Fractionation of soil organic matter

The International Humic Substances Society (I.H.S.S.) has published a gener al procedure for the fractionation and isolation of FA, but crucial informa tion is lacking. Here we give an account of a modified procedure to fractio nate and isolate FA from soil using XAD-8 resin. We also present results wi th respect to the yield of FA and its ash content for a number of soil hori zons. Our results indicate that more NaOH than previously assumed was neede d to remove all adsorbed FA from the XAD-8 resin. By contrast to the IHSS p rocedure we combine several FA fractions prior to purification. To purify F A, two HCl/HF treatments were necessary to reduce the ash content to an acc eptable level. In the four soil horizons investigated in this study, the re lative importance of FA in total humic compounds increases in the order pea t < podzol O < podzol Bhs < podzol Bs.