Molecular differences of humic substances obtained by selective extractants, as revealed by drift infrared spectroscopy

Two humic substances from three agricultural soils that received different organic matter additions were isolated by selective extractants and their c hemical composition investigated by DRIFT infrared spectroscopy. This IR st udy showed that the molecular features of common humic alkaline extracts we re affected more by soil origin than by a short-term incubation with maize straw. Conversely, DRIFT spectra of hydrophobic fractions of soil organic m atter revealed that neither origin nor soil treatment influenced the compos ition of this humus fraction.