Sandbox, pressure plates and WP-4

The relationship between matric potential and volumetric water content, i.e, the soil water retention curve, is obtained by weighing soil samples after a hydrostatic equilibrium is reached. The desired matric potential is either applied by a hanging water column (range 0 to -1 cm) or by increasing the air pressure (range 1 - 150 m). The measured water retention curve is parameterized using an appropriate model (fitting). Higher pressure steps (-10.000 hPa bis -40 MPa) the WP4 device (Decagon Devices, USA) will be used on disturbed samples.