Matéria Orgânica em Solos Desenvolvidos de Rochas Máficas no Nordeste de Roraima

V. F. Melo,C. Schaefer

Published 2009 in Acta Amazonica

ABSTRACT

Soils developed from mafic rocks in Northeastern Roraima are the preferred areas for indigenous shifting cultivation, in view of their high natural fertility. The study was focused on changes in the soil organic matter status, by means of humic substances fractionation, and application of CHNS analyses and termogravimetric studies and EPR. High C values were observed in Chernosol under continuous cultivation. The humin fraction was predominant in all soils, reducing with depth. The Nitosol showed smaller humic/fulvic acids ratio. The Chernosol under cultivation in a more conservative relief, with incorporation of crop residues, there was greater nutrient cycling. In the uncultivated Chernosol and Cambisol the soil organic matter was less stable. In the chernosol under cultivation, increasing polymerisation of humic acids was observed. The virgin soils with chernozemic A horizons were more homogeneous with respect to humic acid quality.

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