Exchange and solution phase chemistry of acid, highly weathered soils .I. Characteristics of soils and the effects of lime and gypsum amendments

Soil Research ◽  
1994 ◽  
Vol 32 (2) ◽  
pp. 251 ◽  
Author(s):  
NW Menzies ◽  
LC Bell ◽  
DG Edwards
Keyword(s):  
Soil Solution ◽  
Exchange Capacity ◽  
Solution Phase ◽  
Exchangeable Cation ◽  
Solution Ph ◽  
Ph Change ◽  
Median Concentration ◽  
Surface Samples ◽  
Weathered Soils ◽  
Highly Weathered Soils

Exchange and solution phase characteristics were evaluated on surface and subsoil horizons of 60 acid, highly weathered soils in the unamended state, and on 39 of the surface horizons following addition of CaCO3 or CaSO4.2H2O. Soil solutions from unamended surface samples were dominated by Na (median concentration 0.65 mM), while the other major cations were present at lower levels (median concentrations: Ca, 0.09; Mg, 0.14; K, 0.28 mM). This pattern was more pronounced in the subsoil samples where the median concentrations of the nutrient cations were < 0.05 mM, whereas the median concentration of Na was 0.28 mM. The cation exchange capacity of surface samples was dominated by Ca, Mg and Al, while Al was the major exchangeable cation in the subsoil. Addition Of CaSO4.2H2O decreased soil solution pH and increased electrical conductivity and the concentration of Ca, Mg, Na, K and Al in the soil solution. The soil solution pH change resulting from CaSO4.2H2O addition could not be predicted on the basis of the characteristics of the soil in the unamended state.

Exchange and solution phase chemistry of acid, highly weathered soils .I. Investigation of mechanisms controlling Al release into solution

Soil Research ◽  
1994 ◽  
Vol 32 (2) ◽  
pp. 269 ◽  
Author(s):  
NW Menzies ◽  
LC Bell ◽  
DG Edwards
Keyword(s):  
Soil Solution ◽  
Solid Phase ◽  
Solution Phase ◽  
Strongly Correlated ◽  
Solution Ph ◽  
Surface Soils ◽  
Weathered Soils ◽  
Highly Weathered Soils ◽  
Phase Chemistry ◽  
Soil Solid Phase

Soil solid phase and soil solution characteristics were evaluated on surface and subsoil horizons of 60 acid, highly weathered soils in the unamended state, and on a subset of 39 surface horizons following the addition of CaSO4.2H2O. The activity of Al3+ Was found to be strongly correlated with the soil solution pH, with Al3+ activity increasing as pH decreased. For surface soils in the unamended state, and for the majority of subsoils, the Al3+ activity calculated was comparable to the theoretical activity supported by the dissolution of gibbsite (Al2O3.3H2O). The Al3+ activity in CaSO4.2H2O-amended samples tended to fall below that maintained by gibbsite dissolution and was more closely correlated with the Al3+ activity supported by the dissolution of jurbanite (AlSO4 (OH).5H2O).

Dissolution behaviour of soil kaolinites in acidic solutions

Clay Minerals ◽  
2013 ◽  
Vol 48 (3) ◽  
pp. 447-461 ◽  
Author(s):  
K. Khawmee ◽  
A. Suddhiprakarn ◽  
I. Kheoruenromne ◽  
I. Bibi ◽  
B. Singh
Keyword(s):  
Steady State ◽  
Dissolution Rate ◽  
Initial Period ◽  
Reference Sample ◽  
Stoichiometric Ratio ◽  
Solution Ph ◽  
Weathered Soils ◽  
Dissolution Behaviour ◽  
Georgia Kaolinite ◽  
Highly Weathered Soils

AbstractHighly weathered soils of the tropics and subtropics commonly have kaolinitedominated clay fractions. Under acidic conditions prevailing in these soils kaolinite dissolution occurs, contributing to the high levels of soluble Al in these soils. This study evaluates the dissolution behaviour of kaolinites from subsurface horizons of highly weathered soils from Thailand, along with a soil kaolinite from Western Australia (WA kaolinite) and Georgia kaolinite (KGa-2). Kaolinite-dominated clay fractions were isolated from soils by sedimentation and chemically treated to remove iron oxides. The dissolution rate of kaolinites was measured in 0.01 M NaCl as a function of pH (1–4; HCl) at 25±1°C using non-stirred flow-through reactors. Kaolinite dissolution rates were calculated from the release of Al and Si at the steady state. In most of the experiments and at all pH values, the release of both Si and Al underwent a distinct transition from an initial period of rapid release to significantly slower release at the steady state. Aluminium and Si concentrations at the steady state were higher for soil kaolinites than the reference sample (KGa-2). At the steady state the dissolution of all kaolinites was stoichiometric except for the soil kaolinites from Thailand at pH 4, where the Al/Si ratio was well below the stoichiometric ratio. Log dissolution rate (RSi) of soil kaolinites ranged from –13.75 to –12.51, with the dissolution rate increasing significantly with decreasing solution pH. However, the dissolution rate was similar or pH independent between pH 2 and 3, which is the pH range of the point of zero net charge (PZNC) for both soil and reference kaolinites. The dissolution rate of soil kaolinite was significantly higher than the KGa-2 sample at pH < 3. The results obtained on kaolinite samples from highly weathered soils show that in highly acidic systems kaolinite is a source of soluble Al. Soil kaolinites with poorly ordered small crystals dissolve faster than better crystalline reference kaolinite (KGa-2) with larger crystals.

Effects of aluminium and calcium in the soil solution of acid soils on root elongation of Glycine max cv. Forrest

1988 ◽  
Vol 39 (3) ◽  
pp. 319 ◽  
Author(s):  
RC Bruce ◽  
LA Warrell ◽  
DG Edwards ◽  
LC Bell
Keyword(s):  
Root Growth ◽  
Soil Solution ◽  
Soil Ph ◽  
Activity Ratio ◽  
Acid Soils ◽  
Exchange Capacity ◽  
Al Toxicity ◽  
Solution Ph ◽  
Diagnostic Indices ◽  
Exchangeable Ca

In the course of three experiments, soybean (Glycerine max (L.) Merr.) cv. Forrest was grown in 21 soils (four surface soils and 17 subsoils) amended with liming materials (CaCO3 and Mg CO3) and soluble Ca salts (CaSO4.2H20 and CaCl2.2H2O). In most soils, the soluble salts increased concentrations and activities of Al species in solution to levels that restricted root growth, and MgCO3, induced a Ca limitation to root growth. Root lengths after three days were related to so11 and soil solution attributes.Suitable diagnostic indices for the prediction of Ca limitations to root growth were either Ca saturation of the effective cation exchange capacity or Ca activity ratio of the soil solution, which was defined as the ratio of the activity of Ca to the sum of the activities of Ca, Mg, Na, and K. Values corresponding to 90% relative root length (RRL) of soybean were 0.05 for the Ca activity ratio and 11% for Ca saturation. Calcium activity and Ca concentration in the soil solution and exchangeable Ca were less useful for this purpose.Soil Al saturation was not a good predictor of Al toxicity, but soil solution measurements were. The activities of Al3+ and AlOH2+ gave the best associations with RRL, and values corresponding to 90% RRL were 4 8M and 0.5 8M respectively. The results suggested that Al(OH)3� , Al(OH)2+, and AlSO4+, were not toxic species. Soil solution pH and soil pH measured in water were more sensitive indicators of root growth than soil pH measured in 0.01 M CaCl2.Using a Ca activity ratio of 0.05 and an Al3+ activity of 4 8M as diagnostic indices, none of the 20 soils in two experiments were toxic in Al, while 13 (all subsoils) were deficient in Ca. Thus the first limitation on root growth was Ca deficiency and not Al toxicity, in spite of high Al saturations and relatively low pH in these soils. However, Al toxicity could be induced by increasing the ionic strengths of soil solutions.

A laboratory study of application of basalt dust to highly weathered soils: effect on soil cation chemistry

Soil Research ◽  
2001 ◽  
Vol 39 (4) ◽  
pp. 799 ◽  
Author(s):  
G. P. Gillman ◽  
D. C. Burkett ◽  
R. J. Coventry
Keyword(s):  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Room Temperature ◽  
Base Cations ◽  
Exchange Capacity ◽  
Weathered Soils ◽  
Soil Cation Exchange Capacity ◽  
Additional Base ◽  
Highly Weathered Soils ◽  
Considerable Period

Surface (0–10 cm) samples from 7 highly weathered soils in tropical coastal Queensland were incubated for 3 months at room temperature and at field moisture capacity with basalt dust applied in 2 size fractions: <150 µm and 40 µm. The basalt application was mixed at 0, 1, 5, 25, and 50 t/ha to cover situations of moderate applications as well as where the amendment might be banded to achieve high local concentrations. Basalt dust application caused desirable increases in soil pH, reduced the content of exchangeable acidic cations, increased soil cation exchange capacity, and increased the content of base cations in all soils. By determining fundamental surface charge characteristics of these variable charge soils, it was possible to show that the additional base cations released from the basalt dust were present as exchangeable cations, and that the amounts released were controlled by the number of negatively charged sites available, i.e. soil cation exchange capacity. Selected treatments were then subjected to a strong leaching environment to assess the longevity of the effects obtained. Soil properties remained virtually unchanged by the leaching treatment, except that significant amounts of monovalent K and Na were removed. At the higher rates of application, the amounts of base cations released from the basalt were small in comparison with the actual amounts applied, indicating that the amendment could be effective over a considerable period of time.

Soil solution pH measurements using in-line chambers with tension lysimeters

2000 ◽  
Vol 80 (2) ◽  
pp. 283-288 ◽  
Author(s):  
Bo Elberling ◽  
Bjarne H. Jakobsen
Keyword(s):  
Soil Solution ◽  
Soil Acidification ◽  
Solution Ph ◽  
Ph Change ◽  
Ph Measurements ◽  
Partial Pressures ◽  
Arctic Soil ◽  
Soil Solutions ◽  
Speciation Modelling ◽  
Ph Range

During soil water extraction, pH can change as a result of atmospheric gas exchange. The pH change is important for monitoring soil acidification and determination of mineralogic controls on the solution composition. As part of a global change programme in Greenland for monitoring long-term changes in Arctic soil solutions we observed that the pH of extracted soil solutions increased in the order of a half pH unit during traditional sampling and handling of the soil solution. CO2 degassing is often considered the most important factor causing such a pH increase. Thus, traditional as well as in-line pH measurements were performed during the summers 1997 and 1998. The in-line method was designed to eliminate atmospheric contact with soil solutions prior to pH measurements. The time-dependent pH error was quantified based on laboratory experiments with soil solution under controlled temperatures and CO2 partial pressures. Equilibrium speciation modelling was used to predict pH values observed in the field and in the laboratory and the model was found to reproduce the observations well. We conclude that traditional pH measurements on extracted soil solutions in the pH range from 5 to 7 are not appropriate for detailed pH measurements due to errors associated with CO2 degassing. In-line measurements provide more accurate measurement necessary for detailed studies on soil acidification dynamics. Key words: pH, carbon dioxide degassing, soil solution, tension lysimeter, arctic soil

Modification to the compulsive exchange method for measuring exchange characteristics of soils

Soil Research ◽  
1986 ◽  
Vol 24 (1) ◽  
pp. 61 ◽  
Author(s):  
GP Gillman ◽  
EA Sumpter
Keyword(s):  
Anion Exchange ◽  
Calcareous Soils ◽  
Acid Soils ◽  
Exchange Capacity ◽  
Exchange Method ◽  
Weathered Soils ◽  
American Society ◽  
Highly Weathered Soils

The compulsive exchange method for the measurement of cation and anion exchange capacities of soil as described by Gillman and subsequently recommended by the American Society of Agronomy for acid soils has been modified to achieve greater simplicity. Though originally intended for the measurement of highly weathered soils, the method has be extended to saline and non-saline calcareous soils, and also to the measurement of the variation of exchange capacity with pH.

Effect of pH and NH4NO3 as a Spray Additive on Penetration of NAA Through Isolated Tomato Fruit Cuticle

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 550a-550 ◽  
Author(s):  
Royal G. Fader ◽  
Martin J. Bukovac
Keyword(s):  
Direct Measurement ◽  
Sodium Citrate ◽  
Tomato Fruit ◽  
Initial Slope ◽  
Control Effect ◽  
Solution Ph ◽  
Ph Change ◽  
Effect Of Ph ◽  
Spray Droplets ◽  
Partition Behavior

We have reported that NH4NO3 (AN, 8 mM, pH 4.2), applied as simulated spray droplets, enhanced penetration of 14C-NAA through isolated leaf and fruit cuticles. One explanation for this response is that AN depresses NAA (pKa= 4.2) dissociation, increasing the nondissociated moiety, which penetrates more readily than the anion (NAA'). Direct measurement of AN (concn. 0-800 mM) effect on NAA (215 μM) dissociation as indexed by change in solution pH revealed no significant effect, with a pH change from 4.19 to 4.05. This change is not sufficient to account for the observed enhancement. When 14C-NAA, buffered (20 mM sodium citrate) at pH 3.2, 4.2, 5.2, 6.2, was partitioned against chloroform, there was a marked increase in NAA partitioning into chloroform as pH was decreased. AN (8 mM) did not alter this partition behavior, also indicating no effect on NAA dissociation. However, in cuticle penetration studies, using a finite dose system with 14C-NAA buffered at pH 3.2, 4.2, 5.2, 6.2, and in the presence and absence of 8 mM AN, there was no marked or consistent pH or AN (-70 to + 232 % of no AN control) effect on penetration as indexed by initial slope (4-12 h) or penetration after 120 h. The possible effects of AN and buffer on penetration of 14C-NAA from the droplet deposit will be discussed.

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