The relation between soil structure and solute transport under raised bed cropping and conventional cultivation in south-western Victoria

Soil Research ◽  
2007 ◽  
Vol 45 (8) ◽  
pp. 577 ◽  
Author(s):  
J. E. Holland ◽  
R. E. White ◽  
R. Edis
Keyword(s):  
Solute Transport ◽  
Soil Structure ◽  
Preferential Flow ◽  
Soil Samples ◽  
Water Volume ◽  
Undisturbed Soil ◽  
Resin Impregnation ◽  
Cultivated Soil ◽  
Raised Bed ◽  
Western Victoria

This study examined the relationship between soil structure and solute transport in a texture contrast soil under 2 different tillage treatments—raised beds and conventional cultivation—in south-western Victoria. Undisturbed soil samples were collected for resin-impregnation and image analysis. This enabled several descriptive parameters of macropore structure to be calculated. Large, undisturbed soil samples were also collected for a solute transport experiment using a KCl solution. A convective log-normal transfer function was used to model Cl– movement. The assessment of soil structure showed that the raised beds contained a better connected pore network than the conventionally cultivated soil. Solute transport was faster through the raised bed soil when close to saturation (at –5 mm tension). Under these conditions, the solute transport parameters showed a smaller ratio of transport volume to soil water volume in the raised bed than the conventionally cultivated soil. Together, these data strongly indicate that the raised beds had greater pore connectivity and were able to transmit solute faster and more efficiently than the conventionally cultivated soil. It is concluded that raised bed soils are better structured and provide less risk from waterlogging than conventionally cultivated soils. However, there is greater potential for preferential flow of pesticides and solutes in raised bed soils.

scholarly journals Field and numerical study of chlorotoluron transport in the soil profile

2011 ◽  
Vol 50 (No. 8) ◽  
pp. 333-338 ◽  
Author(s):  
R. Kodešová ◽  
J. Kozák ◽  
O. Vacek
Keyword(s):  
Adsorption Isotherm ◽  
Solute Transport ◽  
Soil Water ◽  
Soil Profile ◽  
Preferential Flow ◽  
Water Movement ◽  
Numerical Study ◽  
Soil Samples ◽  
Transport Parameters ◽  
Four Square

The transport of chlorotoluron in the soil profile under field conditions was studied. The herbicide Syncuran was applied on a four square meter plot using an application rate of 2.5 kg/ha active ingredient. Soil samples were taken after 119 days to study the residual chlorotoluron distribution in the soil profile. HYDRUS-1D (Šimůnek et al. 1998) was used to simulate water movement and herbicide transport in the soil profile. Soil hydraulic properties and their variability were studied previously by Kutílek et al. (1989). The solute transport parameters, like the adsorption isotherm and the degradation rate, were determined in the laboratory. The Freundlich and Langmuir equations were used to fit the experimental data points of the adsorption isotherm, and the affect of each type of adsorption isotherm equation on the solute transport was studied. The chlorotoluron concentrations in soil water tended to be higher for the simulation performed with the Freundlich isotherm then that of the model using the Langmuir isotherm. In both cases, the solution did not pass a depth of8 cm. The simulated chlorotoluron concentrations in soil samples were higher then the observed concentrations when the chlorotoluron degradation was assumed to be in soil water only. Assumption of the solute degradation in both in the solid and the liquid phase significantly improved the accuracy of the solution. The different characters of the simulated and observed chlorotoluron distributions can probably be attributed to the preferential flow of water and solute in the soil profile and by variability of the transport parameters.

scholarly journals HUBUNGAN PENURUNAN VOLUME AIR DENGAN PEMAMPATAN GAMBUT PADA TINGKAT KEMATANGAN YANG BERBEDA DI KAWASAN GAMBUT BERENGBENGKEL KALIMANTAN TENGAH

2018 ◽  
Vol 4 (2) ◽  
Author(s):  
Rabiatul Wahdah
Keyword(s):  
Moisture Content ◽  
Optical Density ◽  
Peat Soil ◽  
Soil Samples ◽  
Fiber Content ◽  
Water Volume ◽  
Undisturbed Soil ◽  
Central Kalimantan ◽  
Specific Pore Volume ◽  
Peat Area

Gambut merupakan lahan yang tergenang sepanjang tahun, persoalan kemudian muncul manakala lahan gambut alamiah dialihfungsikan. Tujuan dari penelitian adalah mengetahui pemampatan gambut akibat penurunan volume air pada tingkat kematangan yang berbeda, dengan sampel tanah yang digunakan diambil di kawasan gambut Berengbengkel Kalimantan Tengah masing-masing 30 sampel tanah terusik dan tak terusik untuk analisa kadar lengas, berat volume, kadar serat, dan rapat optik yang mana data akan diolah menggunakan program Ms. Excell.  Metode yang digunakan adalah metode deskriptif yang menjelaskan hubungan penurunan volume air dengan pemampatan gambut pada tingkat kematanagn yang berbeda di Kawasan Gambut Berengbengkel Kalimantan Tengah Hasil penelitian menunjukkan bahwa penurunan volume air atau kadar lengas menyebabkan hilangnya volume spesifik pori sehingga mengakibatkan pemampatan tanah gambut. Pemampatan yang terjadi berbeda disetiap tingkat kematangan. Pemampatan pada setiap kematangan berbeda, gambut mentah (fibrik) akan lebih cepat atau mudah mengalami pemampatan dan melambat pada tanah gambut yang sudah mengalami kematangan, sehingga dapat disimpulkan bahwa penurunan volume air atau kadar lengas yang hilang dapat menyebabkan pemampatan dan subsiden pada tanah gambut  Kata Kunci : kematanagan gambut, kadar lengas, kadar serat, rapat optik . Peatlands are areas waterlogged throughout the year. The problems arise when natural peatlands are converted. The aim of the study was to find out the compression of peat due to a decrease in the volume of water at some different levels of maturity. The soil samples were taken from the peat area of Berengbengkel, Central Kalimantan. Each of 30 disturbed and undisturbed soil samples was analyzed for its moisture content, volumetric weight, fiber content, and optical density. The data were then processed using the program of Ms. Excell. The method used in the study was a descriptive method describing relationship between decrease in water volume and compression of peat at different maturity levels in peat area of berengbengkel, central kalimantan. The results showed that the decrease in water volume or moisture content led to the loss of specific pore volume, resulting in compression of peat. The compressions occurring at each maturity level were different from one another. Raw peat (fibric) was quicker or easier to experience compression than the peat soil that had already undergone maturation. Therefore, it can be concluded that the decrease in water volume or moisture content can cause compression and subsidence in peat soil. Keywords: fiber content, moisture content, peat maturity, optical density.

scholarly journals Levels of induced pressure and compaction as caused by forest harvesting operations

CERNE ◽  
2013 ◽  
Vol 19 (1) ◽  
pp. 83-91 ◽  
Author(s):  
Paula Cristina Caruana Martins ◽  
Moacir de Souza Dias Junior ◽  
Josemar da Silva Carvalho ◽  
Arystides Resende Silva ◽  
Sebastião Machado Fonseca
Keyword(s):  
Uniaxial Compression ◽  
Soil Compaction ◽  
Soil Structure ◽  
Forest Harvesting ◽  
Soil Samples ◽  
Uniaxial Compression Test ◽  
Traffic Intensity ◽  
Undisturbed Soil ◽  
Before And After ◽  
Red Latosol

This study aimed to determine levels of pressure and compaction induced by forest harvesting operations in a Red Latosol (LV) under planted eucalyptus. Undisturbed soil samples were collected from layers 0-3 and 15-18 cm and then used in a uniaxial compression test. Sampling was done before and after harvesting operations. Equipment being evaluated included: harvester, feller buncher, forwarder, self-loading adapted tractor, standard truck, wide-tire truck and grapple saw. Average pressures induced by the grapple saw were 320 kPa and 272 kPa, causing compaction in 80% and 20% of samples respectively from layers 0-3 cm and 15-18 cm, which indicates substantial degradation of soil structure in areas where timber is processed. In layer 0-3 cm, average pressures induced by the harvester and by the feller buncher were 240 kPa and 263 kPa respectively, while in layer 15-18 cm pressures were 234 kPa and 239 kPa respectively. The feller buncher caused higher soil compaction than the harvester in layer 0-3 cm, yet in layer 15-18 cm they had similar behavior. All timber forwarding equipment led to soil compaction. The wide-tire truck was the forwarding implement promoting the highest rate of compaction, in both residue conditions. Traffic intensity 7 promoted the highest rate of soil compaction.

scholarly journals Field scale variability of solute transport parameters and related soil properties

1997 ◽  
Vol 1 (4) ◽  
pp. 801-811 ◽  
Author(s):  
B. Lennartz ◽  
S. K. Kamra ◽  
S. Meyer-Windel
Keyword(s):  
Soil Properties ◽  
Solute Transport ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Preferential Flow ◽  
Type I ◽  
Transport Parameters ◽  
Undisturbed Soil ◽  
Soil Hydraulic

Abstract. The spatial variability of transport parameters has to be taken into account for a reliable assessment of solute behaviour in natural field soils. Two field sites were studied by collecting 24 and 36 small undisturbed soil columns at an uniform grid of 15 m spacing. Displacement experiments were conducted in these columns with bromide traced water under unsaturated steady state transport conditions. Measured breakthrough curves (BTCs) were evaluated with the simple convective-dispersive equation (CDE). The solute mobility index (MI) calculated as the ratio of measured to fitted pore water velocity and the dispersion coefficient (D) were used to classify bromide breakthrough behaviour. Experimental BTCs were classified into two groups: type I curves expressed classical solute behaviour while type II curves were characterised by the occurrence of a bromide concentration maximum before 0.35 pore volumes of effluent (MI<0.35) resulting from preferential flow conditions. Six columns from site A and 8 from site B were identified as preferential. Frequency distributions of the transport parameters (MI and D) of both sites were either extremely skewed or bimodal. Log-transformation did not lead to a normal distribution in any case. Contour maps of bromide mass flux at certain time steps indicated the clustering of preferential flow regions at both sites. Differences in the extent of preferential flow between sites seemed to be governed by soil structure. Linear cross correlations among transport parameters and independently measured soil properties revealed relations between solute mobility and volumetric soil water content at time of sampling, texture and organic carbon content. The volumetric field soil water content, a simple measure characterising the soil hydraulic behaviour at the sampling location, was found to be a highly sensitive parameter with respect to solute mobility and preferential flow situations. Almost no relation was found between solute transport parameters and independently determined soil properties when non-preferential and preferential samples were considered separately in regression analyses. Future work should concentrate to relate integrated parameters such as the infiltration rate or the soil hydraulic functions to solute mobility under different flow situations.

scholarly journals Structural sustainability of cambisol under different land use system

2012 ◽  
Vol 36 (6) ◽  
pp. 1724-1732 ◽  
Author(s):  
Paula Cristina Caruana Martins ◽  
Moacir de Souza Dias Junior ◽  
Ayodele Ebenezer Ajayi ◽  
Fátima Maria de Souza Moreira
Keyword(s):  
Land Use ◽  
Bearing Capacity ◽  
Soil Structure ◽  
Secondary Forest ◽  
Soil Samples ◽  
Load Bearing Capacity ◽  
Undisturbed Soil ◽  
Load Bearing ◽  
Land Use Systems ◽  
Land Use System

Incongruous management techniques have been associated with some significant loss of agricultural land to degradation in many parts of the world. Land degradation results in the alteration of physical, chemical and biological properties of the soil, thereby posing a serious threat to sustainable agricultural development. In this study, our objective is to evaluate the changes in a Cambisol structure under six land use systems using the load bearing capacity model. Sampling was conducted in Amazonas Region, Brazil, in the following land use: a) young secondary forest; b) old secondary forest; c) forest; d) pasture; e) cropping, and f) agroforestry. To obtain the load bearing capacity models the undisturbed soil samples were collected in those land use systems and subjected to the uniaxial compression test. These models were used to evaluate which land use system preserved or degraded the Cambisol structure. The results of the bulk density and total porosity of the soil samples were not adequate to quantify structural degradation in Cambisol. Using the forest topsoil level (0-0.03 m) as a reference, it was observed that pasture land use system was most severe in the degradation of the soil structure while the structure were most preserved under old secondary forest, cropping system and forest. At the subsoil level (0.10-0.13 m depth), the soil structure was most degraded in the cropping land use system while it was most preserved in young secondary forest and pasture. At the 0.20-0.23 m depth, soil structure degradation was most severe in the old secondary forest system and well preserved in young secondary forest, cropping and agroforestry.

scholarly journals Thixotropic Hardening of Fao Clay

2019 ◽  
Vol 25 (5) ◽  
pp. 68-78
Author(s):  
Ahmed Shakir Kamil ◽  
Ala Nasir Aljorany
Keyword(s):  
Shear Strength ◽  
Soil Structure ◽  
Thick Layer ◽  
Soil Samples ◽  
Silty Clay ◽  
Driven Piles ◽  
Undisturbed Soil ◽  
Clayey Silt ◽  
Natural Water Content ◽  
Intact Soil

Fao region is characterized by weak soft silty clay to clayey silt thick layer which extends to a depth of about 20 m. The construction of some structures on such soils may needs piles. During the installation of driven piles, the soil geotechnical properties are exposed to significant changes result due to shearing under large shear strains. These changes significantly decrease the shear strength of the virgin soil due to the destruction of soil structure caused by remolding. The degradation of shear strength is usually followed by strength regaining which is called “Thixotropy”. In this study, the thixotropic effect on Fao clay was investigated. Many disturbed and undisturbed soil samples were brought from Fao region. Some of the soil samples were thoroughly remolded in the laboratory in its natural water content and molded as direct shear specimens. More than 180 specimens were prepared and tested over 36 weeks in order to accurately assess the percentage of strength regaining with time passing. The results show that soil remolding causes about a 45 % reduction in shear strength in comparing with the shear strength of the intact soil. This reduced percent in shear strength was almost fully regained after 25 weeks due to thixotropic effect.  

scholarly journals Traffic effects on the soil preconsolidation pressure due to eucalyptus harvest operations

2005 ◽  
Vol 62 (3) ◽  
pp. 248-255 ◽  
Author(s):  
Moacir de Souza Dias Junior ◽  
Fernando Palha Leite ◽  
Edson Lasmar Júnior ◽  
Cezar Francisco Araújo Junior
Keyword(s):  
Soil Compaction ◽  
Soil Structure ◽  
Soil Samples ◽  
Compression Tests ◽  
Undisturbed Soil ◽  
Structure Degradation ◽  
Preconsolidation Pressure ◽  
Before And After ◽  
Two Stages ◽  
Wood Transport

One of the limitations for reaching sustainable forest development is related to the traffic of machines and vehicles during harvest operations and wood transport, which may cause soil structure degradation. Seeking a way to analyze this problem, the objective of this study was to determine the traffic effects due to harvest operations and wood transport, on the preconsolidation pressure (sigmap) in a Typic Acrustox cultivated with eucalyptus. This study was conducted using undisturbed soil samples collected at the 0.1-0.125 m depth. Undisturbed soil samples were used in the uniaxial compression tests. Soil sampling consisted of two stages, before and after the mechanized harvest operations. The traffic effects on the sigmap in the dry season indicated that the soil compaction process was neither evident nor important. However, in the rainy season the traffic effects on the sigmap indicated that the operations performed with Harvester and Forwarder caused greater soil compaction than those with Motorized Saw and Manual, which caused less soil compaction.

scholarly journals Retention and Solute Transport Properties in Disturbed and Undisturbed Soil Samples

2016 ◽  
Vol 40 (0) ◽  
Author(s):  
Lívia Previatello da Silva ◽  
Quirijn de Jong van Lier ◽  
Marcus Metri Correa ◽  
Jarbas Honorio de Miranda ◽  
Luciano Alves de Oliveira
Keyword(s):  
Solute Transport ◽  
Transport Properties ◽  
Soil Samples ◽  
Undisturbed Soil

Re-colonization of sterile soil samples during long term field exposure

2020 ◽  
Author(s):  
Michael Herre ◽  
Bernd Marschner ◽  
Sven Marhan
Keyword(s):  
Microbial Activity ◽  
Preferential Flow ◽  
Soil Samples ◽  
Bulk Soil ◽  
Forest Site ◽  
Field Exposure ◽  
Flow Paths ◽  
Undisturbed Soil ◽  
Preferential Flow Paths ◽  
Colonization Potential

&lt;p&gt;The distribution of soil organic matter and microbial biomass in subsoils is much more heterogeneous than in the topsoil due to a more localized input of fresh substrate and nutrients from rhizodeposition and preferential flow paths forming hotspots of microbial activity. However, the remaining bulk soil also contains substantial amounts of labile substrates that are readily mineralized during lab incubation experiments. We therefore hypothesized that one reason for this is that potential consumers are spatially separated from these substrates due to the low microbial densities in subsoils. Consequently, hotspots are not only formed through high substrate inputs but also through a higher abundance and diversity of microorganisms compared to the bulk soil due to inputs of cells and spores with the soil solution or through hyphal growth. However, little is known about the colonization potential or dynamics of microorganisms in the subsoil.&lt;/p&gt;&lt;p&gt;In November 2018, we started a field experiment to investigate the re-colonization potential of microorganisms by exposing 24-well microplates containing sterilized soil samples in the field at two different depths (topsoil: 10 cm, subsoil 60 cm) at a beech forest site in northern Germany. After 6 and 12 months, samples from each well and from the intact soil compartments above each well were analyzed for enzyme activities (hydrolytic enzymes using MUF and AMC substrates), microbial activity parameters (soil respiration and SIR using the MicroResp&amp;#174;) and the microbial community structure (quantitative PCR).&lt;/p&gt;&lt;p&gt;We expect (1) different temporal dynamics of re-colonization between top- and subsoil samples; (2) that the recolonization potential is related to the microbial activity in the soil compartments above the exposed samples and (3) that the heterogeneous re-colonization is maintained throughout the field exposure and thus indicates the relevance of preferential flow paths for microbial transport especially in subsoils.&lt;/p&gt;&lt;p&gt;First results of the SIR assays after 6 months of field exposure show that in the topsoil microbial activity has been re-established in all of the wells, but is still below the mean activity in the undisturbed soil above the sterilized samples. In all subsoil samples, the re-established microbial activity was much lower and even below detection limit in some of the wells. In both depths, the SIR assays show a very patchy distribution of wells with higher microbial activities indicating that the influx of organisms is limited to small areas from the soil above the exposed containers.&lt;/p&gt;

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