A C-13-NMR STUDY ON THE FORMATION OF SOIL ORGANIC-MATTER FROM GRASS RESIDUES

The development of C-distribution on functional groups in soil organic matter (SOM) was investigated in whole soil samples and organomineral particle-size fractions from the 34-year-old pot experiment Hu3-Loamy marl at Rostock. CPMAS-C-13-NMR spectra of grass roots and whole soil samples indicated the enrichment of carboxyl-C, aliphatic C and aromatic C in SOM. Only minor changes were observed in the SOM-C distribution on functional groups between 13th and 34th experimental year. The investigation of organomineral clay and silt-size fractions showed a specific retention of aliphatics in clay. The most obvious changes in organic matter composition in size-fractions were the increase of carbohydrate-C and decrease of aromatic C.