Evaluation of selected factors influencing aggregate fragmentation using fractal theory

1992 ◽  
Vol 72 (2) ◽  
pp. 97-106 ◽  
Author(s):  
V. Rasiah ◽  
B. D. Kay ◽  
E. Perfect
Keyword(s):  
Fractal Dimension ◽  
Probability Model ◽  
Soil Aggregates ◽  
Fractal Theory ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Red Clover ◽  
Probability Of Failure ◽  
Continuous Corn ◽  
Wet Sieving

Two fractal parameters, probability of failure (P) and fractal dimension (D), were used to evaluate the influence of cropping and wetting treatments, and aggregate size on fragmentation of soil aggregates during wet sieving. Five different sizes of aggregates (4–10, 2–4, 1–2, 0.5–1 and 0.25–0.5 mm) from five cropping treatments [conventionally cultivated continuous corn (CCC), CCC underseeded to red clover (CCR), minimally tilled continuous corn underseeded to red clover (CCRM), alfalfa (AL), and bromegrass (BR)] were subjected to two wetting treatments (rapid and slow) before being wet sieved. P increased nonlinearly with increasing aggregate size. The P of the slowly wetted agggregates was always less than that of the rapidly wetted aggregates. The P of larger aggregates, 2–4 and 4–10 mm, increased in the following order of cropping: BR = AL < CCRM < CCR = CCC. The D for the size distribution of 4- to 10-mm aggregates increased in the same order of cropping as that given previously. The D for the rapidly wetted aggregates was higher than that of the slowly wetted aggregates for all cropping treatments except CCC. The values of P predicted from a fractal probability model correlated well with the observed values. The results show that P and D of soil aggregates are strongly influenced by cropping and wetting treatments and aggregate size. Key words: Probability of failure, fractal dimension, wet sieving, wet aggregate stability, prewetting

Soil aggregates as mass fractals

Soil Research ◽  
1995 ◽  
Vol 33 (5) ◽  
pp. 757 ◽  
Author(s):  
AN Anderson ◽  
AB Mcbratney
Keyword(s):  
Fractal Dimension ◽  
Bulk Density ◽  
Soil Aggregates ◽  
Fractal Theory ◽  
Equivalent Form ◽  
Aggregate Size ◽  
Saturated Water ◽  
Mass Fractal Dimension ◽  
Moisture Characteristic ◽  
Saturated Water Content

Soil aggregates have a fractal mass. That is, they are porous and, as they are studied in greater detail, more pores may be observed. Mass fractals have scale-dependent bulk density. Larger objects, or soil aggregates, have a smaller bulk density. Bulk density in soil studies is sometimes assumed to be constant. If this was the case, soil aggregates would not be mass fractals, and their porosity would not change with scale. The fact that soil aggregates are mass fractals places restrictions on the estimation of the fragmentation fractal dimension (Df) of soil. The mass fractal dimension of soil (Dm) may be calculated from bulk density-aggregate size data. Linear and nonlinear methods of estimating Dm were compared and were shown to give similar results. The Dm is shown to influence porosity and the saturated water content. Fractal theory, in particular Dm, has implications for the calculation of the pore-size distribution and the moisture characteristic. By equating Campbell's (1985) Version of the Brooks-Corey water retention function, � Proportional �(-1 / b)and an equivalent form to the Brooks-Corey relation given by Crawford (1994), � Proportional �(Dm - d) it is suggested that D-m = d - 1/b, where d is the embedding dimension.

Aggregate size distribution and stability of an oxisol under legume-based and pure grass pastures in the eastern Colombian savannas

Soil Research ◽  
1995 ◽  
Vol 33 (1) ◽  
pp. 153 ◽  
Author(s):  
AJ Gijsman ◽  
RJ Thomas
Keyword(s):  
Size Distribution ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Soil Aggregate ◽  
Hot Water ◽  
Aggregate Size Distribution ◽  
Carbohydrate Concentration ◽  
Stability Measurement ◽  
Water Extractable

This study evaluated soil aggregate size distribution and stability of an Oxisol under improved grass-only or grass-legume pastures, established in previously native savanna. Three grass-legume combinations were included at various stocking rates. In all treatments and soil layers, soils were well aggregated, having more than 90% of their weight in macroaggregates (>250 �m). The addition of legumes to pastures did not affect the soil aggregate size distribution, although aggregates showed somewhat more stability against slaking. An increase in stocking rate negatively affected both average aggregate size and aggregate stability. Aggregates showed little or no dispersion of clay particles in any treatment. A positive correlation was found between wet aggregate stability and hot-water extractable carbohydrate concentration, supporting the hypothesis that these carbohydrates equate with plant-derived or microbial polysaccharides which glue soil aggregates together. It is suggested that determination of hot-water extractable carbohydrates may serve as a useful indicator of small differences in aggregate stability, even when these differences are not evident in the stability measurement itself.

Stabilization of Soil Aggregates in Relation to Soil Redistribution by Intensive Tillage on a Steep Hillslope

2014 ◽  
Vol 955-959 ◽  
pp. 3566-3571 ◽  
Author(s):  
Yong Wang ◽  
Zhuang Xiong ◽  
Wu Xian Yan ◽  
Yue Qun Qiu
Keyword(s):  
Soil Aggregates ◽  
Geometric Mean ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Soil Aggregate ◽  
Soil Aggregate Stability ◽  
Mean Weight Diameter ◽  
Tillage Operation ◽  
Sloping Land ◽  
The Impact

The objective of this study was to investigate soil aggregate stability within landscape on hillslopes by intensive tillage. Traditional tillage by consecutive hoeing was performed 5 and 20 times on steeply sloping land of the Sichuan Basin, China, by using the methods of simulated tillage to analyze the impact of long-term tillage on soil aggregates at different slope positions. The dry-sieved method was used to determine distribution of aggregate size in the different landscape positions, and mean weight diameter (MWD) and geometric mean diameter (GMD) as indices of soil aggregate stability. The different times of tillage resulted in different soil aggregate distributions. The results showed that the MWD and GMD values of aggregates were significantly decreased (p< 0.05) after 20-tillage operation, compared with pre-tillage operation. The differences in distributions of MWD and GMD demonstrate that the choice of the tillage times can be an important factor in changing soil aggregate stability and productivity in steeply sloping fields.

scholarly journals Potential Benefits of Polymers in Soil Erosion Control for Agronomical Plans: A Laboratory Experiment

Agronomy ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 276 ◽  
Author(s):  
Tugrul Yakupoglu ◽  
Jesús Rodrigo-Comino ◽  
Artemi Cerdà
Keyword(s):  
Soil Erosion ◽  
Sediment Yield ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Extreme Rainfall ◽  
Rainfall Simulation ◽  
Water Losses ◽  
Total Runoff ◽  
Runoff Sediment

New management and techniques to reduce soil and water losses are necessary to achieve goals related to sustainability and develop useful agronomical plans. Among the strategies to reduce soil losses, the use of polymers has been studied but little is known about the effect of them on soil aggregates under extreme rainfall conditions. The main aim of this study was to compare the effects of polyacrylamide (PAM) and polyvinyl alcohol (PVA) on initial soil erosion process activation. We applied both products on soils and soil aggregate stability was measured on polymer treated and control plots. Laboratory erosion plots (pans) were placed on 15% slope, and sequential simulated rainfalls (under dry and wet conditions) with 360 mm h−1 intensity were applied for 12 min. Time to runoff, total runoff, runoff sediment yield, and splash sediment yield were determined. The results show that polymers do not delay runoff initiation; however, they reduced total runoff, sediment yield, and soil transported by the splash. PVA was not effective in reducing the total runoff during the first rainfall being PAM more effective in this way. However, under the sequential rainfall, both polymers obtained positive results, showing PAM some improvements in comparison to PVA. The effect of the polymer to reduce soil transported by splash after performing the second rainfall simulation was clearly demonstrated, meanwhile the effects during the first simulation were not significant. The effectiveness of the polymers on soil aggregates increased with increasing aggregate size. The application of polymers reached the highest efficiency on aggregates of 6.4 mm in diameter.

Research on the AC-13 Skeleton Dense-Graded Asphalt Mixtures by Fractal Theory

2014 ◽  
Vol 971-973 ◽  
pp. 148-156
Author(s):  
Gui Hua Hu ◽  
Xiao Wei Chen ◽  
Xuan Cang Wang
Keyword(s):  
Fractal Dimension ◽  
Strong Correlation ◽  
Fractal Theory ◽  
Asphalt Mixture ◽  
Aggregate Size ◽  
Asphalt Mixtures ◽  
Degree Of Saturation ◽  
Paper Study ◽  
Mineral Aggregate ◽  
Fractal Character

This paper study on AC-13 skeleton dense-graded asphalt mixtures by fractal theory, obtaining that both aggregate size and gradation have fractal character. Compared three kinds of asphalt mixture, we found that there was a strong correlation between fractal dimension of aggregate and aggregate size distribution. AC-13 skeleton dense-graded asphalt mixtures were tested. The results show that the aggregate fractal dimension has a good correlation with mixture’s bulk density, mineral aggregate gap rate, percentage of voids and asphalt degree of saturation too. The study is useful for reference to the readers who engage in further study of the fractal theory’s application to asphalt mixtures.

scholarly journals The stability of soil aggregates in tilled fallow areas in Hyderabad district, Pakistan

2015 ◽  
Vol 27 (1) ◽  
pp. 51-60
Author(s):  
Ahmed Tagar ◽  
Jan Adamowski
Keyword(s):  
Soil Erosion ◽  
Size Distribution ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Indus River ◽  
Aggregate Size Distribution ◽  
Sieve Size ◽  
The Stability ◽  
The Village

Abstract Arid areas are particularly susceptible to soil erosion due to long dry periods and sudden heavy downpours. This study investigates the aggregate size distribution and aggregate stability of twelve tilled fallow areas of Hyderabad district, Sindh, Pakistan. This study determined aggregate size distribution by dry sieving to evaluate the seedbed condition and aggregate stability using wet sieving to assess the susceptibility of tilled fallow areas to soil erosion. The aggregate size distribution of the soils of the selected areas was highly variable. Gulistan-e-Sarmast had the largest number of clods (51.0%) followed by Kohsar (49.0%), Latifabad # 10 (41.10%) and Daman-e-Kohsar (39.0%). Fazal Sun City, the left side of the Indus River, the Village Nooral Detha and the left side of the Abdullah Sports city had a greater number of large (>8.0 mm) and small aggregates (<0.5 mm). The optimum aggregate size distribution was found in the left side of the channel, which had the largest number of aggregates (50.50%) in the 0.5–8.0 mm sieve size range. Maximum aggregate stability (AS) was found in Gulistan-e-Sarmast (46%), Kohsar (42%) and Latifabad # 10 (34%), while all other soils had minimum aggregate stability (<14%). The minimum aggregate stabilities demonstrate that the tilled fallow areas of Hyderabad district are highly susceptible to erosion. Therefore, the present study suggests investigating potential ways to enhance the aggregate stabilities of soils.

scholarly journals Distribution of a Population of Rhizobium leguminosarum bv. trifolii among Different Size Classes of Soil Aggregates

1998 ◽  
Vol 64 (3) ◽  
pp. 970-975 ◽  
Author(s):  
Ieda C. Mendes ◽  
Peter J. Bottomley
Keyword(s):  
Cover Crop ◽  
Rhizobium Leguminosarum ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Red Clover ◽  
Size Class ◽  
Most Probable Number ◽  
Probable Number ◽  
Size Classes ◽  
Soil Population

ABSTRACT A combination of the plant infection-soil dilution technique (most-probable-number [MPN] technique) and immunofluorescence direct count (IFDC) microscopy was used to examine the effects of three winter cover crop treatments on the distribution of a soil population ofRhizobium leguminosarum bv. trifolii across different size classes of soil aggregates (<0.25, 0.25 to 0.5, 0.5 to 1.0, 1.0 to 2.0, and 2.0 to 5.0 mm). The aggregates were prepared from a Willamette silt loam soil immediately after harvest of broccoli (September 1995) and before planting and after harvest of sweet corn (June and September 1996, respectively). The summer crops were grown in soil that had been either fallowed or planted with a cover crop of red clover (legume) or triticale (cereal) from September to April. The Rhizobiumsoil population was heterogeneously distributed across the different size classes of soil aggregates, and the distribution was influenced by cover crop treatment and sampling time. On both September samplings, the smallest size class of aggregates (<0.25 mm) recovered from the red clover plots carried between 30 and 70% of the total nodulatingR. leguminosarum population, as estimated by the MPN procedure, while the same aggregate size class from the June sampling carried only ∼6% of the population. In June, IDFC microscopy revealed that the 1.0- to 2.0-mm size class of aggregates from the red clover treatment carried a significantly greater population density of the successful nodule-occupying serotype, AR18, than did the aggregate size classes of <0.5 mm, and 2 to 5 mm. In September, however, the population profile of AR18 had shifted such that the density was significantly greater in the 0.25- to 0.5-mm size class than in aggregates of <0.25 mm and >1.0 mm. The populations of two otherRhizobium serotypes (AR6 and AS36) followed the same trends of distribution in the June and September samplings. These data indicate the existence of structural microsites that vary in their suitabilities to support growth and protection of bacteria and that are influenced by the presence and type of plant grown in the soil.

Fate of N in soil amended with 15N-labelled residues of winter cereals combined with an organic N fertiliser

Soil Research ◽  
2016 ◽  
Vol 54 (2) ◽  
pp. 182 ◽  
Author(s):  
Paola Gioacchini ◽  
Daniela Montecchio ◽  
Emanuela Gnudi ◽  
Valeria Terzi ◽  
Antonio Michele Stanca ◽  
...  
Keyword(s):  
Cover Crops ◽  
Crop Residues ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Soil Aggregate ◽  
Organic N ◽  
Initial Amount ◽  
Winter Cereals ◽  
One Year ◽  
Wet Sieving

In organic farming winter cereals, as cover crops, provide nutrients, when they return to soil as crop residues. The fate of N deriving from two decomposing 15N-labelled winter cereals, with or without the supply of an organic N fertiliser, was studied in a field experiment. The stabilisation of residues N in soil aggregates and the portion lost from the system were also evaluated. Barley or triticale residues were incubated alone or with hydrolysed leather (L) in mesocosms over one year. The residues derived N was measured in soil and in soil aggregate size fractions >250 μm (macroaggregates, macro); 53–250 μm (microaggregates, micro); <53 μm (silt and clay, s+c) obtained by wet sieving. Barley degradation (77% of the initial amount) was faster than triticale degradation (55%). The L slowed down the barley degradation (72%) and speeded that of triticale (64%). Greater amount of residues N was in macro and micro than in s+c. The presence of L reduced the residues N stabilised in the finest fractions. The losses of barley N were reduced by the L addition, those from triticale were increased. The fate of residues N was affected by the L application that influenced the residues mineralisation, the stabilisation and the losses of their derived N.

scholarly journals Study of soil aggregate breakdown dynamics under low dispersive ultrasonic energies with sedimentation and X-ray attenuation

2015 ◽  
Vol 29 (4) ◽  
pp. 501-508 ◽  
Author(s):  
Jasmin Schomakers ◽  
Franz Zehetner ◽  
Axel Mentler ◽  
Franz Ottner ◽  
Herwig Mayer
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Size Distribution ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Soil Aggregate ◽  
X Ray ◽  
Aggregate Size Distribution ◽  
Aggregate Breakdown ◽  
Wet Sieving

Abstract It has been increasingly recognized that soil organic matter stabilization is strongly controlled by physical binding within soil aggregates. It is therefore essential to measure soil aggregate stability reliably over a wide range of disruptive energies and different aggregate sizes. To this end, we tested highaccuracy ultrasonic dispersion in combination with subsequent sedimentation and X-ray attenuation. Three arable topsoils (notillage) from Central Europe were subjected to ultrasound at four different specific energy levels: 0.5, 6.7, 100 and 500 J cm-3, and the resulting suspensions were analyzed for aggregate size distribution by wet sieving (2 000-63 μm) and sedimentation/X-ray attenuation (63-2 μm). The combination of wet sieving and sedimentation technique allowed for a continuous analysis, at high resolution, of soil aggregate breakdown dynamics after defined energy inputs. Our results show that aggregate size distribution strongly varied with sonication energy input and soil type. The strongest effects were observed in the range of low specific energies (< 10 J cm-3), which previous studies have largely neglected. This shows that low ultrasonic energies are required to capture the full range of aggregate stability and release of soil organic matter upon aggregate breakdown.

scholarly journals Stability-energy relationships and their application to aggregation studies

1992 ◽  
Vol 72 (4) ◽  
pp. 453-466 ◽  
Author(s):  
L.G. Fuller ◽  
Tee Boon Goh
Keyword(s):  
Soil Aggregates ◽  
Energy Levels ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Order Rate Constant ◽  
Ultrasonic Dispersion ◽  
First Order ◽  
Energy Relationships ◽  
Stability Energy ◽  
Gray Luvisol

The objective of this study was to develop a method to describe aggregate stability-energy relationships using ultrasonic dispersion and to examine the role played by carbohydrate in soil aggregation. Aggregate size fractions (ASF) from three soils were sonified, and dispersed clay and solubilized carbohydrate measured at energy levels ranging from 0 to 1000 kJ L−1. Study soils included an Orthic Black, Orthic Dark Gray, and Orthic Gray Luvisol, representing the change from a prairie ecosystem to an aspen-forest ecosystem. Ultrasonic dispersion of aggregated clay resulted in characteristic "stability curves" for each ASF which obeyed a first-order decay curve and provided two parameters describing the release of clay from soil aggregates with increasing levels of applied energy: the "stability constant" k and the E1/2 value, which are analogous to a first-order rate constant and half-life, respectively. E1/2 values ranged from 51 to 502 kJ L−1.These values were smallest for the Ae horizon of the Orthic Gray Luvisol and greatest for the macroaggregates of the Ahe horizon of the Orthic Dark Gray. Carbohydrates solubilized upon aggregate destruction generally constituted a minor proportion (10%) of the total ASF carbohydrate, indicating that most of the carbohydrate was strongly adsorbed to surfaces. The development of a stability-energy relationship for aggregates provides a means to study the role of binding agents, such as carbohydrate, in the aggregation process. Key words: Aggregates, ultrasonic dispersion, clay, carbohydrate

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