Changes in selected soil properties caused by 30 years of continuous irrigation under Mediterranean conditions

Irrigation water can have an adverse effect on the chemical and physical properties of the soil. In order to detect changes caused by long-term irrigation, the soils from an irrigated area on the Spanish–Portuguese border were monitored, and 1428 georeferenced topsoil samples were analyzed. The results confirm a generalized acidification of the irrigated soils when compared with rain-feed soils. There was also an increase in the electrical conductivity and exchangeable sodium percentage. The irrigated soils showed a significant decrease in organic matter content. All these results evolved significantly over at least a 30-year period. The information was implemented in a Geographical Information System, which allowed the detection of the areas of greatest irrigation impact, and the delimitation of particularly vulnerable zones where special attention is recommendable for soil conservation