High Exchangeable Sodium Percentage Research Articles

Salt conditions and the effectiveness of poly(vinyl alcohol) in reclamation of saline‐sodic soils

AbstractFully hydrolysed poly (vinyl alcohol) (PVA) with molecular weight 14000 was effective in reducing or preventing clay dispersion when columns of mixed sand/Na‐soil aggregates containing a wide range of NaCl salt contents were leached with distilled water. The maximum effect was obtained over a range of soil salt contents in which the applied polymer remained soluble. Above this range, because of polymer precipitation, effectiveness was inversely related to salt content. For soil aggregates with different exchangeable sodium percentage (ESPs), PVA was also effective in reducing or preventing dispersion in water and maintaining the relative hydraulic conductivity of soil columns leached successively with diluted solutions. However, a further relationship was found which showed that the polymer was more effectively incorporated in soils with higher ESP. This was reflected in measurements of dispersion and may be explained by the greater effect of drying (at 70°C) and by the greater adsorption of PVA in the presence of exchangeable sodium than exchangeable calcium.

The engineering geology of clay minerals: swelling, shrinking and mudrock breakdown

AbstractSwelling, shrinking and physical breakdown processes are reviewed with reference to well-known mudrock and overconsolidated clay formations in the UK and USA. Swelling results from two processes: the equilibration of depressed porewater pressures following stress relief, and the physico-chemical (osmotic) response of component clay minerals. Expansion in Na-smectite, and to a lesser extent Ca-smectite, clays is governed by double-layer swelling, whereas in kaolinites it is purely a mechanical unloading phenomenon; illites show an intermediate response. Intraparticle swelling in mudrocks older than the Silurian in the UK, or Upper Mississippian in the USA, can be expected to be reduced because of the removal of expandable layers by burial diagenesis. Shrinkage, like mudrock breakdown, is restricted to the partly saturated zone. Suction pressure-moisture content curves of indurated mudrocks are shown to be different from mudrocks and clays with high proportions of expandable clay minerals. Classification of expansion potential based on activity ratio poses problems with indurated types, but with some modification of method reasonable predictions can be made. Controls on physical disintegration are identified as: (i) incidence of sedimentary structures and discontinuities, (ii) slaking (air breakage), (iii) expandable clay mineral content, especially smectite, and (iv) clay mineral fabric orientation. Exceptionally high exchangeable sodium percentages have been measured in Coal Measures rocks susceptible to breakdown.

Factors Affecting the Stability of Soil Crusts in Subsequent Storms

AbstractConflicting results exist concerning the effect of drying on the properties of soil crusts. In this study the hypothesis that the stability of crust to drying depends on the processes that predominate during its formation was tested by studying the effect of application of distilled (DW) and saline water (SW) (EC = 5 dS m−1) on the infiltration rates (IR) of a crusted soil surface. A Typic Rhodoxeralf and a Calcic Haploxeralf saturated with low (< 3.5) and high (17 < ESP < 20) exchangeable sodium percentages (ESP) were exposed to simulated rain of low and high energy levels. The soils were oven‐dried at 35°C for 24 and 72 h between consecutive storms. The stability of the crust was found to depend on the mechanisms of its formation. The crusts of soils with low ESP exposed to DW and SW rain and the crust of a soil with high ESP exposed to SW rain were found to be unstable and to be affected strongly by (i) the salinity of the rain water in subsequent storms, (ii) the impact energy of the raindrops, and (iii) the length of the drying period between consecutive storms. Conversely, a crust in which chemical dispersion supplemented physical dispersion (a soil with high ESP exposed to DW rain) was found to be stable and to be less affected by the water salinity of the subsequent storm, by its impact energy, or by the extent of drying between storms.

Effect of exchangeable sodium percentage and presubmergence on yield and nutrition of rice under field conditions

The effects of exchangeable sodium percentage (ESP) levels of 82, 72, 65 and 35 and 0, 15 and 30 days of presubmergence (submergence prior to the transplanting of rice) on yield and chemical composition of rice and availability of Fe, Mn, Zn and P in soil were studied factorially in a field experiment. Presubmergence increased rice yields at all ESP levels, the effect being more pronounced at high ESP's. Increasing ESP decreased yields and the contents of Ca, Mg, K, Fe, Mn, Zn and Cu but increased that of P and Na in the crop. Presubmergence enhanced absorption of all the above elements by the crop except P, K, Mg, Zn and Cu in the grain and decreased Na in grain and straw. Growing of rice under submerged conditions also facilitated the improvement of these soils. Effects of submergence and ESP on the availability of Fe, Mn, Zn and P in soil and their role in the nutrition of rice are discussed. The results suggest that 15 to 30 days presubmergence improved rice yields on a calcareous sodic soil of the Indo-Gangetic alluvial plain.

Some aspects of structural and alkalinity problems in spoil from an Ohai coal mine

Abstract Spoil from an Ohai opencast coal mine, pH 9.1, and of very poor structure, was found to have low concentrations of soluble salts associated with a high exchangeable sodium percentage (46%) and low organic matter content. A pot experiment was carried out in which hydrochloric acid and gypsum were applied to the spoil to improve the growth of barley plants. The HCl treatment decreased pH and improved structure, resulting in yield increases. The results are discussed in relation to electrolyte concentration in the soil solution and implications for reclamation of the spoil.

Effects of Drilling Fluids on Soils and Plants: II. Complete Drilling Fluid Mixtures

AbstractSix typical drilling fluids (muds) and a drilling fluid base were mixed with six soils at ratios of 1:1 and 1:4 volumes of liquid mud/soil; these mixtures were tested for their effects on plant growth. Green beans (Phaseolus vulgaris) and sweet corn [Zea mays var. succharata (Sturtev.) Bailey] in pots in the greenhouse grew normally in a few mixtures, but in most instances plants had reduced growth when compared to those growing in soil alone (controls). It was concluded that high levels of soluble salts or the high exchangeable sodium percentages were the primary causes of reduced plant growth.The high salt content in some fluids was mostly from added potassium chloride, sodium hydroxide, and sodium dichromate. Dispersion of mud‐treated soils caused by high exchangeable sodium percentages occurred in these samples because of the sodium hydroxide and sodium dichromate added to typical muds.

EFFECT OF FLUORINE AND PHOSPHORUS APPLIED TO A SODIC SOIL ON THEIR AVAILABILITY AND ON YIELD AND CHEMICAL COMPOSITION OF WHEAT

A replicated pot experiment was conducted to study the effect of five levels of fluorine (0, 25, 50, 100, and 200 ppm F) and four levels of phosphorus (0, 25, 50, and 100 ppm P), applied to a rice crop grown in soils of two sodicities, exchangeable sodium percentage (ESP) 30 and 70, on their transformations in soil and uptake by a subsequent wheat crop. Application of fluorine resulted in increased water-extractable fluorine in the soil, the relative increase being greater in soil of high ESP, which was associated with high pH. Fluorine uptake by plants increased linearly (r = 0.89) with increased water-extractable fluorine in the soil, and this resulted in a significant reduction in the wheat yield. A fluorine content of 35 ppm in mature wheat straw, which was associated with 22 ppm of water-extractable fluorine in the soil, was observed to be the critical concentration for grain yield. Higher uptake of fluorine by the plant resulted in increased uptake of sodium although composition in respect of other constituents remained unaffected. Application of both phosphorus and fluorine resulted in higher extractability of each other in soil, the relative increase being more at higher fluorine levels. The effect of phosphorus on soil fluorine was more marked at low than at high ESP. From the results it seems that while there is a positive effect of phosphorus on soil fluorine, it has a negative effect on its uptake by the plant. Increasing phosphorus in the soil and in the plant resulted in marked reduction in the chlorine content of the plant (r = 0.79).

EFFECT OF EXCHANGEABLE SODIUM ON THE FIELD-DRYING PATTERN OF SOIL AT TWO EVAPORATIVE DEMANDS

The drying pattern of two soils with exchangeable sodium percentages (ESP) of 4 and 38 in the surface 0–15-cm layer was studied in the field in winter and summer seasons when the average evaporative demands were 2.5 and 12.5 mm/day respectively. ESP significantly affected the magnitude and pattern of water content changes in the profile following evaporation. The surface layers of the high ESP soil, with a low upward water flux, dried more rapidly than the surface layer of low ESP soil. The total surface-water loss under both evaporative demands was higher from the low ESP soil than from the high ESP soil because the hydraulic conductivity was greater. For both ESP soils, cumulative water loss at any time was greater under conditions of high evaporative demand than under low evaporative demand conditions. The studies indicate that the adverse effect of high ESP on plant growth is likely to be accentuated under conditions of high evaporative demand, and this would make water management more demanding.

EXCHANGEABLE SODIUM AND SOIL WATER BEHAVIOR UNDER FIELD CONDITIONS

The effect of exchangeable sodium on soil water behavior under field conditions was investigated in five differentially gypsum treated plots of a highly sodic soil. The soil is representative of the sodic soils of the Indo-gangetic plains in northern India. The soil texture is sandy loam in the surface 0–15 cm and the clay fraction is dominantly illitic. Exchangeable sodium percentage (ESP) varied from 4 to 38 in 0–15 cm and 28 to 88 in the 15–30-cm layer. Basic intake rate of the soil increased from 8.7 mm per day in soil of highest ESP to about 25 mm per day in soil of lowest ESP. Higher basic intake rate and increased retention at low suctions resulted in greater profile water storage. Soil water diffusivity values (D) calculated from the water distribution following evaporation showed that at a water content of 0.22 cm3/cm3 while D (cm2/day) decreased from 34 to 26 when ESP increased from 4 to 11, the D value sharply decreased to 8 with a further rise in ESP to 16. Improvement in transmission characteristic resulting from lowered ESP was reflected in the drying pattern of soils. The first stage of drying was delayed in low ESP treatments compared to the high ESP treatment because of regular movement of water from lower layers to the surface to meet the evaporation demand. The effect of treatments on water movement was noticeable to a depth of 90 cm studied in these experiments, although the improvement in layers below 15 cm was very small in treatments receiving lower doses of gypsum.

GYPSUM AS AN AMELIORATING AGENT FOR SOLONETZIC SOILS IN ALBERTA

The application of gypsum to a number of Alberta solonetzic soils in laboratory studies resulted in significant physical and chemical improvements in all soils except those with very high exchangeable sodium percentages. Data obtained in threshold concentration studies indicate that gypsum is effective as an amendment for the amelioration of solonetzic soils only if the exchangeable sodium does not exceed 20–25 per cent of the total exchange capacity, assuming that the effective solubility of gypsum in the field is about one-half that of its saturated concentration.

Título en español.

Durante un reconocimiento de los suelos hecho recientemente en el Valle de Lajas, se observaron tumores o promontorios de los cuales mana una suspensión de suelo en agua. El área en cuestión está ubicada al noroeste de la laguna Guánica y en general se halla cubierta de una vegetación halofítica. Las baterías de pizómetros localizadas en el área indican una alta presión ascendente en toda esta área. Durante épocas de lluvia o cuando se está regando la caña en la vecindad del área afectada, la presión es tan fuerte que el agua asciende a través del suelo trayendo gran cantidad del mismo en suspensión. Los estudios sobre la composición mecánica del suelo de los tumores o promontorios y del suelo de sitios cercanos a los promontorios indican que la mayoría de las partículas en movimiento consiste de arcilla, con cantidades menores de limo y arena muy fina. Sin embargo, este movimiento está limitado, en su mayor grado, a las 48 pulgadas superficiales. Los niveles de materia orgánica y nitrógeno son más altos en el suelo de los sitios cercanos a los tumores que en el de los tumores mismos, pero en ambos casos hay una marcada reducción bajo las primeras 24 pulgadas de profundidad. La capacidad para el intercambio de cationes de los suelos de ambos sitios es moderadamente alta y predomina el sodio intercambiable con poco calcio, magnesio y potasio. El alto porcentaje de sodio intercambiable, conjuntamente con el bajo contenido de sales totales del suelo de los tumores, según lo indica la conductividad de los extractos del suelo, explican el alto grado de dispersión en que naturalmente se encuentra este suelo. Los porcentajes de saturación de humedad de estos suelos son extremadamente altos y en muchos casos pasan del cien por ciento. Esto se debe a su alto contenido de arcilla con estructuras cristalinas del tipo 2:1, la cual se expande y contrae.