Ancient Amazon tribe leaves behind enduring model of soil conservation
Prehistoric Indians living in the Amazon rain forest often spent their entire lives living and growing crops in one location, a feat accomplished by burning unwanted vegetation and putting the black carbon material into the soil. The resulting Terra Preta, literally meaning black earth soil, of the Amazon is a remarkable manmade legacy with higher nitrogen, phosphorus, potassium, and calcium concentrations than other soils in the region. This incredible soil has retained its fertility for thousands of years.
U.S. Forest Service soil scientist Jim Archuleta works on the Umatilla National Forest in southeast Washington and northeast Oregon. In an effort to improve elk forage, he and a friend replicated this ancient method in a place called Fish Creek Desert to keep grass green into August.
Archuleta quickly saw a direct application for biochar in forest restoration work. The Forest Service conducts thinning projects on national forests to reduce crowded tree stands and to remove the excess fuels that make forest fires so dangerous. These projects leave behind piles of slash—cut limbs, tree tops, and brush—that in themselves have no commercial value. An existing technology called the Air Curtain Burner can convert the slash piles into ash, however, it can only make biochar in small batches.
Archuleta and his colleague Debbie Page-Dumroese at the agency’s Rocky Mountain Research Station modified the design of existing Air Curtain Burner technology to produce biochar in large quantities. This faster, more efficient process continuously pumps out commercial quantities of nutrient-rich biochar pellets while workers feed slash into the adapted equipment.
They have filed for patents on this technology with help from Forest Service Technology Transfer Coordinator Tom Moreland. Moreland is also working on a cooperative research and development agreement between the Forest Service and a private company interested in adding their proprietary technology to the processing unit to allow for more use of burned wood.
In addition to improving the soil for forest restoration projects, biochar holds promise for improving farm land in western states, where dry land farming practices are common. Archuleta is collaborating with Stephen Machado, the lead scientist at Oregon State University’s Columbia Basin Agricultural Research Center, to see if it can be used to help dry land wheat farmers.
However, biochar is not a panacea. Because of its water carrying capacity, on the wrong slope, unintended consequences may occur. But used prudently, the potential forests-to-farm applications of biochar are exciting.