SPECTRAL ANALYSIS OF MICROPENETROMETER DATA TO CHARACTERIZE SOIL STRUCTURE

1985 ◽  
Vol 65 (4) ◽  
pp. 789-804 ◽  
Author(s):  
C. D. GRANT ◽  
B. D. KAY ◽  
P. H. GROENEVELT ◽  
G. E. KIDD ◽  
G. W. THURTELL
Keyword(s):  
Spectral Analysis ◽  
Soil Structure ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Spatial Separation ◽  
New Approach ◽  
Low Resistance ◽  
Loose Packing ◽  
Tip Resistance ◽  
Resistance To Penetration

A micropenetrometer with a diameter similar in magnitude to that of a root is capable of measuring variations in tip resistance over distances as small as 0.1 mm. Measurements at this scale offer the potential of characterizing zones of high resistance to penetration and the frequency of occurrence of zones of low resistance which could be exploited by a growing root. Spectral analysis provides a new approach to characterizing soil structure and has been applied to the micropenetrometer tip resistance profiles obtained from beds of aggregates. Nine different aggregate size ranges were considered; the aggregate diameters varied from less than 0.36 mm to 6.4–12.8 mm. The analyses indicate that larger aggregates are more resistant to penetration. In addition, comparison of variance spectra among several of the aggregate sizes reveals information on the structural make up of soil aggregates, namely that larger aggregates are made up of smaller "component" aggregates which offer higher resistance when they occur in large aggregates than when they occur individually in loose packing. The use of spectral analysis also appears to provide information on the spatial separation of zones of low resistance which correlate with aggregate size if the aggregate diameters are larger than 1.6 mm. Key words: Soil strength, soil resistance to penetration, micropenetrometer, aggregate size

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.

Categories of soil structure based on mechanical behaviour and their evaluation using additions of lime and gypsum on a sodic Vertisol

Soil Research ◽  
1999 ◽  
Vol 37 (5) ◽  
pp. 903 ◽  
Author(s):  
K. Y. Chan ◽  
K. Y. Chan ◽  
A. R. Dexter ◽  
A. R. Dexter ◽  
D. C. McKenzie ◽  
...  
Keyword(s):  
Soil Structure ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Soil Aggregate ◽  
Tension Test ◽  
Wetting And Drying ◽  
The Matrix ◽  
Indirect Tension ◽  
Indirect Tension Test ◽  
Soil Behaviour

Measurements of soil aggregate strength were made using a simple crushing (indirect tension) test. The resulting values of strength were used to examine aspects of the internal structure of the soil aggregates. This was done using 2 methods: firstly, by studying the dependence of aggregate tensile strength on aggregate size; and secondly, by studying the variability of strength measurements made on aggregates of one size. Combination of the results from the 2 methods enables some new categories of soil behaviour to be defined. The new categories were evaluated using soil samples collected from a field experiment in which additions of lime and gypsum were made to a sodic Vertisol. The use of the new categories leads to the conclusion that the added compounds resulted in larger aggregates being weaker than the smaller aggregates. This was partly due to a greater amount of micro-cracking in the larger aggregates, and partly due to a greater weakening of the matrix within the larger aggregates. Both of these changes are consistent with the soil being more friable after the additions of the calcareous amendments. It was not possible to distinguish qualitatively between the effects of lime and gypsum. It is suggested that the amendments did not modify the soil structure directly, but that they increased the tendency of the soil to self-mulch in response to wetting and drying cycles.

scholarly journals Vulnerability of soil aggregates in relation to soil properties

2011 ◽  
Vol 48 (No. 8) ◽  
pp. 329-334
Author(s):  
L. Borůvka ◽  
M. Valla ◽  
H. Donátová ◽  
K. Němeček
Keyword(s):  
Soil Properties ◽  
Soil Structure ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Fine Sand ◽  
Mechanical Forces ◽  
Soil Characteristic ◽  
Fine Silt ◽  
Wetting And Drying ◽  
Humus Quality

Stability of soil structure represents an indicator of soil quality. The aim of this paper was to assess the effect of soil properties on structure vulnerability in an Orthic Luvisol. The aggregates were most vulnerable to fast wetting (mean K<sub>v1</sub>&nbsp;= 9.99, i.e. this effect can decrease the aggregate size 9.99 times). Lower destruction was caused by slow wetting and drying (K<sub>v2</sub>&nbsp;= 3.70) and mechanical forces (K<sub>v3</sub>&nbsp;= 1.67). Fine silt (particles of 0.002&ndash;0.01 mm) was the most important soil characteristic decreasing aggregate vulnerability (r = &ndash;0.334, &ndash;0.248, and &ndash;0.393 for K<sub>v1</sub>, K<sub>v2</sub>, and K<sub>v3</sub>, respectively). Silt (0.01&ndash;0.05 mm) increased vulnerability to fast wetting (r = 0.318). Very fine sand (0.05&ndash;0.1 mm) increased vulnerability to mechanical impacts (r = 0.307). Organic carbon decreased vulnerability only slightly. Humus quality was rather related to porosity. Higher moisture of samples in time of collection increased aggregate vulnerability. Multiple regression, used for description of the effect of basic soil properties, provided the best model for K<sub>v1</sub>&nbsp;(R<sup>2</sup>&nbsp;= 27.45%), the poorest for K<sub>v2</sub>&nbsp;(R<sup>2</sup>&nbsp;= 7.23%).

SORPTION OF CARBON AND PHOSPHORUS FROM LIQUID POULTRY MANURE BY SOIL AGGREGATES OF DIFFERING SIZE

1985 ◽  
Vol 65 (3) ◽  
pp. 467-473 ◽  
Author(s):  
V. K. BHATNAGAR ◽  
M. H. MILLER
Keyword(s):  
Soil Aggregates ◽  
Poultry Manure ◽  
Aggregate Size ◽  
Liquid Manure ◽  
Inorganic P ◽  
Supernatant Liquid ◽  
Extractable P ◽  
P Content ◽  
Manure Slurry ◽  
Total P

A series of laboratory experiments was conducted to determine the mechanism(s) responsible for a previously reported observation that addition of liquid manure to soil increased the NaHCO3-extractable P (Ext-P) of large aggregates (> 2 mm) more than that of smaller aggregates whereas addition of an inorganic P solution did not. Application of liquid poultry manure increased the total P, Ext-P and total C concentrations in large aggregates (> 2 mm) much more (> 2.5 ×) than that in small aggregates (< 1 mm). Addition of inorganic P solution or of supernatant liquid from a centrifuged manure slurry increased the P content of the large aggregates only slightly (1.2 ×). A greater increase in Ext-P in large aggregates was observed even when the smaller aggregates were purposely layered on top of the larger ones prior to addition of the liquid manure. A similar but less pronounced effect of aggregate size on increase in P or C concentration was observed when different sized aggregates were left in contact with an effectively infinite source of liquid manure for 24 h. It is concluded that the larger aggregates absorbed more of the bulk manure slurry than smaller aggregates. A partial sealing of small aggregates by particulates is suggested as a possible mechanism. Key words: Carbon, phosphorus, liquid manure, soil aggregates

Quality of soil from the nickel mining area of Southeast Sulawesi, Indonesia, engineered using earthworms (Pheretima sp.)

2021 ◽  
Vol 8 (4) ◽  
pp. 2995-3005
Author(s):  
Hasbullah Syaf ◽  
Muhammad Albar Pattah ◽  
Laode Muhammad Harjoni Kilowasid
Keyword(s):  
Tap Water ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Mining Area ◽  
Size Class ◽  
Soil Conditions ◽  
Total N ◽  
Organic C ◽  
Size Classes ◽  
Nickel Mining

Earthworms (Pheretima sp.) could survive under abiotic stress soil conditions. Furthermore, their activities as ecosystem engineers allow for the creation of soil biostructures with new characteristics. Therefore, this study aimed to investigate the effect of the abundance of Pheretima sp. on the aggregate size, physicochemistry, and biology of the topsoil from the nickel mining area of Southeast Sulawesi, Indonesia. It was carried out by first grouping their abundance into zero, two, four, six, and eight individuals per pot and then carrying out tests. The Pheretima sp. were then released onto the surface of the topsoil and mixed with biochar that was saturated with tap water in the pot overnight. The results showed that the abundance of the species had a significant effect on the size class distribution, and aggregate stability of the soil. Furthermore, the size of the soil aggregates formed was dominated by the size class 2.83 - 4.75 mm under both dry and wet conditions. Under dry conditions, three size classes were found, while under wet conditions, there were five size classes. The results also showed that the highest and lowest stability indexes occurred with zero and eight Pheretima sp., respectively. Furthermore, the abundance had a significant effect on pH, organic C, total N, CEC, and total nematodes. However, it had no significant effect on the total P, C/N ratio, total AMF spores, and flagellate. The highest soil pH occurred with zero Pheretima sp., while with six and two members of the species, the total nematode was at its highest and lowest populations, respectively. Therefore, it could be concluded that the species was able to create novel conditions in the topsoils at the nickel mining area that were suitable for various soil biota.

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.

scholarly journals Factors Determining Soil Water Repellency in Two Coniferous Plantations on a Hillslope

Forests ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 730 ◽  
Author(s):  
Moein Farahnak ◽  
Keiji Mitsuyasu ◽  
Kyoichi Otsuki ◽  
Kuniyoshi Shimizu ◽  
Atsushi Kume
Keyword(s):  
Soil Water ◽  
Overland Flow ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Water Repellency ◽  
Soil Aggregate ◽  
Water Infiltration ◽  
Soil Water Repellency ◽  
Tree Cutting ◽  
Coniferous Plantations

Soil water repellency (SWR) is a cause of low water infiltration, overland flow and soil erosion in mountainous coniferous plantations in Japan. The factors determining SWR intensity were investigated in two coniferous plantations of Chamaecyparis obtusa (Siebold et Zucc.) Endl. and Cryptomeria japonica (L.f.) D. Don, using intact tree plots and cut tree plots on the same hillslope. The SWR of Ch. obtusa plots was stronger than that of Cr. japonica plots. SWR intensity decreased after tree cutting. There were no significant differences in SWR upslope and downslope of individual trees/stumps for both tree species, though areas downslope of individual Ch. obtusa trees had higher SWR intensity than those upslope. SWR intensity and soil aggregate stability were positively correlated in the Ch. obtusa intact tree plot (r = 0.88, p < 0.01), whereas in the cut tree plot, this correlation was weak with no significance (r = 0.29, p = 0.41). Soil aggregate size had a non-significant influence on SWR intensity. These findings suggest that SWR intensity was not related to the soil aggregate size, but SWR intensity seemed have a role in soil aggregation in the Ch. obtusa intact tree plot. Destruction of soil aggregates could occur after tree cutting because of physical disturbances or increased input of different types of organic matter from other vegetation into soil. The presence of Ch. obtusa introduces a source of SWR, although uncertainty remains about how water repellency is distributed around soil aggregates. The distribution pattern of soil water content and soil hydraulic conductivity around Cr. japonica was related to other factors such as the litter layer and non-water-repellant soil.

scholarly journals Latent likelihood ratio tests for assessing spatial kernels in epidemic models

2020 ◽  
Vol 81 (3) ◽  
pp. 853-873
Author(s):  
David Thong ◽  
George Streftaris ◽  
Gavin J. Gibson
Keyword(s):  
Likelihood Ratio ◽  
Kernel Function ◽  
Control Strategies ◽  
Spatial Separation ◽  
Likelihood Ratio Tests ◽  
New Approach ◽  
Competing Models ◽  
Spatio Temporal ◽  
Fully Bayesian ◽  
The Relationship

Abstract One of the most important issues in the critical assessment of spatio-temporal stochastic models for epidemics is the selection of the transmission kernel used to represent the relationship between infectious challenge and spatial separation of infected and susceptible hosts. As the design of control strategies is often based on an assessment of the distance over which transmission can realistically occur and estimation of this distance is very sensitive to the choice of kernel function, it is important that models used to inform control strategies can be scrutinised in the light of observation in order to elicit possible evidence against the selected kernel function. While a range of approaches to model criticism is in existence, the field remains one in which the need for further research is recognised. In this paper, building on earlier contributions by the authors, we introduce a new approach to assessing the validity of spatial kernels—the latent likelihood ratio tests—which use likelihood-based discrepancy variables that can be used to compare the fit of competing models, and compare the capacity of this approach to detect model mis-specification with that of tests based on the use of infection-link residuals. We demonstrate that the new approach can be used to formulate tests with greater power than infection-link residuals to detect kernel mis-specification particularly when the degree of mis-specification is modest. This new tests avoid the use of a fully Bayesian approach which may introduce undesirable complications related to computational complexity and prior sensitivity.

THE INTERPRETATION OF AEROMAGNETIC SURVEYS FOR HYDROCARBON EXPLORATION

1999 ◽  
Vol 39 (1) ◽  
pp. 494
Author(s):  
I. Kivior ◽  
D. Boyd
Keyword(s):  
Spectral Analysis ◽  
Sedimentary Basins ◽  
Hydrocarbon Exploration ◽  
Petroleum Exploration ◽  
Magnetic Data ◽  
Curve Matching ◽  
Aeromagnetic Data ◽  
Profile Data ◽  
Aeromagnetic Survey ◽  
New Approach

Aeromagnetic surveys have been generally regarded in petroleum exploration as a reconnaissance tool for major structures. They were used commonly in the early stages of exploration to delineate the shape and depth of the sedimentary basin by detecting the strong magnetic contrast between the sediments and the underlying metamorphic basement. Recent developments in the application of computer technology to the study of the earth's magnetic field have significantly extended the scope of aeromagnetic surveys as a tool in the exploration for hydrocarbons. In this paper the two principal methods used in the analysis and interpretation of aeromagnetic data over sedimentary basins are: 1) energy spectral analysis applied to gridded data; and, 2) automatic curve matching applied to profile data. It is important to establish the magnetic character of sedimentary and basement rocks, and to determine the regional magnetic character of the area by applying energy spectral analysis. Application of automatic curve matching to profile data can provide results from the sedimentary section and deeper parts of a basin. High quality magnetic data from an experimental aeromagnetic survey flown over part of the Eromanga/Cooper Basin has recently been interpreted using this new approach. From this survey it is possible to detect major structures such as highs and troughs in the weakly magnetic basement, as well as pick out faults, and magnetic layers in the sedimentary section. The results are consistent with interpretation from seismic and demonstrate that aeromagnetic data can be used to assist seismic interpretation, for example to interpolate between widely spaced seismic lines and sometimes to locate structures which can not be detected from seismic surveys. This new approach to the interpretation of aeromagnetic data can provide a complementary tool for hydrocarbon exploration, which is ideal for logistically difficult terrain and environmentally sensitive areas.

The effect of krilium soil conditioner on the yield of wheat

1964 ◽  
Vol 4 (15) ◽  
pp. 363
Author(s):  
TC Stoneman
Keyword(s):  
Field Trial ◽  
Soil Structure ◽  
Soil Aggregates ◽  
Wheat Yield ◽  
Water Stability ◽  
Soil Conditioner ◽  
Barrel Medic

A field trial investigated the effect of improved soil structure on wheat yield. Krilium, a synthetic polyelectrolyte soil conditioner, was used to improve structure. The water stability of the soil aggregates was significantly increased on the plots treated with the conditioner. The conditioner treated plots also had significantly higher yields and 1000-grain weights than the untreated plots. The effect of the soil conditioner persisted into the year after cropping, when the plots were sown to Barrel Medic (Medicago tribuloides Desr.). The Barrel Medic establishment was significantly greater on the conditioner treated plots.

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