Quantifying the effect of historical soil management on soil erosion rates in Mediterranean olive orchards

Olive orchards are an important agro-ecosystem in the Mediterranean. Soil erosion is a widely recognized threat to their sustainability. However, the variability of short-term soil erosion measurements and the limited understanding of driving processes result in a considerable uncertainty over the long-term effects of soil erosion. This study aims at measuring and modelling soil erosion rates in olive orchards over a 250-year period, and relating these to changes in management practices and yield, as documented from historical sources. In three study areas in S-Spain, the height of relic tree mounds was measured in olive orchards dated between 153 and 291 years old to determine soil profile truncation. Measured average soil erosion rates were between 29 and 47 t ha−1 year−1. Historical documents allowed characterizing land management since 1752 in eight distinct periods. This information was then used to calibrate a soil erosion model, combining water and tillage erosion. The model reproduced the temporal patterns in soil erosion rates and showed considerable historical variation: between 8 and 124 t ha−1 year−1 for water and between 3 and 42 t ha−1 year−1 for tillage. Mainly due to improved agronomic practices, yield was not affected by soil erosion and has continuously increased over time.