Soil-Water Laboratory

Water is now widely recognised as a limited natural resource. The knowledge of soil-water status and its movement in soil is important and has practical implications in agricultural, environmental and hydrological situations. Soil-water movement in the field depends on the hydraulic properties of the soil (properties that influence the retention and transmission of water in the soil). The most important properties are the water retention and hydraulic conductivity curves. Modelling soil-water movement requires this information as input.
The water retention curve of a soil describes the relationship between soil-water potential and its volumetric water content, which is a characteristic for different soil types. Hydraulic conductivity describes the ease of water flow in the soil. In saturated conditions the saturated hydraulic conductivity reflects the number of pores and their arrangement. Hydraulic conductivity also depends on the water content and potential of the soil.

The soil-water laboratory at the university of Sydney is now equipped with specialised instruments for measurement of soil hydraulic properties.

	ku-pF apparatus This is an automated version of the evaporation method. The evaporation method measures both water retention and hydraulic conductivity in the pressure range from -5 to -90 kPa. Water is allowed to evaporate from the top of an initially wet soil sample. Pressure heads and water content are measured. With this fully automated set-up apparatus (from UGT), ten samples can be measured simultaneously.
	Pressure cell Pressure cells are used to measure water retention in the potential range from -10 (field capacity) to -1500 kPa (wilting point). Air pressures are imposed on soil samples placed on saturated, very fine porous ceramic.
	Tempe Cell While pressure plate is designed to extract moisture from small disturbed soil samples, tempe cell is designed for individual soil core where soil structure is important. Tempe cells can be used to extract water from the potential range 0 to -100 kPa.
	Vacuum Dessicator Soil samples are placed on a small petri-dish in a constant-humidity vacuum dessicator. Because there is a relationship between matric potential and relative humidity, the soil can be equilibrated at very low potential or very dry (-1500 to -15000 kPa).
	Laboratory permeameter For measurement of saturated hydraulic conductivity. This instument from Eijkelkamp can hold up to 25 soil samples.

For more information on the measurement of soil/other porous media samples contact us.

See also our Field Instruments for measurement of soil hydraulic properties.