Soil Organic Matter Management: The Roles of Residue Quality in C Sequestration and N Supply - Sustainable Management of Soil Organic Matter - page 179

increased soil moisture, reduced erosion, increased SOM, conservation of
SOM, weed control and pest control (Patrick and Toussoun, 1965; FAO,
1975; Sanchez, 1976, p.181; Kamara, 1986). Likewise, the importance
of soil microbiota in healthy and productive agroecosytems is well
documented (Lopez-Real and Hodges, 1986; Sylvia et al ., 1998). Cochrane
and Sanchez (1982) demonstrated that Amazonian soils managed with
inputs of ash and mulch can produce high yields continuously for at least
5 years. The Kayapó, whose agricultural technologies have remained
relatively intact, cultivate their fields intensively for 5 years, and less
intensively for an additional six, employing a sophisticated array of soil
management techniques including composting, mulching and burning.
Many local farmers throughout Amazonia also recognize the benefits
of applying mulch and ash (by burning slash) but, unlike the Kayapó and
the prehistoric farmers responsible for the creation of the TM expanses,
most choose to practise short fallow shifting cultivation instead of a more
intensive cultivation supported by soil management practices. The advent
of steel tools with European contact has certainly made clearing new fields
easier (Denevan, 1992), and the rapid rotation of fields explains why TM
does not appear to form under today's shifting cultivation (though local
farmers in our study area do notice a gradual darkening of continuously
cultivated home gardens). Mulch-based cultivation need not be prohibi-
tively labour intensive, however, as the Urarina people of Upper Amazonia
recognize (Kramer, 1977). Moreover, as the persistence and regenerative
qualities of ADE attest, improvements to notoriously infertile tropical soils
through burning and organic inputs (or other direct manipulations of pH,
cation exchange capacity and soil biota) can be significant and long lasting.
Once infused with the self-perpetuating life force of an active soil biota
and an adequate nutrient retention capacity, under proper management
additional inputs may not be necessary to maintain a reasonable fertility.
As growing numbers of shifting cultivators place ever greater pressure on
forest resources, the soil-enhancing agricultural practices of pre-contact
Amerindians and their legacy of rich, 'living' soils warrant further study
in the search for high-yield, land-intensive, yet sustainable forms of land
management in the humid tropics.
Acknowledgements
J. Shenk and M. Westerhaus provided comments on NIRS interpretation.
A. Martignoni II compiled Table 3.10.1. Supported by Southern Illinois
University Edwardsville Graduate School research grants to W. Woods and
Fulbright-Hays and NSF grants for dissertation research to J. McCann.