Understanding of a soil system derived from a single bed-rock, for

Abstract: The 'Massif de La Clape ' in Southern France is a calcareous hill with a semi-arid Mediterranean climate. All the agricultural lands are under vineyards managed by differ-ent chateaux. The objective of this work was to understand the soil system of Chateau X to solve a problem of vineyard mortality and to show how the exceptional variability of the soil conditions could be taken into account for optimal vineyard management. The soils of Chateau X are derived from sandstone that fills a basin of about 40 ha, surrounded by a calcareous formation. The study of the soil system showed the presence of four soil domains, two located at the top of the basin and mainly derived from eluviation, and two located at the bottom of the basin, which are mainly derived from illuviation. The domain located at the very bottom of the basin showed an accumulation f swelling clays in its BtM horizon. The zones of highest vine mortality were located at the bottom of the basin, on the soil with the BtM horizon. This mortality was explained by the strong discontinuity between the E and the BtM horizons, with the accumulation f Cu at toxic concentrations as a consequence of lateral water flows. In this soil, root growth was hindered by the high bulk density of the BtM horizon. In order to solve the problem of vine mortality an