Soil structure recovery following compaction: Short‐term evolution of soil physical properties in a loamy soil

Abstract

Soil compaction by farm machinery may persist for decades, hampering soil productivity and functioning. Assessing compaction costs and guiding recovery strategies are hindered by paucity of data on soil structure recovery rates. A long-term Soil Structure Observatory was established on a loamy soil in Switzerland to monitor soil structure recovery after prescribed compaction, and to better assess the roles of natural processes (vegetation, macrofauna, and shrink-swell cycles) on recovery patterns. The aim of this study was to quantify short-term soil structure recovery under natural conditions in the presence and absence of plant cover (ley and bare soil). We measured soil porosity and gas and water transport capabilities at 0.1 and 0.3 m depth. Two years after the compaction event, soil physical properties have not recovered to precompaction levels, even within the topsoil. Surprisingly, no differences were observed in the recovery patterns of ley and bare soil treatments. Measurements show that recovery rates differ among soil properties with the most severely affected properties by compaction (permeability) exhibiting highest recovery rates. Total soil porosity shows no recovery trend, suggesting lack of soil decompaction. Improved soil functions and decompaction are distinct aspects of soil structure recovery, with the latter requiring net upward transport of soil mass. We suggest that soil structure recovery proceeds at two fronts: from the soil surface downward, and expanding around local biologically-active pockets (marked by biopores) into the compacted soil volumes. This concept could be tested with additional data of longer time series at our site as well as in other soils and climates.

Bio‐tillage improves soil physical properties and maize growth in a compacted Vertisol by cover crops

“…In two previous meta‐analysis studies, a negligible effect of cover crops on bulk density was also reported (Alvarez et al., 2017; Blanco‐Canqui & Ruis, 2020). The change in bulk density usually results from vertical movement of soil particles (Keller et al., 2021). The cover crop roots only exert radial pressure on the surrounding soil and result in compression of the soil at approximately 1 mm around the roots (Angers & Caron, 1998; Koebernick et al., 2019), which does not necessarily induce vertical movement of soil particles and subsequent changes in bulk density.…”

“…Keller et al. (2021) suggested that air permeability and saturated hydraulic conductivity in compacted soil can be quickly improved, because they are determined by highly continuous biopores that can be easily formed by the roots of cover crops (Zhang et al., 2019). In this study, the strong taproots of the cover crops were able to create new continuous biopores or unblock the existing biopores, consequently enhancing the K s and K a60 .…”

“…Cover cropping had a significant effect on the K s and K a60 in both the soil layer depths of 20-30 cm and 30-50 cm in this study (Table 1), indicating that air permeability and saturated hydraulic conductivity were much more sensitive to cover cropping than bulk density. Keller et al (2021) F I G U R E 6 Maize root biomass density and root length density in the soil compaction and cover crop treatments in 2018. Different letters indicate significant differences at P < .05 among the four cover crop treatments at each compaction level.…”

Spatio-Temporal High-Resolution Subsoil Compaction Risk Assessment for a 5-Years Crop Rotation at Regional Scale

“…In this study, we modelled and analyzed the subsoil compaction risk at a soil depth of 40 cm. Since this depth will not be reached by regular primary tillage and related loosening effects, soil compaction persists (Keller et al, 2017;Keller et al, 2021) and may not recover in short-term.…”

“…Overall, analyses of the spatio-temporal dynamics revealed that 1 year with increased precipitation can considerably affect the soil risk. This is particularly problematic as soil compaction, especially subsoil compaction, can be persistent for many years (Etana et al, 2013;Keller et al, 2017;Keller et al, 2021;Seehusen et al, 2021). Thus, 1 year of increased soil compaction risk accompanied by unsuited field traffic activities can be sufficient to affect soil functions and soil health in the long term.…”