Criterious preparation and characterization of earthworm-composts in view of animal waste recycling. Part I. Correlation between chemical, thermal and FTIR spectroscopic analyses of four humic acids from earthworm-composted animal manure

Humic acids (HA) were extracted from sheep (SH), cow (CO), goat (GO) and ra bbit (RA) manures which were vermicomposted with the earthworm Eisenia foet ida. HA DSC curves showed well-defined thermal events indicative of intramo lecular bonds (300 degrees C) and intermolecular organomineral linkages (50 0 degrees C). All samples showed high nitrogen contents (from peptide chain s and probably N-heterocycles) and aromatic and/or unsaturated aliphatic co njugated structures, as well as a low carboxylic functionality content. The SH-HA was the most similar to a medium soil HA and the RA-HA being the lea st similar. The results show that it is possible to prepare distinct worm-c omposts to solve specific problems of degraded soils.