EFFECTS OF CROPPING ON MACRO-AGGREGATION OF A MARINE CLAY SOIL

1988 ◽  
Vol 68 (4) ◽  
pp. 723-732 ◽  
Author(s):  
D. A. ANGERS ◽  
G. R. MEHUYS
Keyword(s):  
Soil Structure ◽  
Clay Soil ◽  
Initial Conditions ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Field Conditions ◽  
Growth Chamber ◽  
Marine Clay ◽  
Hordeum Vulgare L ◽  
Medicago Sativa L

Field and growth chamber experiments were conducted to evaluate the short-term effects of selected crops on macro-aggregation of a Kamouraska clay soil. Under field conditions, the growth of barley (Hordeum vulgare L.) and alfalfa (Medicago sativa L.) for up to 2 yr resulted in increased macro-aggregate size and stability compared to a fallow control and to initial conditions. Under these two crops, the proportion of water-stable aggregates of the 2- to 6-mm fraction increased from 25% in May 1986 to 40% in September 1987 at the expense of the 0.25- to 1.0-mm fraction which decreased from 37% to 19% over the same period. Macro-aggregation after 2 yr was not different in corn (Zea mays L.) and fallow control. Seasonal variations in aggregate stability were significant but small and less important than the effects of cropping treatments. Results of the growth chamber experiment agreed with those obtained under field conditions suggesting that controlled environment experiments can be used to model cropping effects on the aggregation of this soil. Key words: Aggregation, soil structure, clay soil, corn, barley, alfalfa

Tillage-induced changes to soil structure and organic carbon fractions in New Zealand soils

Soil Research ◽  
2001 ◽  
Vol 39 (3) ◽  
pp. 465 ◽  
Author(s):  
T. G. Shepherd ◽  
S. Saggar ◽  
R. H. Newman ◽  
C. W. Ross ◽  
J. L. Dando
Keyword(s):  
Organic Carbon ◽  
Size Distribution ◽  
Soil Structure ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Aggregate Size Distribution ◽  
Binding Agents ◽  
Rate Of Decline ◽  
Humic Soil

The effects of increasing cropping and soil compaction on aggregate stability and dry-sieved aggregate-size distribution, and their relationship to total organic C (TOC) and the major functional groups of soil organic carbon, were investigated on 5 soils of contrasting mineralogy. All soils except the allophanic soil showed a significant decline in aggregate stability under medium- to long-term cropping. Mica-rich, fine-textured mineral and humic soils showed the greatest increase in the mean weight diameter (MWD) of dry aggregates, while the oxide-rich soils, and particularly the allophanic soils, showed only a slight increase in the MWD after long-term cropping. On conversion back to pasture, the aggregate stability of the mica-rich soils increased and the MWD of the aggregate-size distribution decreased, with the humic soil showing the greatest recovery. Aggregate stability and dry aggregate-size distribution patterns show that soil resistance to structural degradation and soil resilience increased from fine-textured to coarse-textured to humic mica-rich soils to oxide-rich soils to allophanic soils. Coarse- and fine-textured mica-rich and oxide-rich soils under pasture contained medium amounts of TOC, hot-water soluble carbohydrate (WSC), and acid hydrolysable carbohydrate (AHC), all of which declined significantly under cropping. The rate of decline varied with soil type in the initial years of cropping, but was similar under medium- and long-term cropping. TOC was high in the humic mica-rich and allophanic soils, and levels did not decline appreciably under medium- and long-term cropping. 13C-nuclear magnetic resonance evidence also indicates that all major functional groups of soil organic carbon declined under cropping, with O-alkyl C and alkyl C showing the fastest and slowest rate of decline, respectively. On conversion back to pasture, both WSC and AHC returned to levels originally present under long-term pasture. TOC recovered to original pasture levels in the humic soil, but recovered only to 60–70% of original levels in the coarse- and fine-textured soils. Aggregate stability was strongly correlated to TOC, WSC, and AHC (P < 0.001), while aggregate-size distribution was moderately correlated to aggregate stability (P < 0.01) and weakly correlated to AHC (P < 0.05). Scanning electron microscopy indicated a loss of the binding agents around aggregates under cropping. The effect of the loss of these binding agents on soil structure was more pronounced in mica-rich soils than in oxide-rich and allophanic soils. The very high aggregate stabilities of the humic soil under pasture was attributed to the presence of a protective water-repellent lattice of long-chain polymethylene compounds around the soil aggregates.

scholarly journals Timing and conditions modify the effect of structure liming on clay soil

2021 ◽  
Author(s):  
Jens Erik Blomquist ◽  
Kerstin Berglund
Keyword(s):  
Clay Soil ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Soil Conditions ◽  
Simulated Rainfall ◽  
Rainfall Events ◽  
Inner Diameter ◽  
One Year ◽  
Stability Measurements ◽  
Effect Of Structure

Two dates (early, normal) for application and incorporation of structure lime to clay soil were examined at four field sites, to test whether early liming had more favourable effects on aggregate stability. Aggregate size distribution measurements revealed a finer tilth at the early liming date (20 August) than the normal date (14 September). Aggregate stability estimated one year later, using as a proxy turbidity in leachate from 2–5 mm aggregates subjected to two simulated rainfall events, was significantly improved (11% lower turbidity) with early compared with normal liming date. Three years after structure liming, soil structural stability measurements on lysimeters (15 cm high, inner diameter 18 cm) subjected to repeated simulated rainfall events showed no significant differences in turbidity in leachate between the early and normal liming dates. However, there was a strong interaction between liming date and site indicating different reactions at different sites. Our results suggest that early spreading and incorporation can improve the success of structure liming, but only if soil conditions are favourable.

Persistent improvements in the structure and hydraulic conductivity of a Ferrosol due to liming

Soil Research ◽  
2007 ◽  
Vol 45 (3) ◽  
pp. 218 ◽  
Author(s):  
J. M. Kirkham ◽  
B. A. Rowe ◽  
R. B. Doyle
Keyword(s):  
Hydraulic Conductivity ◽  
Organic Carbon ◽  
Soil Structure ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Soil Surface ◽  
Penetration Resistance ◽  
Organic C ◽  
Soil Penetration Resistance ◽  
Wet Aggregate Stability

Changes in the soil structure and hydraulic conductivity of an Acidic Red Ferrosol were measured in a long-term (1968–2003) fertiliser experiment on pasture in north-western Tasmania, Australia. Studies were initiated following observations of both softer soil surface and cracking on plots that had received 15 t/ha of ground agricultural limestone. Liming decreased penetration resistance and increased hydraulic conductivity. These structural improvements were associated with increased mean dry aggregate size, a small increase in wet aggregate stability, higher exchangeable calcium levels, and increased plant growth, but a 9% decrease in total soil organic carbon in the surface 50 mm. This decrease in organic carbon was not associated with deterioration in soil structure, as may have been anticipated. This was probably because total organic C was still 82 g/kg on unlimed plots. Decreases in soil penetration resistance due to liming increased the likelihood of pugging from livestock but may improve ease of tillage. This research demonstrates that liming can improve the structure of a well-aggregated Ferrosol as well as its previously reported effects of increasing soil pH and yields of pasture and barley despite decreasing organic C.

ALTERATIONS OF SOIL STRUCTURE UPON FREEZING AND THAWING AND SUBSEQUENT DRYING

1968 ◽  
Vol 48 (2) ◽  
pp. 193-197 ◽  
Author(s):  
W. C. Hinman ◽  
Frederick Bisal
Keyword(s):  
Moisture Content ◽  
Soil Structure ◽  
Room Temperature ◽  
Clay Soil ◽  
Soil Aggregates ◽  
Initial Moisture Content ◽  
Aggregate Size ◽  
Freezing And Thawing ◽  
Initial Size ◽  
Freeze Dried

A laboratory investigation of a clay soil indicated that the percentage of aggregates < 1 mm in diameter might be increased, decreased or unaffected by freezing and thawing depending on the initial moisture content, the initial size of soil aggregates and the method of drying the sample. Little or no changes in aggregate size occurred if the initial moisture content was at 15 atmospheres. At 0.1 atm, aggregates which were initially coarse (> 4 mm) tended to break down slightly when exposed to alternate freezing and thawing followed by air-drying at room temperature. On the other hand, a substantial decrease in aggregates < 1 mm in diameter occurred when aggregates which were originally fine received the same sequence of treatments. However, if the samples were freeze-dried following the same treatments, all aggregates were reduced to < 1 mm in diameter. Similar trends were established with samples which were continuously frozen and when the initial moisture content was at 0.33 atm, although the magnitude of the change was much smaller. It is proposed that forces engendered during freezing disrupt aggregates, but this process is reversed during thawing and drying at room temperatures.

INFLUENCE OF AGGREGATE DIAMETER, SURFACE AREA AND ANTECEDENT WATER CONTENT ON THE DISPERSIBILITY OF CLAY

1990 ◽  
Vol 70 (4) ◽  
pp. 655-671 ◽  
Author(s):  
B. D. KAY ◽  
A. R. DEXTER
Keyword(s):  
Water Content ◽  
Surface Area ◽  
Soil Structure ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Specific Area ◽  
Unit Surface Area ◽  
Surface Areas ◽  
Fallow Soil ◽  
Unit Surface

The percentages of spontaneously dispersed clay, Ms, and mechanically dispersed clay, Mm, in a suspension of a given ionic strength were hypothesized to be controlled by the specific area of exposed aggregate surfaces and the dispersibility of clay per unit specific aggregate surface area. This hypothesis was evaluated using different sized aggregates collected in 1988 from wheat-fallow and continuous pasture rotations established in 1925 on a red-brown earth in southern Australia. Aggregates which were initially air-dry were wetted to matric water potentials ranging from −10 to −0.3 kPa, then placed in distilled water and Ms and Mm measured. Ms increased, as hypothesized, with increasing surface area of aggregates. However, the spontaneously dispersed clay per unit surface area of aggregates increased with increasing size of aggregates and increasing antecedent soil water content. The effect of water content was greatest in the larger aggregates of the less stable wheat-fallow soil. Mm was approximately 12 times larger than Ms and increased with increasing initial aggregate size and increasing antecedent water content. The sensitivity of Mm to water content was greatest on the least stable soil. Calculations showed that the higher values of Mm on unstable soils were due to both larger exposed aggregate surface areas and higher dispersibility of the clay on these surfaces. Keywords: Soil structure, aggregate stability, dispersion

Soil structure changes: aggregate size and soil texture effects on hydraulic conductivity under different saline and sodic conditions

Soil Research ◽  
2009 ◽  
Vol 47 (7) ◽  
pp. 688 ◽  
Author(s):  
M. Ben-Hur ◽  
G. Yolcu ◽  
H. Uysal ◽  
M. Lado ◽  
A. Paz
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Texture ◽  
Structural Damage ◽  
Soil Structure ◽  
Clay Soil ◽  
Aggregate Size ◽  
Loamy Sand ◽  
Structural Degradation ◽  
Order Of Magnitude ◽  
Ks Values

Hydraulic conductivity of soil is strongly dependent on soil structure, which can be degraded during wetting and leaching. It was hypothesised that this structural degradation is dependent on initial aggregate size distribution and soil texture. The general aim of this study was to investigate the effects of aggregate sizes and soil textures, and their interactions, on the structural degradation and saturated hydraulic conductivity (Ks) of smectitic soils under different saline and sodic conditions. The studied soils were clay and loamy sand soils with low (~4.5) or high (~10) exchangeable sodium percentages (ESP), and with aggregate sizes in the ranges: (i) <1 mm (small aggregates); or (ii) 2–4 mm (large aggregates). The Ks values of the samples in a column after slow or fast pre-wetting were determined by means of a constant head device. Different wetting rates and leaching under various saline and sodic conditions had no effect on the Ks of the loamy sand; however, the Ks values of this soil with large aggregates were an order of magnitude greater than those of the soil with small aggregates. In contrast, in the clay soil with large aggregates, the Ks values after fast pre-wetting were significantly smaller than those after slow pre-wetting, probably because of aggregate slaking. No significant effects of the wetting rates on Ks were found in clay soil with small aggregates. An increase in the ESP in the clay soil decreased the Ks by a factor of 1.5 for the large aggregates and by an order of magnitude for the small aggregates, mainly as a result of increased clay swelling. Leaching the clay soil with deionised water significantly decreased the Ks values, partly because of clay dispersion. Although significant structural degradation of the clay soil occurred during leaching, the Ks values were smaller in the soils with small aggregates than in those with large aggregates, indicating the importance of the initial aggregate size on Ks even in soils that are prone to structural damage.

Crop rotation effects on soil carbon and physical fertility of two Australian soils

Soil Research ◽  
2000 ◽  
Vol 38 (1) ◽  
pp. 71 ◽  
Author(s):  
Nelly Blair ◽  
G. J. Crocker
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Carbon ◽  
Soil Structure ◽  
Clay Soil ◽  
Aggregate Stability ◽  
Labile Carbon ◽  
Red Clay ◽  
Carbon Fractions ◽  
Rotation Crops

The effect of using different crop rotations, including legumes and fallows, on soil structural stability, unsaturated hydraulic conductivity, and the concentration of different carbon fractions was examined in a long-term rotation trial established in 1966 on a Black Earth (Pellic Vertisol) and a Red Clay (Chromic Vertisol) soil. There was a large decrease in the concentration of soil carbon fractions following cropping and cultivation on both soils. The inclusion of some legume rotation crops resulted in an increase in labile carbon concentrations compared with continuous wheat or a long fallow treatment. Aggregate stability to wetting under both immersion and tension wetting was reduced as a result of cropping and cultivation for both soil types. However, there was an improvement in aggregate stability with immersion wetting, on the Red Clay soil, for the lucerne (Medicago sativa), clover (Trifolium subterraneum), and continuous wheat (Triticum aestivium) treatments compared with the long fallow. Similar results were found for the Black Earth soil; however, on this soil the medic (Medicago scutella) rotation also showed an improvement in soil structure. On the Red Clay soil there was a decrease in hydraulic conductivity (K) with cropping, at all tensions measured. K for the Black Earth soil was higher at 30 and 40 mm tension on the cropped soil than on the uncropped reference soil, but at 10 mm tension the reference soil had a higher K value than all rotations except the lucerne. There was a significant correlation between labile carbon and all determinations of aggregate stability for the Red Clay soil. Farmers should be encouraged to eliminate long fallowing and to adopt no-till techniques combined with the return of residues from either the primary crop or rotation crops which have a slower breakdown rate, as this management is likely to have a better potential for increasing soil carbon content and improving soil structure. The investigation of ways to better increase the quantity and quality of soil organic matter and hence soil chemical and physical fertility is necessary if long-term sustainable agriculture is to be possible.

scholarly journals Sludge amendment accelerating reclamation process of reconstructed mining substrates

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dan Li ◽  
Ningning Yin ◽  
Ruiwei Xu ◽  
Liping Wang ◽  
Zhen Zhang ◽  
...  
Keyword(s):  
Soil Structure ◽  
Aggregate Stability ◽  
Soil Aggregate ◽  
Soil Reclamation ◽  
Soil Restoration ◽  
Total Biomass ◽  
Soil Aggregate Stability ◽  
Mining Soil ◽  
Positive Correlations ◽  
Reclamation Process

AbstractWe constructed a mining soil restoration system combining plant, complex substrate and microbe. Sludge was added to reconstructed mine substrates (RMS) to accelerate the reclamation process. The effect of sludge on plant growth, microbial activity, soil aggregate stability, and aggregation-associated soil characteristics was monitored during 10 years of reclamation. Results show that the height and total biomass of ryegrass increases with reclamation time. Sludge amendment increases the aggregate binding agent content and soil aggregate stability. Soil organic carbon (SOC) and light-fraction SOC (LFOC) in the RMS increase by 151% and 247% compared with those of the control, respectively. A similar trend was observed for the glomalin-related soil protein (GRSP). Stable soil aggregate indexes increase until the seventh year. In short, the variables of RMS determined after 3–7 years insignificantly differ from those of the untreated sample in the tenth-year. Furthermore, significant positive correlations between the GRSP and SOC and GRSP and soil structure-related variables were observed in RMS. Biological stimulation of the SOC and GRSP accelerates the recovery of the soil structure and ecosystem function. Consequently, the plant–complex substrate–microbe ecological restoration system can be used as an effective tool in early mining soil reclamation.

Uplift and Settlement Prediction Model of Marine Clay Soil e Integrated with Polyurethane Foam

2019 ◽  
Vol 9 (1) ◽  
pp. 481-489
Author(s):  
D.C. Lat ◽  
I.B.M. Jais ◽  
N. Ali ◽  
B. Baharom ◽  
N.Z. Mohd Yunus ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Clay Soil ◽  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Effective Thickness ◽  
Marine Clay ◽  
Uplift Pressure ◽  
Pu Foam ◽  
Improvement Method

AbstractPolyurethane (PU) foam is a lightweight material that can be used efficiently as a ground improvement method in solving excessive and differential settlement of soil foundation mainly for infrastructures such as road, highway and parking spaces. The ground improvement method is done by excavation and removal of soft soil at shallow depth and replacement with lightweight PU foam slab. This study is done to simulate the model of marine clay soil integrated with polyurethane foam using finite element method (FEM) PLAXIS 2D for prediction of settlement behavior and uplift effect due to polyurethane foam mitigation method. Model of soft clay foundation stabilized with PU foam slab with variation in thickness and overburden loads were analyzed. Results from FEM exhibited the same trend as the results of the analytical method whereby PU foam has successfully reduced the amount of settlement significantly. With the increase in PU foam thickness, the settlement is reduced, nonetheless the uplift pressure starts to increase beyond the line of effective thickness. PU foam design chart has been produced for practical application in order to adopt the effective thickness of PU foam within tolerable settlement value and uplift pressure with respect to different overburden loads for ground improvement works.

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