The effect of long term conservation tillage (CT) application on the stratification ratio (SR) of soil organic carbon (SOC), soil nutrient (P and K) contents, loss of the soil CaCO3 and on the crops performance was studied. The SR was established dividing the SOC content at 0-5 cm and 5-10 cm soil depths by the SOC at deeper depths (10-25 cm and 25-35 cm). Results were compared with those obtained under traditional tillage (TT). The study was conducted in a wheat-sunflower crop rotation established in 1991 under rainfed conditions in south-west Spain; results shown here correspond to the years 2001 (sunflower) and 2002 (wheat). The results show that, under studied conditions, CT improved soil quality by reaching a greater SR (> 2) than that in TT (< 2) (SR > 2 indicates better soil quality), decreasing the loss of CaCO3 and increasing the P and K contents at the soil surface (0-5 cm and 5-10 cm). Crop performance was in general better under CT than under TT.