The desertion of large agricultural lands in Mediterranean areas has important consequences on soil erosion. The aim of this study was to quantify runoff and water soil erosion evolution during the period 1994-97. Runoff and erosion were measured in erosion plots (20* 4 m). Four different treatments were applied, namely bare soil maintained with herbicide, no-tilled barley crop, spontaneous vegetation and leguminous sowing before desertion. These trials were carried out in four areas with different types of soils. The areas are located in the centre of Spain, under a Mediterranean-continental climate. In bare soils, annual runoff coefficient was higher than 10%, increasing through the time because of the soil compaction. These plots showed high soil erosion rates, between 1.3 and 28 t ha/year. Spontaneous vegetation plots produced the lowest erosion rates (from 0.0002 to 0.15 t ha/year). Annual runoff coefficient in no-tilled barley plots increased lightly through the four years, because the minimum ploughing favoured a light soil compaction. Soil erosion rate was low, ~0.3 t ha/year, showing the efficiency of this crop on erosion control. Runoff coefficient in abandoned plots (with spontaneous vegetation) and plots with leguminous sowing before desertion, decreased through the time. The lowest erosion rates were recorded when plant cover was higher than 50%, that is, from 6 months to 2.5 years after crops desertion. It is shown that in these environments soil erosion is not a continuous process, because the main water erosion measured during the four years period were produced only in two or three big storms.
