Impacts of Soil Management Practices on the Organic Matter Structure - Investigations by CPMAS 13CNMR-Spectroscopy

Humus properties of 42 soil samples or humic extracts of Ap horizons of Cambisols and Luvisols, from different field plots, kept for a long time under continuous management conditions, have been studied by quantitative CPMAS ¹³C NMR-spectroscopy. The shift range of the spectra were divided into 8 regions, with carbon absorptions from 0–45 (aliphatics), 45–60 (OCH₃), 60–80 (CO? CN), 80–110 (anomeric carbons), 110–140 (aryl—C), 140–160 (O-aryl-C) and 160–210 (COOH? C?O) ppm, respectively. Although soil samples and humic extracts were obtained from plots from different locations and sometimes widely differing organic carbon contents, variances in the relative absorptions of the selected ranges were rather small. Several absorptions were significantly correlated among each other or with soil carbon and microbial biomass contents. These correlations were discussed with the applied management and with other results about humus formation and properties. CPMAS ¹³C NMR-spectroscopy allows a reliable and comprehensive characterization of soil organic matter from soils without previous fractionation.