[en] The residual effect of P fertilizers previously applied to a soil on plant P nutrition was examined using both the isotopic dilution method (pot experiment) and the isotopic exchange kinetics method (laboratory test) using ³²P as the tracer. The fraction of P derived from fertilizer in plant (%Pdff in plant) was compared with the fraction of P derived from fertilizer in soil solution (%Pdff in soil solution), which is a new laboratory index proposed by Morel and Fardeau to predict %Pdff in plant. Four soil samples of a humic Andosol from long term experimental plots were tested; they received no fertilizer (A1 soil), a readily soluble fertilizer (RSF) (A2 soil), the same RSF plus a fused magnesium phosphate (A3 soil), and a combination of RSF with Florida phosphate rock (A4 soil). In the pot experiment, maize (Zea mays) was grown for 38 days and the dry shoot weight, P uptake and specific radioactivity were measured. The dry shoot weight, P uptake and L value were highest in the A3 soil, followed by the A4, A2 and A1 soils. The %Pdff values in plant were 71.9, 51.9 and 15.4% in the A3, A4 and A2 soils, respectively. A laboratory study using the ³²P isotopic exchange kinetics methods was carried out to examine the three status parameters of soil P: the intensity, quantity and capacity factors. Good agreement was obtained between the quantity factor (E₁ value) and the pot experimental data, i.e. the P uptake and L value. The %Pdff values in soil solution were similar to those in plant, except for the A4 soil. Enhancement of the P uptake by the plant from the phosphate rock obtained in the A4 soil could be attributed to specific plant factors and the soil moisture conditions. (author). 14 refs, 3 tabs