The challenge in estimating soil compressive strength for use in risk assessment of soil compaction in field traffic

TY - CHAP

T1 - The challenge in estimating soil compressive strength for use in risk assessment of soil compaction in field traffic

AU - Schjønning, Per

AU - Lamandé, Mathieu

AU - De Pue, Jan

AU - Cornelis, Wim M.

AU - Labouriau, Rodrigo

AU - Keller, Thomas

N1 - Funding Information: The technical assistance of Bodil B. Christensen, Michael Koppelgaard, Jørgen M. Nielsen and Stig T. Rasmussen is gratefully acknowledged. The text was linguistically improved by Margit Schacht. The experimental part of this study was financially supported by the Ministry of Food, Agriculture and Fisheries of Denmark (‘Innovation’ project No. 3412-07-01997). Funding Information: Monitoring and modeling approaches have revealed that 25%–50% of the subsoils of arable land in Europe has been compacted by field traffic ( Brus and van den Akker, 2018 ; Schjønning et al., 2016 ; Schneider and Don, 2019 ; van den Akker and Hoogland, 2011 ; Widmer, 2013 ). Given the steady increase in power and weight of machinery, the size of the affected area is supposed to grow rapidly. Hence, there is an increasing focus on sustainable management from policymakers and society at large. Many projects address soil protection measures to prevent soil degradation (e.g., the current European Joint Programme on soil: www.ejpsoil.eu ). A policy brief developed by the RECARE project (2013–2018; financially supported by the EU Commission; https://www.recare-hub.eu/ ) promoted policy options including training and risk assessment elements under the Common Agricultural Policy ( https://www.ecologic.eu/sites/default/files/publication/2018/2730_recare_subsoil-compaction_web.pdf ). Publisher Copyright: © 2023 Elsevier Inc.

PY - 2023/1

Y1 - 2023/1

N2 - Society calls for protection of agricultural soils in order to sustain the production of foods for a growing population. Compaction of subsoil layers is an increasing problem in modern agriculture and a cause of serious concern because of the poor resilience in natural amelioration. The concept of soil precompression stress has been adapted from civil engineering, although in soil science it is applied to unsaturated soils that have developed a secondary structure from the action of weather, biota and tillage. It assumes strain is elastic at loads up to the precompression stress, while plastic deformation is expected at higher stresses. To determine this threshold we performed uniaxial, confined compression tests for a total of 584 minimally disturbed soil cores sampled at three subsoil layers on nine Danish soils ranging in clay content from 0.02 to 0.38 kg kg−1. The cores were drained to either of three matric potentials (−50, −100 or − 300 hPa) prior to loading. Stress was applied by a constant-strain rate method. We estimated the point of maximum curvature of the strain-log10(normal stress) relation by a numerical procedure. This point is considered here as a compactive stress threshold, typically labeled the soil precompression stress, σpc. The preload suction stress (PSS) was calculated as the product of initial (i.e., before loading) water suction and initial degree of pore water saturation. Multiple regressions were performed to evaluate the effect of soil properties (textural classes, volumetric water content, bulk density (BD), soil organic matter (SOM), and PSS) on σpc. The best model explained 39% of the variation in σpc, and indicated that σpc increases with increasing PSS, BD and SOM. For a given combination of clay, BD and SOM, PSS affected σpc negatively. We recommend our regression model for use in risk assessment tools for estimating sustainable traffic on agricultural soils. The model was validated by five independent data sets from the literature. Our study shows that caution should be applied when regarding σpc as a fixed threshold for compressive strength. We hypothesize that plastic deformation is initiated over a range of stress rather than at a distinctive single value. Further studies are needed to better understand—and potentially quantify—to what extent the predicted σpc can be regarded a central estimate of allowable stress for a given soil.

AB - Society calls for protection of agricultural soils in order to sustain the production of foods for a growing population. Compaction of subsoil layers is an increasing problem in modern agriculture and a cause of serious concern because of the poor resilience in natural amelioration. The concept of soil precompression stress has been adapted from civil engineering, although in soil science it is applied to unsaturated soils that have developed a secondary structure from the action of weather, biota and tillage. It assumes strain is elastic at loads up to the precompression stress, while plastic deformation is expected at higher stresses. To determine this threshold we performed uniaxial, confined compression tests for a total of 584 minimally disturbed soil cores sampled at three subsoil layers on nine Danish soils ranging in clay content from 0.02 to 0.38 kg kg−1. The cores were drained to either of three matric potentials (−50, −100 or − 300 hPa) prior to loading. Stress was applied by a constant-strain rate method. We estimated the point of maximum curvature of the strain-log10(normal stress) relation by a numerical procedure. This point is considered here as a compactive stress threshold, typically labeled the soil precompression stress, σpc. The preload suction stress (PSS) was calculated as the product of initial (i.e., before loading) water suction and initial degree of pore water saturation. Multiple regressions were performed to evaluate the effect of soil properties (textural classes, volumetric water content, bulk density (BD), soil organic matter (SOM), and PSS) on σpc. The best model explained 39% of the variation in σpc, and indicated that σpc increases with increasing PSS, BD and SOM. For a given combination of clay, BD and SOM, PSS affected σpc negatively. We recommend our regression model for use in risk assessment tools for estimating sustainable traffic on agricultural soils. The model was validated by five independent data sets from the literature. Our study shows that caution should be applied when regarding σpc as a fixed threshold for compressive strength. We hypothesize that plastic deformation is initiated over a range of stress rather than at a distinctive single value. Further studies are needed to better understand—and potentially quantify—to what extent the predicted σpc can be regarded a central estimate of allowable stress for a given soil.

KW - Pedotransfer function

KW - Precompression stress

KW - Risk assessment

KW - Soil compaction

KW - Soil degradation

KW - Soil strength

KW - Suction stress

KW - Sustainability

KW - Uniaxial compression test

U2 - 10.1016/bs.agron.2022.11.003

DO - 10.1016/bs.agron.2022.11.003

M3 - Book chapter

AN - SCOPUS:85145601268

SN - 9780443192609

VL - 178

T3 - Advances in Agronomy

SP - 61

EP - 105

BT - Advances in Agronomy

A2 - Sparks, Donald L.

PB - Academic Press

CY - Cambridge

ER -