Response of humic acid structure to soil tillage management as revealed by analytical pyrolysis

摘要

The effects on the structural features of humic acids (HA) from dryland farming soils under long term management practices have been approached by analytical pyrolysis (Curie-point pyrolysis-gas chromatography/mass spectrometry, Py-GC/MS). The field experiments (started in 1987) include conventional, minimum and no-tillage plots, as well as non cultivated plots. The HAs isolated from the various plots showed significant differences in their pyrolytic behavior, in particular regarding the total abundances of alkyl pyrolysis compounds (fatty acids, alkenes and alkanes). The occurrence of very short chain fatty acids (C-5-C-11) in uncultivated plots could be indicative of constitutional alkyl structures in the relictual HA from undisturbed soil. The effect of soil tillage managements substantially increased total abundances of fatty acids in plots under conservation practices (mainly no-tillage).