Links between soil properties and steady‐state solute transport through cultivated topsoil at the field scale

Abstract

[1] It is known that solute transport through soil is heterogeneous at all spatial scales. However, little data are available to allow quantification of these heterogeneities at the field scale or larger. In this study, we investigated the spatial patterns of soil properties, hydrologic state variables, and tracer breakthrough curves (BTCs) at the field scale for the inert solute transport under a steady-state irrigation rate which produced near-saturated conditions. Sixty-five undisturbed soil columns approximately 20 cm in height and diameter were sampled from the loamy topsoil of an agricultural field site in Silstrup (Denmark) at a sampling distance of approximately 15 m (with a few exceptions), covering an area of approximately 1 ha (60 m  165 m). For 64 of the 65 investigated soil columns, we observed BTC shapes indicating a strong preferential transport. The strength of preferential transport was positively correlated with the bulk density and the degree of water saturation. The latter suggests that preferential macropore transport was the dominating transport process. Increased bulk densities were presumably related with a decrease in near-saturated hydraulic conductivities and as a consequence to larger water saturation and the activation of larger macropores. Our study provides further evidence that it should be possible to estimate solute transport properties from soil properties such as soil texture or bulk density. We also demonstrated that estimation approaches established for the column scale have to be upscaled when applied to the field scale or larger.

Field-scale Variation in Colloid Dispersibility and Transport: Multiple Linear Regressions to Soil Physico-Chemical and Structural Properties

“… where μ 2 is the second central temporal moment or variance, σ 2 , of the pdf; L is the length of the sample; and μ 1 is the normalized first moment of the pdf. See Koestel et al (2012) for a detailed description of modeling breakthrough curves and calculation of apparent dispersivity.…”

Long-Term Effect of Different Carbon Management Strategies on Water Flow and Related Processes for Three Loamy Soils

“…The content of organic matter was also, in this study, hypothesized to reduce preferential flow as was found by Jarvis et al (2007). Koestel et al (2013) found a positive correlation between preferential flow and the degree of water saturation. The time for 5% breakthrough (T 5 ) of an applied dissolved nonreactive tracer has also been used as an indicator for preferential flow Norgaard et al, 2013).…”

Effects of Soil Compaction and Organic Carbon Content on Preferential Flow in Loamy Field Soils

“…The parameterization of the double log-normal distribution functions was conducted with R software (version 2.14.1) closely following the procedure provided in Koestel et al (2013). In brief, the measured BTC data points (f(t)) were first discretized to a temporal resolution of 2 min by linear interpolation.…”

“…Koestel et al (2012) reported a negative correlation between bulk density (BD) and the magnitude of preferential flow and transport based on analysis of 733 breakthrough curves (BTC). More recently, Koestel et al (2013) reported that the extent of preferential transport was positively correlated to BD and the degree of water saturation.…”