Terra Preta Theory

How were the rich terra preta soils in the Amazon created (the most productive soil in the world)? Terra preta soils maintain their fertility forever. Scientists are racing to unlock the secrets to help feed a hungry planet, restore depleted topsoil and curb adverse climate change. A reader who wishes to remain anonymous sent me a summary of his theory.

“With the key ingredients in place, Time created terra preta. There is no recipe to make it all at once. Microbes formed from natural farming practices and have been alive in that soil for a very long time. The materials found in the soil are just natural farming products of that region and culture: manure, bones, wood ash or charcoal, etc… It’s all normal and natural inputs. People want the recipe or the secret to exploit it for all of the wrong reasons. Maybe we should just grow food in it instead of digging it up and selling it.”

His idea seems the most plausible to me. There’s *no way* the makers of terra preta soil gathered and transported 3′ of prime topsoil for their gardens. And there’s no way they built up 30′ of organic materials or so that composted down to 3′. They seem to have brought together the essentials of life (microbes/fungi, primary and trace elements, worms, biochar, moisture, etc.) and over the years the soil naturally bio-accumulated. The microbes are growing/increasing the new, rich topsoil. Biochar provides a porous structure that helps retain the nutrients. This concept is very important since modern agriculture has depleted most of the topsoil, and obviously humans can’t live without food. This means the world’s soil could be rebuilt once the current corporate-controlled system fails and the bulk of humanity chooses to live sustainably.

My personal goal is to create a self-maintaining forest garden using these concepts.

7 thoughts on “Terra Preta Theory”

  1. I disagree with the original poster’s concept of nature creating terra preta. To understand the nature of this ultra fertile soil, one must understand the culture and farming practices of the ancient inhabitants of the Amazon river basin.

    The soil around the Amazon river and rainforest is nutritionally very poor, and the concept of slash and burn has been used in this part of the world for a thousand years or more. Slash and burh has the ability of breaking down the nutrients in the jungle, but these nutrients are rapidly depleated and/or washed away by the rains and flooding.

    When the ancients of this area began to expand in population density, they had to devise a farming method that would allow them to remain in one place, they could not just cut down another patch of jungle and move on when the soil was worn out. They developed fields, seperated by dikes to keep out flood waters and to retain moisture via irrigation during the dry season.

    Once the crops were harvested, the vegatative debris was collected into piles and burned. They discovered that if they restricted the amount of oxygen getting to the fire that it would turn to charcoal (which lasts a long time) instead of the quickly depleted ash. They piled on broken pottery and dirt before lighting the fires.

    This charcoal, or biochar as we now call it, is incredibly light and porus and when the rains fell onto the dirt covering the mound, the microbes in the dirt were washed down to the charcoal level. Thus was terra preta created.

    This sequestered carbon takes many years to decompose, and holds moisture in addition to the beneficial bacteria. Over time, as the villagers continued this practice, the thickness of the piles grew, forming mounds in the relatively flat savanna. Aerial photography has revealed the isolated mounds of terra preta, covered in lush vegitation, and the farm fields connected by ditchs and dikes, along with raised paths that in some cases, stretch for miles through the land. These fields are now savanna, or grasslands.

    At one time, it is estimated that over a million residents lived in this area of South America. Disease brought by spanish explorers devestated the region in the span of less than 50 years, resulting in the death of more than 90% of the natives. This caused the abandonment of many of the farming areas that were not rediscovered until the last century.

    • It sounds to me like you’re adding historical details to describe the same thing we are (unless you think natives built up 3′ layers of terra preta by only burning plant wastes). We’re saying the soil naturally bio-accumulated over time when the necessary ingredients were brought together (that includes biochar from burning agro waste). This happens naturally in nature. Remember the stories of pioneers crossing the American continent and discovering thick, black soil? It’s the same thing as far as I can see.

    • I think your disagreement with the original post is more of a semantic argument than anything.

      If we want to split semantic hairs, neither nature nor man alone likely “created” Terra Preta. It seems clear that it was a combination of efforts between man and nature. When man worked WITH nature, instead of simply exploiting nature, Terra Preta was the result.

      I don’t think the soil is exclusively a result of biochar, although it seems clear that was an important influence. Microorganisms, fungi, and other life forms also have played a huge role, and man didn’t create those life forms.

      The important point of all this is that success in farming should not be measured by harvest yields ALONE. The BEST farmers work with nature, to not only produce a sizeable harvest to feed people and livestock today, but also work with nature to consistently increase the capability of the soil to produce the next crop even more bountiful. The farmer that produces a big harvest today at the expense of DECREASING the future productivity of the soil is essentially stealing today’s harvest from the future and starving his children and their children. The ultimate deficit spender worse than spending trillions on needless wars and pointless government programs because productive soil is more valuable than money.

      • That’s a good way to put it — work with nature. Man helped bring the necessary ingredients together (burned plant wastes, pottery shards, fish bones, etc.) and then nature was able to do the rest.

        It’s also worth pointing out, in case anyone doesn’t know, that those thick, black soils in the US midwest are gone or nearly gone due to modern farming techniques. This is what Jay is describing. (I’m restating the obvious because we get readers from all over the world who may not know.)

        • It’s not just the American Midwest.

          5000 years ago or so, the Sahara was lush and populated.

          Easter Island was once heavily forested and supported many people with numerous crops.

          Meanwhile, areas like the Amazon Basin were heavily populated continuously and thrived agriculturally. This is largely attributable to practices that grew the soil instead of depleting it.

          • Right. I watched Bill Mollison’s permaculture videos about 12 years ago. He showed a map of the world’s forests thousands of years ago. The Middle East as well as much of the rest of the world (Europe, Sahara, etc.) were all covered in trees.

  2. I applaud the thought.

    Nature is extremely powerful when man works with it instead of trying to over exploit it or over manipulate it.

    It just makes too much sense that the best way to create soil is to get out of natures way and let our gardening and farming practices grow soil in addition to whatever crops or produce we glean from it.

    Think of soil as a bank account. We can spend our soil faster than nature can replenish it and go bankrupt, or we can constantly invest in our soil leaving a surplus for our children, grandchildren, and their children. Anyone that believes in a balanced budget should also believe in a balanced farming system. I dare say a balanced farming system is more important than the latest governmental economic budget plan.

    Anyone that is in favor of using artificial fertilizers, is blowing their soil budget at a drastically faster pace than they are creating soil. They are selling their children’s and grandchildren’s future for small, temporary, and fragile gains today.


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