ANALYSIS OF C-13 AND N-15 CPMAS NMR-SPECTRA OF SOIL ORGANIC-MATTER AND COMPOSTS

N-15 and C-13 CPMAS spectra of composted plants are presented. The plants (L. rigidium and Zea mays) were grown in N-15 enriched medium and fermented for several months until an approx. 80% of the dry matter was lost. In all N-15 spectra the secondary amide/peptide peaks at 87 ppm contributes more than 80% of the total intensity. No new N-15 peaks are formed during the fermentation process. Older attempts to assign a significant fraction of humic acid nitrogen to heteroaromatic structures formed in the fermentation process are thus most probably wrong.