Olive orchards a threat to Mediterranean soil
The olive tree is a species native to the coastal areas of the Eastern Mediterranean, but which is now widely cultivated in many regions of the world with a Mediterranean climate and which today has become a dominant one within the Mediterranean basin, where it is grown for food, namely the fruit and olive oil, but also for fine wood. Economic relevance of olive cultivation has increased considerably since the second half of the 20th century.
In an article currently in press on Agriculture, Ecosystems & Environment, Spanish researchers measured soil erosion rates over a 250 year period.
Erosion is the process by which sediment material is removed from one place, transported and eventually leads to its deposition elsewhere. Soil erosion is a natural process, which is increased in agricultural areas particularly through poor soil management practices.
Results obtained from this study suggest an average annual soil loss between 29 and 47 t ha−1 year−1, which are relatively high values when compared to measurements of contemporary erosion rates.
Soil management practices have changed considerably throughout this period, especially since the 18th century and which include improvement in tillage implements, changes of soil use in the area between the tree lanes, mechanization and the introduction of herbicides.
Current soil management proved to be the most unfavourable from a soil conservation perspective. However, soil loss rates were consistently above critical sustainability thresholds even during periods with less intensive management.
Even though soil loss would normally result in lower yield, it is apparent that enhanced efficiency of agricultural management practices has actually resulted in a progressive increase in olive yield.
The authors finally point that management effects are not expected to generate additional yield increase and it is likely that the continuing loss of fertile soil will result in a collapse in a few generations if effective soil conservation measures remain absent.
Top Image Credit: © Tom Bayer