Relationship between Aggregate Stability Indices of Four Contrasting Textural Classes of Soils as Influenced by different Periods of Soaking

2017 ◽  
Vol 4 (4) ◽  
pp. 036-045
Author(s):  
I.A. Nweke ◽  
◽  
A.C. Ijeh ◽  
Keyword(s):  
Aggregate Stability ◽  
Stability Indices

scholarly journals Soil Sensitivity to Wind and Water Erosion as Affected by Land Use in Southern Iran

Earth ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 287-302
Author(s):  
Hasan Mozaffari ◽  
Mahrooz Rezaei ◽  
Yaser Ostovari
Keyword(s):  
Land Use ◽  
Wind Erosion ◽  
Aggregate Stability ◽  
Water Erosion ◽  
Land Use Management ◽  
Southern Iran ◽  
Land Use Types ◽  
Mean Weight Diameter ◽  
Wind And Water Erosion ◽  
Stability Indices

Land degradation by soil erosion is one of the most severe environmental issues that is greatly dependent on land use management. In this study, the effects of long-term land use management (including annual cultivated field (ACF), fallow field (FF), rangeland (R), and orchard field (OF)), soil depth (0–10 and 10–20 cm), and soil organic matter content (SOM) on wind- and water-erosion indices were investigated in calcareous soils of southern Iran. Soil samples were collected from four above-mentioned land-use types, and some soil properties and erosion indices were measured. Results showed that the most of soil aggregates stability indices in the surface layer (0–10 cm) of OF were higher than those in ACF, FF, and R, respectively, by nearly 39%, 32%, and 47% for dry mean weight diameter of aggregates (MWDdry); 10%, 10%, and 48% for dry geometric mean weight diameter of aggregates (GMDdry); 21%, 17%, and 15% for water-stable aggregates (WSA); and 11%, 16%, and 31% for aggregate stability index (ASI). Moreover, the mean of the soil wind erosion indicators in OF (0–10 cm) were lower than those in ACF, FF, and R, respectively, by nearly 18%, 24%, and 26%, for wind-erodible fraction (EF); 43%, 38%, and 49% for soil erodibility to wind erosion (K); and 36%, 32%, and 41% for wind erosion rate (ER). In ACF, despite the high clay content, some aggregate stability indices such as MWøDdry and WSA were the lowest among studied land-use types which showed the negative effects of conventional tillage practices. Depth factor had only a significant effect on dust emission potential (DEP) in ACF, FF, and OF. In addition, there were significant and strong correlations between SOM and MWDdry (r = 0.79), WSA (r = 0.77), EF (r = −0.85), K (r = 0.74), and ER (r = 0.74) in all datasets.

scholarly journals Micro-aggregate Indices and Structural stability of Soils under Different Management

2018 ◽  
pp. 66-71
Author(s):  
Udom B.E ◽  
Anozie H.
Keyword(s):  
Structural Stability ◽  
Oil Palm ◽  
Aggregate Stability ◽  
Rubber Plantation ◽  
Physical Conditions ◽  
Oil Palm Plantation ◽  
Continuous Maize ◽  
Intensity Of Cultivation ◽  
Land Use And Management ◽  
Stability Indices

Low water stability of soil micro-aggregates accentuated by increased intensity of cultivation and soil degradation are among the significant issues that draw the atten- tion of Soil Scientists due to their effects on soil physical conditions. The study was carried out to quantify changes in micro-aggregate stability indices of soils on coastal plain sands under contrasting land use and management. Soil samples were collected from cassava plots, plantain, maize, rubber plantation, oil palm and 2-season fallow plots with Calapogonium mucunoides. Results revealed significant changes in micro-and macro-aggregate stability indices. Clay dispersion index (CDI) was 0.46 and 0.39 respectively in cassava and maize plots. Parameters such as aggregated silt and clay (ASC), clay flocculation index (CFI) and saturated hydraulic conductivity (Ksat) used as estimates of soil structural stability were significantly (p < 0.05) increased due to 2-season fallow and 10-year oil palm plantation. Two-year fallow increased ASC and CFI by 57 % and 86.5% respectively compared with continuous maize culti- vation. Ten-year cultivation to cassava and maize increased sand content by 18 and 9% respectively and decreased the mean weight diameter (MWD) of water stable aggregates and Ksat. Relationships showed significant (p < 0.05) positive correlation between ASC and CFI and Ksat. Two-year fallow with Calapogonium mucunoides and 10-year oil palm plantation improved the soil micro- and macroaggregate indices. They could be used to conserve the soil and reduce the degradation of soil resources.

Estimation of aggregate stability indices in Mediterranean soils by diffuse reflectance spectroscopy

Geoderma ◽  
2010 ◽  
Vol 158 (1-2) ◽  
pp. 78-84 ◽  
Author(s):  
J.C. Cañasveras ◽  
V. Barrón ◽  
M.C. del Campillo ◽  
J. Torrent ◽  
J.A. Gómez
Keyword(s):  
Diffuse Reflectance ◽  
Diffuse Reflectance Spectroscopy ◽  
Aggregate Stability ◽  
Reflectance Spectroscopy ◽  
Mediterranean Soils ◽  
Stability Indices

Lack of Stability of Aggregates after Thrombin-Induced Reaggregation of Thrombin-Degranulated Platelets

1992 ◽  
Vol 67 (04) ◽  
pp. 453-457 ◽  
Author(s):  
Raelene L Kinlough-Rathbone ◽  
Marian A Packham ◽  
Dennis W Perry ◽  
J Fraser Mustard ◽  
Marco Cattaneo
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Aggregate Stability ◽  
Relative Importance ◽  
Platelet Aggregates ◽  
The Stability ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

SummaryThe stability of platelet aggregates is influenced by the extent of the release of granule contents; if release is extensive and aggregation is prolonged, deaggregation is difficult to achieve. The relative importance of the contributions of released substances to aggregate stability are not known, although stable thrombin-induced aggregates form in platelet-rich plasma from patients with barely detectable plasma or platelet fibrinogen, and ADP stabilizes thrombin-induced aggregates of platelets from patients with delta storage pool deficiency which otherwise deaggregate more readily than normal platelets. We degranulated platelets with thrombin (0.9 U/ml caused greater than 90% loss of delta and alpha granule contents) and recovered them as individual platelets in fresh medium. The degranulated platelets were reaggregated by thrombin (2 U/ml). To prevent continuing effects of thrombin, FPRCH2C1 was added when thrombin-induced aggregation of thrombin-degranulated platelets reached its maximum. EDTA (5 mM) or EGTA (5 mM) added at maximum aggregation did not deaggregate these platelets, indicating that the stability of these aggregates does not depend on Ca2+ in the medium. Whereas with control platelets a combination of PGE1 (10 μM) and chymotrypsin(10 U/ml) was required for deaggregation, with thrombin-degranulated platelets either PGE1 or chymo-trypsin alone caused extensive deaggregation. The rate and extent of deaggregation of thrombin-degranulated platelets by a combination of PGE1 and chymotrypsin was greater than with control platelets.Electron microscope gold immunocytochemistry using antihuman fibrinogen IgG, anti-von Willebrand factor and anti-fibronectin showed a) that fibrinogen in the vacuoles of degranulated platelets was visible at focal points of platelet contact in the aggregates, but that large areas of platelet contact had no fibrinogen detectable between them; and b) in comparison to fibrinogen, little fibronectin or von Willebrand factor (vWf) was detectable in the platelets.Since the linkages between thrombin-degranulated platelets reaggregated by thrombin can be disrupted either by raising cAMP (thus making glycoprotein IIb/IIIa unavailable) or by proteolysis, these linkages are less stable than those formed between normal platelets. It might therefore be expected that platelets that take part in thrombus formation and then recirculate are likely to form less stable thrombi than platelets that have not released their granule contents.

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