Salt sieving within clay soil aggregates

Soil Research ◽  
1976 ◽  
Vol 14 (2) ◽  
pp. 149 ◽  
Author(s):  
AV Blackmore
Keyword(s):  
Clay Soil ◽  
Soil Aggregates ◽  
Normal Activity ◽  
Exchangeable Cation ◽  
High Concentration ◽  
Sodium Cations ◽  
Heavy Clay ◽  
Anion Exclusion ◽  
Cation Type ◽  
Negative Adsorption

The rates at which salt diffuses from the stable non-swelling aggregates of a heavy clay soil are studied in relation to both exchangeable cation type and free electrolyte content. Although the material is completely stable, it exposes a large clay surface of normal 'activity'. The results support a hypothesis that salt is constrained in some pores by salt-sieving within the aggregate; regions of anion exclusion, associated with surfaces in the narrower pores, restrict the cross section for diffusion from larger interior pores. It is shown that, when circumstances favour negative adsorption, that is with sodium cations and salt of relatively low concentration, salt is trapped within the microfabric; with calcium ions and salt of high concentration anion exclusion is suppressed and salt moves out of the aggregates much more easily. When the aggregates are in a saline sodic condition salt diffuses from them into saturated gypsum solution much more rapidly than it does into distilled water. This is in accord with the suggested model and implies that the ameliorative use of gypsum may involve a mechanism additional to those associated with swelling and flocculation. Application of the concept to soil in the field is briefly discussed.

Interpretation of electrical conductivity in a clay soil containing salts

Soil Research ◽  
1978 ◽  
Vol 16 (3) ◽  
pp. 311 ◽  
Author(s):  
AV Blackmore
Keyword(s):  
Electrical Conductivity ◽  
Clay Soil ◽  
Soil Aggregates ◽  
Exchangeable Cation ◽  
Simple Relationship ◽  
Stable Range ◽  
Soil Electrical Conductivity ◽  
Salt Exclusion ◽  
Exclusion Mechanism ◽  
Soil Conductivity

The use of directly measured electrical conductivity of soil to provide an index of soil salinity is discussed. It is suggested that if an anion exclusion mechanism within the microfabric of a wet clay soil can lead to a non-uniform, but stable, range of salt concentrations, then the validity of such an index would be jeopardized. Experiments involved the monitoring of soil electrical conductivity during leaching and diffusion of salts from stable clay-soil aggregates packed in columns and cells. The equilibrium values of conductivity are inversely related to exchangeable cation valence, but are not affected by the type of anion involved. The soil conductivity was often much smaller than the value inferred from the amount of salts actually extracted from the columns or contained in the small isolated electrical conductivity cells. The results are consistent with the operation of a salt exclusion mechanism in the smaller pores of the soil fabric. With monovalent cations and relatively low electrolyte concentrations, the trapping of salts within the microfabric is maximized, while in contrast, with aluminium and aged hydrogen clays the exclusion effect is almost completely suppressed, in accord with double-layer theory. If salts are retained against concentration gradients within the fine structure units of the soil, current-transmitting regions between the units are of correspondingly high resistance, and this is reflected in a soil electrical conductivity value that is low relative to the amount of electrolyte between the electrodes. The observed soil conductivity may, however, bear a simple relationship to the salt fraction of the soil actually 'available' to plant roots.

scholarly journals Effects of Initial Water Content on Microstructure and Mechanical Properties of Lean Clay Soil Stabilized by Compound Calcium-Based Stabilizer

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1933 ◽  
Author(s):  
Chenglong Yin ◽  
Wei Zhang ◽  
Xunli Jiang ◽  
Zhiyi Huang
Keyword(s):  
Water Content ◽  
Soil Stabilization ◽  
Clay Soil ◽  
Soil Aggregates ◽  
Optical Microscope ◽  
Initial Water Content ◽  
Reaction Products ◽  
Unconfined Compression Test ◽  
Initial Water ◽  
X Ray

Initial water content significantly affects the efficiency of soil stabilization. In this study, the effects of initial water content on the compressibility, strength, microstructure, and composition of a lean clay soil stabilized by compound calcium-based stabilizer were investigated by static compaction test, unconfined compression test, optical microscope observations, environment scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The results indicate that as the initial water content increases in the range studied, both the compaction energy and the maximum compaction force decrease linearly and there are less soil aggregates or agglomerations, and a smaller proportion of large pores in the compacted mixture structure. In addition, for specimens cured with or without external water supply and under different compaction degrees, the variation law of the unconfined compressive strength with initial water content is different and the highest strength value is obtained at various initial water contents. With the increase of initial water content, the percentage of the oxygen element tends to increase in the reaction products of the calcium-based stabilizer, whereas the primary mineral composition of the soil-stabilizer mixture did not change notably.

Investigation into the effect of tillage on solute movement to drains through a heavy clay soil

2006 ◽  
Vol 15 (2) ◽  
pp. 94-100 ◽  
Author(s):  
C.D. Brown ◽  
V.L. Marshall ◽  
A. Deas ◽  
A.D. Carter ◽  
D. Arnold ◽  
...  
Keyword(s):  
Clay Soil ◽  
Heavy Clay ◽  
Solute Movement

Investigations in crop husbandry. III. Effect of time of application of sulphate of ammonia to wheat

1936 ◽  
Vol 26 (2) ◽  
pp. 316-327 ◽  
Author(s):  
F. H. Garner ◽  
H. G. Sanders
Keyword(s):  
Field Experiments ◽  
Clay Soil ◽  
Foot Rot ◽  
Plant Establishment ◽  
Poor Condition ◽  
Time Of Application ◽  
Gravelly Soil ◽  
Heavy Clay ◽  
Crop Husbandry

1. Over a period of six years seven field experiments were carried out to study the effect of the time of application of sulphate of ammonia to autumn-sown wheat.2. Three experiments were located on light gravelly soil which had been farmed highly for some years, and in those three cases sulphate of ammonia decreased yield, irrespective of time of application; the reduction in yield was of the order of 10 per cent. and is ascribed to more lodging and greater incidence of “foot-rot”.3. Three experiments were located on heavy clay soil in poor condition; in these sulphate of ammonia gave percentage increases in yield of 18, 20 and 7.4. Evidence is produced that early dressings of sulphate of ammonia do not affect germination or plant establishment, but that they tend to increase tiller formation by the end of February.

scholarly journals Reclamation of a Saline-Sodic Soil by Use of Molasses and Distillery Slops

1969 ◽  
Vol 50 (3) ◽  
pp. 209-217
Author(s):  
Raúl Pérez Escolar
Keyword(s):  
Puerto Rico ◽  
Organic Acids ◽  
Clay Soil ◽  
Mass Action ◽  
Soil Reclamation ◽  
Exchangeable Sodium ◽  
Dry Period ◽  
Action Effect ◽  
Saturation Extract ◽  
Heavy Clay

Data are presented on a laboratory study conducted to determine the effects of the use of blackstrap molasses and rum distillery slops on the reclamation of a highly saline-alkali heavy clay soil of southwestern Puerto Rico. The study revealed that even the lowest levels of distillery slops and diluted molasses, around 2.3 acre-inch, were sufficient to lower the conductivity of the soil-saturation extract from 67 mmhos/cm. to less than 3, and the exchangeable sodium percentage from 43 to less than 1 percent. It is believed that most of the Ca and Mg found in leachates of columns treated with the most slops or molasses may be attributed to the production of organic acids during the decomposition of slops and molasses. These organic acids rendered soluble the soil-free CaCO3 and MgCO3, widening the Ca and Mg:Na ratio to substitute the sodium by a mass action effect. Subjecting the soil to a dry period in between, the 6 and 7 acre-feet of water did not alter the movement of water and resulted in a complete soil reclamation.

scholarly journals Surface irrigation with saline water on a heavy clay soil in the Medjerda Valley, Tunisia.

1967 ◽  
Vol 15 (4) ◽  
pp. 281-303
Author(s):  
J.A. Van 't Leven ◽  
M.A. Haddad
Keyword(s):  
Electrical Conductivity ◽  
Clay Soil ◽  
Saline Water ◽  
Surface Irrigation ◽  
Soil Extracts ◽  
Fallow Period ◽  
Salinity Effects ◽  
Heavy Clay ◽  
Winter Crops ◽  
Resting Period

On a clay soil rich in lime, with drain spacings of 30 and 60 m, one section (A) after four crops of artichokes over a two-year period, with fairly intensive irrigation with saline water (approx 700 mm annually) showed no harmful salinity effects; in the upper 120 cm the electrical conductivity of soil extracts (EC) seldom exceeded five. On section B, with well-distributed irrigation, which was not intensive except for tomatoes in one summer, salinity was fairly uniform in the profile (EC 4-6). In section C, under continuous lucerne and with 1000-1200 mm water annually, salinity increased, especially with depth, and a fallow period was needed. In section D, under four artichoke crops followed by maize, with more intensive irrigation than in A and B, EC of the 80-120 cm layer was 7-8, and maize growth was retarded slightly. In addition to fallowing, the inclusion in rotations of winter crops and of perennials with a resting period in summer, e.g. artichokes, is recommended. A drain spacing of 60 m was adequate. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Ethylene: A Witchweed Seed Germination Stimulant

Weed Science ◽  
1975 ◽  
Vol 23 (5) ◽  
pp. 433-436 ◽  
Author(s):  
Robert E. Eplee
Keyword(s):  
United States ◽  
Seed Germination ◽  
Clay Soil ◽  
Soil Surface ◽  
Field Studies ◽  
The United States ◽  
Major Contributor ◽  
Single Treatment ◽  
Striga Asiatica ◽  
Heavy Clay

Ethylene gas (C2H4) was found to stimulate the germination of witchweed [Striga asiatica(L.) O. Kuntze] seeds. Ethylene diffuses greater than 120 cm horizontally from point of injection and more than 90 cm below the soil surface. Rates of 0.42 kg/ha induced germination of witchweed seeds in sandy soil; but 1.1 kg/ha is required on a heavy clay soil. Witchweed seeds respond to ethylene after a period of preconditioning that is necessary to break dormancy. Under field conditions in the Carolinas, maximum response of seeds to ethylene occurs between late April and late July. Field studies indicate a 90% reduction in viable witchweed seeds occurs where a single treatment with ethylene has been applied. The use of ethylene appears now to be a major contributor toward the eventual eradication of witchweed from the United States.

Survival and Growth of Three Hardwood Species (Fraxinus angustifolia, Ulmus laevis and U. minor) on a BottomlandSite with Heavy Clay Soil

2007 ◽  
Vol 2 (2) ◽  
pp. 233-237 ◽  
Author(s):  
Emrah Cicek ◽  
Fahrettin Tilki ◽  
Semsettin Kulac ◽  
Murat Yilmaz ◽  
Faruk Yilmaz
Keyword(s):  
Clay Soil ◽  
Hardwood Species ◽  
Heavy Clay ◽  
Fraxinus Angustifolia ◽  
Survival And Growth ◽  
Ulmus Laevis
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