ANALYSIS OF DESIGN CRITERIA FOR VINEYARD TERRACES IN THE MEDITERRANEAN AREA OF NORTH-EAST SPAIN

The Penedes and Anoia regions in NE Spain are important areas for the cultivation of grapes used in the production of high quality wines. Th e Mediterranean climatic conditions define a xeric soil moisture regim e. Rainfall are concentrated in spring and autumn while the summer is warm and dry. The climate is characterized by high rainfall intensitie s, being one of the main factors responsible for soil erosion in the a rea. Since grape quality depends on the availability of water for the vineyards and since soil erosion is an important parameter dictating t he sustainability of vineyards, soil and water conservation can not be forgotten in the area. The most widely used measure for soil conserva tion in the area is terracing (hillside ditches, local name rases). Lo cal technical solutions have been studied and in this paper different types of terraces are described and analysed in terms of its effective ness for runoff control. Mean potential soil losses are evaluated acco rding to the USLE and compared with field measurements in experimental plots. The distances between terraces have been calculated using the criteria proposed by several authors. Owing to the wide diversity of r esults, an acceptable value for 'soil loss tolerance' (T-value) has be en used in order to establish some criteria to make recommendations, t aking the values of soil loss measures in the field as a reference. Ac cording to these preliminary results based on measurements taken over a period of two years, some advisable distance between terraces (rases ) in vineyards can be proposed in view to improve local criteria. With a slope of 6%, a distance of is 28 m would be advisable, and in field s with a slope of 8% the distance should be 20 m. Bennett's criteria t o calculate distances between terraces are the more advisable being cl osely related with experimental results in the area.