VARIACION DEL POTENCIAL MATRICO DURANTE EL MOVIMIENTO DE AGUA EN ANDISOLES

Abstract

The aim of this research was to evaluate the dynamics of matric potential during wetting and drying processes of three Andisols, located in the VIIth, IXth and Xth Regions of Chile, submitted also to two different uses (forest and pasture). The matric potential during 24 h after a simulated irrigation of 30 mm, was measured and the advance of the water front was registered for non disturbated soil samples with an artificial water table. With the same set of sensors, variations of matric potentials were measured during a period of drying of 24 h. Furthermore, porosity distribution of all soils was determined. The advance of the water fronts took between 8 and 16 minutes to wet the complete forest soil profiles, time that was related to the size distribution of pores. Due to the more intense management of the pasture, which causes a decrease of total porosity and drainable pores (>50-10ºm), the time of water distribution increased and the gradient of potentials was more irregular. After 24 hours, in all soils and in both uses, distribution of potentials reached a balance with the water table, similar to the distribution previous to irrigation. In conclusion, with the increase of drainable porosity the advance of the water front tended to be bigger and constant, specially in forest soils.