Predicting the phytoavailability of toxic trace elements such as cadmium (M) in soils is an important issue for crop quality. A set of partial differential equations can be derived for simulating the root influx of M2+, the transport by diffusion and convection, the kinetics of sorption/desorption, and the kinetics of complexation in solution, for the free ionic species (M2+), for a mean ligand, and for the complex. The aim of this study was to develop a simple meta-model that would be easier to handle than these partial differential equations. d and are out of equilibrium in a reaction layer of thickness μ < d; in this reaction layer the concentration of the complex is assumed constant, and the association rate of the complex is neglected. Under these assumptions and for two extreme behaviors of the complex, i.e. when complex is totally labile (μ=0) or totally inert (μ=d), the analytical equation for calculating the concentration of trace element at the root surface, and therefore the uptake, was derived. For intermediate complex lability (0 <μ < d), the uptake was obtained by linear interpolation of the uptake between μ=0 and μ=d. The meta-model was evaluated for cadmium in the context of French agricultural soils. For a dataset of about 105 simulations covering the variability of soil characteristics, the meta- model estimates of the uptake fitted very well the values obtained by the numerical integration of the partial differential equations (r²=0.996). Indeed, for 95% of the simulations, the values of the relative error of prediction ranged between -14 and 27%, and the mean absolute relative error of prediction is quite excellent (5.9%).