Details
Original language | English |
---|---|
Pages (from-to) | 139-148 |
Number of pages | 10 |
Journal | Soil and Tillage Research |
Volume | 99 |
Issue number | 2 |
Publication status | Published - Jun 2008 |
Externally published | Yes |
Abstract
In many land use systems all over the world soil deformation is a major problem due to increasing land use intensity. On arable soils machine traffic is continuously intensified with respect to load and wheeling frequency leading to (sub-)soil compaction and deeper soil degradation concerning hydraulic or pneumatic functions. Altered soil functions, in particular reduced hydraulic conductivities and impeded aeration, may decrease crop growth and productivity as well as the filtering and buffering capacity of soils. Prevented gas exchange and longer lasting anoxia in soils due to the reduced pore continuity and pore functioning also affects global change processes. In order to evaluate potential risks for irreversible soil deformation, it is necessary to quantify their mechanical stability. A commonly applied method is the determination of the pre-compression stress, commonly under static loading conditions in oedometer tests. The determination of pre-compression stresses under static loading may not quite resemble the conditions encountered in the field where soils are loaded repeatedly with a sequence of short intermittent loading-unloading-reloading events. Such dynamic loading conditions are encountered, e.g. at multiple wheel passes or in grassland soils due to animal trampling. In this study we present a comparison of a standard (static loading) and a modified (cyclic/dynamic loading) oedometer test using data of a Calcic Chernozem from the Inner Mongolian steppe under various grazing intensities. Static loading lasted for 10 min per loading step, while the dynamic/cyclic loading was carried out by 30 s loading and following 30 s unloading (=1 cycle) for in total 20 cycles. Differences between statically and cyclically determined pre-compression stresses at an identical time of loading show lower values for the statically determined pre-compression stress values compared to those determined cyclically. Among the dynamically determined pre-compression stresses, the values decrease with increasing number of loading steps and loading time, respectively. This is particularly true for the ungrazed sites. Thus, it could also be proofed that increased grazing intensities lead to structure deformation and increased sensitivity to wind- and water erosion followed by severe land degradation of grassland soils, particularly in semi-arid areas. Furthermore, hydraulic effects, e.g. positive pore water pressure due to intense shearing and kneading processes induced by grazing animals can enhance this structural deterioration. Thus, dynamic or cyclic loading results in an intense soil deformation which also causes serious changes in ecological and soil physical properties like hydraulic conductivity or gas flux.
Keywords
- Compaction, Cyclic loading, Dynamic loading, Effective stress, Grazing, Pre-compression stress, Steppe soil
ASJC Scopus subject areas
- Agricultural and Biological Sciences(all)
- Agronomy and Crop Science
- Agricultural and Biological Sciences(all)
- Soil Science
- Earth and Planetary Sciences(all)
- Earth-Surface Processes
Sustainable Development Goals
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In: Soil and Tillage Research, Vol. 99, No. 2, 06.2008, p. 139-148.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Determination of pre-compression stress of a variously grazed steppe soil under static and cyclic loading
AU - Krümmelbein, J.
AU - Peth, S.
AU - Horn, R.
N1 - Funding Information: The authors thank the German Research Foundation (DFG) for the generous funding of the research group FG536.
PY - 2008/6
Y1 - 2008/6
N2 - In many land use systems all over the world soil deformation is a major problem due to increasing land use intensity. On arable soils machine traffic is continuously intensified with respect to load and wheeling frequency leading to (sub-)soil compaction and deeper soil degradation concerning hydraulic or pneumatic functions. Altered soil functions, in particular reduced hydraulic conductivities and impeded aeration, may decrease crop growth and productivity as well as the filtering and buffering capacity of soils. Prevented gas exchange and longer lasting anoxia in soils due to the reduced pore continuity and pore functioning also affects global change processes. In order to evaluate potential risks for irreversible soil deformation, it is necessary to quantify their mechanical stability. A commonly applied method is the determination of the pre-compression stress, commonly under static loading conditions in oedometer tests. The determination of pre-compression stresses under static loading may not quite resemble the conditions encountered in the field where soils are loaded repeatedly with a sequence of short intermittent loading-unloading-reloading events. Such dynamic loading conditions are encountered, e.g. at multiple wheel passes or in grassland soils due to animal trampling. In this study we present a comparison of a standard (static loading) and a modified (cyclic/dynamic loading) oedometer test using data of a Calcic Chernozem from the Inner Mongolian steppe under various grazing intensities. Static loading lasted for 10 min per loading step, while the dynamic/cyclic loading was carried out by 30 s loading and following 30 s unloading (=1 cycle) for in total 20 cycles. Differences between statically and cyclically determined pre-compression stresses at an identical time of loading show lower values for the statically determined pre-compression stress values compared to those determined cyclically. Among the dynamically determined pre-compression stresses, the values decrease with increasing number of loading steps and loading time, respectively. This is particularly true for the ungrazed sites. Thus, it could also be proofed that increased grazing intensities lead to structure deformation and increased sensitivity to wind- and water erosion followed by severe land degradation of grassland soils, particularly in semi-arid areas. Furthermore, hydraulic effects, e.g. positive pore water pressure due to intense shearing and kneading processes induced by grazing animals can enhance this structural deterioration. Thus, dynamic or cyclic loading results in an intense soil deformation which also causes serious changes in ecological and soil physical properties like hydraulic conductivity or gas flux.
AB - In many land use systems all over the world soil deformation is a major problem due to increasing land use intensity. On arable soils machine traffic is continuously intensified with respect to load and wheeling frequency leading to (sub-)soil compaction and deeper soil degradation concerning hydraulic or pneumatic functions. Altered soil functions, in particular reduced hydraulic conductivities and impeded aeration, may decrease crop growth and productivity as well as the filtering and buffering capacity of soils. Prevented gas exchange and longer lasting anoxia in soils due to the reduced pore continuity and pore functioning also affects global change processes. In order to evaluate potential risks for irreversible soil deformation, it is necessary to quantify their mechanical stability. A commonly applied method is the determination of the pre-compression stress, commonly under static loading conditions in oedometer tests. The determination of pre-compression stresses under static loading may not quite resemble the conditions encountered in the field where soils are loaded repeatedly with a sequence of short intermittent loading-unloading-reloading events. Such dynamic loading conditions are encountered, e.g. at multiple wheel passes or in grassland soils due to animal trampling. In this study we present a comparison of a standard (static loading) and a modified (cyclic/dynamic loading) oedometer test using data of a Calcic Chernozem from the Inner Mongolian steppe under various grazing intensities. Static loading lasted for 10 min per loading step, while the dynamic/cyclic loading was carried out by 30 s loading and following 30 s unloading (=1 cycle) for in total 20 cycles. Differences between statically and cyclically determined pre-compression stresses at an identical time of loading show lower values for the statically determined pre-compression stress values compared to those determined cyclically. Among the dynamically determined pre-compression stresses, the values decrease with increasing number of loading steps and loading time, respectively. This is particularly true for the ungrazed sites. Thus, it could also be proofed that increased grazing intensities lead to structure deformation and increased sensitivity to wind- and water erosion followed by severe land degradation of grassland soils, particularly in semi-arid areas. Furthermore, hydraulic effects, e.g. positive pore water pressure due to intense shearing and kneading processes induced by grazing animals can enhance this structural deterioration. Thus, dynamic or cyclic loading results in an intense soil deformation which also causes serious changes in ecological and soil physical properties like hydraulic conductivity or gas flux.
KW - Compaction
KW - Cyclic loading
KW - Dynamic loading
KW - Effective stress
KW - Grazing
KW - Pre-compression stress
KW - Steppe soil
UR - http://www.scopus.com/inward/record.url?scp=43749117329&partnerID=8YFLogxK
U2 - 10.1016/j.still.2008.01.008
DO - 10.1016/j.still.2008.01.008
M3 - Article
AN - SCOPUS:43749117329
VL - 99
SP - 139
EP - 148
JO - Soil and Tillage Research
JF - Soil and Tillage Research
SN - 0167-1987
IS - 2
ER -