Nutrient losses by runoff in vineyards of the Mediterranean Alt Penedès region (NE Spain)

This paper deals with nutrient (N and P) losses by runoff in vineyards of the Penedès area (north-eastern Spain), and their relationship with rainfall erosivity. The study was carried out in a commercial vineyard, which was levelled previous to vineyard establishment in order to adapt fields to mechanised labours, leaving on top of the surface soils very low in organic matter content and very susceptible to erosion. After levelling, large inputs of organic wastes before and/or after planting were incorporated in order to improve soil properties. The analysis was done under natural rainfall during the period 2000–2001, in which 17 rainfall events were recorded. Runoff ratios varied from 2.9 to 28.6%, except for two extreme events in which by up to 55.8 and 80% of rainfall ran off, respectively. Sediment concentration in runoff was very variable ranging between 2.9 and 25.3 g L−1 depending on the rainfall erosivity, which also affected nutrient losses. Erosion processes exported significant amounts of nutrients, which represent about 8 kg ha−1 year−1 of N and 6.5 kg ha−1 year−1 of P, without taking into account losses in the extreme events. The results point out that most soil and nutrient losses are due to a small number of events recorded every year, which can contribute to more than 60% annual soil and nutrient losses.