Gravel mulching in vineyards of southern Switzerland

The growing awareness of the potential of traditional agricultural techniques has resulted in a recent scientific interest in these techniques. As modernisation and mechanisation often lead to the abandonment of these measures, it is vital to document them. Gravel mulching is such a traditional technique that is still practised in Chamoson (southern Switzerland). As no written information about this technique in Chamoson was found, an inquiry was set up amongst the wine-growers of Chamoson. The main objective of this inquiry is to document gravel mulching, based on the experiences of the wine-growers themselves. The results of the inquiry showed that these practitioners in Chamoson consider the effects of the gravel mulch on the thermal (temperature) and hydraulic (infiltration and evaporation) characteristics of the soil, to be the most important for wine-growing. In addition to the inquiry, field experiments were set up to investigate the effects of a gravel mulch on soil temperature and evaporation during summer. The results of these experiments show that a gravel mulch causes a significant increase in the soil temperature at two measured depths (mean increase of 0.97 degrees C at 3-cm depth and 1.5 degrees C at 10 cm; measuring period: 21/07/94-14/08/94) and at the surface (mean increase of 2.2 degrees C; measuring period: 24 h). As for the effect on evaporation, field experiments show an increase of the cumulative evaporation depth, due to the presence of a gravel mulch. This unexpected result can be explained when considering the soil characteristics of the mulched field (i.e., a very stony topsoil with a discontinuous mulch) and the rainfall regime during the measuring period (limited amounts of rainfall; non-saturated soils). The results of the evaporation experiment in the field, agree with the results from similar laboratory experiments reported in the literature. (C) 1998 Elsevier Science B.V. All rights reserved.