Heavy soil loading its consequence for soil structure, strength, deformation of arable soils

Abstract

SummaryThe alteration of mechanical soil properties by a single stress application exceeding all previously applied stresses is analyzed for a conventionally tilled and a conservational managed (since 1992) Stagnic Luvisol. Despite the more pronounced compactness of the plough layer under conventional management, it turned out to be less rigid compared to the "relictic" plough layer under conservation management. We assume that wheeling with a sugar beet harvester (rear wheel 140 kPa, front wheel 110 kPa, total mass 37 Mg) resulted in a break up of the plough pan. This was most obvious in the conventionally tilled soil whereas under conservation tillage, the plough pan seemed to resist the induced forces. Our results suggest that a break up of the compact plough layer and the subsequent re-arrangement of newly formed fragments results in a smaller mechanical stability of the deformed soil. Soil structural changes within the plough pan are also indicated by the alteration of the anisotropy of cohesion and precompression stress, respectively. Altered mechanical properties induced by heavy soil loading affects the soil response to subsequent loading events, which could be shown by finite-element simulations of stress-strain properties. The simulations showed that a decrease in soil stiffness reduces the stress attenuation within the plough pan causing compressive and shear stresses to be transmitted into deeper soil levels, while at the same time shear strain increased.

Cumulative effect of annually repeated passes of heavy agricultural machinery on soil structural properties and sugar beet yield under two tillage systems

“…But, effects were not as drastic as hypothesised by Peth et al (2006) who speculated about breakage of the plough pan layer and complete structure deterioration in the subsoil caused by a single pass of a SBH 6 on our experimental site (Koch and Mä rlä nder, 2007).…”

Direction-dependent behaviour of hydraulic and mechanical properties in structured soils under conventional and conservation tillage

“…Thus, the direction-dependent shear strength is the consequence of the spatial orientation of aggregates, the shrink swell induced changes of the aggregate shape and orientation as well as the anthropogenic effect in the plough pan through the platy structure. As the normal stress exceeds the precompression stress of the soil, structural changes (assessed also by changes in matric potential) take place and consequently a non-direction-dependent shear strength was observed which was also found by Peth et al (2006).…”

“…in the plough pan) was not found. We explain it by the large variability between the replicates, which was also indicated in the results of Peth et al (2006) for such horizons. To improve these results, a greater number of samples will be needed in order to have at least 3 repetitions at 2 applied loads for both ranges, i.e.…”

“…Dö rner (2005) concluded that, hydraulic modelling could be significantly improved, when the structure-dependent hydraulic anisotropy is considered. On the other hand, a direction-dependent behaviour of mechanical properties affects the fracture mechanics as showed and validated by Peth et al (2006) using Finite Element Modelling approaches.…”

Compressive behaviour of the soil in buffer zones under different management practices in Finland

“…Soil compression and shearing are widely recognized risks for structural deformation when heavy machinery is used in agriculture (e.g. Håkansson et al 1988, Alakukku 1996a, 1996b, Peth et al 2006) and in forestry ). Similar problems were also attributed to trampling by wild ruminants in pasture-based forest ecosystems in Canada (Donkor et al 2002), by cattle in intensive rotational grazing systems in the USA (Warren et al 1986) or by cattle in pastures and vegetated BZs in Finland (Pietola et al 2005(Pietola et al , 2006.…”