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J Letey

Bio: J Letey is an academic researcher. The author has contributed to research in topics: Soil water & Montmorillonite. The author has an hindex of 1, co-authored 1 publications receiving 545 citations.

Papers
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Journal ArticleDOI
01 Jan 1984
TL;DR: In this article, the main mechanism for hydraulic conductivity reduction in waters of medium to high exchangeable sodium percentage (ESP) values, if the solution concentration is above a critical (threshold) level, is discussed.
Abstract: The interaction between soil particles and the soil solution depends on the types and amounts of soil clays. Montmorillonite is the most reactive clay. Ca-clay forms tactoids (quasi crystals) and has limited swelling and dispersion. Na-clay forms single platelets and disperses freely. In a mixed Na/Ca system, “demixing” of the cations occurs as the Na ions concentrate on the external and the Ca ions on the internal surfaces of the tactoids. The demixing explains why a small percentage of exchangeable Na sharply increases the zeta potential and dispersion of montmorillonite clay. The hydraulic conductivity of a soil depends on both Na and the total salt concentration of the percolating solution. High hydraulic conductivity may be maintained, even at high exchangeable sodium percentage (ESP) values, if the solution concentration is above a critical (threshold) level. When waters of very low salt content are used, decreases in hydraulic conductivity and clay dispersion occur even in soils with low ESP values (<10). The main mechanism for hydraulic conductivity reduction in waters of medium to high salinity (replacecodegt0.5 dS/m) is clay swelling. High content of expansible clays increases the susceptibility of soils to intermediate (10

566 citations


Cited by
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Book ChapterDOI
01 Jan 1996
TL;DR: The origin of cation exchange capacity (CEC) lies in the negative charges carried by soil particles, usually clay, organic matter and sesquioxides as discussed by the authors, which fall into two distinct categories, being either permanent or variable.
Abstract: The origin of cation exchange capacity (CEC) lies in the negative charges carried by soil particles, usually clay, organic matter and sesquioxides. A full discussion of the origin and nature of these charges is presented in Chapter 41 (Zelazny et aI., 1996). Basically these charges fall into two distinct categories, being either permanent or variable (i.e., pH dependent) depending on whether or not ambient conditions (pH or salts) in the soil solution affect their magnitude. Much confusion in the literature concerning the measurement and interpretation of CEC has stemmed from the lack of recognition that these charges fall into two distinct categories exhibiting different behavior. These problems will be addressed in the discussion of the methods for the determination of CEC.

1,430 citations

Journal ArticleDOI
TL;DR: Examining soil processes that dictate the exact edaphic environment upon which root functions depend and can help in research on plant improvement is examined.
Abstract: Salinization is the accumulation of water-soluble salts in the soil solum or regolith to a level that impacts on agricultural production, environmental health, and economic welfare. Salt-affected soils occur in more than 100 countries of the world with a variety of extents, nature, and properties. No climatic zone in the world is free from salinization, although the general perception is focused on arid and semi-arid regions. Salinization is a complex process involving the movement of salts and water in soils during seasonal cycles and interactions with groundwater. While rainfall, aeolian deposits, mineral weathering, and stored salts are the sources of salts, surface and groundwaters can redistribute the accumulated salts and may also provide additional sources. Sodium salts dominate in many saline soils of the world, but salts of other cations such as calcium, magnesium, and iron are also found in specific locations. Different types of salinization with a prevalence of sodium salts affect about 30% of the land area in Australia. While more attention is given to groundwater-associated salinity and irrigation salinity, which affects about 16% of the agricultural area, recent investigations suggest that 67% of the agricultural area has a potential for "transient salinity", a type of non-groundwater-associated salinity. Agricultural soils in Australia, being predominantly sodic, accumulate salts under seasonal fluctuations and have multiple subsoil constraints such as alkalinity, acidity, sodicity, and toxic ions. This paper examines soil processes that dictate the exact edaphic environment upon which root functions depend and can help in research on plant improvement.

1,288 citations

Journal ArticleDOI
TL;DR: This paper reviews the different methods of measurement of soil aggregate stability used in the literature, paying attention to the conditions of sample collection in the field and sample preparation and treatmen's conditions.
Abstract: Soil aggregate stability is a crucial soil property affecting soil sustainability and crop production A broad outline of the processes and agents of aggregate formation and aggregate stabilization are presented and discussed in this review Aggregate stability is difficult to quantify and interpret The aim of aggregate stability tests is to give a reliable description and ranking of the behavior of soils under the effect of water, wind and management Numerous methods have been used to determine aggregate stability with varying success The different methodologies complicate the comparison among aggregate stability data It is also difficult to obtain a consistent correlation between aggregate stability and other important soil properties such as soil erodibility or crusting potential This paper reviews the different methods of measurement of soil aggregate stability used in the literature, paying attention to the conditions of sample collection in the field and sample preparation and treatmen

942 citations

Journal ArticleDOI
TL;DR: Two strategies have shown the potential to improve crop production under irrigated agriculture while minimizing the adverse environmental impacts and could be the key to future agricultural and economic growth and social wealth in regions where salt-affected soils exist and/or where saline-sodic drainage waters are generated.

465 citations