Effects of humic and fulvic acids on growth of tobacco

Summary

Organic matter was extracted with a mixture of 0.1M Na₄P₂O₇ and 0.1M NaOH from soil and a commercial organic matter product, ‘Aqua Humus’, and separated into humic and fulvic acids according to their solubility in acid and alkaline solutions. They were purified by passage through a cation exchange resin, freeze-dried, and used for characterization and seedling growth studies. The CEC increased with pH for both humic and fulvic acids. Data from tobacco seedling studies show that humic and fulvic acids from both sources increased root number and length at low concentrations while at high concentrations, humic acids inhibited length and number of roots but fulvic acids had no effect. The results support the proposition that fractions of organic matter referred to as humic and fulvic acids affect root development by means other than as a source of nutrients.