  Sulfur is a volatile chemical element that plays an important role in tracing
the chemical evolution of galaxies. However, its nucleosynthesis origin and
abundance variations are still unclear. The goal of the present article is to
accurately and precisely study the S-content of large number of stars located
in the solar neighbourhood. We use the parametrisation of thousands of HR
stellar spectra provided by the AMBRE Project, and combine it with the
automated abundance determination GAUGUIN to derive LTE sulfur abundances for
1855 slow-rotating FGK-type stars. This is the largest and most precise
catalogue of S-abundances published to date. It covers a metallicity domain as
high as ~2.5dex starting at [M/H]~-2.0dex. We find that the [S/M] abundances
ratio is compatible with a plateau-like distribution in the metal-poor regime,
and then starts to decrease continuously at [M/H]~-1.0dex. This decrease
continues towards negative values for supersolar metallicity stars as recently
reported for Mg and as predicted by Galactic chemical evolution models.
Moreover, sulfur-rich stars having [M/H] in the range [-1.0,-0.5] have very
different kinematical and orbital properties with respect to more metal-rich
and sulfur-poor ones. Two disc components, associated with the thin and thick
discs, are thus seen independently in kinematics and sulfur abundances. The
sulfur radial gradients in the Galactic discs have also been estimated.
Finally, the enrichment in sulfur with respect to iron is nicely correlated
with stellar ages: older metal-poor stars have higher [S/M] ratios than younger
metal-rich ones. This work has confirmed that sulfur is an alfa-element that
could be considered to explore the Galactic populations properties.
