Comparison of two methods of preparation of humic and fulvic acids, IHSS method and NAGOYA method

Abstract

Abstract Two methods for preparing soil humus samples, NAGOYA (Nagoya University) method and IHSS (International Humic Substances Society) method, were compared using A-horizons of an acid brown forest soil and an ando soil. Alkali-extractable humus was recovered more effectively by the NAGOYA method, while the IHSS method recovered only 80 and 26% of the maximum yield by extraction with 0.1 N NaOH from both soils, respectively. The recoveries of fulvic acids (FAs) by the IHSS method in which XAD-8 was used as adsorbent to obtain only humic substances in the FA fraction from the brown forest soil and the ando soil were only 1/5 and 1/40, respectively, of those by the NAGOYA method in which the whole FA fraction was recovered. The FAs obtained by the NAGOYA method were further fractionated into adsorbed and non-adsorbed fractions with XAD-8 or insoluble polyvinylpyr-rolidone (PVP). The recoveries of the XAD-8-adsorbed fraction increased 3.8 and 26 times by changing the volumes of the extractant and adsorbe...