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Mogens Humlekrog Greve

Comparative Mapping of Soil Physical-Chemical and Structural Parameters at Field Scale to Identify Zones of Enhanced Leaching Risk

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Preferential flow and particle-facilitated transport through macropores contributes significantly to the 3 transport of strongly-sorbing substances such as pesticides and phosphorus. The aim of this study was 4 to perform a field-scale characterization of basic soil physical properties like clay and organic carbon 5 content and investigate whether it was possible to relate these to derived structural parameters such as 6 bulk density and conservative tracer parameters and to actual particle and phosphorus leaching patterns 7 obtained from laboratory leaching experiments. Sixty-five cylindrical soil columns of 20 cm height and 8 20 cm diameter and bulk soil were sampled from the topsoil in a 15 m × 15 m grid in an agricultural 9 loamy field. Highest clay contents and highest bulk densities were found in the northern part of the 10 field. Leaching experiments with a conservative tracer showed fast 5% tracer arrival times and high 11 tracer recovery percentages from columns sampled from the northern part of the field, and the leached 12 mass of particles and particulate phosphorus was also largest from this area. Strong correlations were 13 obtained between 5% tracer arrival time, tracer recovery, and bulk density, indicating that a few well14 aligned and better connected macropores might change the hydraulic conductivity between the 15 macropores and the soil matrix, triggering an on-set of preferential flow at lower rain intensities 16 compared to less compacted soil. Overall, a comparison mapping of basic and structural characteristics 17 including soil texture, bulk density, dissolved tracer, particle and phosphorus transport parameters 18 identified the northern one-third of the field as a zone with higher leaching risk. This risk assessment 19 based on parameter mapping from measurements on intact samples was in good agreement with nine 20 years of pesticide detections in two horizontal wells and with particle and phosphorus leaching patterns from a distributed, shallow drainage pipe system across the field.
TidsskriftJournal of Environmental Quality
Sider (fra-til)271-283
Antal sider13
StatusUdgivet - 2013

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