbon terra preta-like dark soils were discovered in Japan, Holland, South Africa and Indonesia and are currently being studied.
Can carbon inputs other than charcoal be used?
The Japanese are extensively investigating the use of coal dust for promoting field fertility. Coal dust does seem to reproduce many of the positive effects of wood charcoal. The research of Siegfried Marian on the benefits of carbon incorporation, as reported in Leonard Ridzon and Charles Walters' The Carbon Connection and The Carbon Cycle, led to the development of Ridzon's NutriCarb product (no longer being produced), which claimed agricultural benefits very similar to those claimed for terra preta. Those who want to use coal dust for soil fertility need to make certain that the dust is from brown coal, which is more humic, and that the coal does not contain toxins.
Why is terra preta linked to alternate energy & climate change?
Terra preta is a carbon sink, as is most carbon in the soil. Slash-and-burn agriculture contributes greatly to global warming. If terra preta technologies were applied to tropical farming, less land would have to be cleared for farming, and if farmers in temperate zones such as the Midwest incorporated charcoal or other chars into their soil, more carbon could be sequestered. If' this char is produced by appropriate technology, such as pyrolysis, both fuel and a "restorative, high-carbon fertilizer" can be produced. This process does not require wood—it is just as effective when agricultural wastes, such as peanut shells, are used as input. A good place to learn about this technology is at www.eprida.com.
How much charcoal needs to be incorporated?
In published reports on pot tests of the effect of charcoal on plant growth, incorporation at 20-30% by weight tended to consistently produce the most benefit. In row crops, this would translate to 30% by weight of the top six inches.
Are there benefits for plant health from terra preta?
Better plant growth and health is evident with use of native terra preta. Current investigations are primarily conducted by archaeologists, geologists and soil scientists. There is no evidence of terra preta studies by an agriculturist, but positive reports from growers suggest eco-farmers are well advised to investigate terra preta technology.
The Earth Renewal and Restoration Alliance — www.ancientforests.us — www.carbon-negative.us — www.nutrient-dense.info — 2/14/2009