Elemental composition of humic acids of sod-podzolic clay loam soil of Cisuralia during long-term use of fertilizer systems

The effect of various fertilizer systems on the elemental composition of humic acids of sod-podzolic soil has been studied in a long-term field experiment. The mineral fertilizer system promoted an increase in carbon content in the peripheral part of humic acid molecules and the organic system some increase in the aromatic part of humic acid molecules, their oxidation, and enrichment with nitrogen. With the organomineral fertilizer system, transformation of humic acids occurred toward an increase in the proportion of aromatic structures against the background of a high content of unsaturated aliphatic radicals.