CARACTERIZACIóN DE LA MATERIA ORGáNICA DEL HORIZONTE SUPERFICIAL DE UN ANDISOL HIDROMóRFICO DEL ORIENTE ANTIOQUE？O (COLOMBIA)

a study was carried out to determine the soil organic matter content and characteristics from a surface horizon of an aquatic moisture regime andisol. most of the mos was constituted by nonhumic organic materials with low degree of evolution. the content of organic-mineral complexes in this surface horizon was low. the a horizon exhibited a considerable thickness (31.2 cm), dark color, high mos (17.65 %), higher content of humic acids than fulvic acids, low e4/e6 ratio (3.55) and low im (1615). the humic acids showed low values of δlog k (0.54) and rf (17.58). the humic fraction of the mos was constituted by high molecular weight humic acids that had low degree of both polymerization and condensation of aromatic compounds. the humic acids of all samples corresponded to the p-type, mostly po-type. the accumulation and limited evolution of mos was seems to be associated with the wet cold weather, restricted soil drainage and relief of field.