A soil phosphorus dynamics (SPD) model

The dynamics of soil phosphorus (P) control its bioavailability. Yet, it remains a challenge to quantify soil P dynamics. Here, we developed a soil P dynamics (SPD) model. We then assimilated eight datasets of 426-day changes in Hedley P fractions into the SPD model, to quantify the dynamics of six major P pools in eight soil samples that are representative of a wide type of soils. The performance of our SPD model was better for labile P, secondary mineral P, and occluded P than for non-occluded organic P (Po) and primary mineral P. All parameters describing soil P dynamics were approximately constrained by the datasets. The average turnover rates were labile P 0.040 g g^-1 d^-1, non-occluded Po 0.051 g g^-1 d^-1, secondary mineral P 0.023 g g^-1 d^-1, primary mineral P 0.00088 g g^-1 d^-1, occluded Po 0.0066 g g^-1 d^-1, and occluded inorganic P 0.0065 g g^-1 d^-1, in the greenhouse environment studied. Labile P was transferred on average more to non-occluded Po (transfer coefficient of 0.42) and secondary mineral P (0.38) than to plants (0.20). Soil pH and organic C concentration were the key soil properties regulating the competition for P between plants and soil secondary minerals. We also determined how soil P turnover rates and transfer coefficients were related and which of these parameters were important for simulating and forecasting the amount of soil labile P. Overall, we suggest data assimilation can contribute significantly to an improved understanding of the dynamics of soil P.