Saturday, 15 July 2006

Creating Terra Preta in Homegardens?: A Preliminary Assessment.

Antoinette Winklerprins, Michigan State Univ, Dept of Geography, 207 Geography Building, East Lansing, MI 48824-1117

In the last few years there has been an explosion of research on terra preta or Amazonian Dark Earths (ADEs), organic-rich anthropogenic soils found in patches throughout the Amazon Basin. These soils are embedded in a landscape of infertile soils but are locally recognized for their superior productive potential. Recent research has indicated that these soils possess excellent fertility and long-term nutrient retention. The existence of these soils has profound implications for theories of past occupancy of the region, present land-use of the Amazon region, and possibly other tropical areas as well. One of the least understood aspects of ADEs is their initial formation. Various theories point to some combination of long-term human occupancy of sites, intensive agriculture, microbial activity, and the possible effect of a system of ‘slash and char' that produces recalcitrant carbon that is resistant to weathering. Slash and char is a system of biomass management at agricultural sites that involves the light burning and smoldering of organic debris. It is the incomplete combustion that produces aromatic carbon that seems key to the persistence of terra preta in the landscape. Wim Sombroek's dream was to pursue research that would lead to an understanding of the process of ADE formation in such as way that it could be reproduced elsewhere in the humid tropics and help farmers throughout the world. Recent intensive ethnographic research in 50 home-gardens in the Brazilian Amazon demonstrates that gardeners could be creating terra preta through their daily actions of sweeping and burning garden and household debris. This poster will explore preliminary data on these activities in the Municipality of Santarém, Pará, Brazil. Local residents, particularly smallholder farmers of mixed ethnic ancestry, utilize a soil management strategy locally termed terra quiemada (burned earth), to improve the soil quality in home-gardens in both rural and urban areas. On a daily basis gardens are swept clear of leaf litter and other debris. This material is swept to an area of the yard where it accumulates and is sometimes combined with other organic household refuse. Periodically, often on a weekly basis, this debris is charred. The remains of this process are then used as a soil conditioner and directly applied to the base of recently planted fruit trees and other productive plants in the garden. Is this sweeping and burning activity something that will contribute to the eventual formation of ADEs? This is unclear at this time, but certainly the routine and pervasiveness of the activity, and the self-reported darkening of the soils through application of terra quiemada, indicates an area of potential future research. Wim Sombroek's dream was to find ways of making terra preta (terra preta nova) and these preliminary findings in home-gardens offer some ideas how daily praxis may contribute to this.

Back to 1.6B Amazonian Dark Earth Soils (Terra Preta and Terra Preta Nova): A Tribute to Wim Sombroek - Poster
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