Apr 15, 2010

Terra Preta: Making Soil Fertile | The Seminal

You’ve probably heard the phrase, terra firme (or its more familiar spelling, terra firma). Literally translated, it means "solid earth." What you may not have heard of is terra preta, a type of soil that is extremely fertile and takes a long, long time to lose its nutrient-housing sustainability (think centuries). Terra preta means "dark earth", for obvious reasons: it is black, nutrient-rich soil, and much of its properties are the result of adding biochar — a type of charcoal, bones, ash, human and animal excrement, and pottery fragments (which help keep the soil loose to allow for water absorption) to soil. Terra firme has few nutrients because in the Amazon the hot and humid conditions cause organic matter to break down far more quickly, making it necessary for plants and animals to get to it first. The result is that very little nutrition is locked in the soil — it is instead contained within living creatures such as plants and animals. But recent archeological studies in the Amazon river basin (written about most recently in the March/April 2010 issue of Science Illustrated) have revealed that Amazonian cultures fed tens of thousands, perhaps even millions, by turning vast swaths of the river basin area into fertile growing lands using this mixture of organic components. Lead author of the research, Michael J. Heckenberger, says that the complex of communities could be just one of many complexes in the Amazon region. These societies were long overlooked by archeologists because they did not build the large cities and rock structures seen among the Mayans, Aztecs and Incas. Since stone is not widely available in the Amazon, settlements were constructed of wood, clay, bone and other materials that deteriorate rapidly in the warm, humid climate of the rainforest. Thus, once abandoned, buildings and roads constructed by Amazon dwellers quickly disappeared back into the jungle. Amazonian societies supported large populations by the careful management of their surrounding environment. Instead of the European farm system where single crop monocultures were common, Amazon farmers may have cultivated and managed entire ecosystems. In his account of the pre-Colombian Indian societies, 1491, Charles Mann explains, "Indians survived by cleverly exploiting their environment. Europeans tended to manage land by breaking it into fragments for farmers and herders. Indians often worked on such a grand scale that the scope of their ambition can be hard to grasp. They created small plots, as Europeans did (about 1.5 million acres of terraces still exist in the Peruvian Andes), but they also reshaped entire landscapes to suit their purposes… Unlike Europeans, who planted mainly annual crops, the Indians, he says, centered their agriculture on the Amazon’s unbelievably diverse assortment of trees: fruits, nuts, and palms." In an environment like the Amazon, without the benefits of iron tools or domesticated animals, clearing and sowing agricultural fields was a difficult and time-consuming process. Instead, Indians planted trees, yielding twenty years of productivity from their labor, as opposed to two or three years with a standard low-growing crop. Creating orchards, instead of field, early inhabitants of Amazonian regions served themselves with great economy. Planting trees in the fertile river basin, Indians capitalized on the benefit of rich soil quality and the deep reaching roots of trees helped agriculture to survive during the dry season and in periods of drought. Experts now estimate that a significant portion of lowland forests, perhaps as much as 15 percent, were organized to benefit humans. The concept of a "built environment" contrasts sharply with the idealist and traditional version of an all-natural, virgin territory. Terra preta fields, many of them up still fertile after more than two thousand years, have been known to be six feet deep and cover large areas. But soil fertility fit for growing is not the only benefit of terra preta; it may even help slow the process of global warming by absorbing carbon. A U.N. task force on global warming has proposed using the technique, prominently citing research by UGA research scientist Christoph Steiner, who studied terra preta for years in Brazil and now is researching ways biochar might help modern humans. The Kyoto Protocols, an international agreement designed to slow down global warming, names two techniques for sequestering carbon to keep the greenhouse gas out of the atmosphere: reforestation, or restoring forested areas, and afforestation, or converting other kinds of landscapes to forest. Steiner thinks biochar could become a third major technique. The U.N. Convention to Combat Desertification last month said biochar should be added to the list when world governments adopt a new climate change agreement to replace the Kyoto Protocol, which expires in 2012. Biochar – what most of us think of as charcoal – is created by a thermochemical process called pyrolysis by applying heat, like burning, but without air. When wood burns or rots, its carbon diffuses into the atmosphere, but biochar can stay in the soil for centuries, Steiner said. Through means scientists do not completely understand, the biochar improves soil fertility – and for a long time. Biochar has the potential to drastically reduce the amount of carbon dioxide and other greenhouse gases in the atmosphere, said Steiner, a member of UGA’s engineering faculty and one of several UGA scientists in UGA’s Biorefinery and Carbon Cycling Program. The Science Illustrated article points out that yields increase 100% in terra preta-based soils. Fruit crops such as mango and papaya grow up to three times faster in terra preta than they do in conventionally treated soil. As we struggle to feed growing populations while soil-depleting farm techniques make that task ever more difficult, terra preta could go a long way toward halting or even reversing some of the damage we’re doing to our planet. Here are some web sites that offer information on making terra preta yourself. http://terrapreta.bioenergylists.org http://www.opednews.com/articles/Making-Terra-Preta-Soil-R-by-Ramona-Byron-080821-153.html http://terrapreta.bioenergylists.org/taxonomy/term/59

No comments: