INFLUENCE OF ICE SEGREGATION AND SOLUTES ON SOIL STRUCTURAL STABILITY

1990 ◽  
Vol 70 (4) ◽  
pp. 571-581 ◽  
Author(s):  
E. PERFECT ◽  
W. K. P. van LOON ◽  
B. D. KAY ◽  
P. H. GROENEVELT
Keyword(s):  
Water Content ◽  
Structural Stability ◽  
Aggregate Stability ◽  
Frost Heave ◽  
Unfrozen Water Content ◽  
Soil Structural Stability ◽  
Frost Penetration ◽  
Wet Aggregate Stability ◽  
Dispersible Clay ◽  
Ice Segregation

Most Canadian soils contain dissolved salts and are subject to freezing. However, the structural consequences of freezing in the presence of solutes are unknown. The effects of ice segregation and solutes on soil structural stability were investigated in a laboratory experiment. Nine 27-cm-diameter by 19-cm-high columns were used. These were packed with air-dry Conestogo silt loam soil (Gleyed Melanic Brunisol or Aquic Eutrochrept) and wetted with CaCl2 solutions at 1, 2, and 4 g L−1. Slow freezing took place from the top down in an environmental chamber maintained at −3.4 ± 0.4 °C. Depth of frost penetration, temperature, frost heave, and unfrozen water content were monitored within each column. After 20 d, the mean frost penetration was 107 ± 18 mm and the soil surface had heaved 9 ± 4 mm, indicating ice segregation. At the end of the experiment, the frozen and unfrozen zones of each column were sampled destructively. Samples were equilibrated at 4 °C and analyzed for wet-aggregate stability (WAS), dispersible clay (DC), gravimetric water content, and CaCl2 concentration. Samples which had been frozen had significantly more water and CaCl2 in the thawed state than those which had remained unfrozen. These increases were attributed to a freezing-induced redistribution of the saturating solutions. DC decreased with increasing CaCl2 concentration, indicating an electrical double-layer effect. Soil that had been frozen and thawed had a more stable structure (in terms of both DC and WAS) than the unfrozen soil. No interaction was found between solutes and freezing. In contrast, there was a significant interaction between water content and freezing. WAS increased with decreasing water content for those aggregates which had been frozen and thawed, but not for those which had remained unfrozen. Key words: Soil structure, wet-aggregate stability, dispersible clay, frost heave, soil solution, bulk electrical conductivity

EFFECT OF ROOT EXUDATES FROM CORN AND BROMEGRASS ON SOIL STRUCTURAL STABILITY

1990 ◽  
Vol 70 (3) ◽  
pp. 351-362 ◽  
Author(s):  
T. POJASOK ◽  
B. D. KAY
Keyword(s):  
Structural Stability ◽  
Root Exudates ◽  
Soil Structure ◽  
Aggregate Stability ◽  
Clay Content ◽  
Flash Evaporation ◽  
Metal Organic ◽  
Loam Soil ◽  
Wet Aggregate Stability ◽  
Dispersible Clay

The effect of root exudates on structural stability and the hypothesis that the growing roots of corn (Zea mays L.) can destabilize soil structure by chelating Fe and Al involved in mineral-metal-organic matter linkages were investigated. Exudates were removed from 14C-labelled corn and bromegrass (Bromus inermis Leyss.) plants grown in sand using sequential leaching with water and acetone. The exudates were concentrated by flash evaporation and incubated with 1–2 mm aggregates of a calcareous silt loam soil for up to 240 h. Aggregates to which exudates from bromegrass were added had a higher wet aggregate stability (WAS) and lower dispersible clay content (DC) than aggregates to which exudates from corn were added. The greatest increase in stability occurred on addition of the water-extracted exudates (9.6% for WAS, 27.1% for DC). The increase in stability correlated positively with a release into solution of Ca and Mg from the soil solids. Addition of CaCl2 to the aggregates, to give corresponding amounts of Ca and Mg in solution, had similar effects on stability suggesting that the ions released by the exudates were not in a chelated form. The quantity of carbon added in the exudates and the mineralization of this carbon were positively and negatively correlated with stability, respectively. There was little evidence that corn exudates caused a destabilization of structure. Key words: Wet aggregate stability, dispersible clay, corn, bromegrass, flocculation, calcium

Structural stability of sodic soils in sugarcane production as influenced by gypsum and molasses

2002 ◽  
Vol 42 (3) ◽  
pp. 315 ◽  
Author(s):  
A. Suriadi ◽  
R. S. Murray ◽  
C. D. Grant ◽  
P. N. Nelson
Keyword(s):  
Structural Stability ◽  
Aggregate Stability ◽  
Clay Loam ◽  
Exchangeable Sodium ◽  
Sodic Soils ◽  
Clay Dispersion ◽  
Sugarcane Production ◽  
Mechanical Dispersion ◽  
Wet Aggregate Stability ◽  
Dispersible Clay

The aim of this work was to determine whether molasses, a by-product of sugar manufacture, alone or combined with gypsum, could improve the structural stability of sodic soils used for sugarcane production. A Burdekin sandy clay loam with an exchangeable sodium percentage (ESP) of 7.9, and a Proserpine loamy sand with an ESP of 18.8 were incubated with molasses (0 and 10 t/ha) and gypsum (0 and 10 t/ha) for 12 weeks, during which time they were leached 5 times with water (0.5 pore volumes each time). In the Burdekin soil, molasses and gypsum, either alone or combined, decreased spontaneous clay dispersion from 2.6 to <0.2 g/kg soil. Mechanical dispersion was reduced from 21.2 to <0.2 g/kg soil by gypsum alone, and to 14.9 g/kg soil by molasses alone. Molasses and gypsum both increased wet aggregate stability, with the combined effect being greatest; the proportion of aggregates >250 μm was 31% in the control and 71% with molasses + gypsum. Electrical conductivity (EC 1:5) was 0.1 and 1.9 dS/m, pH1:5 in water was 7.7 and 7.1, and ESP was 4.1 and 0.2 in the control and molasses + gypsum treatments respectively. In the Proserpine soil, the amounts of dispersible clay were much less than in the Burdekin soil. The effects of molasses and gypsum in decreasing spontaneous and mechanical clay dispersion were similar to those in the Burdekin soil, but less pronounced. Molasses and gypsum, either alone or combined, improved the structural stability of both soils by decreasing dispersion and/or slaking. An implication of this work is that molasses may be a useful ameliorant for sodic soils, either alone or combined with gypsum.

ASSESSMENT OF A COMBINATION OF WET SIEVING AND TURBIDIMETRY TO CHARACTERIZE THE STRUCTURAL STABILITY OF MOIST AGGREGATES

1990 ◽  
Vol 70 (1) ◽  
pp. 33-42 ◽  
Author(s):  
T. POJASOK ◽  
B. D. KAY
Keyword(s):  
Organic Matter ◽  
Structural Stability ◽  
Organic Matter Content ◽  
Aggregate Stability ◽  
Clay Content ◽  
Matter Content ◽  
Wet Aggregate Stability ◽  
Large Investment ◽  
Dispersible Clay ◽  
Wet Sieving

A method of measuring the structural stability of moist soils using a combination of turbidimetry and wet sieving has been developed and assessed. Aggregates of 1–2 mm in diameter are shaken end-over-end in test tubes and dispersed clay and stable aggregates greater than 0.25 mm diameter measured. Stabilities determined using this method were compared to stabilities determined using a modification of the Yoder wet-sieving method on 20 soils of different textures, organic-matter content, and recent cropping history. Wet aggregate stabilities determined by the two methods were correlated although the two measurements exhibited different sensitivities to clay content, organic-matter content and moisture content at the time of sampling. Dispersible clay was found to be a function of total clay content, organic-matter content and water content at the time of sampling. The new method offers the advantage of stability measurements of structural units of much different size using the same energy input and can be readily adapted to the routine analysis of a large number of samples without a large investment in equipment or space. Key words: Wet aggregate stability, dispersible clay, cropping history, soil structure

Amending soil with sludge, manure, humic acid, orthophosphate and phytic acid: effects on aggregate stability

Soil Research ◽  
2014 ◽  
Vol 52 (4) ◽  
pp. 317 ◽  
Author(s):  
A. I. Mamedov ◽  
B. Bar-Yosef ◽  
I. Levkovich ◽  
R. Rosenberg ◽  
A. Silber ◽  
...  
Keyword(s):  
Humic Acid ◽  
Phytic Acid ◽  
Structural Stability ◽  
Organic Amendments ◽  
Aggregate Stability ◽  
Loamy Sand ◽  
Soil Aggregate Stability ◽  
Before And After ◽  
Soil Structural Stability ◽  
The Stability

Recycling of organic wastes via their incorporation in cultivated lands is known to alter soil structural stability. Aggregate stability tests are commonly used to express quantitatively the susceptibility of soil structural stability to deformation. The objective of this study was to investigate the effects of biosolids addition, namely composted manure (MC) and activated sludge (AS), and spiking of the soils with orthophosphate (OP), phytic acid (PA) or humic acid (HA), on soil aggregate stability of semi-arid loamy sand, loam and clay soils before and after subjecting the soils to six rain storms (each 30 mm rain with a break of 3–4 days). Aggregate stability was determined from water-retention curves at high matric potential. The effects of the applied amendments on pre- and post-rain aggregate stability were inconsistent and soil-dependent. For the pre-rain state, all of the tested amendments improved aggregate stability relative to the control. For the post-rain condition, aggregate stability was lower in the MC, OP and PA treatments and higher in the AS and HA treatments than in the control. The coarse-textured loam and loamy sand soils were more affected by the soil amendments than the clay soil. For the pre-rain state, addition of organic matter significantly improved macro-porosity and hence the stability of apparent macro-aggregate (>250 μm). Our results indicate a possible advantage for separation of aggregates into macro- and micro-aggregates for more precise evaluation and understanding of the effects organic amendments might have on aggregate stability.

Field frost heave measurement and prediction during periods of seasonal frost

1990 ◽  
Vol 27 (3) ◽  
pp. 393-397 ◽  
Author(s):  
H. N. Hayhoe ◽  
D. Balchin
Keyword(s):  
Temperature Gradient ◽  
Displacement Transducer ◽  
Linear Displacement ◽  
Time Domain Reflectometry ◽  
Frost Heave ◽  
Unfrozen Water ◽  
Data Logger ◽  
Unfrozen Water Content ◽  
Frost Penetration ◽  
Displacement Transducers

Frost heave measurements were taken over two winter seasons on a clay loam soil located near Ottawa, Canada. Heaving was measured using linear displacement transducers attached to a metal frame that was anchored in the soil below the depth of frost penetration. The output of the displacement transducer was recorded hourly using a microcomputer-based data logger. The system functioned reliably and the observed data compared well with published measurements.Soil temperature was recorded simultaneously using thermocouples. Time-domain reflectometry was used to measure the unfrozen water content. The study shows that soil temperature measurements can be used to estimate the temperature gradient at the freezing front for determining the cumulative frost heave, as suggested by the Konrad–Morgenstern theory of ice segregation processes. Key words: frost heave, temperature, gradient, displacement transducer, segregational potential.

scholarly journals Soil chemical management drives structural degradation of Oxisols under a no-till cropping system

Soil Research ◽  
2017 ◽  
Vol 55 (8) ◽  
pp. 819 ◽  
Author(s):  
Márcio R. Nunes ◽  
Alvaro P. da Silva ◽  
José E. Denardin ◽  
Neyde F. B. Giarola ◽  
Carlos M. P. Vaz ◽  
...  
Keyword(s):  
Surface Layer ◽  
Structural Stability ◽  
Subsurface Layer ◽  
Structural Degradation ◽  
Chemical Management ◽  
No Till ◽  
Cultivated Soil ◽  
Water Percolation ◽  
Soil Structural Stability ◽  
Dispersible Clay

Physical degradation of the subsurface layer of soils reduces the effectiveness of no-till (NT) as a sustainable soil management approach in crop production. Chemical factors may reduce the structural stability of Oxisols and thereby exacerbate compaction from machinery traffic. We studied the relationship between chemical management and structural degradation in Oxisols cultivated under NT at three sites in southern Brazil. The surface and subsurface layers of the soils were characterised chemically and mineralogically and three physical attributes related to soil structural stability (readily dispersible clay in water, mechanically dispersible clay in water, and water percolation) were quantified for each layer. The same characterisations were performed on Oxisols collected from adjacent non-cultivated areas, to provide reference data for non-degraded soil. The levels of dispersed clay in the cultivated soil from the surface layer matched those of the non-cultivated soil, but for the subsurface layer higher dispersed clay levels in the cultivated soil showed that it was physically degraded relative to the non-cultivated soil. Water percolation was found to be slower through the Oxisols cultivated under NT, irrespective of the soil layer. The relationships between the three indicators of soil structural stability and the measured chemical and mineralogical variables of the soils were explored through an analysis of canonical correlation. The principal variables associated with the lower stability of the cultivated vs non-cultivated Oxisols were the lower concentrations of organic carbon and exchangeable aluminium and, for the surface layer, the higher pH. It is argued that structural degradation of Oxisols cultivated under NT, observed predominantly in the subsurface layer, has been aggravated by the accumulation of amendments and fertilisers in the surface soil and reduced levels of organic matter, especially in the subsurface layer.

scholarly journals Modelling Alternatives for Highland Soil Structural Degradation and Erodibility, Bui Plateau, Cameroon

2020 ◽  
Vol 1 (6) ◽  
Author(s):  
Reeves M. Fokeng ◽  
Zephania N. Fogwe
Keyword(s):  
Structural Stability ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Stability Index ◽  
Soil Improvement ◽  
Organic Carbon Content ◽  
Soil Biochemistry ◽  
Annual Biomass ◽  
Soil Structural Stability ◽  
Physical Degradation

Highland triggers of soil physical degradation through the fragilisation of soil aggregates are primarily factors of soil biochemistry and anthropogenic mishandling of land resources. Soil degradation forms are challenging the sustenance of human systems on earth. This study probes into soil physical degradation and exposure to external stressors using 60 soil samples collected and analysed for soil aggregate stability, vulnerability and erodibility to determine soil structural stability/resilient capacity. The soils were found to be stable in structure, but highly vulnerable to stress and erodible. Coarse-granitic sandy soils just as the less evolved erosion soils of the eastern slopes of the plateau were proven to be most erodible and vulnerable to physical degradation. Soil Structural Stability Index (ISS) was very low (≤ 4.3%: severe physical degradation) for disturbed soils under grazing with similar tendencies on cultivated humid volcanic soils. High erosion vulnerability/erodibility soils are indicative of low organic matter and organic carbon content issuant of heavy and uncontrolled grazing, annual biomass burning and long-term cropping without soil improvement schemes which calls for guided land use practices over the Bui Plateau.

Comparison of the effects of latex and poly(DADMAC) on structural stability and strength of soil aggregates

Soil Research ◽  
1995 ◽  
Vol 33 (2) ◽  
pp. 369 ◽  
Author(s):  
SM Bernas ◽  
JM Oades ◽  
GJ Churchman ◽  
CD Grant
Keyword(s):  
Structural Stability ◽  
Cropping Systems ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Structural Condition ◽  
Mechanical Action ◽  
Water Stable Aggregates ◽  
The Face ◽  
Wet Aggregate Stability ◽  
Aromatic Oils

Two types of high molecular weight polymers having contrasting charge properties and molecular shapes [latex and poly(DADMAC)] were applied at different rates to three Alfisols and a Mollisol to examine the effects of these polymers on soil strength and structural stability, and to identify some of the mechanisms by which these polymers act to stabilize soils. Wet aggregate stability, mechanically dispersible clay, and soil friability tests were used to assess treatment effects, which were found to be greatest in soils having a poor structural condition. Each polymer acted differently. Latex, which acted like a coat of paint (because of its inability to penetrate beyond the surface of aggregates), dramatically increased the proportion of water stable aggregates >2 mm in all soils examined, and this was achieved without the traditional (expensive) use of aromatic oils and stabilizers. The latex coating produced a conglomeration of smaller soil aggregates, but did not extensively alter either the dispersibility of the aggregates in the face of mechanical action, or their strength and friability. Results indicate latex may be best suited to minimum tillage cropping systems. Poly(DADMAC), by contrast, was capable of entering most pores accessible to water. This enabled it to minimize clay dispersion, increase soil friability, and to modestly increase the size of water stable aggregates. In many ways, poly(DADMAC) would appear to be an ideal soil conditioner, although the economic suitability of this polymer and its effects on erosion control and plant growth have yet to be assessed.

Freezing cycle effects on water stability of soil aggregates

2013 ◽  
Vol 93 (4) ◽  
pp. 473-483 ◽  
Author(s):  
Daryl F. Dagesse
Keyword(s):  
Water Content ◽  
Structural Stability ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Clay Content ◽  
Initial Water Content ◽  
Water Stability ◽  
Initial Water ◽  
Freeze Thaw ◽  
Freezing Cycle

Dagesse, D. F. 2013. Freezing cycle effects on water stability of soil aggregates. Can. J. Soil Sci. 93: 473–483. The freezing process is commonly implicated as a key factor in defining the state of soil structural stability following the winter months. Controversy exists, however, regarding the efficacy, and even the net effect, of this process. The objective of the study was to establish the separate effects of the freezing, freeze–thaw and freeze-drying processes in defining soil structural stability following the over-winter period. Aggregates from soils of varying clay content (0.11, 0.33, 0.44 kg kg−1) and initial water content (0.10, 0.20 or 0.30 kg kg−1) were subjected to freeze-only (F), freeze–thaw (FT) and freeze-dry (FD) treatments. Post-treatment aggregate stability determination was via wet aggregate stability (WAS) and dispersible clay (DC). Freezing alone and freeze-dry treatments generally resulted in greater aggregate stability, while the freeze–thaw generally resulted in lower aggregate stability as compared with a control, not frozen treatment (T). These data suggest the freezing-induced desiccation process improves aggregate stability, while the addition of a thaw component following freezing, with the attendant liquid water, is responsible for degradation of aggregate stability. Clay content and initial water content are important factors governing the magnitude of this process.

Sign in / Sign up

Export Citation Format

Share Document