Saturday, 15 July 2006

Proposal of New Subgroups for Arents with Andic Characteristics.

Marisa Tejedor1, Concepción Jiménez1, Silvia Armas-Espinel1, and Jose Manuel Hernández-Moreno2. (1) Univ de La Laguna, Dept. Edafología y Geología, Facultad de Biología, Avda. Astrofísico Fco.Sánchez s/n, La Laguna, 38204, Spain, (2) Univ de La Laguna, Dept. Edafología y Geología, Facultad de Biología, Avda. Astrofísico Fco.Sánchez s/n, La Laguna, 38204, Spain

In the mountainous islands of the Canarian archipelago (Spain), the large climatic variability along with the different lithological chronology explains the existence of a wide range of soil types: Andisols, Oxisols, Vertisols, Mollisols, Alfisols, Inceptisols, and Entisols. The more evolved soils, with the best characteristics for cultivation, are located in the humid, fresh northern sides while in the lowlands, soils have been generally eroded or degraded (salinity-sodicity, petrocalcic horizons, etc). This explains the common practice to transport soil materials from the high-mid altitudes to the lowlands for cultivation, mainly export crops (bananas, tomatoes), taking advantage of the more suitable climatic conditions. The new artificial soils are locally named ‘‘sorribas''. The soil types transported are generally Andisols and soils with more or less andic properties (Inceptisols, Alfisols, and Ultisols). No horizon selection is made; thus, topsoils are mixed with B horizons and weathered tephra. In the new environment, the “sorriba” soils undergo salinisation and sodification processes, induced by irrigation and heavy fertilization, among other potential threats to soil degradation. Previous studies by the authors on a limited set of data of sorriba-soils from the island of Tenerife showed that relevant soil properties associated to andic characteristics remained little affected after 10 years of cultivation. The aim of this work was to extend the sorriba-soils database to other islands and cultivation periods up to 30 years. Soils with a range of andic properties and management practices were selected. The results showed that physical properties such as hydraulic conductivity and water retention remained at high values and bulk density was around 1. Phosphate retention capacity did not decline under 60%. From the point of view of the sorriba-soils classification they can be generally included in the Torriarents, but there is no subgroup to accommodate their andic character. Therefore, the inclusion of the subgroups Andic and Vitrandic in the Arents suborder is proposed.

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