The main aim of this study is to develop a mechanistic model of fertilization for recommending the application of zinc (Zn) fertiliser for maize based on the mass balance of Zn. The model would consider the critical Zn level for maize (Zn-CL), Zn availability in the soil (Zn-A) and Zn buffering capacity (Zn-b). Soil samples were collected from 78 maize fields for chemical and physical characterization including measuringZn(A)and Zn-b. Additionally, a crop management survey was carried out in each field. The classification and regression trees method (CART) was used and relationships between Zn(b)and some soil properties were established, clay content being the most relevant to the model, besides soil reaction (pH) and silt content. The application of Zn fertilizer can be adequately calculated by a mechanistic model that considersZn(A), Zn(b)andZn(CL)above that which maize crop yields do not increase. This work highlights the importance of Zn(b)evaluation by the incubation procedure and the extraction of available Zn by DTPA solution. As hypothesised and then demonstrated in this work, Zn(b)is closely related to soil pH and texture (clay and silt). Our results suggest that, in between 51 and 97% of fields examined, it would be necessary to apply Zn fertilisers to produce the maximum maize yield.