New Mechanistic Phosphorus Fertilizer Recommendation Model Based on Two Intrinsic Phosphorus Pools in Tropical Soils

No mechanistic model for phosphorus (P) fertilizer recommendation is available for nutrient management in tropical soils. Soil intrinsic P pools, including a weakly and a tightly adsorbed P pool, were proposed to quantify actual soil available P. The goal of this study was to develop a new mechanistic P fertilizer recommendation model based on the two pools. The public data set of a corn ( Zea mays L.) field experiment was used to estimate the daily corn P uptake. Seven soils were used to demonstrate the effects of P‐sorption site density (PSSD) and desorption rate of the tightly adsorbed P pool on the P fertilizer recommendation. Dynamics of soil P pools in a corn–soil system were modeled based on the transformation between the pools, the daily crop P uptake, and P fertilizer added at the beginning of planting. The weakly adsorbed P pool was required to be positive to represent no constraint of crop P nutrition. Results showed that the derived P recommendation model was a linear model of the total crop P uptake minus the two pools with three different coefficients. The weakly adsorbed P pool was readily available for crop uptake. The coefficients of the total crop P uptake and the tightly adsorbed P pool were >1.0 and <1.0, respectively, and they changed slightly with PSSD but were dependent on the desorption rate. The coefficient of the total crop P uptake showed a maximum 1.679 at the desorption rate 0.0118 d −1 . Core Ideas A P recommendation model was developed based on dynamic soil surface reaction and crop uptake. Intrinsic weakly and tightly adsorbed P pools quantify dynamics of soil P supply. P requirement was a linear function of crop uptake and initial values of P pools. Model parameters were determined by soil P‐sorption site density and desorption rate.