CAUSES OF SOIL MALFUNCTIONING IN DEGRADED AREAS OF EUROPEAN AND TURKISH VINEYARDS

A study was carried out in nineteen vineyards of five countries, well representative of major viticultural districts, which showed areas with fertility problems, consequence of strong soil erosion occurred during either pre-planting or ordinary cultivation. The comparison between degraded and non-degraded areas highlighted that the soil features limiting water nutrition and enhancing potential water stress were the most frequent discriminant soil conditions. Low nitrogen availability was the second most important cause of soil malfunctioning, together with low organic matter content. The degradation was also reflected in the very low values of the C/N ratio, pointing to a difficulty of microbiota in synthetizing humus. Other limiting factor were excessive skeleton or lime content, and poor drainage. Nutrient unbalance or toxicity, and low cation exchange capacity, occurred sporadically. Since physical and hydrological limitations are hardly modifiable, the study underlines the difficulties to restore the fertility of degraded soils, and suggests caution in planning new vineyards