Evaluation of the impact of citrus cultivation on carbon and nitrogen stocks of light organic matter fractions of amazonian dark earth (ADE) and surrounding soils (Oxisoil) from central Amazonia

Abstract

The Amazonian Dark Earth (ADE), that is extremely efficient soils in retaining great amount of organic matter of the soil, and for long time, they are still little known with relationship to the effects on the physical fractions of those soils in these adapt tropical region. Therefore, the objective of the present study was to evaluate the space distributions and in depth of the light organic fractions and the stock of carbon and nitrogen in ADE and Yellow Oxisoil (Latossolo Amarelo), under cultivation of orange Pêra Rio (Citrus sinensis (L.) Osbeck) in Laranjal Cost, Manacapuru - AM. The physical fractionation of the organic matter was done by densimetric method, where they were extracted the free light fractions and intra-aggregated light fraction in solution of iodeto of sodium. Granulometria analyses, fertility and total organic carbon were accomplished (C) of the soils. The results showed that C, when comparing ADE and LA, was larger in ADE , having also been expressed in the stocks of carbon. The contents of carbon from free light fraction have been major as the contents of carbon from intra-aggregated light fraction on ADE and LA.