Using Dye Tracer for Visualization of Preferential Flow at Macro‐ and Microscales

Abstract

The detection of a nonequilibrium water flow and solute transport in structured soil at various scales is essential for better understanding of these phenomena. This study focused on the visualization of preferential flow in a Haplic Luvisol and Haplic Cambisol and their horizons by performing field ponding dye infiltration experiments. In addition, thin soil sections were made and micromorphological images were used to study soil aggregate structure and dye distribution at the microscale. The staining patterns within the vertical and horizontal field‐scale sections documented the different nature of preferential flow in different soil types and also within the soil profiles. While preferential flow in the Haplic Luvisol was caused by soil aggregation and biopores, preferential flow in the Haplic Cambisol was caused only by biopores, large soil fractures, and incorporated straw material. Micromorphological images showed that, in the case of the Haplic Luvisol, the dye was primarily distributed either in the interaggregate pores and then in the pores inside the aggregates or in the isolated large pores connected to the dye source and then into the matrix pores. The dye distribution in the soil matrix was uneven as well. Accumulated organic matter, clay coating, and isolated larger capillary pores, which initially did not contain the dye tracer, behaved as less‐permeable or impermeable barriers. Uneven distribution was caused by hierarchical pore size distribution of the soil matrix. Results indicated a multimodal character of preferential flow in this soil. In the case of the Haplic Cambisol, the dye pattern studied at the microscale was mostly affected by fractures and the size and shape of mineral grains.

Droplet infiltration dynamics and soil wettability related to soil organic matter of soil aggregate coatings and interiors

“…However, larger WDPT values measured at surfaces with coatings than those at uncoated surface were also associated with generally lower hydraulic conductivity of coatings (consisted of fine grained material) in comparison to hydraulic conductivity of aggregate interiors. Considerable differences between the hydraulic conductivities of aggregate coating and interiors were observed for soil aggregates taken from the same soil horizon by Fér and Kodešová (2012) and Kodešová et al (2012). Results of our measurements on dry soil samples showed a slightly different relationship between WDPT and PWI, than those results of Leue et al (2015), who observed a non-linear relationship between PWI and WDPT (R = 0.5, p < 0.001) for different types of preferential flow path surfaces.…”

“…Aggregate coatings and biopore walls are characteristic soil structural features (e.g., Gerke and Köhne, 2002;Kodešová, 2009;Kodešová et al, 2011Kodešová et al, , 2015Rogasik et al, 2014) that are of great importance when attempting to describe preferential flow and transport processes in soils (e.g., Gerke, 2012;Kodešová, 2009;Kodešová et al, 2008Kodešová et al, , 2009Kodešová et al, , 2010Kodešová et al, , 2012. Clay-organic coatings often cover aggregates and biopores in the clay-illuviation Bt-horizons of Luvisols (IUSS Working Group WRB, 2014).…”

“…An additional task of this study was to evaluate the clay mineralogical composition of coatings and interiors of aggregates (using Xray diffraction) as another potential factor affecting soil surface wettability. Kodešová et al (2012), are shown in Table 1. Kodešová (2009) ;Kodešová et al (2008Kodešová et al ( , 2009) reported intensively developed blocky, and large and long prismatic aggregates in the Bt1 and Bt2 horizons, respectively.…”

Modelling of Cd, Cu, Pb and Zn transport in metal contaminated soil and their uptake by willow (Salix × smithiana) using HYDRUS-2D program

“…The roots' volume may have varied due to their water content oscillation, which corresponded to the soil water content changes (Hillel 1998). Thus a preferential pathway could be created along the roots (Köhne et al 2009;Kodešová et al 2011Kodešová et al , 2012b. In such case a dual-permeability model (Gerke and van Genuchten 1993) in HYDRUS-2D would be more suitable to approximate the observed data .…”

Heterogeneity of water flow in grassland soil during irrigation experiment

“…The flow pathways of water through field soils are highly irregular in many cases, as it was demonstrated by dye tracer infiltration experiments (e.g., Flury et al 1994;Dohnal et al 2009;Homolák et al 2009;Kodešová et al 2012). To quantify the heterogeneity of water flow in soils, Täumer et al (2006) proposed to use the effective cross section (ECS).…”