Fig. 2. Fraction (calculated from the sum of the four fractions) of P in the supernatant (from the sequential extractions, the results of which are shown in Fig. 1), which was molybdate reactive. Samples 519 and 525 are controls (C), and samples 129, 181, 182 are alum amended (A). Molybdate-reactive P is considered to be predominantly an inorganic P species.