Bodenveränderungen und Typisierung von Fahrspuren nach physikalischer Belastung | Changes in the soil and the classification of ruts according to physical loading

In Swiss environment legislation, protection of the soil is defined by reference to the long-term maintenance of soil fertility. To fulfil this commitment, long-lasting damage to the soil must be prevented, respectively reduced to a minimum. When the forest floor is driven over with heavy logging machinery, this can lead to profound and long-lasting changes in the soil structure in the ruts thus formed. Based on driving trials under controlled conditions in the Heiteren region of the forest near Bern, investigations were made to find out whether the classification of ruts into three distinct types showing morphologically determined changes in the soil could be substantiated with the help of known values in soil physics. It was shown that the non-compacted reference soils could be clearly distinguished from all three types of rut by comparison of the stratification density, the total pore space and the saturated water permeability. In addition, the three types significantly differed from each other. Damage to the soil can be reduced to a minimum through consequent planning of skidding tracks and by paying due attention to the prevailing humidity of the soil at the time when vehicles are used. Thanks to the connection established between the character of the ruts and soil functionality, the classification of rut types provides a practically relevant and objective instrument for effective physical soil protection.

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Influence of cropping and fertilization on soil pore characteristics in a long-term field study

10.5194/egusphere-egu2020-4624 ◽

2020 ◽

Author(s):

David Nimblad Svensson ◽

Jumpei Fukumasu ◽

Gunnar Börjesson ◽

John Koestel

Keyword(s):

Organic Carbon ◽

Pore Size Distribution ◽

Pore Size ◽

Soil Structure ◽

Management Practices ◽

Pore Space ◽

Pore Characteristics ◽

Bare Fallow ◽

Term Field

Soil porosity, pore size distribution and pore characteristics such as connectivity are important for a range of soil processes including ease of root growth and air and water transport. The pore structure is therefore an important part of soil fertility. The pore space is sensitive to management practices such as tillage, fertilization and cropping. Understanding how these practices influence the pore space is important for maintaining a good soil structure that is well aerated and has sufficient drainage. X-ray computed tomography has become a widely used method for studying the pore space as it offers the advantage of enabling soil to be studied in its undisturbed form. In this study it was used to compare the effects of crop growth, tillage and N-fertilizing with Ca(NO3)2 or farm yard manure (FYM). Soil samples were taken just below the surface from the long-term experiment in Ultuna, Sweden which was started in 1956. The bare fallow, FYM and Ca(NO3)2-treatment were sampled with minimum disturbance in two column sizes with inner diameters of 22.2 and 65.5 mm. Differences in pore space morphology were quantified and compared through pore size distribution and a range of connectivity measures, including the Euler number, the critical pore diameter and Gamma connectivity. Biopores were separated from non-biopores and their volume was quantified. Soil organic carbon was determined by dry combustion. Visible porosity and pores in the 150-500 &#181;m class were significantly larger in the FYM and Ca(NO3)2-treatment compared to the bare fallow. The porosity occupied by biopores was not found to significantly differ between treatments but the biopores were found to have the largest diameters in the FYM-treatment. Despite that the organic carbon content was 1.7 times higher in the FYM compared to the Ca(NO3)2-treatment the visible porosity was similar. This may be due to the positive effects calcium has on the soil structure. The connectivity measures indicated that the FYM-treatment had the best connected pore networks. This may be partly due to the larger biopores. Ca(NO3)2 showed to be a promising alternative to increase porosity. However, as all the management practices in the long-term field study are done by hand, future studies will have to investigate if the effect is equally similar to FYM under field conditions which are subject to heavy machineries.&#160;&#160;

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Sodicity and soil structure

Soil Research ◽

10.1071/sr9910935 ◽

1991 ◽

Vol 29 (6) ◽

pp. 935 ◽

Cited By ~ 199

Author(s):

P Rengasamy ◽

KA Olsson

Keyword(s):

Soil Structure ◽

Plant Performance ◽

Sodic Soils ◽

Electrolyte Conductivity ◽

Soil Solutions ◽

Biological Amelioration ◽

Soil Behaviour ◽

Poor Soil

Sodic soils are widespread in Australia reflecting the predominance of sodium chloride in groundwaters and soil solutions. Sodic soils are subject to severe structural degradation and restrict plant performance through poor soil-water and soil-air relations. Sodicity is shown to be a latent problem in saline-sodic soils where deleterious effects are evident only after leaching profiles free of salts. A classification of sodic soils based on sodium adsorption ratio, pH and electrolyte conductivity is outlined. Current understanding of the processes and the component mechanisms of sodic soil behaviour are integrated to form the necessary bases for practical solutions in the long term and to define areas for research. The principles of organic and biological amelioration of sodicity, as alternatives to costly inorganic amendments, are discussed.

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Effects of liming on soil structure and GHG fluxes at three spruce sites in SW Germany

10.5194/egusphere-egu21-4223 ◽

2021 ◽

Author(s):

Martin Maier ◽

Valentin Gartiser ◽

Verena Lang ◽

Raphael Habel ◽

Lelde Jansone ◽

...

Keyword(s):

Soil Ph ◽

Forest Soils ◽

Soil Structure ◽

Pore Space ◽

Mineral Soil ◽

Soil Gas ◽

Long Term Effects ◽

Gas Diffusivity ◽

Humus Layer

Forest soils in Central Europe received massive atmospheric deposition of SO2 and NOx during the second half of the 20th century. The resulting fast acidification of the soils was accompanied by massive forest dieback and problematic nutrient imbalances at some sites. After the emissions of SO2 have been reduced in the 80&#180;s and 90&#180;s, the situation of acidic deposition has been gradually improving. Yet, the deposition of N compounds remains high and still has an impact on forest ecosystems. Natural soil development and &#8220;regeneration&#8221; is a slow process, which is why other options were investigated to recover heavily affected forest soils. A well-known means to mitigate the observed effects of the anthropogenic acidification surges is liming, i.e. the application of minerals such as CaCO3 and CaMg(CO3)2 that are able to buffer strong acids. Liming directly affects soil pH which is a &#8220;master variable&#8221; of the soil. Soil pH, and thus, liming, affects and interacts with many soil processes from mineralization of organic matter and humification, to (de-) stabilization soil structure, nutrient availability and mobility, plant growth and more.Several study sites were established in the 1980 in Baden-Wuerttemberg to study long term effects of liming on soil structure and forest growth. At all sites a &#8220;control&#8221; plot and a &#8220;limed&#8221; plot were established next to each other. The limed plots were treated with approx. 3 t ha-1 of CaCO3 in the 1980&#180;s and 6 t ha-1 of Ca/MgCO3 in 2003. Here we report on results from three sites (Bad Waldsee, Hospital, Herzogenweiler) with Spruce stands (70-110 years), where long term effects of liming on the physical soil structure and soil gas profiles (2017-2019) were studied (Jansone et al., 2020). Liming resulted in a reduction of the thickness of the humus layer and a blurring of the previously clearly separated boundary between the mineral soil and the humus layer. Even though total pore space in the top soil was slightly reduced at the limed plots, soil gas diffusivity was higher at a given air-filled pore-space. This indicates a better connectivity in the air-filled pores, that means more larger pores connecting the atmosphere at the soil surface and the mineral soil. Soil CO2 concentrations showed clear seasonal patterns and a typical increase with depth. Higher CO2 concentrations tend to be found in the un-limed control plots. Soil CH4 concentrations at the soil&#8211;humus interface were closer to atmospheric concentrations in the limed plots compared to the control plots. This can be interpreted as an effect of the decrease in the thickness of the humus layer and the increase in the soil gas diffusivity (better aeration) or in a reduced activity of the methanotrophic community.&#160;AcknowledgementThis research was financially supported by Bundesministerium f&#252;r Ern&#228;hrung und Landwirtschaft (BMEL), grant number 28W-B-4-075-02 (2018&#8211;2021).LiteratureJansone, L., von Wilpert, K. and Hartmann, P., 2020. Natural Recovery and Liming Effects in Acidified Forest Soils in SW-Germany. Soil Systems, 4(38): 1-35.

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Experimental Investigation of Cement/Soda Residue for Solidification/Stabilization of Cr-Contaminated Soils

Advances in Civil Engineering ◽

10.1155/2020/8890149 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Fusheng Zha ◽

Fanghua Zhu ◽

Bo Kang ◽

Long Xu ◽

Yongfeng Deng ◽

...

Keyword(s):

Contaminated Soils ◽

Soil Structure ◽

Pore Space ◽

Curing Time ◽

Reaction Products ◽

Microstructural Characteristics ◽

Strong Adsorption ◽

Soil Pore Space ◽

Binder Ratio

Adopting more efficient and sustainable remediation materials is of great importance for the development of solidification and stabilization (S/S) technology. Among them, soda residue could be considered as a desirable binder due to its strong adsorption for heavy metals. For understanding of the performance of Cr-contaminated soils treated by cement/soda residue, the strength, leaching and microstructural characteristics, and the long-term effectiveness under wetting-drying cycles were comprehensively investigated in this study. The results showed that the unconfined compressive strength (UCS) increased and the leached Cr3+ concentration decreased with curing time, binder content, and binder ratio. Increasing the soda residue from C6S14 to C6S24 could improve soil strength and reduce leachability of Cr3+, while a reverse trend was presented with increasing initial Cr3+ concentration. With subsequent wetting-drying cycles, the UCS further increased and then decreased; inversely, the leached Cr3+ decreased, followed by an increase of Cr-contaminated soils. For the specimens of C6S14 and C6S24, the maximum UCS of 6.04 MPa and 6.48 MPa was reached; correspondingly, the minimum leached Cr3+ concentration of 2.78 mg/L and 1.93 mg/L was reached after 3 wetting-drying cycles, respectively. Microstructure analysis results found that reaction products like calcium silicate hydrate (C-S-H) and ettringite (AFt) increasingly occupied the soil pore space and caused a denser soil structure after 3 wetting-drying cycles, which indicated the long-term effectiveness of contaminated soils treated by cement/soda residue.

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