Soil organic matter plays an important role in soil biological, chemical and physical properties. In fact, these properties are considered critical indicators for the quality and productivity of the soil. One of the main aims of this work was to assess the effect of leonardite on soil organic matter in an Inceptisol cultivated with vine (Vitis vinifera L.), through the development of a predictive model for such parameter in the topsoil area affected by the organic amendment. One leonardite material (Humita-40®) was used at two doses: 0.5 and 1.0 t ha-1 during three growing seasons. The soil organic matter content as well as iron, manganese, copper and zinc levels were monitored at topsoil (0-30 cm) during three years (2008-2010). There were differences in soil organic matter levels (P<0.001), as well as in iron (P<0.001), manganese (P<0.001), copper (P<0.01) and zinc (P<0.05) levels, but all of them were influenced by year of sampling (P<0.05). A linear model for the second and third year after leonardite incorporation have been proposed to predict the soil organic matter content on the vineyard calcareous topsoil where amendment doses were incorporated. Finally, there were no differences on leaf micronutrient (P>0.05) between the different doses of leonardite applied.