Humic acids (HA) extracted from sheep (SHHA), cow (COHA), goat (GOHA) and rabbit (RAHA) vermicomposted manure were analyzed by electron paramagnetic resonance and hydrogen nuclear magnetic resonance spectroscopies. Carboxylic acids, amine, amide, ester, ether and phenol functions bonded to saturated aliphatic, unsaturated aliphatic conjugated double and single bonds, and aromatic chains constitute the backbone structure of these fresh humic substances (HS). Mn2+ outer sphere complexes (SHHA, COHA), Fe3+ axial (COHA, RAHA) or rhombic (SHAHA, COHA, GOHA, RAHA) complexes and Cu2+ as weak field (COHA, GOHA, RAHA) and strong field (SHAHA, COHA, GOHA, RAHA) complexes were characterized.
vermicomposts; humic acids; EPR and ¹H-NMR spectroscopies
