Although soil is one of the factors in the biology of Tuber melanosporum (black truffle of Périgord), which has been the subject of much study, there are few quantitative analyses relating to its effects on carpophore production. The aim of this work is to establish the statistical relationship between T. melanosporum productivity in 20 soil surface horizons and their conventional soil properties (granulometric texture, pH, calcareous fractions, organic carbon, total nitrogen, exchangeable cations). The study area is situated in the centre of the Iberian Peninsula under a Mediterranean climate. Statistical analysis shows that the collective influence of these conventional soil features is low, as principal component analysis explains only 27% of the variance in T. melanosporum production. However, a high percentage of active limestone (calcium carbonate extractable with ammonium oxalate) accounts for 40% of the variance in T. melanosporum production. Active limestone is very important to T. melanosporum because it regulates soil pH and exchangeable Ca²⁺ availability and participates in the organisation and maintenance of the soil structure; it also plays a role in the truffle’s nutrition. These results obtained for active limestone may be of use in truffle cultivation.