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Rock fragments influence the water retention and hydraulic conductivity of soils
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  • Mahyar Naseri,
  • Deep C. Joshi,
  • Sascha C. Iden,
  • Wolfgang Durner
Mahyar Naseri
Division of Soil Science and Soil Physics, Institute of Geoecology, Technische Universität Braunschweig

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Deep C. Joshi
Division of Soil Science and Soil Physics, Institute of Geoecology, Technische Universität Braunschweig
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Sascha C. Iden
Division of Soil Science and Soil Physics, Institute of Geoecology, Technische Universität Braunschweig
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Wolfgang Durner
Division of Soil Science and Soil Physics, Institute of Geoecology, Technische Universität Braunschweig
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Abstract

Rock fragments (RF) influence soil hydraulic properties (SHP) and knowledge about the SHP of stony soils is important in vadose zone hydrology. However, experimental evidence on effective SHP of stony soils is still scarce and mostly restricted to water-saturated conditions and low volumetric contents of RF. We examined the influence of RF on SHP through a series of measurements. Stony soils were prepared by packing 250 cm3 cylinders with soils of two textures (sandy loam and silt loam) and with different volumes of RF (up to 50 % v/v) with a diameter of 8-16 mm. Samples were prepared in a way that the background soils (diameter smaller than 2 mm) had identical bulk density. The simplified evaporation method was used to determine the effective SHP of stony soils. We used the obtained SHP data to evaluate the performance of models, which predict the effective SHP of stony soils from SHP of the background soil. The results highlight the systematic dependency of SHP on volumetric content of RF. The difference between modeled and measured SHP was substantial for cases in which the soil contained a high amount of RF. Accounting for the moisture content of RF improved the prediction of the effective WRC of stony soils compared with a simple scaling that used only the content of RF. Among the evaluated models for the effective HCC, the model based on the general effective medium theory (GEM) showed the best performance, particularly for low RF contents.