Tension infiltrometers (TI) are widely used for the determination of saturated and near saturated soil hydraulic properties. Complete contact between the tension disc and the soil is essential for reliable data. Any vegetation within the sample should be trimmed to ground level. The vast majority soils are uneven, hence contact material is generally placed over the undisturbed soil surface to create a level and smooth surface (Perroux & White 1988). The characteristics of the contact material should include a hydraulic conductivity higher than that of the soil and a water entry value lower than the minimum pressure head applied.

In general, use of the contact material affects the infiltration. Furthermore, applying pressure heads near saturation might cause that mobile fine-textured particles of the contact material clog the macropores. The result is a decrease of the true near-saturated conductivity. Finally, preparing the soil surface for TI measurement could lead to alterations of the original properties of the soil surface.

A new type of TI, a so-called hood infiltrometer (HI), is presented which could overcome the critical aspects mentioned. In contrast to the TI no preparation of soil surface is required.

A hood connected to a Mariotte bottle is placed on the undisturbed infiltration surface. Inside of the hood water is ponded. An additional negative pressure compensates the depth of water ponding and hence, water can be supplied at different pressure heads. Our experimental setup allows the measurement of hydraulic properties from saturation up to the air entry value of the soil. The effective pressure head on the soil surface can be measured by an U-tube manometer with a precision of ± 1 mm.

Tension infiltrometer and hood infiltrometer measurements were carried out to evaluate the effects of contact material and soil surface preparation on the saturated and near-saturated conductivity. Additionaly soil cores were taken to analyze the hydraulic properties using laboratory methods.