Spatial variability of soil properties and soil erodibility in the Alqueva reservoir watershed

摘要

The aim of this work is to investigate how the spatial variability of soilproperties and soil erodibility ($K$ factor) were affected by the changes inland use allowed by irrigation with water from a reservoir in a semiaridarea. To this end, three areas representative of different land uses(agroforestry grassland, lucerne crop and olive orchard) were studied withina 900 ha farm. The interrelationships between variables were analyzed bymultivariate techniques and extrapolated using geostatistics. The resultsconfirmed differences between land uses for all properties analyzed, whichwas explained mainly by the existence of diverse management practices(tillage, fertilization and irrigation), vegetation cover and local soilcharacteristics. Soil organic matter, clay and nitrogen content decreasedsignificantly, while the K factor increased with intensive cultivation. TheHJ-Biplot methodology was used to represent the variation of soilerodibility properties grouped in land uses. Native grassland was the leastcorrelated with the other land uses. The K factor demonstrated high correlationmainly with very fine sand and silt. The maps produced with geostatisticswere crucial to understand the current spatial variability in the Alquevaregion. Facing the intensification of land-use conversion, a sustainablemanagement is needed to introduce protective measures to control soilerosion.