| Summary: | Fulvic acid is a natural tampon and an appropriate chelating agent that has high ion-exchange ability and increasing absorption of minerals in plants. This paper examined the effects of extractants (sodium hydroxide, sodium polyphosphate, urea and EDTA) and the extraction time (1, 7 and 9 days) on the physicochemical properties of vermicompost-produced fulvic acid. Finally, various methods were compared to the universal method of humic substances. Different qualitative and quantitative analysis such as detecting the functional groups (FTIR), measurement of functional groups, spectrophotometric ratios and humification indices were carried out on fulvic acid. Results showed that the highest and lowest amounts of fulvic acid were extracted by the sodium hydroxide and urea, respectively. Various extractants made negligible changes in the type and quality of the Fulvic acid functional groups. Results indicated that sodium hydroxide was the best extractant and the minimum amounts of fulvic acid were extracted by the urea. Urea-extracted fulvic acid had the most functional groups of total acidity and phenolic OH. The most carboxyl functional groups and spectrophotometric ratios were detected in EDTA solution. At the end, by the comparison of various methods, universal method despite the low extraction amount had more functional groups and higher efficiencies compare to others.
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