Influence of management with salic mulch on soil temperature

Abstract

The use of salic pyroclasts as soil mulch is a common management practice in arid conditions in southern and south-eastern parts of the island of Tenerife (Canary Islands, Spain). It forms the basis for a traditional farming technique, which is known locally as 'jable'. In its various forms the practice, used at heights of 300-1500 metres, covers an area of 3,850 hectares. The present work examines its influence on soil temperature and particularly on the estimation of Classes of Soil Temperature (Soil Survey Staff, 1999). Soil temperature was measured monthly at 50 cm depth in six covered plots and in adjacent uncovered plots, all located at different altitudes: 325-375, 600, 825 and 1275 m. In each season, measurements were also taken at 0, 10, 20, 30, 40 and 50 cm. The thickness of the mulch covering varied between 23 cm and 43 cm. The natural altitudinal soils sequence was as follows: aridisols, vertisols and vertic inceptisols, and inceptisols. The covered soil is currently used to grow grapes and/or potatoes while the natural soil has natural vegetation. The results evidence the buffering effect of the system, which is more marked at the lower heights of the sequence. Whereas the natural soils have a hyperthermic temperature regime (annual soil temperature, mean ≥ 22ºC, and a difference between mean summer temperature, mst, and mean winter temperature, mwt, > 6ºC) the soils under the pumice are isohyperthermic (mean ≥ 22ºC and mst-mwt < 6ºC). At approximately 600 m, the natural soils are thermic (15≤mean<22ºC and mst-mwt >6ºC) and the covered soils are isothermic (mst-mwt < 6ºC). This situation is maintained up to 800/900 m, where the buffering effect of the pumice is less pronounced. The temperature profiles are also influenced by the system. In the natural soils, temperature decreases with depth, while in the covered soils this occurs only in summer. The management system helps prevent high temperatures and enables the soil to be used for farming.