History, Current Knowledge and Future Perspectives of Geoecological Research Concerning the Origin of Amazonian Anthropogenic Dark Earths (Terra Preta)

Abstract

Soil degradation is one of the most severe problems of land use in the lowland humid tropics (Zech 1997) largely due to the fact that soil organic matter (SOM) is mineralized rapidly under the optimum growth temperatures for micro-organisms (Tiessen et al. 1994). However, SOM is of particular importance for sustainable agricultural use of the heavily weathered tropical soils. It contributes substantially to nutrient supply, cation exchange capacity (CEC), and to a favorable soil structure (Ross 1993). A loss of SOM after slash-and-burn and other agricultural and pastoral land uses progresses the soil degradation of many tropical soils, resulting in infertile soils after a few years of cultivation. Soil amelioration by application of mineral fertilizers or compost is often unaffordable for poor smallholder farmers or remains ineffective due to the low CEC of the soils or the lack of knowledge about the nutrient release from organic fertilizers (Tiessen et al. 1994).