ABSTRACT
The most important information about the elemental composition of humic substances was generalised by earlier. The variability of published data on the elemental composition of humic substances is due to three groups of factors: variability in space and time of humification conditions and hence of the humic substances per se; differences in techniques used to isolate humic substances from soil and errors in sample preparation and analytical procedure. In the last 10—15 years considerable new information has been published, on the elemental composition of humic substances of a large number of soils from vastly different regions of all the continents. Data on the elemental composition of humic substances of Vietnam soils, also obtained in laboratory, make it possible to identify the same general patterns, albeit for a somewhat higher level of carbon content in humic acids as well as fulvic acids.
