A13C‐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‐13C‐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.