Resíduos de mandioca na composição química da Terra Preta arqueológica

Abstract

In the Amazon there are areas, called Terra Preta Arqueológica (TPA), which were significantly affected by prehistoric man. They have high levels of Ca, Mg, Mn, P and C, possibly resulting from the large accumulation of unconsumed organic matter (food leftovers, leaves, seeds, vegetable peels, etc), increasing their fertility. Cassava, due to its wide use as a subsistence crop by Amazonian prehistoric people, may have been one of the components responsible for the accumulation of Zn and Mn in TPA. The objective of this work was to evaluate the influence of cassava residues in archeological soils. Research was carried out on the species of cassava known in the Amazon, as well as its use by the population. The field work was carried out in the region of Caxiuanã-Pa. The collected samples were classified and chemically analyzed, and the chemical composition of the leaves, stems and roots (including the peels) of wild and mango cassava were determined. The results showed Mn values ranging from 848 to 5144 ppm in the stems and 939 to 9001 ppm in the leaves. While for Zn was obtained 304 to 1305 ppm in the stems and 335 to 1221 ppm in the leaves. It was also noted that the variety of cassava mansa showed higher levels of Zn and Mn when compared to varieties of cassava bravas. Considering that in Amazonian soils the contents of Zn and Mn are below the limit of detection and that the organic animal waste contribute with insignificant portion (traces) to the elevation of these contents, it is suggested that cassava is one of those responsible for the high levels of Zn and Mn in TPA, which have average values of 50 and 600 ppm respectively.