Towards a model for soil structural behavior

Soil Research ◽  
1991 ◽  
Vol 29 (6) ◽  
pp. 829 ◽  
Author(s):  
JP Quirk ◽  
RS Murray
Keyword(s):  
Soil Aggregates ◽  
Particle Interaction ◽  
Wheat Yield ◽  
Field Capacity ◽  
Threshold Concentration ◽  
Double Layers ◽  
Diffuse Double Layer ◽  
Sodic Soils ◽  
Desorption Isotherms

Clay particle interaction as mediated by water is considered within the context of attractive and repulsive inter-particle forces-van der Waals forces, ion correlation forces responsible for the potential minimum between Ca-clay particles, cation hydration, ion induced structural forces and diffuse double layer forces especially in relation to the threshold concentration concept. In relation to diffuse double layers, the surface potentials, as determined by co-ion exclusion, are shown to be near constant with respect to concentration. Consideration is also given to the nature of the matrix within which the interparticle forces operate, that is the domain and quasicrystal entities. The particle separations within these entities are defined by the application of the Kelvin equation to the low temperature N2 desorption isotherms. The close agreement between the surface areas obtained from the application of the BET equation to the nitrogen adsorption isotherm and the areas obtained from the desorption isotherms leads to the concept of intrinsic failure; that is the presence of pores external to domains and quasicrystals which permit ready access to the total surface area. The role of electrolyte concentration in controlling the permeability of sodic soils (the threshold concentration concept) is reviewed and discussed with respect to recent studies on the behaviour of red-brown earth soils. At a macroscopic level some consideration is given to the role of oxides and organic matter in stabilizing soil aggregates against slaking. The interaction of rainfall, structure and wheat yield for red-brown earth soils is discussed in terms of a critical rate of wetting which causes incipient failure. In relation to incipient failure the hypothesis is advanced, that the role of organic mater in protecting against slaking, is in strengthening coarse pores; it appears that the pores involved are those with a high probability of continuity and which are responsible for the rapid attainment of field capacity.

Soil permeability in relation to sodicity and salinity

1986 ◽  
Vol 316 (1537) ◽  
pp. 297-317 ◽  
Keyword(s):  
Irrigation Water ◽  
Soil Structure ◽  
Particle Interaction ◽  
Threshold Concentration ◽  
Double Layers ◽  
Soil Permeability ◽  
Clay Particles ◽  
Irrigation Practice ◽  
Repulsive Forces ◽  
Soil Colloids

Difficulties encountered in the irrigation of sodium-affected soils or in the reclamation of sodic—saline soils can be circumvented by controlling the electrolyte level in the irrigation water, which prevents deterioration of the soil structure. The threshold concentration concept simply expresses the minimum level of electrolyte required to maintain the soil in a permeable condition for a given degree of sodium saturation of the soil colloids. It is shown that decreases in permeability at concentrations below the threshold concentration are occasioned by increased clay-particle interaction owing to the extensive development of diffuse double layers which give rise to enhanced swelling. Mechanical failure is associated with this swelling and deflocculation of clay particles. This behaviour of sodium-affected soils is considered in relation to the operation of van der Waals forces, hydration forces and osmotic repulsive forces arising from the development of diffuse double layers on particle surfaces. Considerations of ion-exchange equilibria between particle surfaces and the soil solution (irrigation water) are discussed in relation to the threshold concentration concept, and the application of the concept in irrigation practice is illustrated by reference to several case histories.

scholarly journals THE ROLE OF FLAG LEAVES AND AWNS IN THE FORMATION OF WINTER WHEAT PRODUCTIVITY (REVIEW)

2018 ◽  
pp. 32-34 ◽  
Author(s):  
S. N. Gromova ◽  
P. I. Kostylev
Keyword(s):  
Winter Wheat ◽  
Leaf Surface ◽  
Wheat Yield ◽  
Complex Trait ◽  
Genetic System ◽  
Flag Leaves ◽  
Grain Productivity ◽  
Agricultural Yield ◽  
Yield Formation

The article presents the results of the conducted analysis of research works about the effect of size of flag leaves and awns on winter wheat productivity. The genetic potential of the variety, which can be realized on the basis of its biologic characteristics largely influences on its productivity. Productivity is a complex trait that is controlled by a complex genetic system closely connected with many factors of environment. The size and duration of assimilation surface are the most important components of biologic and agricultural yield of wheat. Many researchers showed that the amount and duration of photosynthesis by leaf surface are the main factors limiting productivity in the definite conditions of growing, and the size of leaf surface correlates with grain productivity. Photosynthetic parts of winter wheat include not only leaves, but also stems, heads, awns, etc. The conducted analysis of the literature showed that there is no consensus on the effect of flag leaves on wheat yield formation. Therefore it’s necessary to fulfill the study and evaluation of the part of flag leaves and awns in the formation of winter soft wheat productivity in the Rostov region.

scholarly journals Functionalized Silicon Electrodes Toward Electrostatic Catalysis

2021 ◽  
Vol 9 ◽  
Author(s):  
Long Zhang ◽  
Xiaohua Yang ◽  
Shun Li ◽  
JianMing Zhang
Keyword(s):  
Electric Fields ◽  
Silicon Surfaces ◽  
Double Layers ◽  
External Electric Fields ◽  
Space Charges ◽  
Surface Models ◽  
Solid Liquid ◽  
Static Electric Fields ◽  
Mediator Catalysis

Oriented external electric fields are now emerging as “smart effectors” of chemical changes. The key challenges in experimentally studying electrostatic catalysis are (i) controlling the orientation of fields along the reaction axis and (ii) finely adjusting the magnitudes of electrostatic stimuli. Surface models provide a versatile platform for addressing the direction of electric fields with respect to reactants and balancing the trade-off between the solubility of charged species and the intensity of electric fields. In this mini-review, we present the recent advances that have been investigated of the electrostatic effect on the chemical reaction on the monolayer-functionalized silicon surfaces. We mainly focus on elucidating the mediator/catalysis role of static electric fields induced from either solid/liquid electric double layers at electrode/electrolyte interfaces or space charges in the semiconductors, indicating the electrostatic aspects is of great significance in the semiconductor electrochemistry, redox electroactivity, and chemical bonding. Herein, the functionalization of silicon surfaces allows scientists to explore electrostatic catalysis from nanoscale to mesoscale; most importantly, it provides glimpses of the wide-ranging potentials of oriented electric fields for switching on/off the macroscale synthetic organic electrochemistry and living radical polymerization.

scholarly journals Spontaneous shrinking of soft nanoparticles boosts their diffusion in confined media

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Pierre-Luc Latreille ◽  
Vahid Adibnia ◽  
Antone Nour ◽  
Jean-Michel Rabanel ◽  
Augustine Lalloz ◽  
...  
Keyword(s):  
Double Layers ◽  
Transport Systems ◽  
Soft Particle ◽  
Significant Challenge ◽  
Deformable Particles ◽  
Long Range Interactions ◽  
Confined Media ◽  
Crowded Environments ◽  
Soft Nanoparticles

Abstract Improving nanoparticles (NPs) transport across biological barriers is a significant challenge that could be addressed through understanding NPs diffusion in dense and confined media. Here, we report the ability of soft NPs to shrink in confined environments, therefore boosting their diffusion compared to hard, non-deformable particles. We demonstrate this behavior by embedding microgel NPs in agarose gels. The origin of the shrinking appears to be related to the overlap of the electrostatic double layers (EDL) surrounding the NPs and the agarose fibres. Indeed, it is shown that screening the EDL interactions, by increasing the ionic strength of the medium, prevents the soft particle shrinkage. The shrunken NPs diffuse up to 2 orders of magnitude faster in agarose gel than their hard NP counterparts. These findings provide valuable insights on the role of long range interactions on soft NPs dynamics in crowded environments, and help rationalize the design of more efficient NP-based transport systems.

scholarly journals Earthworm Burrowing Activity and Its Effects on Soil Hydraulic Properties under Different Soil Moisture Conditions from the Loess Plateau, China

2020 ◽  
Vol 12 (21) ◽  
pp. 9303
Author(s):  
Shuhai Wen ◽  
Ming’an Shao ◽  
Jiao Wang
Keyword(s):  
Soil Moisture ◽  
Loess Plateau ◽  
Hydraulic Properties ◽  
Soil Depth ◽  
Soil Aggregates ◽  
Field Capacity ◽  
Soil Hydraulic Properties ◽  
The Loess Plateau ◽  
Burrowing Activity ◽  
Soil Hydraulic

Earthworm activity has become more important in the Loess Plateau, where hydrological processes are crucial for ecosystem sustainability. In this study, we conducted a laboratory microcosm experiment to determine the various burrowing activities of Eisenia fetida and their impact on the soil hydraulic properties in response to different levels of soil moisture (50%, 70%, 90% of field capacity) in two common soil types (loessial and Lou soil) obtained from the Loess Plateau. Burrowing activity of E. fetida increased with higher soil moisture and was greater in loessial than in Lou soil. Most burrowing activities occurred within the top 5 cm and decreased with increasing soil depth. Macropores and burrow branching, which are highly related to the earthworm burrowing, were more prevalent in wetter soil. Earthworms significantly altered the formation of large soil aggregates (AGL, diameter >2 mm) under different soil moistures and depths. Distinct earthworm burrowing activities, controlled by soil moisture, altered soil hydraulic properties. However, soil saturated hydraulic conductivity (Ks) showed little differences between different treatments due to the horizontal and high–branched burrows of E. fetida, although higher burrowing activities were found in wetter soil. Soil field capacity was highest in drier soil due to the less macropores and burrowing activities.

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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