Vertical bulk density distribution in C-horizons from marley till as indicator for erosion history in a hummocky post-glacial soil landscape

J. Plant Nutr. Soil Sci.

Sommer

2017

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Agricultural soil landscapes of hummocky ground moraines are characterized by 3D spatial patterns of soil types that result from profile modifications due to the combined effect of water and tillage erosion. We hypothesize that crops reflect such soil landscape patterns by increased or reduced plant and root growth. Root development may depend on the thickness and vertical sequence of soil horizons as well as on the structural development state of these horizons at different landscape positions. The hypotheses were tested using field data of the root density (RD) and the root lengths (RL) of winter wheat using the minirhizotron technique. We compared data from plots at the CarboZALF‐D site (NE Germany) that are representing a non‐eroded reference soil profile (Albic Luvisol) at a plateau position, a strongly eroded profile at steep slope (Calcaric Regosol), and a depositional profile at the footslope (Anocolluvic Regosol). At each of these plots, three Plexiglas access tubes were installed down to approx. 1.5 m soil depth. Root measurements were carried out during the growing season of winter wheat (September 2014–August 2015) on six dates. The root length density (RLD) and the root biomass density were derived from RD values assuming a mean specific root length of 100 m g−1. Values of RD and RLD were highest for the Anocolluvic Regosol and lowest for the Calcaric Regosol. The maximum root penetration depth was lower in the Anocolluvic Regosol because of a relatively high and fluctuating water table at this landscape position. Results revealed positive relations between below‐ground (root) and above‐ground crop parameters (i.e., leaf area index, plant height, biomass, and yield) for the three soil types. Observed root densities and root lengths in soils at the three landscape positions corroborated the hypothesis that the root system was reflecting erosion‐induced soil profile modifications. Soil landscape position dependent root growth should be considered when attempting to quantify landscape scale water and element balances as well as agricultural productivity.

Section: Discussionmentioning

confidence: 99%

Section: Root Development At Contrasting Landscape Positionsmentioning

confidence: 99%

Root development of winter wheat in erosion‐affected soils depending on the position in a hummocky ground moraine soil landscape

Herbrich

J. Plant Nutr. Soil Sci.

Sommer

2017

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“…Herbrich et al (2017) observed widely scattered paired values of suction and volumetric water content in eroded Luvisols that deviated from retention curves of soil cores measured in the laboratory. These differences could hardly be explained by a spatial heterogeneity of texture and bulk density (e.g., Gerke and Hierold, 2012).…”

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confidence: 99%

Scales of Water Retention Dynamics Observed in Eroded Luvisols from an Arable Postglacial Soil Landscape

Herbrich

2017

Vadose Zone Journal

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Soil water retention is frequently described by unique main drying curves measured in the laboratory on intact soil cores. In the field, however, soil pore structure changes as a result of swelling and shrinkage, wetting and drying, or tillage operations. For erosion-affected arable soils characterized by truncated profiles, water retention dynamics could be even more complex. The objective of this study was to separate shorter term hysteretic from longer term seasonal dynamics in field-measured water retention data of eroded Luvisols. Soil water content and matric potential data were from tensiometers and time-domain reflectometry sensors of six lysimeter soil monoliths from two sites. For 2012 through 2014, drying and wetting periods were identified and fitted with the van Genuchten (VG) retention function. The results confirmed that drying water retention curves were steeper than those obtained in the laboratory. Steepness increased and fitted VG parameter values of saturated water content decreased within seasons, indicating that rewetting rates successively declined after each dry-wet cycle. Drying water retention curves returned to a similar level in each spring except for soils of transferred monoliths, where drying water retention tended to increase. Results suggested that water retention dynamics of eroded Luvisols was affected by continual incorporation of subsoil material in the Ap horizon and crop management practices in addition to hysteresis and seasonal dynamics. The disentangling of dry-wet cycles from time series of soil water content and matric potential was found useful for identifying the processes responsible for water retention dynamics and could eventually help improve flow and transport models.

“…Uneroded Luvisol and strongly eroded Regosol profiles therefore present the extreme of a soil catena within erosion‐affected soil landscapes. Continuous plowing at the same depth creates a plow pan with a tillage‐induced platy structure (Dörner and Horn, 2006; Schwen et al, 2014) in the uneroded Luvisol, whereas the formation of a plow pan in the Regosol is prevented due to erosion (e.g., Gerke and Hierold, 2012).…”

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confidence: 99%

“…Uneroded Luvisol and strongly eroded Regosol profiles therefore present the extreme of a soil catena within erosion-affected soil landscapes. Continuous plowing at the same depth creates a plow pan with a tillage-induced platy structure (Dörner and Horn, 2006;Schwen et al, 2014) in the uneroded Luvisol, whereas the formation of a plow pan in the Regosol is prevented due to erosion (e.g., Gerke and Hierold, 2012). Soils in eroding landscapes are undergoing gradual changes, which could affect functional properties such as the soil hydraulic characteristics before these changes are manifested in pedogenetic modifications of the soil horizons (McIntosh et al, 1999).…”

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confidence: 99%

Tracer, Dissolved Organic Carbon, and Colloid Leaching from Erosion‐Affected Arable Hillslope Soils

Rieckh

Glæsner

et al. 2015

Vadose Zone Journal

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Core Ideas Pedogenetic processes are spatially related to the slope positions in arable soil landscapes. The Regosol is affected by erosion‐induced CaCO3 and reduced organic C contents. The leaching potential for colloids and DOC was reduced in the truncated Regosol soil. Soil erosion modifies transport properties in the form of the effective dispersivity. In a morainic arable soil landscape, tillage and water erosion created truncated soil profiles at exposed steep slope positions and colluvial soils in depressions. This study examined the effects of erosion‐induced pedogenetic dynamics on flow and transport properties, colloid mobilization, and dissolved organic C (DOC) leaching for an uneroded Luvisol (LV) at the plateau and a strongly eroded Regosol (RG) at the slope position. Unsaturated steady‐flow experiments were performed on intact soil columns (20‐cm diameter, 16–18 cm high) extracted from the Luvisol (Ap, E, and Bt horizons; three depths) and the Regosol (Ap and CBkl horizons; two depths) in three replicates. Together with a 3H2O tracer, the leaching of colloids and DOC and the electrical conductivity were determined in the percolate. Colloid concentration was obtained from turbidity data. Effective dispersion coefficients, Deff, were determined by fitting the convection–dispersion equation and the mobile–immobile transport model (program CXTFIT) to 3H2O breakthrough curves (BTCs). Values of Deff were lower for Luvisol (20.1 ± 0.3 cm2 d−1; mean ± standard deviation) than for Regosol columns (30.2 ± 12.6 cm2 d−1). The pore structure of the Regosol topsoil was influenced by incorporation of CaCO3 from glacial till. The plow pan in the Luvisol caused an increased heterogeneity in the BTCs. Differences in transport properties and leaching potentials for colloids (LV: 98 ± 9 mg L−1; RG: 15 ± 4 mg L−1) and DOC (LV: 13.7 ± 3.7 mg L−1; RG: 6.9 ± 1.1 mg L−1) suggested a gradual change in the solid‐phase composition and structure of these contrasting soils.