Organic phosphorus extracted in sodium hydroxide was separated into fulvic acid associated (moderately labile) and humic acid associated (nonlabile) fractions, although the precipitation of humic acids was achieved in more acidic conditions (pH 0.2) than in the Bowman and Cole [54] scheme (pH 1.0–1.5). This is significant because it can influence the apparent organic phosphorus content of the humic and fulvic fractions [57]. For example, phytic acid remains in solution at pH 0.2, but is precipitated with humic substances in less acidic conditions [37].