Relative significance of electrolyte and cation exchange effects when gypsum Is applied to a sodic clay soil

Soil Research ◽  
1976 ◽  
Vol 14 (3) ◽  
pp. 361 ◽  
Author(s):  
J Loveday

The hydraulic conductivity of disturbed samples of a sodic clay taken from a field experiment at Benerembah, in the Riverina of New South Wales, was increased markedly by the addition of gypsum (at 12.5 t ha-1). This initial response is considered to result mainly from an electrolyte effect rather than from cation exchange. After three seasons of irrigation of cotton, essentially all the gypsum had dissolved and the response had declined very considerably. Residual cation exchange accounted for an increase of about 10% in exchangeable calcium, and a decrease of 20 % and 5 % in exchangeable sodium and magnesium contents respectively, in the top 30-40 cm. The exchange involved 40-50% of the calcium applied and represented, in terms of exchangeable sodium lost, a replacement efficiency of some 20-30%. Below 60 cm the situation was reversed with an apparent loss of exchangeable calcium and an increase in exchangeable sodium. Leaching of soluble calcium, magnesium and sodium chlorides, somewhat greater than that in normally tilled soil, occurred especially from between 40 and 120 cm in the gypsum treated-deep tilled soil. Soluble sulphate, on the other hand, was retained in the profile above 130 cm, in amounts about equal to that applied as gypsum. The soluble chlorides accumulated below 130 cm, including apparently the unaccounted applied calcium and exchangeable calcium lost from depths below 60 cm. Deep tillage alone enhanced leaching of soluble calcium and sodium in the upper 80 cm to a similar degree to that when combined with gypsum treatment.

1958 ◽  
Vol 38 (2) ◽  
pp. 105-115
Author(s):  
W. A. Ehrlich ◽  
R. E. Smith

The analysis of the principal horizons of 11 halomorphic profiles was undertaken in an attempt to ascertain, chiefly, the kind and quantity of soluble salts and exchangeable cations assumed to be the main causative agents in the formation of solonetzic soils in Manitoba. The results showed that water-soluble sodium was equal to or greater in quantity than water-soluble calcium or water-soluble magnesium; that exchangeable calcium followed closely by exchangeable magnesium dominated the exchange complexes; and that exchangeable sodium in excess of 15 per cent of the exchangeable cations was found only in some horizons of the Solonchak, Solonetz and Solodized-Solonetz soils in the Chesterfield Association.


1984 ◽  
Vol 64 (1) ◽  
pp. 139-146
Author(s):  
THERON G. SOMMERFELDT

The effects of soil and solution pH and Na:Ca ratio in solution on the exchangeable Na, Ca, and (Na + Ca) of a Na-saturated Dark Brown Chernozemic soil were studied. At soil pH 9.0, the exchangeable Na, Ca, and (Na + Ca) were 14.5, 25.4, and 21.8% greater than at soil pH 6.0. Solution pH (6.0–9.0) had small but statistically significant effects on the amount of Na and Ca adsorbed by the soil. The logarithm of exchangeable sodium percentage (ESP) was related to the Na fraction in the solution by a polynomial equation, log ESP = 0.93 [Na/(Na + Ca)]2 + 0.16 [Na/(Na + Ca)] + 0.82. Not only is replacement of exchangeable Na with Ca important in the reclamation of this soil, should it become sodic and have a high pH, but also lowering of its surface charge, through lowering of its pH, would be an important factor in its reclamation. It appears impractical to reduce soil pH by applying acidified irrigation water. Acidic amendments such as gypsum and sulfur may be more suitable. Key words: Cation exchange, solution pH, soil pH


Soil Research ◽  
1990 ◽  
Vol 28 (4) ◽  
pp. 539 ◽  
Author(s):  
CJ Chartres ◽  
RW Cumming ◽  
JA Beattie ◽  
GM Bowman ◽  
JT Wood

Samples were collected from unimproved road reserves and adjacent paddocks on a 90 km transect crossing red-brown earth soils in the west and red earth soils in the east. Measurements of pH in water and CaCl2 indicated that the red earths have been acidified by approximately 0.5 pH units over the last 30-40 years. Small increases in CaCl2-extractable A1 were also recorded for the acidified red earths. The red-brown earths do not appear to have been markedly affected by soil acidification to date. Clay mineralogical data and measurements of cation exchange capacity of the <2 �m fraction indicate that red-brown earths are better buffered against acidification than red earths. However, small differences in management practices and rainfall along the transect may also be partially responsible for differences in acidification between soil types.


Soil Research ◽  
2002 ◽  
Vol 40 (4) ◽  
pp. 615 ◽  
Author(s):  
W. H. Vance ◽  
B. M. McKenzie ◽  
J. M. Tisdall

Three hundred and six soil samples were classified for sodicity on the basis of exchangeable sodium percentage (ESP), and for spontaneous or mechanical dispersion on the basis of a dispersion test (Emerson 1991). Each sample was analysed for pH, electrical conductivity (EC), concentrations of exchangeable and soluble cations (Ca2+, Mg2+, Na+, K+), and concentration of organic carbon (OC). These variables were used to explain the sodicity and dispersive classifications of the 306 samples. Concentrations of exchangeable and soluble Ca2+, Mg2+, and Na+ along with EC and total cation concentration (TCC) significantly affected the sodicity and dispersion classification of the soil. A sodic soil was expected to disperse spontaneously, a non-sodic soil was not expected to disperse spontaneously. From this hypothesis the expected and observed dispersion class was compared with sodicity class. The expected result corresponded to the observed result 77% of the time and the hypothesis was accepted (P &lt; 0.001).


Soil Research ◽  
1996 ◽  
Vol 34 (2) ◽  
pp. 229 ◽  
Author(s):  
RE Liefering ◽  
CDA Mclay

Disposal of strongly alkaline industrial liquid wastes, which contain large monovalent cation concentrations, by means of land treatment systems is becoming increasingly common. This study investigated the effects of solutions with large monovalent cation concentrations and high pH on cation exchange properties in four New Zealand soils with different clay mineralogies. The soils were shaken with a range of concentrations (0–0.3 M) of NaOH, KOH, NaCl, and KCl. Cation exchange capacity (CEC) and exchangeable cations (Ca2+, Mg2+, K+, and Na+) were measured following shaking and washing procedures. Although the hydroxide solutions dissolved significant amounts of organic matter from all soils, there was still a net increase in CEC measured at all hydroxide concentrations. The magnitude of the CEC increase was dependent on hydroxide concentration. The increase in CEC is attributed to newly generated negative charge on surfaces which possess variable charge (i.e. pH dependent) characteristics such as edge sites of clay minerals, sesquioxides, and the undissolved organic matter remaining in the soil. In contrast to hydroxide solutions, no increase in CEC was measured in chloride-treated samples. Increases in the concentration of all treatment solutions resulted in increases in the exchangeable ion concentration of the index cation used in the treatment solution (either Na+ or K+) and decreases in concentration of the other three exchangeable cations. In general, higher exchangeable sodium percentage (ESP) values were measured in samples treated with NaOH than samples treated with NaCl at all concentrations. Similarly, higher exchangeable potassium percentage (EPP) was measured in samples treated with KOH than samples treated with KCl at all concentrations. The higher ESP and EPP values recorded when hydroxide solutions were used as treatments are attributed to the newly generated negative charges being counter-balanced by the monovalent index cation present in the treatment solution. It is suggested that existing equations commonly used to predict ESP and EPP values are unsuccessful for accurately predicting changes when soils are treated with hydroxide solutions, due to their inability to account for the newly generated exchange sites. The equations did, however, adequately predict the effects of both chloride solutions on ESP and EPP.


1997 ◽  
Vol 19 (1) ◽  
pp. 80 ◽  
Author(s):  
WS Semple ◽  
TB Koen

In some areas the increase of woody plants is a problem whereas in others, the lack of regeneration is viewed with a similar degree of concern. The experiments described in this paper were an attempt to further understand factors affecting regeneration of woody plants. The effect of seedbed on the emergence and survival of hopbush (Dodonaea viscosa ssp. angustissima) and on several species of Eucalyptus was evaluated at two sites in the Central West of New South Wales. Seed was sown in two springs, two summers and two autumns from 1990 to 1992 and seedlings monitored for 12 months after sowing. Seedbeds compared were prepared by cultivation, scalping, burning, applying herbicide (glyphosate) and mowinglgrazing (control). Following failure of surface sowing in spring 1990 and summer 1990191 due to poor seasonal conditions, all subsequent experiments included direct drilled controls. Emergents were recorded in most treatments in the four succeeding seasons but hopbush and eucalypts responded differently to treatments. Numbers of hopbush emergents and seedlings after 12 months were consistently higher following direct drilling into scalped seedbeds. In contrast, the maximum number of eucalypt emergents was not consistently associated with any seedbed type, though emergence was generally higher following direct drilling. However, higher numbers of eucalypt seedlings were present in scalped plots after 12 months. It was concluded that weed control following emergence was the main effect of seedbed preparation on the number of eucalypt seedlings present after 12 months. Though this also applied to hopbush. seedbeds which provided the opportunity of seed burial enhanced emergence. This was believed to be due to the breaking of seed dormancy.


1961 ◽  
Vol 12 (2) ◽  
pp. 273 ◽  
Author(s):  
JS Russell

Changes in the cation exchange complex are one of the secondary effects arising out of the increasing organic matter content of soils, due to the influence of phosphorus fertilizers on leguminous pastures. Analysis of solonetzic soils from the long-term Kybybolite P plots indicates that there is a close relation between organic matter increase and increases in cation exchange capacity. For each increase of 0.1 % soil nitrogen, there has been a corresponding increase of 3.48 m-equiv.jl00 g in cation exchange capacity. Associated with these changes there have been increases in the level of exchangeable calcium and exchangeable hydrogen. Changes in exchangeable calcium appear related to the amount and form of fertilizer or amendment applied. Where little calcium has been added, the increase in cation exchange capacity has been satisfied almost entirely by hydrogen, and base saturation has decreased. There appears to have been little upward movement of metal cations from the lower horizons to the surface by plants, possibly owing to the species involved, or to the intractable nature of the B horizon. The possible effects of changes in the cation exchange complex on plant growth are discussed. Also, the possibility of maintaining base saturation on infertile soils where cation exchange capacity is being increased, is examined.


1983 ◽  
Vol 23 (121) ◽  
pp. 181 ◽  
Author(s):  
SM Bromfield ◽  
RW Cumming ◽  
DJ David ◽  
CH Williams

Changes in soil pH, manganese and aluminium as a result of long periods under subterranean clover pasture were examined in soils formed on granite, basalt and sedimentary rocks near Goulburn, New South Wales. Decreases in the pH of yellow duplex soils formed on granite, sedimentary rocks and basalt had occurred to depths of 60, 40 and 30 cm, respectively. The smaller depth of acidification in the latter two soils is considered to be due to their shallower A horizons over well buffered, clay B horizons. Under the oldest pastures (55 years) the decreases exceeded one pH unit throughout the entire sampled depth (60 cm). In some soils, under old improved pastures, calcium chloride-extractable manganese had increased to more than 20 ppm throughout the 60 cm profile and to greater than 50 ppm in the surface 10 cm. These levels are considered toxic to sensitive plant species and the highest levels may be toxic to subterranean clover. The amounts of extractable manganese in soils appear to be determined by both pH and the amounts of reactive manganese. In general, the amounts of total and reactive manganese were appreciably higher in the soils of basaltic origin. Substantial increases in extractable and exchangeable aluminium had also accompanied the decrease in pH and, in the surface 10 cm, were greatest in the soils formed on sedimentary parent materials. In many of the soils under old improved pastures, exchangeable aluminium, as a percentage of the effective cation exchange capacity, now exceeds 12%, especially in the 5-10 cm layer, and is probably harmful to sensitive species. Increases in exchangeable aluminium also occurred below the surface 10 cm and, in the granitic soils under the oldest pastures, exchangeable aluminium accounted for 30-50% of the effective cation exchange capacity throughout the 5-50 cm soil depth. The adverse changes in pH, manganese and aluminium observed in this study can be expected to continue under many improved pastures and to generate soil conditions unsuitable for many agricultural plants. The use of lime to arrest or reverse these changes seems inevitable.


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