Abstract
Three vermicomposts derived from animal manures exposed to
the action of the earthworms Eisenia foetida or Lumbricus
rubellus were investigated to determine the nature of the humic
acid fraction in relation to the potential fertility of the
vermicomposts. The isolated humic acid fractions were analysed by
pyrolysis-gas chromatography-mass spectrometry. The greater part
of the humic acids consisted of lignin and/or lignin residues as
revealed by the very prominent and characteristic methoxy and
dimethoxy-phenols pyrolysis products. The chromatograms of the
pyrolysates are similar to those of grass lignin. This points to
an incomplete degradation or selective preservation of grass
lignin during earthworm composting. The results further indicate
that neither the quality nor the quantity of the humic acids has
changed considerably by vermicomposting. | 13 pages, 3 figures, 2 tables, 15 references. Trabajo presentado por Cesáreo Sáiz-Jiménez en la tesis doctoral para la obtención del grado de doctor en la Technische Universiteit Delft.