Soil Moisture Regime Changes in Tephra‐Mulched Soils

Large areas of the Canarian archipelago are catalogued as aridic according to U.S. soil taxonomy. A traditional system of cultivation, based on the application of a mulch layer of tephra, is widely practiced. The objective of this work is to compare the classification of soils with and without mulch using U. S. soil taxonomy, and illustrate the problems in estimating the soil moisture regime on the basis of meteorological data. In this study the moisture regime of a natural soil and an adjacent soil mulched with a 12-cm layer of basaltic tephra was characterized on the basis of gravimetric moisture measurements, taken over a period of >1 yr, at 10-cm intervals to a depth of 1 m. The moisture regime of the soil was also estimated using meteorological data. Results obtained for the natural, nonmulched soil using measured values and those estimated from atmospheric data are very similar, and both indicate an aridic soil moisture regime. The difference with the soil covered with basaltic tephra is noteworthy. In the latter case, the soil remained moist throughout the year, representing a udic moisture regime. This noteworthy difference is reflected in the classification of the soils: Aridisols in the first case and Inceptisols in the second. A proposal is made to include mulching with tephra as a cultural practice along with irrigation and fallowing in the definition of the classes of soil moisture regimes in U.S. soil taxonomy. This would prevent the practice of mulching with tephra from changing the soil order placement in U.S. soil taxonomy.