Malleable disc base for direct infiltration measurements using the tension infiltrometry technique

Abstract

Abstract:The correct use of the tension disc infiltrometer requires the membrane of the disc base to be completely in contact with the soil surface. To achieve this contact, a thick layer of sand is commonly placed between the soil surface and the disc base. This paper presents an alternative disc (M DB ), which, by incorporating a malleable membrane, allows direct infiltration measurements without using a contact sand layer. Infiltration curves obtained with this new design in a soil under three different tillage management treatments were compared with the corresponding curves obtained with a conventional disc (C DB ) that uses a contact sand layer. The cumulative infiltration curves measured with C DB were analysed by the differentiated linearization (DL) method, and the corresponding curves obtained with M DB were analysed using both the DL and the cumulative linearization (CL) models. The values of hydraulic conductivity (K 0 ) and sorptivity (S 0 ) estimated with C DB were also compared with those obtained with M DB . Finally, the cumulative infiltration curves measured with C DB and M DB were compared with the corresponding modelled function for the respective K 0 and S 0 values calculated with the CL and DL models. The results show that, compared with C DB without a contact sand layer, M DB allows complete soil surface wetting even when non-smoothed soil surfaces are used. The C DB , which yielded average K 0 values 18% lower than those estimated with M DB , gave the highest values of standard error for the hydraulic parameters calculated. Furthermore, the subjective method employed in the C DB -DL technique, which requires the first points of the differential infiltration line corresponding to the sand layer to be manually removed, introduces additional uncertainties in estimating S 0 and K 0 . Comparison between the modelled and measured infiltration curves demonstrates that the DL or CL methods applied to M DB gave excellent estimates of S 0 and K 0 .

Soil hydraulic properties estimation from one‐dimensional infiltration experiments using characteristic time concept

“…Vadose Zone Journal Vandervaere et al (2000) method was mainly intended for disc infiltrometer measurements, where a contact sand layer is placed between the soil surface and the base disc. According to Moret-Fernández, Blanco, Martínez-Chueca, and Bielsa (2013), without a contact sand layer, the Smiles and Knight (1976) method performs much better than the Vandervaere et al (2000) one. Therefore, since we are working with 1D infiltration curves generated without using a contact sand layer, it was rational to exclude this method from further analysis.…”

“…(2000) method was mainly intended for disc infiltrometer measurements, where a contact sand layer is placed between the soil surface and the base disc. According to Moret‐Fernández, Blanco, Martínez‐Chueca, and Bielsa (2013), without a contact sand layer, the Smiles and Knight (1976) method performs much better than the Vandervaere et al. (2000) one.…”

Estimate of soil hydraulic properties from disc infiltrometer three-dimensional infiltration curve. Numerical analysis and field application

“…The diameter disc and internal diameter of the water reservoir tower was 100 mm and 34 mm, respectively. Two different base discs were used: (i) a conventional disc (C DB ) which base was covered with a tightened nylon cloth of 20-lm mesh and uses contact sand layer between the soil surface and the base disc; and (ii) a malleable base disc (M DB ), which base was covered with a loosened malleable nylon cloth of 20-lm mesh filled with 100 g of coarse sand (1-1.5 mm grain size; 0.5-cm-thick layer, approximately) (Moret-Fernández et al, 2013b). This alternative design allows adapting the base disc to the soil surface without using contact sand layer.…”

Sequential infiltration analysis of infiltration curves measured with disc infiltrometer in layered soils

“…However, such an approximation remains valid only for short to intermediate infiltration times. Although this simplified model has been largely employed for characterizing soils (Vandervaere et al, 2000;Lassabatere et al, 2006;Moret-Fernández et al, 2013), its reduced temporal validity makes its use uncertain. To solve this limitation, Latorre et al (2105) determined the soil hydraulic properties form the inverse analysis of the QEI model, instead of using approximations like in BEST methods (Lassabatere et al, 2006, Yilmaz et al, 2010, and Bagarello et al, 2014.…”