Soil water retention curve (SWRC) has been built using several strategies and methodologies. For low tension the use of tension tables has predominated. This paper presents prototypes and test the use of sand suction columns to measure soil water retention from 0 to 100hPa tension. An initial test was set up in a sand column instrumented with tensiometers every 0.1m from top to 1.0m depth. The column was set in a plastic tube 0.25m diameter with devices to have water inlet and to allow water table level. The column was filled with sieved sand, saturated and drained till a given water table depth. The total water potential distribution inside of column and water tension variation at sand surface indicated that, after hydrostatic equilibrium, the depth of water table regulates the potential distribution and the water tension at sand surface is equal to depth of water table. Sand column models (low and high cost) were set up and tested. In these columns a tensiometer was installed at sand surface and saturated soil samples in cylinders with tensiometers inside were set on top of sand and on top of filter paper laid on sand. Tensiometers located at sand surface and inside of soil samples indicated that tension targets were achieved from 8 to 12 hours at both, sand surface or inside of soil samples.
soil moisture characteristic curve; tension table; physical properties
