Abstract
There are several field methods and techniques for measuring Ks . In this study, double-ring (DI) and tension infiltrometer (TI) infiltration techniques were combined with dye tracer application and compared for estimating K s and the mobile soil fraction on a structured sandy loam soil (Gleyic Luvisol), in Rostock, Germany. Water was infiltrated into soil by using three methods: DI, TI (without contact with sand), and TI sand (with contact with sand), until steady-state conditions were obtained. At different positions, three pulse depths of 25 mm, 50 mm, and 100 mm, with a 2 g L -1 Brilliant Blue (BB) FCF dye solution, were used. The results showed variable K s values for DI of 820-2,020 cm d -1 , which were 7 to 13 times higher, when compared to TI values, and 12 to 33 times higher than for TI sand . For the 25 mm and 50 mm BB applications, the mobile (dye-stained) soil regions constituted up to 60% in the top 25 cm and varied little, when considered the infiltration methods. Only the 100 mm application, using the DI, yielded significant BB displacement into the subsoil. Hence, both K s values and their corresponding dye pattern depended on the boundary conditions. For DI, more than 90% of the dye was constrained below the infiltration area, revealing that flow was essentially vertical.
Highlights
The saturated hydraulic conductivity (Ks) controls, together with the gradient in hydraulic potential, the upper limit of water flow in soils. Ks is an important soil physical property for various agronomic, engineering, and environmental problems
The results showed variable Ks values for double-ring infiltrometer (DI) of 820-2,020 cm d-1, which were 7 to 13 times higher, when compared to tension infiltrometer (TI) values, and 12 to 33 times higher than for TIsand
The very large S values for DI are only listed for completeness and are certainly not realistic, since ponded flow conditions caused even the initial infiltration to be strongly affected by gravity, which e-ISSN 1983-4063 - www.agro.ufg.br/pat - Pesq
Summary
The saturated hydraulic conductivity (Ks) controls, together with the gradient in hydraulic potential, the upper limit of water flow in soils. Ks is an important soil physical property for various agronomic, engineering, and environmental problems. There are several field methods and techniques to measure Ks. The double-ring infiltrometer (DI) can be used to assess Ks from measuring infiltration at a constant positive pressure equal to the water ponding depth, while the tension infiltrometer (TI) is applied to derive Ks or unsaturated hydraulic conductivity from infiltration measurements performed at zero or negative pressures (White & Sully 1987, Perroux & White 1988, Ankeny et al 1991). The double-ring infiltrometer (DI) can be used to assess Ks from measuring infiltration at a constant positive pressure equal to the water ponding depth, while the tension infiltrometer (TI) is applied to derive Ks or unsaturated hydraulic conductivity from infiltration measurements performed at zero or negative pressures (White & Sully 1987, Perroux & White 1988, Ankeny et al 1991) Both DI and TI offer a fast and convenient means for determining Ks and other soil hydraulic properties based on in situ infiltration measurements at the soil surface
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