The genesis of irrigated terraces in al-Andalus. A geoarchaeological perspective on intensive agriculture in semi-arid environments (Ricote, Murcia, Spain)

Irrigated terraces in the Iberian Peninsula are associated with al-Andalus; the name with which the region was known following the migration of Arabic–Berber tribes across the Strait of Gibraltar, starting from 711 AD. Several of these agricultural areas have remained in use in the west Mediterranean to the present day. Historical texts usually refer to later extensions of the original Andalusi irrigated terrace fields, yet little is known about their foundation period. In this study we examined the micromorphology and undertook physico-chemical analyses and radiocarbon dating of a buried soil found in Ricote (Murcia, Spain) to provide relevant information to understand the initial stages of terrace building within al-Andalus. Results of our study show that: (1) Andalusi peasants selected a saline Hipercalcic Calcisol developed on colluvial materials on which to build the first irrigated terraces, (2) The soil was probably cleared of bushes by fire prior to terrace construction, (3) The shifting of sediments implied in the building of terraces seems to have entailed the inversion of the original soil stratigraphy, (4) Radiocarbon dating of submillimetric fragments of charred wood embedded in the top horizon of the buried Hipercalcic Calcisol (2σ 647–778 AD) suggests the original irrigated terraces of Ricote were built shortly after the arrival of Arabic and Berber tribes in the Iberian Peninsula.

► We study a soil buried under an Andalusi irrigated terrace in Ricote (Murcia).
► We estimate that the original hydraulic system was built shortly after 711 AD.
► We propose semi-arid environmental conditions prior to terrace building.
► Terrace construction process may have involved fire clearance.
► Arab-Berber tribes modified semi-arid terrains to allow intensive agriculture.