An interdisciplinary approach towards improved understanding of soil deformation during compaction

Abstract

International audienceSoil compaction not only reduces available pore volume in which fluids are stored, but it alters the arrangement of soil constituents and pore geometry, thereby adversely impacting fluid transport and a range of soil ecological functions. Quantitative understanding of stress transmission and deformation processes in arable soils remains limited. Yet such knowledge is essential for better predictions of effects of soil management practices such as agricultural field traffic on soil functioning. Concepts and theory used in agricultural soil mechanics (soil compaction and soil tillage) are often adopted from conventional soil mechanics (e.g. foundation engineering). However, in contrast with standard geotechnical applications, undesired stresses applied by agricultural tyres/tracks are highly dynamic and last for very short times. Moreover, arable soils are typically unsaturated and contain important secondary structures (e.g. aggregates), factors important for affecting their soil mechanical behaviour. Mechanical processes in porous media are not only of concern in soil mechanics, but also in other fields including geophysics and granular material science. Despite similarity of basic mechanical processes, theoretical frameworks often differ and reflect disciplinary focus. We review concepts from different but complementary fields concerned with porous media mechanics and highlight opportunities for synergistic advances in understanding deformation and compaction of arable soils. We highlight the important role of technological advances in non-destructive measurement methods at pore (X-ray tomography) and soil profile (seismic) scales that not only offer new insights into soil architecture and enable visualization of soil deformation, but are becoming instrumental in the development and validation of new soil compaction models. The integration of concepts underlying dynamic processes that modify soil pore spaces and bulk properties will improve the understanding of how soil management affect vital soil mechanical, hydraulic and ecological functions supporting plant growth

Plant exudates improve the mechanical conditions for root penetration through compacted soils

“…3 and 7). The mechanical conditions of structured soils are driven by a myriad of processes, so simple relationships with bulk pore structure or water retention should not be expected (Keller et al 2013), even for a model system that begins with homogenised soils, simple biological amendments and controlled drying and wetting.…”

Beyond the “Least Limiting Water Range”: Rethinking Soil Physics Research in Brazil

“…The resistance that solid particles in the soil apply against a motion or displacement results from complex relations of cohesive forces of solid-solid interactions, adhesive forces of solid-liquid interactions and frictional forces generated during displacement (Keller et al, 2013). When a root penetrates the pores of a soil, its growth will cause a significant displacement of the particles when it does not change its geometry to fit the irregular geometry of the pore space, when it forces its way through the pore cavity that it had filled or when pore space must be created (Bengough et al, 1997(Bengough et al, , 2006(Bengough et al, , 2011Clark et al, 2003).…”

Duração das alterações em propriedades físico-hídricas de Latossolo argiloso decorrentes da escarificação mecânica

“…O entendimento do processo de compactação do solo e a busca por alternativas para mitigar seus efeitos têm motivado a realização de estudos em escala global, uma vez que a compactação é considerada uma das principais ameaças à manutenção da qualidade do solo em áreas agrícolas (Schjønning et al, 2009;Keller et al, 2013). No cenário agrícola brasileiro, áreas manejadas em plantio direto ocupam mais de 30 milhões do total de 48,8 milhões de hectares cultivados com espécies temporárias (Federação Brasileira de Plantio Direto na Palha, 2014).…”