ABSTRACT.
DETERMINATION OF UNSATURATED CONDUCTIVITY BY THE INSTANTANEOUS PROFILE METHOD

Celerino Quezada L.1 y Benjamín Fernández M.2
 
The unsaturated conductivity of a granitic soil located in the coastal area of the VIII Region, Chile, were determined by the instantaneous profile method. Moisture contents at different depths and time were determined with a Troxler neutron-meter (Model 2651, Series 2600). Matric suctions at depths of 30 - 60 - 90 - 120 - 150 and 175 cm were measured at differents times by means of tensiometer readings. Volumetric water contenst as well as tensiometer readings were obstained under conditions of internal drainage alone (evapotranspiration prevented). The unsaturated conductivity values (3.2 x 10-4 to 0.345 cm/day) revealed a marked impedance to unsaturated flow. This was due to the higher percentage of soil pores smaller than 0.20 microns (arround 60%). On account of, the measurements in fine texture soils must not long as many as 30 days. The unsaturated conductivity is directly dependent on valumetric wettness and inversely to the matric suction. To apply this method in the field, is conenient to know the profile characteristics and soil slope. This is essential to determine the reading depths and to minimize the lateral drainage.
Keywords:
1Ing. Agr., M. S., Universidad de Chile, Casilla 933, Osorno, Chile. 2Ing. Agr., M. S., Departamento de Suelos, Escuela de Agronomía, Universidad de Concepción, Chillán, Chile.