There is a lack of knowledge regarding the variation physicochemical characteristics of humic substances (HS) extracted from various feedstock. For this purpose, humic acid (HA) and fulvic acid (FA) were extracted from soil, compost and clover straw to present several types of feedstock. The physicochemical properties of these humic substances were characterized for organic elements (C and N), total acidity and functional groups as well as IR spectra analysis.Data showed  the feedstock recorded a significant effect on physicochemical properties of HS. Carbon and nitrogen concentrations varied widely among the extracted HS. The carbon and nitrogen concentrations in the extracted HA were more than the isolated fulvic acid. The C/N value of humic acid extracted from the soil was less than the other humic acids extracted from other sources. This trend was the same with FA indicating that the HA and FA extracted from the soil are more humified than other feedstock. Total acidity of FA was higher than HA with the superiority to those extracted from soils. The total content of active functional groups (COOH, total –OH, Phenolic –OH and Alcoholic-OH groups) was higher in FA as compared with HA, and the soil type was the most abundance source in most cases.Fourier transform infrared (FTIR) spectra confirm the presence of hydroxyl , aromatic and aliphatic fractions including quinone groups in humic and fulvic acids but in different values based on the feedstock.