Compulsive Exchange Method Research Articles

Contribution of Soil Organic Carbon to the Ion Exchange Capacity of Tropical Soils

ABSTRACT Highly weathered soils represent about 3 billion ha of the tropical region. Oxisols represent about 60% of the Brazilian territory (more than 5 million km2), in areas of great agricultural importance. Soil organic carbon (SOC) can be responsible for more than 80% of the cation exchange capacity (CEC) of highly weathered soils, such as Oxisols and Ultisols. The objective of this study was to estimate the contribution of the SOC to the CEC of Brazilian soils from different orders. Surface samples (0.0 to 0.2 m) of 30 uncultivated soils (13 Oxisols, 6 Ultisols, 5 Alfisols, 3 Entisols, 1 Histosol, 1 Inceptisol, and 1 Molisol), under native forests and from reforestation sites from São Paulo State, Brazil, were collected in order to obtain a large variation of (electro)chemical, physical, and mineralogical soil attributes. Total content of SOC was quantified by titulometric and colorimetric methods. Effective cation exchange capacity (ECEC) was obtained by two methods: the indirect method—summation—estimated the ECECi from the sum of basic cations (Ca+ Mg+ K+ Na) and exchangeable Al; and the direct ECECd obtained by the compulsive exchange method, using unbuffered BaCl2 solution. The contribution of SOC to the soil CEC was estimated by the Bennema statistical method. The amount of SOC varied from 6.6 g kg−1 to 213.4 g kg−1, while clay contents varied from 40 g kg−1 to 716 g kg−1. Soil organic carbon contents were strongly associated to the clay contents, suggesting that clay content was the primary variable in controling the variability of SOC contents in the samples. Cation exchange capacity varied from 7.0 mmolc kg−1 to 137.8 mmolc kg−1 and had a positive correlation with SOC. The mean contribution (per gram) of the SOC (1.64 mmolc) for the soil CEC was more than 44 times higher than the contribution of the clay fraction (0.04 mmolc). A regression model that considered the SOC content as the only significant variable explained 60% of the variation in the soil total CEC. The importance of SOC was related to soil pedogenetic process, since its contribution to the soil CEC was more evident in Oxisols with predominance of Fe and Al (oxihydr)oxides in the mineral fraction or in Ultisols, that presented illuviated clay. The influence of SOC in the sign and in the magnitude of the net charge of soils reinforce the importance of agricultural management systems that preserve high levels of SOC, in order to improve their sustainability.

Measurement of Cation Exchange Capacity of Organic‐Matter Fractions from Soils using a Modified Compulsive Exchange Method

This article describes a modified compulsive exchange method suitable for the determination of cation exchange capacity (CEC) over a pH range on solid, separated organic‐matter fractions. The method is demonstrated to be a reproducible and relatively simple means of measuring CEC on fractions separated by physical means in conjunction with hydrofluoric acid (HF) treatment. By including a modification for measuring the residual magnesium (Mg2+) content by dilution and conductivity, the method is simplified to measure CEC versus pH using a single sample; the only laboratory instruments required are pH and conductivity meters and a balance. The lack of agreement between this method and the silver thiourea (AgTU) method for some fractions at low pH is attributed to the uncontrolled variation in solution ionic strength when acid is introduced to effect solution pH changes in the AgTU method.

Mineralogy and ion exchange properties of the particle size fractions of some Brazilian soils in tropical humid areas

The inorganic fractions of 25 samples from 12 representative Brazilian soils were separated into six subfractions (clay, silt, very fine sand, fine sand, medium sand, coarse+very coarse sand) and their effective cation and effective anion exchange capacity (ECEC and EAEC, respectively) evaluated by the compulsive exchange method using unbuffered BaCl 2 solution. The soils had developed from a range of parent material, such as sandstones, Tertiary unconsolidated sediments, siltstones, silty shales, basalts, metapelites and mica schists. The silt fraction of sandstone-derived soils had an ECEC of at most 2 mmol c kg −1 while the silt fraction of basaltic soils had ECEC which reached 106 mmol c kg −1. The silt fraction of the soil derived from mica schists had an EAEC of 9 mmol c kg −1, which was the highest of all the soils analyzed. The highest ECEC recorded was close to 300 mmol c kg −1 for the fine sand fraction of soil derived from silty shales. Sand fractions from Tertiary unconsolidated sediments were practically inert, while those from sandstones made only a small contribution to the effective exchange capacity. The origin of these differences may lie in the characteristics of the parent materials of the soils. Primary micas, illite and feldspars together with inactive quartz were the major components of the coarse fractions of the soils. We attributed the high ECEC of the coarse fractions to several factors, including feldspars and mica being subjected to intense weathering, accelerated cation release from the mineral structure, and silt and sand-sized clay mineral pseudo-aggregates. In highly weathered tropical soils, the coarse fractions can play an important role in active soil fertility because they are not chemically inert and in potential fertility because of their importance as reservoirs of nutrients.

Variable charge characteristics of selected Andisols from the Azores, Portugal

The point of zero charge (pH 0), point of zero net charge (PZNC), permanent charge and the charge variation at pH measured in 0.002 M BaCl 2 were assessed on six pedons covering a representative range of Andisols from the Azores, Portugal, and related to soil constituents. The capacity of these soils to exchange cations and anions by the compulsive exchange (CE) method at field soil pH was also determined. Values of pH 0 were positively correlated with allophane and Al o contents. A Typic Hapludand with significant amounts of layer silicate minerals showed very low pH 0 values and a high negative charge at field soil pH. Organic C-rich horizons, especially Ah horizons of Acrudoxic Hydrudands and Acrudoxic Hapludands, also showed a low pH 0 and a significant negative charge. The pH 0 values were less in the surface than in the subsurface horizons. Allophane-rich horizons showed high pH 0 and a predominance of positive charge at field soil pH. The PZNC values were close to pH 0 and, except in the Typic Hapludand, showed nil to low negative permanent charge. A wide variation of negative and positive charge from pH 4 to 7 was found. Differences in negative charge development within this pH range were largest for horizons rich in organic C and least for those with significant amounts of layer silicate minerals. The largest differences in positive charge were in horizons rich in allophane. CEC B (amount of Ba 2+ sorbed at an ionic strength of 0.002 M, i.e. the amount of negative charge) and AEC A (sorbed Cl − at an ionic strength of 0.002 M, i.e. the amount of positive charge) values extrapolated from the charge variation curves (at field pH) were strongly correlated with those determined by the CE method. Allophane-rich soils showed very low CEC CE, especially those poor in organic matter. In most of the Andisols, the capacity to retain cations is mostly located in the surface horizons and is strongly dependent on the organic C content. Because of the large AEC CE values of the subsurface allophane-rich horizons, the soils can retain mobile anions such as nitrate beneficial for crops.

Cation and anion exchange properties of Andisols from the Azores, Portugal, as determined by the compulsive exchange and the ammonium acetate methods

The cation exchange capacity (CEC) and the anion exchange capacity (AEC) of 31 soil horizons from a representative range of Andisols and related soils from the Azores, Portugal, were measured using the 1 M NH 4OAc standard method (SM) and the compulsive exchange method (CE). The effective cation exchange capacity (ECEC) was also measured by these two methods and by a 1 M NH 4OAc simplified method (sm). The amount of base cations extracted by sm, SM and CE, as well as Al extracted by 1 M KCl and 0.1 M NH 4Cl/BaCl 2 reagents, were compared. The amounts of Ca, Mg, K and Na determined by SM, sm and CE were highly correlated. A high correlation for values of total base cations obtained by the three methods was also observed. Soils with high allophane and/or organic C content showed higher values of Ca and of sum of basic cations by CE than by SM. The inverse was observed in the other soils. The sm extracted higher amounts of Na than SM. Generally, the amounts of Al extracted by 1 M KCl and 0.1 M NH 4Cl/BaCl 2 reagents were not significantly different, and were highly correlated. Values of effective cation exchange capacity by SM, sm and CE were also strongly correlated. The CEC values measured by CE were much lower than those measured by SM. The CEC values obtained by SM were positively correlated with organic C and Al o contents. CEC CE values were negatively correlated with Al o and allophane contents. These values were highly correlated with the amount of basic cations determined by SM, sm and CE. Values of AEC showed a wide variation and were correlated with both allophane and Al o contents. In the presence of high amounts of allophanic materials and low content of organic matter, the AEC becomes more important than the CEC whereby soils have a very low capacity to retain cations.

Measuring the cation exchange capacity of forest soils

Various methods have been proposed for assessing the cation exchange capacity (CEC) of soils. A pH 7 buffered ammonium acetate solution is the most widely used method but its use for forest soils has been questioned as it may result in an overestimation of CEC in soils with pH dependent charges. The objective of this study was to determine the most appropriate method for measuring the natural CEC of forest soils using variations of 3 common methods. These methods included: (1) pH 7 buffered ammonium acetate (2) unbuffered 1.0, 0.5, and 0.1 M ammonium chloride, and (3) the compulsive exchange method using the original method and with magnesium chloride. The CEC of three reference materials (kaolinite, vermiculite and humified organic matter) was predetermined and used for comparison. In addition, samples from the major genetic horizons of 8 soils from Washington State, USA, the North Island, New Zealand, and Indonesia were analyzed for CEC. Results showed that the compulsive exchange method resulted in consistently low CEC values, and did not reflect changes in soil organic matter or pH. The pH 7 buffered ammonium acetate resulted in artificially high CECs in soils high in organic matter and low pH, undoubtedly due to increases in pH dependent charges. Although the 0.5 and 0.1 M NH4Cl would work well for many forest soils, there may be insufficient NH4 + to completely displace all cations and fill all exchange sites in soils with high CEC. The unbuffered 1.0 M NH4Cl saturation solution is recommended for forest soils.

Compulsive exchange method for determining soil exchange capacities: Proposed time and labor saving modifications

Abstract Although the compulsive method for measuring the cation exchange properties of soils is being widely accepted particularly for highly weathered soils, part of the procedure is rather tedious involving the addition of water in a stepwise fashion to attain the specific conductance of a standard ionic strength which approximates that of many soil solutions. A modification, which estimates this quantity of water by measuring the specific conductance of the solution before addition of water, is proposed. This estimate was based on calibrations conducted on thirty‐one top‐ and sub‐soils comprising examples from six soil orders. Results obtained by both the original and modified methods were compared over 118 top‐ and sub‐soils and were highly correlated (R2= 0.99) with a slope of 1.02. The proposed modification is accurate as well as time and labor saving.

Measurement of Exchange Properties of Andisols by the Compulsive Exchange Method

AbstractFollowing recent criticism that the compulsive exchange method for the determination of cation exchange capacity (CEC) and anion exchange capacity (AEC) is not appropriate for Andisols, the method has now been applied to 22 samples from eight Andisol profiles from Papua New Guinea. Results obtained for CEC and AEC compared favorably with those obtained by a Schofied‐type method, and amounts of soil exchangeable cations could be explained by the CEC values measured. Specific adsorption of sulphate, if it occurs, following addition of MgSO4 in the procedure, does not affect the CEC value obtained.

Comments on “Modification of the Compulsive Exchange Method for Cation Exchange Capacity Determination”

Soil Science Society of America JournalVolume 51, Issue 3 p. 841-841 Comment and Letter to the Editor Comments on “Modification of the Compulsive Exchange Method for Cation Exchange Capacity Determination” Koji Wada, Koji Wada Faculty of Agriculture, Kyushu University 46, Fukuoka, 812 JapanSearch for more papers by this authorNaoto Matsue, Naoto Matsue Faculty of Agriculture, Ehime University, Matsuyama, 790 JapanSearch for more papers by this author Koji Wada, Koji Wada Faculty of Agriculture, Kyushu University 46, Fukuoka, 812 JapanSearch for more papers by this authorNaoto Matsue, Naoto Matsue Faculty of Agriculture, Ehime University, Matsuyama, 790 JapanSearch for more papers by this author First published: 01 May 1987 https://doi.org/10.2136/sssaj1987.03615995005100030054xCitations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume51, Issue3May-June 1987Pages 841-841 RelatedInformation

Modification of the Compulsive Exchange Method for Cation Exchange Capacity Determination

Soil Science Society of America JournalVolume 51, Issue 3 p. 840-841 Comment and Letter to the Editor Modification of the Compulsive Exchange Method for Cation Exchange Capacity Determination Gavin Gillman, Gavin Gillman CSIRO, Davies Laboratory-Townsville, University Road, Douglas Townsville, Queensland, 4814 AustraliaSearch for more papers by this author Gavin Gillman, Gavin Gillman CSIRO, Davies Laboratory-Townsville, University Road, Douglas Townsville, Queensland, 4814 AustraliaSearch for more papers by this author First published: 01 May 1987 https://doi.org/10.2136/sssaj1987.03615995005100030053xCitations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume51, Issue3May-June 1987Pages 840-841 RelatedInformation

Surface charge characteristics and lime requirements of soils derived from basaltic, granite and metamorphic rocks in high rainfall tropical Queensland

The cation and anion exchange capacities of a large number of soils formed on basaltic, granitic, and metamorphic parent materials in the high rainfall area (approximately 4000 mm) of tropical north Queensland have been examined. Aspects studied included the changes in CEC and AEC between pH 4 and pH 6, the relative amounts of permanent and variable charge over this pH range, and the lime requirements of these highly weathered soils. A distinction is made between the Total Cation Exchange Capacity (CECT), defined as the Ca + Al adsorbed, and the Basic Cation Exchange Capacity (CECB), which is the Ca adsorbed. At low pH, CECB may be much less than CECT. The CEC, increase with pH in the highly oxidic basaltic soils is largely due to changes in surface charge, while in the granitic and metamorphic soils, increasing occupation of exchange sites by Al as pH decreases is the factor responsible for the increase in CECB. A good estimation of CECB at soil pH is obtained with a previously described compulsive exchange method, and there is high correlation between CECT at soil pH and the Effective Cation Exchange Capacity (= Ca + Mg + K + Na + Al). The amount of lime required to raise soil pH to pH 5.5 in the granitic and metamorphic soils was equivalent to the amount of exchangeable Al, but in the basaltic soils the lime requirement was two to three times greater than the amount of exchangeable Al.

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

Exchange characteristics of some acid organic rich forest soils

The cation exchange characteristics were determined for several acid organic-rich soils formed under sub-alpine eucalypt forests growing in the Australian Capital Territory. Most of the exchange sites in the red and yellow earths studied are occupied by Al and are associated with soil organic matter. Unbuffered salt solutions extract more Al than could be associated with exchange sites, so that the sum of cations in the extracts is an overestimate of the effective cation exchange capacity (CECe). The CECe is not a unique property but depends upon pH and ionic strength (I) of the equilibrating solution. The exchange sites mainly carry negative charges of both permanent and variable nature. Higher carbon contents of the soils are correlated with increases in CECe due to increasing I, and with greater negative charge due to increasing pH. Some modifications to the compulsive exchange method of Gillman for determining CECe are proposed for its use with acid organic-rich soils.