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70-20,509

PAILOOR, Govind, 1940- VARIATIONS IN CATION EXCHANGE CAPACITIES OF SOME REPRESENTATIVE MICHIGAN SOILS WITH ANALYTICAL PROCEDURES AND THEIR RELATIONSHIPS TO ACIDITY, CLAY MINERALOGY AND ORGANIC MATTER.

Michigan State University, Ph.D., 1970 Agriculture, soil science

U n iv e rs ity M icro film s, A XEROX C o m p a n y , A n n A rb o r, M ic h ig a n VARIATIONS IN CATION EXCHANGE CAPACITIES OF SOME

REPRESENTATIVE MICHIGAN SOILS WITH ANALYTICAL

PROCEDURES AND THEIR RELATIONSHIPS TO

ACIDITY, CLAY MINERALOGY AND

ORGANIC MATTER

By

Govind Pailoor

A THESIS

Submitted to Michigan State University in partial fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

Department of Crop and Soil Sciences

1969 ABSTRACT

VARIATIONS IN CATION EXCHANGE CAPACITIES OF SOME REPRESENTATIVE MICHIGAN SOILS WITH ANALYTICAL PROCEDURES AND THEIR RELATIONSHIPS TO ACIDITY, CLAY MINERALOGY AND ORGANIC MATTER

By

Govind Pailoor

The CECs were determined by the following common methods on 38 representative acid to near neutral Michigan soil samples from 15 soil types: (1) the CaCl 2 method, (2) the KC1 method, (3) the NH^OAc method, (4) the cation sum­ mation method and (5) the NaOAc method.

The results obtained were grouped according to the following kinds of soil horizons and subjected to statisti­ cal analyses: (1) the surface Ap and A^, (2) the illuvial spodic B^, and B^r, (3) the illuvial Bt and Bg, and (4) the A 2 , A '2 and C^ horizons of uncoated materials.

The predictive equations for CEC among the five meth­ ods were all highly significant on all but the spodic hori­ zons. In spodic horizons, however, only NH^EC vs NaEC and

KEC vs CaEC could be predicted highly significantly for the soils used in this study.

The multiple regression analysis showed an 11 to 4 5 meq of charge contribution per 1 0 0 g of clay as would be Govind Pailoor

normally expected from soils of dominantly mixed clay minera-

logy.

The charge contribution from organic matter to NaEC was highest of all horizons and unreasonably high though

highly significant in surface horizons. The CaEC and KEC

on spodic horizons showed a low charge contribution from

organic matter, 14 and 25 meq per 100 g respectively. The

organic matter charge contribution was within the normally

expected range of 87 to 255 meq per 100 g for all other CEC values on all horizons other than the illuvial B+.t and B_ g horizons. The high charge contribution from organic matter

found in B. and B horizons for all CEC values indicated t g that a different kind of organic exchange complex is pre­

sent there.

The marked increase in both CaEC and KEC values on

the same soil samples after 1 N NaOAc treatment were shown

as evidence that 1 N NaOAc commonly employed in CEC deter­

mination alters the native soil exchange properties to a

significant extent. This is due to one or more of the

mechanisms of anion retention, dissolution of amorphous

coatings of Fe 20 3 and A ^ O ^ , dissolution of organic Fe and

A1 complexes and partial removal of the Al-interlayers when

present. Some or all of these characteristics are present

in surface horizons of most Michigan soils particularly

Spodosols, and the spodic horizons.

Due to the reasonable charge contributions from both

clay (23 to 45 meq/100 g) and organic matter (156 to 392 Govind Pailoor meq/100 g) contents of soils revealed in NH^EC on all hori­ zons, and the value of NH^EC being intermediate between

CaEC and NaEC, it was thought to be the best estimate of the net negative charge of the Michigan soil materials.

The soil exchange acidity values were obtained by:

(1) BaCl2+TEA method, (2) KC1 method, (3) the NH^OAc method, and (4) the Shoemaker, McLean and Pratt (SMP) buffer method.

It was concluded that the EA(BaCl 2 +TEA) and the SMP buffer method could be predicted significantly on all horizon groupings of the acid to near neutral representative Michi­ gan soil materials % Higher values were obtained by the SMP method particularly on spodic horizons. This indicated that the lime requirement recommendations for Spodosols may be overestimated due to the mixing of spodic horizons, norm­ ally occurring at a depth of six to twelve inches, with the surface horizons by plowing. It was concluded therefore that the determination of exchange acidity by BaCl2+TEA or an adjustment of the EA(SMP) values based on its relation­ ship to EA(BaCl 2+TEA) may give a more reliable estimate of the lime requirement of common Michigan soil materials, particularly the Spodosols. TO MY

FATHER, MOTHER

UNCLE, AUNT

SISTERS, BROTHERS

SWEET SHARADE

PEOPLE AT HOME AND IN MICHIGAN ACKNOWLEDGMENTS

The author expresses his solemn gratitude to his major professor. Dr. E. P. Whiteside, for his kind assist­ ance, criticisms and encouragement throughout this study.

He sincerely appreciates the guidance of Dr. B. G. Ellis as co-director of this thesis. He has a high esteem for the other members of his guidance committee. Drs. R. L. Cook,

M. M. Mortland, A. E. Erickson and H. Eick for their co­ operation in this study. The author thanks in earnest Dr.

G. L. Johnson for the concepts in Agricultural Economics developed through his association. He is mindful of the pleasant atmosphere of reassurance amongst his colleagues and members of the Department.

The author admires the title of an Yearbook of Agri­ culture, Soils and Men. He is grateful to his Alma Mater,

Michigan State University, for giving him an opportunity to peep into the nature of both these. TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS ...... iii

LIST OF TABLES ...... V

LIST OF FIGURES ...... vii

INTRODUCTION ...... 1

LITERATURE REVIEW ...... 3

Early History of Cation Exchange Capacity .... 3 Cation Exchange Theories ...... 4 Sources of Cation Exchange in Soils ...... 11 Exchangeable Aluminum and Soil Acidity as Factors Influencing Cation Exchange ...... 18 Methods of Cation Exchange Capacity Determination ...... 22

MATERIALS AND M E T H O D S ...... 25

Soils Used in the S t u d y ...... 25 Methods Used in this Study ...... 35 C aC l 2 method for CEC determination ...... 36 KC1 method for CEC determination ...... 37 NH 4OAC method for determination of CEC and exchangeable bases ...... 37 NaOAc method for CEC determination ...... 39 Barium chloride plus triethanolamine method for the determination of exchange acidity . 40 KC1 extraction and fluoride titration pro­ cedure for determination of extractable acidity and exchangeable a l u minum ...... 41

RESULTS AND DISCUSSION ...... 4 3

SUMMARY AND CONCLUSIONS ...... 82

NEED FOR FURTHER RESEARCH ...... 87

LITERATURE CITED ...... 88

APPENDIX 99 LIST OF TABLES

Table Page

1. Soil type names and legal descriptions of loca­ tions of the profiles studied ...... 26

2. Information on soils studied ...... 30

3. Effect of washing procedures in CaCl~ method of CEC determination ...... 45

4. Relationship between effective replacement of K+ by NH^+ with increasing number of washings . . 48

5. Cation exchange capacity values for 15 soil samples determined by the NaOAc method at pHs 7.0 and 8 . 2 ...... 49

6 . The mean CEC values determined by five methods grouped according to the kinds of soil hori­ zons ...... 53

7. Regression equations and correlation coefficients among CEC values determined by five methods grouped according to the kinds of soil h o r i z o n s ...... 56

8 . Relationships between CEC values and clay and carbon contents, their partial and multiple correlation coefficients and levels of signifi­ cance, on soils grouped according to horizons . 57

9. Relative charge contributions from clay to CEC values grouped according to the kinds of soil horizons ...... 58

10. Relative charge contributions from organic matter to CEC values grouped according to the kinds of soil horizons ...... 60

11. The effect of IN NaOAc on CEC of soil materials . 70

12. The mean values of acidity components grouped according to the kinds of soil horizons .... 74

v LIST OF TABLES - Continued. Table Page

13. Relationships between soil acidity measurements and clay and organic carbon contents grouped according to the kinds of soil horizons . . . 76

14. Relative acidity contributions from clay to excahnge acidities grouped according to the kinds of soil horizons ...... 77

15. Relative acidity contributions from organic matter to exchange acidities grouped accord­ ing to the kinds of soil horizons ...... 78

16. Data on chemical analyses of soils studied . . . 100

17. Estimation of clay minerals in the clay frac­ tion of the horizons of similar soil types as used in this study ...... 10 2 LIST OF FIGURES

Figure Page

1. The charges on the edges of clay particles under acid and alkaline conditions as affected by mineralogical composition ...... 13

2. Map of Michigan showing location of representa­ tive soils used in this s t u d y ...... 27

3. Depth functions of pH of soils studied ...... 32

4. Depth functions of percent clay in soils s t u d i e d ...... 33

5. Depth functions of percent carbon in soils s t u d i e d ...... 34

6 . Depth functions of CaEC and NaEC in soils s t u d i e d ...... 52

7. Depth functions of soil acidity components in soils studied ...... 73 INTRODUCTION

Ever since Way published a paper "On the power of soils to retain manure" over a hundred years ago, the in­ terest in studying ion exchange has continued in order to better understand the physico-chemical processes that af­ fect soil fertility. The chemical and physical processes more or less intimately connected with ion exchange in­ clude: weathering of minerals, nutrient absorption by plants, swelling and shrinking of clay and leaching of electrolytes. The weathering processes in time alter the composition of the soil material resulting in changes in ion exchange and other physico-chemical properties. These in turn change the soil profile properties, land use cap­ abilities and management requirements. Nutrient cations and hydrogen exchange reversibly with soil colloidal sur­ faces, and those surfaces act as a storehouse of food for plants. Cation exchange capacity, therefore, is a measure of the potential nutrient cation retention status of a s o i l . Kelly (1948) defines cation exchange as "the total cations that can be replaced from a given substance under a set of given conditions." Although cation exchange capac­ ity is one of the most commonly measured soil properties, it is seldom highly precise. It is a known fact that no two analytical methods agree with each other in their

1 2 values. These variations may be attributed to the pH of the equilibrium system, the nature and concentrations of the reacting and replacing ions, wash solvents used, time of interaction and other variables.

As a valuable soil measurement, the cation exchange capacity ideally needs to be a defined characteristic under a given set of conditions so that the soil data can be accurately interpreted or diagnosed.

In the light of the inherent variations mentioned above, an attempt has been made in this study to compare the results of commonly used methods of cation exchange capacity, their relationship to each other, and the main soil properties that affect them. A suitable method for routine use which is reproducible but economical and that gives a reliable estimation of the net negative charge of the kinds of soil materials common in Michigan would be very helpful in facilitating efficient soil management.

Failing such a generally applicable method, the limitations of the methods most suitable for particular kinds of soils need to be evaluated. LITERATURE REVIEW

Early History of Cation Exchange Capacity

According to Kelly (1948), recognition of the phen­

omenon of cation exchange is attributed to two Englishmen,

Thompson (1850) and Way (1850). Way (1850) in his first

publication listed several conclusions of his work. They w e r e :

1. In reaction between soil and salt solutions,

calcium in the soil exchanges places with cations

in solution, anions remaining in solution unless

an insoluble calcium salt is formed.

2. Salts of lime are not adsorbed when filtered

through the soil, but Ca(OH) 2 and CatHCO^^

are adsorbed whole (in molecular form) like alka­

line compounds of other cations.

3. The clay portion of soil has the power to adsorb

cations. Sand, raw organic matter, calcium car­

bonate and free alumina do not possess this power.

4. Preheating of soil diminishes its adsorptive

p o w e r .

5. Adsorption is a rapid reaction, as between mineral

acid and alkalies.

6 . Ammonium carbonate and ammonium hydroxide are

adsorbed as molecules.

3 4

7. Adsorptive power of clay increases with increas­

ing concentration of solution and as the ratio of

solution to soil increases.

8 . Cation exchange is exhibited with the soil by K+ ,

Na+ and Mg^+ in addition to NH^+ .

9. Cation exchange is irreversible.

Interestingly, except for conclusions 2, 6 and 9, others for the most part have proved to be correct. Organic matter particularly as humus, is of course known to exhibit the exchange property. Of course calcium ions are not the only, though they are commonly the chief, exchangeable cations present in the soil.

Cation Exchange Theories

There have been several explanations proposed for the ion exchange behavior. When dealing with negatively charged colloids, if we consider the cation distribution between the solid and liquid phases, we observe the phen­ omenon of cation exchange. Any equation that gives the distribution of cations between a suspension and its dialy- zate may be called a cation exchange equation. Generally, simple stoichiometric equivalence between ions taken up and ions released is assumed to be present in the reactions.

But the exceptions are usually explained in terms of ad­ sorption or by the formation of complex ions. From another point of view, the phenomenon of adsorption is a precursor 5 of the ion exchange. Adsorption is a net result of the interaction between attractive and repulsive forces that are acting between the negatively charged surface and the nearby exchangeable cations. According to Norrish (1954), when the relationship of the cation to the surface is simi­ lar to that of a point charge to a thick plane conductor, the attractive energy is expressed in the following form:

e a - (1>

Where a is the surface charge density, v is the ionic val­ ence, e is the electronic charge, d is the distance between the ions and the surface and e is the dielectric constant.

However, if the interparticle cations and charged surfaces are regarded as the plates of a parallel plate condenser, the attractive energy becomes:

EA - 2_jr_afa (2)

Actually, the attractive energy will likely be a compromise between the above two equations. When the cations are far apart, equation (1 ) will apply; when they are close to­ gether, equation (2) will apply. Primarily, the attraction between the clay surface and the exchangeable cation is electrostatic in nature obeying Coulomb's law. In short ranges, other forces like hydrogen bonding between oxygen atoms and hydroxyl groups in adjacent surfaces occur. Also van der Waal *s-London forces contribute to attraction in the short range. Many of these forces depend on the nature and properties of the atoms under consideration and there­ fore on the mineralogical composition of the surfaces. Re­ pulsion occurs when the atoms in adjacent surfaces are in such close proximity that their outer shell electrons over­ lap. This repulsion is the so-called Born repulsion. The resulting repulsive energy ER is given by the following equation from Pauling (1945):

Where B is a constant, e is the electronic charge, R is the distance between atoms in adjacent surfaces and n has a value in the neighborhood of 9 but which depends on the kinds of atoms involved. Dipole-dipole interaction also causes repulsion according to Olphen (1954). Also, when mineral surfaces undergo hydration, they are forced apart

(Low and Deming, 1953; Hemwall and Low, 1956; MacEwan, 1954)

The adsorption phenomenon has been considered in great detail by several workers beginning from Freundlich1s classical adsorption isotherm equation (Langmuir, 1918;

Wiegner and Jenny, 1927; Vageler and Waltersdorf, 19 30;

Barken, 1940; Dunken, 1940). Hogfeldt (1955, p. 151) re­ viewed empirical equations of Krocker, Vageler, Weisz,

Boedeker, Freundlich, Wiegner and Jenny, Van Dranen,

Rothmud-Kornfield, and Yamabe and Sato. Mokrushin (1945) 7 showed how such basic equations of colloid chemistry, or

Gibb's adsorption equation, and Langmuir and Freundlich adsorption equations, and others can be deduced by use of the Maxwell-Boltzman equations. According to Grim (1968) the applications of these empirical equations is limited by such variables as nature of the clay mineral, nature of the ion, ionic concentration, clay concentration and other factors.

Theories of ion exchange equilibria in soils are usually based on the distribution of ions in water about a negatively charged plate. Of the two major categories of model systems, the double layer theory employs the Gouy distribution equation. Helmholtz (1879) provided the basis for this theory. In this theory, charge density on the surface of the particles is assumed to be uniform, the ions are taken as point charges, and any specific interactions between the particle and the ion are neglected. This dis­ tribution is such that the bulk of the cations are near the < surface of the negatively charged particle and the remain­ ing cations are distributed so that the concentration de­ creases with distance from the particle. Anion concentra­ tion increases as the cation concentration decreases, and these changes continue as a function of distance from the particle until the concentration of both ions is equal.

Stern (1924) proposed two corrections to the Gouy distribution theory: (1) The size of the ions determines 8

the distance of closest approach of the center of their

positive charge to the particle, and (2 ) specific adsorp­

tion potentials exist which may be different for each ion

species. Shainberg and Kemper (1966) cited the work of

Bolt (1955) to indicate that no appreciable short-range

interaction is possible unless dehydration of the ions

occurs close to the surface and stated "in case of cations

as counter ions, dehydration does not seem probable, in

general, unless the dielectric constant of the colloid ex­

ceeds that of water."

According to Rich (1968), such ion distributions in

soils should be viewed with reference to the cations

studied, their concentration and particularly the spacial

relationships of particles, surfaces, and solution. For

example, if the individual layers of montmorilIonite parti­

cles saturated with divalent ions or ions of higher valence, O do not separate more than 10 A a Gouy distribution cannot develop in this interlayer space (Norrish and Rausell-

Colom, 1963; Aylemore and Quirk, 1962). Many soil mont- morilIonites and vermiculites are less subject to expan­ sion. Thus, the cations on internal surfaces of expansible

layer silicates of most soils should be viewed as different

from those in a model based on the Gouy distribution.

Oe Haan's work (1965) indicated that the inter-layer region of soil minerals is not included in the diffuse layer. The surface area of 12 soils determined by anion exclusion was 9 an average of only 26 per cent: of that determined by an ethylene glycol method. El-Swaify et al. (1967), also on the basis of anion exclusion measurements, stated that vermiculite has two distinct and separated ionic regions.

Shainberg and Kemper (1966) have suggested an im­ provement on the diffuse double layer theory which takes into consideration the hydration energy of the ions. Ad­ sorbed cations are classified as being in the diffuse or

Stern layer according to them, depending on whether the energy of hydration (resulting from ion dipole interaction) is sufficient to maintain a molecule of water between the adsorbed cation and the mineral surface and thus the pre­ diction of difference in the adsorption characteristics of ions with the same valences can be made.

In the second model explaining the ion exchange equilibria, the suspension is assumed to be composed of two discrete phases. One phase contains only the exchangeable ions and an infinitesimal amount of electrolyte and the other is a homogeneous solution of electrolyte: This model is the basis for the mass-action approach and the statisti­ cal thermodynamic approach. In the mass-action theory, two discrete unambiguous phases in the suspension are the "ex­ change phase" and the "solution phase." The process of cation exchange may then be represented as an interchange of ions between these two phases. But this idea conflicts with the diffuse double layer concept in which adsorbed ions and solution ions are not definable as separate 10 entities (Kelly, 1948, p. 42). On the basis of the double layer theory, cation exchange is merely the rearrangement of cations and cannot be considered a chemical reaction in the opinion of Davis (1945). Davis has critically analyzed the significance of the cation exchange equilib­ rium concept and has suggested that the entire concept as a true thermodynamic equilibrium is not valid. However,

Wiklander (1964) maintains that the law of mass action can be applied to the study of ion exchange because of the pre­ sent knowledge about the structure of the diffuse double layer and its relationship to the surroundings being de­ pendent on the activity of the diffusible ions and also connected with changes in free energy.

The statistical thermodynamic model assumes discrete adsorption sites and localization of the adsorbed ions.

Babcock (1963) favors this approach as it should be applic­ able when the distance between the adsorption sites is large relative to the size of the ions. This model was developed by Krishnamoorthy and others (1949) and is based on statistical thermodynamics of Guggenheim (1945).

Donnan equilibrium theory is concerned with the state of equilibrium in a system composed of ordinary electro­ lytes and colloidal electrolytes separated by a membrane which is impermeable to colloidal particles. In soils, a clay particle with its surrounding diffuse double layer may be looked upon as a micro-Donnan system where the attractive electric forces between particle surface and 11

counter Ions act as a restraint, causing a non-uniform dis­

tribution of the counter ions in the micellar solution

(Babcock, 1963). Thermodynamically, the equilibrium con­ dition of a Donnan system is characterized by the fact that

the chemical potential (v) of every diffusible electrolyte and the electrochemical potential of every diffusible ion species are constant throughout the system. Employing this concept, Wiklander (1964) has shown that the product of

ion activity is a constant and that its magnitude is de­ pendent on the temperature and on the electrochemical po­

tentials of the two ions, and thus on the structure of the diffuse double layer, ion concentration, ion interaction, and interaction with the exchanger both in electrostatic and non-electrostatic ways.

Sources of Cation Exchange in Soils

The sources of cation exchange in soils can be con­ sidered in two broad categories: the inorganic or the clay fraction and the organic matter. In the inorganic fraction, depending on the kind of clay mineral, the dominant source of cation exchange may be due to: broken bonds at mineral terminations which could be balanced by adsorbed cations, isomorphous substitution in the lattice, or the hydrogen of 3+ 4+ the exposed hydroxyls. Substitutions of A1 for Si in the tetrahedral layer framework of silicates and in allophane and/or substitution of cations of lower valence for higher valence ions in the octahedral layer account for 12

the "permanent charge" (Schofield, 1949) which does not

change in magnitude or s t r e n g t h by changes in pH of the

system. In the three layer silicates, illite, vermiculite

and smectites, permanent charge accounts for three fourths

of the cation exchange capacity. This negative charge

neutralized by a counter charge M+ may be represented in

the ideal beidellite formula as:

M y + (Si8 _yA l y )Al4O 2 0 nH 2°

In the two layer silicates, permanent charge may account

for only a small portion of the exchange capacity (Robert­

son, et al., 1954; Coleman and Craig, 1961). Follet (1965) observed the retention of positively charged iron oxides

on kaolinite plane faces, but not on edges. This is addi­

tional evidence that supports the presence of a permanent negative charge in kaolinite. Studies of Brown (1965), and

Bailey (1966) have indicated that the mineralogical com­ position affects the proximity of multivalent cations and

thus its susceptibility for replacement or exchange, the degree of localized charge imbalance, the interionic dis­

tances and the interionic bond angles. In the smectites and vermiculites, the site of negative charge may be in the

tetrahedral sheets, the octahedral sheets, or both (Foster,

1960) .

Since the interlayer cations would be at different distances with respect to the site of charge, one would ex­ pect cations to be held more tightly where tetrahedral 13 rather than octahedral charge is dominant. Work of Scho­ field and Sampson (1953) has shown that the edges of the clay particles may be either positively or negatively charged depending on the pH of the system. Low (1968) has discussed the work of Schofield and Sampson (1953) with the aid of a modified diagram (Figure 1).

Moderately acid Very slightly alkaline Alkaline 2+ Edge charges, with Mg in octahedral positions

OH OH OH \ / \ / \ / Si Si Si A /I A , OH +1/3 OH +1/3 , 0 -2/3 / \l / \l / Mg Mg Mg / | \ / | \ OH +1/3 OH -2/3 A\ OH -2/3

+2/3 -1/3 -1 1/3

Edge charges, with Al3+ in octahedral positions

OH OH OH v y v A A A OH +1/2 OH +1/2 O -1/2 \l / W / \l A1 AI A] /W /(\ /I OH +1/2 OH -1/2 OH -1/2 H + 1 0 -1

Figure 1. The charges on the edges of clay particles under acid and alkaline conditions as affected by mineralogical composition. 14

Atomic groupings at the edges of the clay minerals con- 2+ 3+ taining Mg (as in 2:1 layer silicates) and A1 (as in

1 :1 layer silicates) in octahedral positions are shown in

upper and lower parts of Figure 1, respectively. In both 4+ cases Si occupies tetrahedral positions and the coorina-

ted anions are determined by the pH. Because of mass ac­

tion, H+ tends to associate with O- atoms at the edge at

low pH values, it tends to dissociate from these atoms at

high pH values. The bonds joining the cations to the co­

ordinated anions have strengths equal to the valence of

the cation divided by the coordination number. For elec­

tro-neutrality to be maintained, the sum of the bond

strengths to each anion must have a value equal to its valence. Otherwise, there is a localized charge imbalance that is equal in magnitude to the difference between the

two quantities. Thus, different edge charges can occur de­ pending on the pH of the system. It is possible, there­

fore, for attraction to exist between positive edges and negative planar surfaces under acid conditions. Probably the attractive energy is described by either equation (1 ) or equation (2). From Figure 1 it can well be seen that 2+ 3+ a (surface charge density) depends on whether Mg or A1 occupies the octahedral positions or by the mineralogical composition of the clay. It can also be noted from Figure

1 that the ionization of Si-OH groups (Si-OH SiO“ + H+) once thought to be contributory to pH dependent CEC is an oversimplification. The silicic acid is too weak for SiOH 15

to ionize appreciably in the pH range of concern in soils

(Goates and Anderson, 1956). The pK for Si-OH = SiO“ + H+

is about 9.7 (Kargin and Rabinowitsch, 1935). And thus,

this group would be active only at very high pH. The group + 1/2 (-A1 O^) is similar to that probably present at the 3+ edge of gibbsite, hydroxy-Al polymers, and hydrated A1

ions (Jackson, 1960, 1963a). Fripiat (1964) has summarized

the cation exchange behavior of allophanes which appear to

be poorly crystallized halloysites, in terms of their Al

content, whether the Al was in 4 or 6 coordination, and how

the coordination number depended upon pH. Another pH de­ pendent component of CEC, characteristic of clays from many acid soils and of clay minerals like kaolinite or montmor-

ilIonite are those that have been interlayered with Al or

Fe hydrous oxides (Thomas and Swoboda, 1963; Coleman et al.

1964; de Villiers and Jackson, 1967). Apparently, the hydrous oxide coatings are positively charged (Hsu and

Rich, 1960; Jackson, 1963a, b., Hsu and Bates, 1964) with the magnitude of the positive charge varying inversely with pH. Coleman and Thomas (1967) in their review on basic chemistry of soil acidity have discussed the cation exchange behavior of layer silicate-sesquioxide complexes as result­ ing from the negative charge of the layer silicate which does not vary with pH but the changing opposite charge on the clay-sesquioxide complex does. The net charge, there­ fore, varies from positive at low pH to negative at high pH

(Coleman and Thomas, 1964; Schwertmann and Jackson, 1964; 16

Volk and Jackson, 1964). It is zero when the positive charge of the sesquioxide just equals the lattice charge of the layer silicate and reaches a net negative charge which essentially equals lattice charge of the layer sili­ cate at pH near 8 . Schematically they can be represented as follows: ([Layer silicate]X~\x + ^H^ /[Layer silicate]X“ [Al(OH)3_ 2x ]2X+ I OH” \[A1(OH)3 _x ]X+

pH 2 pH ^ 4

[Layer silicate]X“\x

[A1(0H)3]0 J

p H 8

This leads to the large variation in effective CEC with pH and prevents the identification of CEC at pH 6 with lattice c h a r g e .

The number of OH” groups on the sesquioxide group

increases as pH rises and thus, the positive charge of the polycation is reduced. This liberates negative sites on which other cations can be retained. Other tightly held anions besides OH have the same effect of increasing CEC.

Thus, F" or H 2P04~ ions, which are bound more tightly by 3+ Fe and Al than is the clay, result in apparent increases

in cation exchange capacity. Sulphate and even chloride or nitrate salts also interact with clay mineral sesquiox­

ide complexes, with the sorption of the anion on the 17 hydrous oxide component and the cation on the layer sili­ cate (Thomas and Swoboda, 1963; Chang and Thomas, 1963).

The acid functional groups of organic matter as the source of cation exchange capacity are carboxyls, phenols, enols, and perhaps the alcoholic hydroxyls (Gillam, 1940;

Broadbent and Bradford, 1952; Lewis and Broadbent, 1961;

Mortensen and Himes, 1964; Schnitzer and Desjardins, 1962;

Schnitzer and Gupta, 1964, 1965; Schnitzer and Skinner,

196 3; and Schnitzer and Wright, 1960). Thus the contribu­ tion to CEC from organic matter depend on the source of humic compounds and the stage of decomposition. Bulk of the exchange sites are associated with the lignin fraction.

Coleman and Thomas (1967) in their review state that only the carboxyl groups are strongly enough acidic to ionize appreciably when the pH is below 7.0. However, some polyphenols and substituted phenols may contribute as well

(Lewis and Broadbent, 1961). Carboxyls accounted for ap­ proximately 55 per cent of CEC of organic matter according to Broadbent and Bradford (1952) in their study. Phenolic and enolic groups contributed another 35 per cent and imide nitrogen, 10 per cent. Schnitzer and Skinner (1963) also attributed 55 per cent of the CEC of organic matter from the Bh horizon of a podzol to carboxyl groups. The remain­ der was due to phenolic and enolic groups. The weak acid character of organic matter results from the fact that 3+ 34. metal organic ion complexes, primarily Al and Fe , rather than the COOH groups present (Martin, 1960; 18

Martin and Reeve, 1960; Mortensen, 1963; Schnitzer and

Gupta, 1964; Bhuxnbla and McLean, 1965). Pratt and Bair

(1962) measured CECs of 15 acid California surface soils at pH's between 3 and 8 and concluded that the pH dependent

CEC was due both to clay and organic matter. Helling et al.

(1964) measured CEC of 60 Wisconsin soils at pH values be­ tween 2.5 and 8 and by multiple correlation analysis deter­ mined the contributions of organic matter and clay at each pH and the variation in CEC of each as pH was changed.

They found that for the soils they studied, organic matter was the major contributer to the pH dependent CEC. These results showed CEC of clay was nearly constant in the pH range of 5 to 7. This near constancy of CEC of clay was also found in the studies of Ross et al. (1964) for some

Michigan soils.

Exchangeable Aluminmn and Soil Acidity as Factors Influencing Cation Exchange

Robinson (1961) has made a good brief review of the following factors influencing cation exchange; the binding forces, accessibility of cations, ionization of adsorbed cations, relative size of the ions hydrated and non-hydra- ted, particle size, surface area, temperature, valence, dilution effects, pH, clogging at cation exchange posi­ tions, hydrolysis, heat of wetting, anions, complementary ions and zeta potential. The sources of pH dependent com­ ponent of CEC are mentioned earlier in the review as due to the mineralogical composition and organic matter. 19

Aluminum, because of its abundance and atomic pro­

perties , plays as important role in soil mineral structure o and behavior. Its trivalent radius, 0.51 A (Sienko and

Plane, 1963), is favorable for accommodation to both tetra

hedral and octahedral coordination with oxygen. In strong

ly acid solutions, aluminum exists as a trivalent cation 3+ complex with each Al ion surrounded by 6 water molecules

in 6 coordination. Schofield and Taylor (1954) suggested

the first stage of Al hydrolysis as:

[A1(6H2 0]3+ + H 2O v * [Al(OH) (5H20 ) ] 2 + + H 30 +

As pH is further increased, monovalent hydroxy Al cations

form (Rich, 1960):

[Al (OH) (5H20) ) 2++ H 20 ^ = ^ [Al (OH) 2 (4H20) ] ++ H 3Q +

[Al(OH)2 (4HzO)]+ + H 20v *[Al(OH)3 (3H20 ) ] + H 30 +

The A l ( O H )3 . 3H20 is insoluble and precipitates. The ex­

tent of precipitation depends on the ionic strength of the

solution, density of charge on the clay mineral (Rich,

1960) and ionic species present (Jackson, 1963a). With

further increase in pH above 7, the fourth water molecule

loses an H+ ion forming the aluminate ion Al(OH)^. 2H 20~

and the solubility of Al increases. Data on solubility of

Al in solutions at different pH values were given by Magi-

stad (1925). 20

It can be seen, therefore, that mildly acid weather­

ing causes octahedral aluminum to react with protons at

crystal edges and thereby producing exchangeable Al (Mar- 3+ shall, 1964), postulated to exist primarily as AldJjO)^

(Jackson, 1963a). These aluminum ions tend to be adsorbed

by the remaining clay minerals (Jackson, 1963a). Since

most of the exchange sites of the 2:1 expanding layer

silicate minerals are on the faces of the crystals due to

isomorphic substitutions, many of the aluminum ions re­

leased by weathering will be adsorbed in the interlayer

areas. As the exchange sites become saturated with hydra­

ted aluminum ions the hydrated ion structures are subjected

to steric pinching (Jackson, 1960) because the area occu­

pied by individual exchange sites is less than the size of

an aluminum hexahydroxy polymer. This is especially true

for vermiculite (Jackson, 1963a) which has a high charge

density. The adjacent aluminum polymers tend to polymer­

ize by sharing hydroxyls, but the polymers retain a net pos i tive charge.

The resulting charged hydroxy aluminum polymer may be very large and thus becomes essentially unexchangeable.

Studies by Thomas (1960) and Rich (1960) also indicated

that these Al hydroxy ions are strongly adsorbed by soils

as they are not extractable by neutral salt solutions of

1 N concentration. Ca:Al exchange studies by Coulter (1969) have also shown strong aluminum adsorption by soil minerals,

the strength of which depended on the type of clay and the 21 mlneralogical composition. This results in a net reduction

of the cation exchange capacity of the clay.

The exchangeable Al is postulated to exist primarily 3+ as A 1 ( H 20 )6 (Jackson, 1963a); whereas, Al polymers pre- cipitated on clay surfaces (Jackson, 1963a; Ragland and

Coleman, 1960; and Schwertman and Jackson, 1963) and Al complexed by organic matter (McLean et al., 1965; and

Schnitzer and Skinner, 1964) have been proposed as non-ex- cahngeable forms. The a L neutralized upon liming includes both exchangeable and non-exchangeable forms and is often referred to as acidic Al. Poinke and Corey (1967), in their studies on the relations between acidic aluminum and soil pH, clay and organic matter, considered the Al extracted by

1 N NH^OAc at pH 4.8 as exchangeable plus non-exchangeable acidic Al, and proposed the following reactions of acidic

Al in soil:

A l ( O H ) 3

2+ Al OH

The symbols used are defined as follows: Al 3+ represents the activity of hydrated trivalent Al ions in the soil solution; Al-X refers to KC1 exchangeable Al; Al-OM refers to that component of non-exchangeable acidic Al 22 complexed by organic matter; and A^y (°H);3y _z refers to that component of non-exchangeable acidic Al that is poly­ merized and probably residing on particle surfaces.

Poinke and Corey (1967) explained that this diagram predicts an increase in the non-exchangeable acidic Al for an increase in organic matter for soils at a constant pH 3+ and a given concentration of Al in solution; whereas an increase in clay would increase the exchangeable Al at the expense of Al-OM. The addition of salt would displace ex­ changeable Al to the soil solution, altering the equilib­ rium in favor of the formation of Al-OM complexes and in­ organic polymers. The hydrolysis resulting from polymer formation would depress soil pH by releasing hydrogen ions to the soil solution. In accordance with this, Poinke and

Corey have found better correlation of pH with exchange­ able Al when KC1 is used and also with the observed re­ lationships of exchangeable Al and non-exchangeable acidic

Al with percent clay and percent organic matter.

Methods of Cation Exchange Capacity Determination

The CEC determination involves measuring the net negative charges per unit weight of soil. The CEC values obtained vary depending on the method employed, particu­ larly: the exchanging salt, salt concentration, the time of interaction, and pH. Several methods of CEC determina­ tion are now in vogue and many have been proposed. Robin­ son (1961) has briefly reviewed the following: ammonium 23

method, barium method, radioactive tracer chromatogram method, colorimetric method, conductometric method, using methylene blue dye, and by emulsification. Chapman (1965)

has grouped the methods for determining CEC into the fol­

lowing categories: (1 ) those in which the soil is electro- dialyzed or leached with a dilute acid, e.g. HC1, and the hydrogen and aluminum saturated exchange material is

titrated to pH 7.0 with Ba(OH ) 2 or to about pH 8.5 with

NaOH: (2) those in which exchange capacity is considered

to be the sum of replaceable hydrogen and replaceable bases; (3) those in which the exchangeable cations are re­ placed by the acetate of ammonium, barium, calcium or sodium and the amounts of the cation adsorbed are deter­ mined by appropriate means; (4) those which involve equi­ librating soils (preleached with Ca(OAc)2) with a dilute 45 40 solution (100 ppm Ca) of Ca(N O ^ ) 2 containing Ca and Ca

(Blume and Smith, 1954).

The CEC values are generally determined at pH 7 or

8.2 (Jackson, 1958). The preference for pH 7.0 arises from the fact that it is the neutral point of water and may more nearly represent the pH of the soil-bicarbonate- carbonic acid buffer system at partial pressure of C0 2 likely to prevail in the atmosphere of a fertile soil dur­ ing the season of active growth. The pH 8.2 is preferred because it is closer to the equilibrium pH between soil and CaCO^ at the partial pressure of C0 2 in the atmosphere and also because the exchange materials of soils are weak 24 acidoids. Studies of Coleman and Thomas (1964) have in- 3+ dicated that the complete neutralization of sorbed Fe or 3+ Al ions occurs at or near pH 8 . The CEC determination may also be made at the pH of the soil, or at least at the pH of the soil-salt solution mixture using an unbuffered salt solution like KC1 or CaCl 2 (Coleman, et al., 1959;

Pratt and Bair, 1962; Bhumbla and McLean, 1965).

Chapman (1965) has described two commonly used

NH^OAc and NaOAc methods of CEC determination. He mentions the advantages of the NH^OAc method as its high buffering capacity, ease of determination, and the ease of determin­ ation of displaced cations because of its volatility.

According to Chapman (1965) the disadvantages of this method are that in soils containing high amounts of 1:1 layer silicates or organic matter it will give lower CEC values as compared to Ba(OAc)2 method (Mehlich, 1945) due to + 3+ incomplete replacement of adsorbed H and Al . Also, when soils contain vermiculite clay, interlayer cations 2+ 2+ + +

Soils Used in the Study

The fifteen soil types selected for study represented the acid to near neutral mineral soils widely distributed in Michigan. The legal descriptions of locations of the soils are given in Table 1 and their approximate locations are shown in Figure 2. These soil types may be breifly described as follows:

Miami loam is a well drained, Typic Hapludalf (Gray

Brown Podzolic soil) which has developed in highly calcar­ eous loam till of Wisconsin age. It is the well-drained member of the drainage sequence that includes the moder­ ately well-drained Celina, somewhat poorly or imperfectly drained Conover, the poorly drained Brookston and the very poorly drained, very dark colored Kokomo soils.

Plainfield loamy sand includes very weakly developed

Typic Udipsamments (Regosol) developed in very strongly acid sands. Plainfield soils are the well-drained members of the catena that includes the moderately well-drained

Nekoosa, imperfectly drained Morocco, poorly to very poorly drained Newton, and the very poorly drained, very dark- colored Dillon soils.

Volinia loam includes well-drained, Typic Argiudoll

(Brunizem soils) developed in loamy and silty materials.

25 TABLE l.«— Soil type names and legal descriptions of locations of the profiles studied.

Soil type Location

1 Miami loam NW 1/4 of NE 1/4, Section 31, T 4 N, R 1 W. 4 Plainfield loamy sand NE 1/4 of NW 1/4, Section 26, T 5 S, R 19 W. 6 Volinia loam SW 1/4 of SE 1/4, Section 19, T 4 S, R 11 W. 8 Kalamazoo sandy loam SW 1/4 of NW 1/4, Section 4, T 2 S, R 10 W. 11 Saugatuck sand SE 1/4 of SW 1/4 of SW 1/4, Section 12, T 18 N, R 4 E. 14 Onaway loam SW 1/4 of SW 1/4 of Section 33, T 40 N, R 24 W. 15 Brookston loam NW 1/4 of NE 1/4 of NW 1/4, Sect. 28, T 6 N, R i6 W. 17 Ontonagon silty clay NE 1/4 of SE 1/4 of SW 1/4, Sect. 9, T 48 N, R. 41 W. 19 Iron River silt loam NW 1/4 of NE 1/4 of NE 1/4, Sect. 11, T 43 N , R. 36 W. 23 Munising loamy sand SW 1/4 of NE 1/4 of Section 4, T 51 N, R. 31 W. 24 Spinks loamy fine sand S 1/2 of NW 1/4 of SE 1/4, Section 1, T 4 N, R. 1 W. 34 Kalkaska sand SE 1/4 of SE 1/4 of NE 1/4, Sect. 10, T 20 N , R 10 W. 37 Blount clay loam NE 1/4 of SW 1/4 of NW 1/4, Sect. 6 , T 5 N, :R 3 W. 38 Hillsdale sandy loam NE 1/4 of SE 1/4 of NW 1/4, Sect. 24, T 1 N, R 1 W. 39 Pewamo clay loam NW 1/4 of NW 1/4 of NW 1/4, Sect. 6 , T 5 N, :R 3 W. 27

Oi

r - I n a n a 1 O I I IM A R O U IT T t • o s ir ic i ___ I ' I L--y - PODZOL I ALRRR ^REGION i t9 ! itcNOOLCRArrlooLCRArr L _ --- -L-, | . d k l t a I

r /N^ :> f UCT |cMUOr«JM\ iniHiK I 1 ,ri' irfomL _ .J J

1 ______a l p e n a Soil Soil ANTRIM if No. Series (f/L____ 1___ ± ____ i____ !««J'M “ lcRAMf0R0,o,eo°* R I l c o n a 1 Miami E AND. TRAV.J | I | 4 Plainfield -L— /M ANItTI^W CXTO RO ^g^^^ ROICON. I OSKNAV i IORCO 6 Volinia / _ -lPODIZOL^REQION L. 8 Kalamazoo ^ ia r o n T l a r i ro»fOLAfCLA)ll Hil a o m Tn7 a r i n a c * i * 4 i l I 11 Saugatuck • i i , i ■ i * i '■*>/ HURON 14 Onaway OCIANA 1MECOSTA |I*A R E L LA I m io LANO .//( 1 i i ’ V SANILAC 15 Brookston J I 17 Ontonagon ; i _ _j I — 1 ,->larccr1 19 Iron River . istTiTl a i r ' IONIA I CLINTON .RHIAWA. | ■ . -

23 Munising IK ' I 3 9 ,x | _ l I _ Uj © I g \24 I r--4- 24 Spinks _ __ i_ ~ __.___ . OASLIOAKLAND |W C O i, l 1 ft AAftYrt T luv,",*T0". 34 Kalkaska 37 Blount 38 Hillsdale • CMICN 39 Pewamo MAIiCH T“ILl5MtxflcNAVCC J *■«' PODZOLlC REGIQN I L, i I -

Figure 2. Map of Michigan showing locations of representa­ tive soils used in this study. 28

24 to 42 inches thick, over stratified, non-calcareous

gravel and sand.

Kalamazoo sandy loam is a well-drained, Typic Haplu-

dalf (Gray Brown Podzolic soil) developed in silty or loamy

outwash material underlain by stratified non-calcareous

gravel and sands at depths from 24-42 inches.

Saugatuck sand is a somewhat poorly drained, Aerie

Haplaguod (sandy Ground-Water Podzol).

Onaway loam consists of well-drained and moderately

well-drained Alfic Haplorthod (soils with a Podzol upper

sequence and a lower Gray-Wooded sequence) which developed

in reddish or pinkish calcareous loam till.

Ontonagon silty clay is a moderately well-drained,

Typic Eutroboralf (Gray-Wooded soil) developed from clay

to silty clay lacustrine sediments derived from a variety

of rocks, but with colors strongly influenced by the highly

ferruginous formations of the Lake Superior region.

Iron River silt loam is a well-drained to moderately well-drained Alfic Fragiorthod (Podzol soil) on glacial upland developed from glacial drift in the Lake Superior region.

Munising loamy sand is a well to moderately well- drained, Alfic Fragiorthod (minimal to medial Podzol, with a fragipan) developed in strongly acid, reddish sandy loam glacial till derived from red sandstone of the Lake Super­ ior region of the Northern Lake states. 29

Spinks loamy fine sand is a well-drained, Psanunentic

Hapludalf (Gray Brown Podzolic soil) developed in calcar­

eous or neutral loamy sands, sands or fine sands.

Kalkaska sand is a well-drained Typic Haplorthod

(Podzol) developed in deep sands that may contain a little

calcareous material.

Blount clay loam is an Aerie Ochraqualf (somewhat poorly drained, Gray Brown Podzolic soil) developed in

calcareous clay loam to silty clay loam till.

Hillsdale sandy loam is a well-drained Typic Haplu­ dalf (Gray Brown Podzolic soil) developed in calcareous sandy loam till with thickness of the solum ranging from

40 to 66 inches or more.

Pewamo clay loam is a poorly to very poorly drained

Typic Argiaquoll (Humic Gley soil) developed in calcareous silty clay loam or clay loam till.

Other relevant information on these soil types, shown in Table 2, include: their parent materials, their natural drainages, their family placements in the new Soil

Classification System, 7th Approximation 1965 (as revised to July, 1969) in addition to their Great Soil Groups in the 1947 Classification System in the U.S. Table 2, also shows the horizons in these profiles chosen for this study as the ones more commonly developed in Michigan.

The soil materials, from the horizons studied, varied widely in their physical and chemical properties. The range of some of their characteristics relevant to the TABLE 2.— Information on soils studied.

Great Soil 7th Approximation Natural Parent Horizons* Soil Type Group, U.S. nomenclature (as Drainage Material Studied 1947 System revised to July 1969)

Miami loam Gray Brown Typic Hapludalf, WD Loamy till Ap, A 2 , B*,. Podzolic fine-loamy, 1 2 3 mixed, mesic Plainfield Regosol Typic Udipsamment WD Sand Ap loamy sand mixed, mesic 4 Volinia loam Brunizem Typic Argiudoll, WD Stratified, fine-loamy over loams/sand 6 7 sandy or sandy and gravel skeletal, mixed, mesic

Kalamazoo Gray Brown Typic Hapludalf, WD Stratified, Ap, ^1 loam Podzolic fine-loamy over loams/sand 8 9 101 sandy or sandy skele­ and gravel tal, mixed, mesic Saugatuck SWP Sand Ground Water Aerie Haplaquod, Al' B21h' B3ir sand Podzol sandy, mixed, frigid, orstein 11 12 13

Onaway loam Podzol Alfic Haplorthod, WD-MWD Loamy till A p / ® 22ir' B21t Bisegua fine-loamy, mixed, 14 32^ir 33 frigid Brookston Humic Gley Typic Argiaquoll PD Loamy till Blg* B22g loam fine-loamy, mixed, non-calc., mesic 15 16 Ontonagon Gray Wooded Typic Eutroboralf, MWD Lacustrine Ap, Blt silty clay very fine, illitic, clay frigid 17 18 TABLE 2.— Information on soils studied, (continued).

Great Soil 7th Approximation NatUral Parent Horizons* Soil Type Group, U.S. nomenclature (as 1947 System revised to July 1969) Dralnage Materlal Studied

Iron River Podzol, Alfic Fragiorthod, WD-MWD Silt over Ap, Bhir' A 2 ' silt loam Bisegua coarse-loamy, loamy till mixed, frigid 19 20 21 22 Munising Podzol, Alfic Fragiorthod, WD-MWD Acid, sandy Ap, A 2 ' B 22ir' loamy sand Bisegua coarse-loamy, loam drift 23 27 28 mixed, frigid A 1 2x , B 22t # C1 29 30 31 Spinks Gray Brown Psammentic Hapludalf, WD-MWD Sandy Ap, A 22' A 2B3t loamy fine Podzolic sandy, mixed, mesic drift sand 24 25 26 Kalkaska Podzol Typic Haplorthod, WD Sand A 22 ' B22ir' C 1 sand sandy, mixed, frigid 34 35 36 Blount clay Gray Brown Aerie Ochragualf, SWP Clay loam Ap loam Podzolic fine, illitic, mesic till 37 Hillsdale Gray Brown Typic Hapludalf, WD-MWD Sandy loam Ap sandy loam Podzolic coarse-loamy, till 38 mixed, mesic Pewamo clay Humic Gley Typic Argiaguoll, PD Clay loam Ap loam fine, mixed, non- till 39 calcareous, mesic

Numbers below the designated horizons were used for laboratory identification of the soil samples and their identifications elsewhere follows on page 1 0 1 . Depth (in inches) 40 20 50 60 50 10 Figure 3. Depth functions of pH of soils studied.soils of ofpH functions Depth 3.Figure Kalkaska Sand Onaway Loam Iron River Iron Loam Onaway Sand Kalkaska PH 7 Miami Loam Miami /////////////, 4 4

5 5

6 6

B 7 4 7 21 t //////////////// Loam Kalamazoo 4

5 5

6 6 B R

2 2 21 1

7 7 t ir / / / / / / / / / / ' //////// % ////,~ W Silt Loam Silt Fine Sand Fine Spinks Loamy Loamy Spinks 7 4 //////////

5

6 A

22 7 //////// Munising Munising om sand Loamy Ontonagon Ontonagon Silty Clay Silty 4

5

Blt P 6

22 7 ir //M W ///////////, oii om Brookston Loam Volinia Saugatuck Sand Saugatuck 4 4

5 5

6 6 A,

3ir 21 4 7 7 » h z / / / / / / / / / / / / / / / / m Loam

5

B 6 22

g 7 B ig w IO Figure 4. Depth functions of per cent clay insoils clay cent perof functions Depth 4.Figure

Depth (in inches) 20 40 60 40 30 30 20 SO 10 60 90 10 Per cent clay clay cent Per >////////, Miami Loam Miami Kalkaska Onaway Loam Iron River Iron Loam Onaway Kalkaska Sand Silt Loam Silt Sand B a f 22 22 20 20 „ ir

B 40 020 40 21 t //////, m ////// Loam Kalamazoo 20

21 22 40 40 t ir Fine Sand Fine Spinks Loamy Loamy Spinks 3t 2 20 20

40 40 studied. ///////////////////// Munising Loamy Saugatuck Saugatuck Loamy Munising Ontonagon Volinia Loam Volinia Ontonagon ad Sand Sand Silty Clay Silty A B 20 20 22 2

ir 40 40

1 " A B id B I B 20 20 3ir 21 B

h

22 t 40 40 Depth (in inches) Figure 5. Depth functions of per cent carbon in soils studied.carbon soilsincent per functionsof Depth 5.Figure 30 40 20 •0 50 o i Per cent carbon carbon cent Per ? F ^ Miami Loam Miami Kalkaska Sand B21t a A“ I 22 2 ir Loam Kalamazoo Onaway Loam Iron River Iron Loam Onaway 21 t | 2B3t A 1 Fine Sand Fine Spinks Loamy Loamy Spinks Silt Loam Silt

22 Bi B I hir 2 1 A Munising Munising Loamy sand Loamy Ontonagon Volinia Loam Loam Volinia Ontonagon Silty Clay Silty B 2 22 I x t 2 ■ B Sand Saugatuck 22 I t 2 21 Loam Brookston h I 2 35 study are shown as depth functions in Figures 3, 4 and 5 and grouped according to horizons in Table 16 of the Appen­ dix. The pH of the horizons studied (Figure 3), ranged from 4.3 in Kalkaska A 22 horizon (sample 34) to 7.1 in the

Ap horizon of Miami loam (sample 1). The percent clay,

Figure 4, ranged from 0.6 per cent in the A 22 horizon of

Kalkaska sand (sample 34) to 54.4 per cent in Blt horizon of Ontonagon silty clay (sample 18). The carbon content,

Figure 5, ranged from 0.02 per cent in the horizon of

Munising (sample 31, Table 16) to 2.46 per cent in the Ap horizon of Pewamo clay loam (sample 39) not shown.

Methods Used in this Study

The five methods of CEC determination are described below. The CaCl 2 method and the KC1 method are modifica­ tions of the Alexiades and Jackson (1965) procedure. The

NH^OAc method, the NaOAc method and the summation method are modifications of those desdribed by Chapman (1965) .

The barium chloride plus triethanolamine method for the determination of exchange acidity and KC1 extraction and fluoride titration procedure for determination of extract- able acidity and exchangeable aluminum are also modifica­ tions from Chapman (1965) . 36

C a Cl 2 Method for CEC Determination

Five grains of soil were placed in a 100 ml Pyrex cen­ trifuge tube with 10 ml of 1 N CaCl 2 and mixed well with a

Vortex Jr. mixer for 1 minute. The side wall of the centri­ fuge tube was rinsed with 5 ml of 1 N CaCl 2 and centrifuged at 3500 r.p.m. for 10 minutes. The supernatant liquid when clear was decanted. This treatment was repeated 5 times to 2+ 2+ assure complete Ca saturation of the sample. The Ca saturated soil sample was then washed similarly once with

15 ml water and then five times with 99% methanol. Finally, 2+ 2+ the Ca was exchanged with Mg by washing and centrifug­ ing five times in the same manner as above with 1 N M g C l 2 .

This time, mixing was done 2 minutes each to assure complete replacement and 5 ml of water was added to rinse the wall of the centrifuge tube before centrifugation. The superna­ tant solution was collected in a 100 ml volumetric flask and made to volume with water to obtain approximately 0.5 N 2+ MgCl2. The Ca was determined on a 303 Atomic Absorption 2 + Spectrophotometer against standard Ca solutions using 1% lanthanum oxide to prevent interference by other ions.

Other workers (Rich, 1962; and Frink, 1964) have in­ dicated that the procedure for washing the excess salts 2+ from Ca saturated soil samples can be done more efficient­ ly by using a low concentration of the same salt used for saturation, instead of 99% methanol. Then by knowing the weight of the retained solution, the correction for excess 37

salt retained can be made. Therefore, a comparison was made using 0.0001 N CaCl 2 as the washing solution and 99% methanol to obtain CEC values. The fourth and fifth cen­ trifugations usually needed 30 minutes to obtain clear suspensions; some finer textured soil samples also needed

5 ml or 10 ml of 99% acetone to prevent dispersion during the fourth and fifth washings.

Thorough mixing of the soil with the solution pre­ sented a problem particularly with fine textured samples.

To accomplish this the clay globules present were carefully dispersed by triturating with a rubber tipped glass rod.

KC1 method for CEC determination

A 5 gram soil sample was saturated with potassium using 1 N KC1, but otherwise the same procedure as for the

CaCl 2 method was followed. For washing out the excess salts

0.001 N KCl was used. The K+ saturated sample was then dried in an oven at 100° C over-night. The unfixed K+ was then exchanged by washing with 1 N NH^Cl. Care was taken every time to see that there was a thorough mixing of the sample with the solution as stated for the CaCl 2 procedure.

The supernatant solution was collected in a 100 ml volumet­ ric flask. Potassium was determined with a Coleman flame photometer.

NH^OAc method for determination of CEC and exchangeable bases

Five grams of soil were placed in a 100 ml centrifuge 38

tube, mixed well twice with 10 ml of 1 N NH^OAc, the wall

washed with 5 ml of 1 N NH^OAc and allowed to stand over­

night. The suspension was then centrifuged and the clear

supernatant solution was collected in a 100 ml volumetric

flask. Centrifugation was repeated five times using 10 ml

of 1 N NH^OAc to mix and 5 ml of 1 N NH^OAc for washing the

wall of the tube. From the third time of NH^OAc treatment

onwards the clear supernatant solution was tested, on dup­

licate samples, for presence of calcium. The calcium test

consisted of adding five drops each of 1 N NH^ Cl and 10%

ammonium oxalate and 2 ml of 0.1 N NH^OH to 2 ml of the

clear supernatant solution and heating the solution to near

boiling point. The presence of calcium was indicated by a

white precipitate or turbidity. In this experiment all the

fourth washings showed negative results for Ca++ and there­

fore five washings were quite sufficient to assure complete

NH^+ saturation. On the collected supernatant solution

diluted to a volume of 100 ml the exchangeable bases were

determined.

The NH^+ saturated soil sample in the centrifuge tube was then treated four times with 1 N NH^Cl using 10 ml each

time to mix and 5 ml to rinse off the wall of the centri­

fuge tube. The excess NH4+ was washed out with 99% isopro­

pyl alcohol. The presence of chloride was tested using 0.1

N AgNO^. All samples gave negative chloride tests in the 39

third or fourth washings and therefore five washings were

considered sufficient for removing the excess NH^+ .

The adsorbed NH.+ was determined as follows: The 4 NH^ saturated soil sample in the centrifuge tube was

treated with acidified 10% NaCl and mixed well, centrifuged

and the clear supernatant solution was collected in a 100 ml volumetric flask. This wash procedure was repeated 5

times and made to volume with acidified NaCl. A 2 ml, 5 ml or 10 ml aliquot of this solution was placed in the micro

Kjeldahl falsk depending on the amount of NH4+ adsorbed.

Ten ml of 1 N NaOH was added and about 40 ml was distilled

into 5 ml of 2% BO^. Five drops of Fleisher (Fisher) methyl purple indicator was added and the boric acid solu­ tion was titrated against standard sulfuric acid to a purple end point. Blanks were run on the reagents. The titration figure was corrected for the blanks and milliequivalents of ammonium in 100 grams of soil were calculated.

NaOAc Method for CEC Determination

Five grams of soil were placed in a 100 ml pyrex centrifuge tube. Ten ml of 1 N NaOAc (pH 8.2) was added, mixed well for 5 minutes and centrifuged. The supernatant liquid was decanted. This Na+ saturation procedure was repeated 5 times. Then the sample was washed with 99% isopropyl alcohol 4 times. Usually for the second or third washing, ferric chloride yielded a negative test for acetate. 40

The adsorbed sodium was replaced by washing five times with 10 ml plus 5 ml portions of 1 N NH^OAc decanting each washing into a 100 ml volumetric flask. The solution was made to volume with NH^OAc and the Na+ was determined with a Coleman flame photometer.

Barium chloride plus Tri. ethanol amine method for the deter­ mination of exchange acidity.

Five grams of soil were placed in a 100 ml Pyrex centrifuge tube. Ten ml of 0.5N BaCl 2 + 0.055N Triethan- olamine at pH 8.0 was added two times mixing well each time. The wall of the centrifuge tube was rinsed with an additional 5 ml of extracting solution and allowed to stand overnight. The suspension was centrifuged and the clear solution was collected in a 100 ml volumetric flask. The procedure was repeated five times using 10 ml of the ex­ tracting solution to mix and 5 ml to wash off the wall of the centrifuge tube and the clear solution was collected in a 100 ml volumetric flask. A known aliquot of the solution was titrated against standard HC1 to a pink end point

(pH 5.1) with the usual bromcresol green-methyl red indica­ tor. The mixed indicator solution was 0.22 gram of brom­ cresol green and 0.075 gram of methyl red dissolved in 96 ml of 95% ethanol containing 3.5 ml of 0.1 N NaOH.

Exchange acidity (EA) in meq per 100 grams of soil was calculated as follows:

EA - (B-S) N (20 D) 41 where B - ml of acid required to titrate an equal aliquot of original extracting solution.

S - ml of acid required to titrate a known aliquot of the soil extract.

N » normality of the acid.

D * dilution factor.

KC1 extraction and fluoride titration procedure for deter­ mination of extractable acidity and exchangeable aluminum.

Five grams of soil were plac&d in a 100 ml Pyrex centrifuge tube. Ten ml of 1 N KC1 was added and mixed well. The wall of the centrifuge tube was rinsed with 5 ml of 1 N KC1, centrifuged and the clear solution was decanted into a 100 ml volumetric flask. This operation was repeated five times and the solution was made to volume with 1 N KC1.

A known aliquot of this extracted solution containing ex- 3+ i. changeable A1 and H was transferred to a 200 ml Erlen- meyer flask and titrated against standard NaOH to a perman­ ent pink end point with alternate stirring and standing, using 5 drops of phenolphthalein indicator. A few more drops of the indicator was added to replace that adsorbed by the precipitate of Al(OH)^, if needed. The amount of the base used was equivalent to the total amount of acidity in the aliquot taken. One drop of standard 0.1 N HC1 was then added to bring the solution back to the colorless con­ dition and 10 ml of NaF solution was added. While stirring the solution constantly, the solution was titrated against standard 0.1 N HC1 until the color just disappeared. One or two drops of the indicator was added. If the color 42 appeared, additions of acid were continued until the color just disappeared and did not return within two minutes.

The milliequivalents of acid used was a measure of the ex- 3+ changeable A1 . This value was subtracted from the milli­ equivalents of total acidity (initial base titration) to obtain the milliequivalents of exchangeable H+ . RESULTS AND DISCUSSION

The five methods used in this study for the CEC deter mination involved essentially the saturation of the ex­ change sites of the soil material with the reference cation which is then replaced and determined. The four main steps involved in such determination are:

(a) treatment of the soil sample with a salt solu­ tion to replace the native exchangeable cations with the reference cation,

(b) removal of the occluded salt solution by extrac­ tion with a solvent,

(c) replacement of the adsorbed reference cation and

(d) determination of the replaced reference cation.

Each of the first three steps may encounter some analytical error. Thus, in the first step, the displace­ ment of native cations may be incomplete; in the second step, error may result unless the loss of the adsorbed ref­ erence cation by hydrolysis is balanced by retention of some excess of the saturating salt; and in the third step, the replacement of the adsorbed reference cation should be complete but excessive use of the replacing salt could re­ sult in mineral solution. In order to avoid or keep these errors to a minimum, some preliminary observations were made in this study. The salt solution of the reference cation of 1 N concentration was considered more than ade­ quate to replace the native exchangeable cations and to fill in the exchange sites of the soil material in step (a)

43 44

A minimum of two hours of total contact time of the satur­

ating or replacing solution was considered sufficient to

reach the exchange equilibrium. Malcolm and Kennedy (1969),

using specific ion electrode techniques, measured the rate

of cation exchange on kaolinite, illite, vermiculite and + + 2+ 2+ 2+ montmorilIonite between K and Na and Ba , Ca and Mg

They concluded that more than 85 per cent of the exchange

takes place within the first two minutes of mixing and

equilibrium is essentially complete within 17 minutes of

mixing time.

To accomplish removal of the occluded salt solution

in step (b), Alexiades and Jackson (1965) employed one washing with H20 and 5 washings with 99.0% methanol, adding

acetone as required to prevent dispersion. Okazaki, et al.

(1962) suggested no washing after saturation of the sample with the reference cation but calculating the amount of

the occluded salt solution by weight difference and using

this correction in the final CEC value. Frink (1964) sug­ gested the use of 0 . 0 0 1 N salt solution of the reference cation for occluded salt determination and correction for soil samples in the CaCl 2 method of CEC determination. He agrees with Peech, et al. (1962) on isopropyl alcohol as a wash solvent for use in the conventional NH^OAc procedure.

Lower alcohols were found to solubilize some ammoniated organic matter complexes. TABLE 3.— Effect of washing procedures in CaC]^ method of CEC determination

CaEC meg/100 g soil Differences in CEC

Soil Once water Once water Once water + 4 CaEC CaEC Sample + 5 MeOH + 7 MeOH washings with (I-H) (I—III) No. washings washings 0.0001 N CaCl2 I II III

1 9.0 9.0 7.5 0 1.5 2 5.2 5.2 4.4 0 0.9 3 8.4 8.1 7.4 0.2 1.0 6 10.9 11.1 10.5 -0.2 .4 8 5.6 5.2 5.0 0.4 .6 13 0.8 0.7 0.6 0.1 .1 15 24.2 22.0 21.8 2.2 2.5 18 14.2 14.4 14.2 -0.2 -0.1 21 2.5 2.3 2.0 0.1 .5 23 3.7 3.3 2.9 0.4 .8 26 1.3 1.1 0.9 0.2 .4 32 4.6 4.7 3.4 -0.1 1.2 35 1.7 1.4 1.2 .4 .5 39 30.0 29.0 28.5 1.0 1.5 46

In the present study a comparison of the CEC values

was made to know the effectiveness of methanol (Alexiades

and Jackson, 1965) and 0.0001 N CaCl 2 as wash solvents.

The data in Table 3 indicate that washing the samples

once with water plus five times with methanol after calcium

saturation gave consistently higher values as compared to

procedures II and III where the samples were washed once with water plus 7 times with methanol or once with water

plus 4 times with 0.0001 N CaCl2, respectively.

In procedure III where 0.0001 N CaCl 2 was used as the washing solution, the weight difference between the wet

sample after washing, centrifuging and decanting the super­

natant liquid and the dry sample could be used to calculate 2+ the exact amount of occluded Ca

For samples studies, weight of the 0.0001 N CaCl 2 2+ usually did not exceed 2.5 grams. The Ca present in this 2*f weight of solution is 0.00025 meq. This amount of Ca was

considered negligible to deduct from the meq Ca++/100 g

soil obtained. At this low concentration of 0.0001 N

CaCl 2 the possibility that water as a polar solvent may 2+ hydrolyze Ca is negligible because of the saturation of 2+ clay and the presence of a low amount of Ca ions in the solution. The CEC values obtained by procedure III were used for the purposes of comparison in this study as they were more precise.

To determine the number of washings that are neces­ sary to insure complete replacement of the reference cation 47 in step (c) of the KC1 method of CEC, K+ was determined in each successive washing as shown in Table 4. These data indicate that 5 times washing with a salt solution of the displacing cation displaces the reference cation effic­ iently.

Among the five methods of CEC determination employed in this study, the NaOAc procedure was done at pH 8.2, the

H+ used in Sum EC was determined at pH 8.0, and the other three procedures were employed at pH 7.0. CEC determina­ tions were made with the NaOAc procedure (Table 5) at pH

7.0 and 8.2 to see if the pH difference would significantly affect the CEC values. The CEC values determined by the

NaOAc method at pH 7.0 and pH 8.2, as shown in Table 5, agree well with each other for the soils studied. It therefore seems that essentially the same external and in­ ternal charges of the soil exchange sites are satisfied at pHs 7.0 and 8.2. Apparently, the CEC values determined by

NaOAc method at pH 8.2 can well be compared with CEC values determined by other methods at pH 7.0 without a reasonable doubt that there may be an appreciable contribution to the

CEC values between these two pH values. The comparable values between the SumEC and the NH^EC also bear out this relationship, Table 6 . The five methods of CEC determination used in this study were: (1) calcium saturation or CaCl 2 method, (2) potassium saturation or KC1 method, (3) ammonium saturation or NH^OAc method, (4) sodium saturation or NaOAc method, TABLE 4.— Relationship between effective replacement of K+ by NH^+ with increasing number of washings.

Soil Total 1st 2nd 3rd 4th 5th 6th 7th Mo. K+ PPi

1 62.5 14.0 3.0 0.4 0.1 0 0 80.1

2 25.0 7.5 1.3 0.2 0 0 0 34.0

4 59,0 9.0 2.1 0.3 0 0 0 70.4

6 132.5 19.0 7.4 2.2 0.5 0.2 0 161.6

9 112.0 16.0 6.3 1.7 0.5 .1 0.1 137.1 00

13 11.0 1.4 .5 0.1 0.1 0 0 13.0

15 222.5 63.0 19.1 6.0 2.3 0.8 0.3 313.1

16 162.5 44.0 12.0 3.3 1.2 .3 0.1 223.0 TABLE 5,-^Cation exchange capacity values for 15 soil samples determined by the NaOAc method at pHs 7.0 and 8.2.

Soil So^ NaEC meg/100 g Increase with pH Sampie Series Horizon pH 7.0 pH 8.2 meq/100 g MO •

1 Miami Ap 11.1 11.4 + .3 3 Miami 15.1 15.7 + .4 B21t 6 Volinia Ap 24.3 23.9 - .4 7 Volinia 13.6 13.6 0. B22t 9 15.2 16.0 +0.8 Kalamazoo B2t 12 Saugatuck 22.3 23.1 + .9 B21h 14 Onaway Ap 20.0 20.9 + .9 15 Brookston Big 32.5 33.4 + .8 17 Ontonagon Ap 29.4 31.0 +1.6 19 Iron River Ap 26.4 26.5 + .1 20 Iron River 14.1 14.5 + .4 Bhir 27 9.4 9.2 munising A 2 - .2 33 Onaway 21.5 21.3 - .3 B21t 35 Kalkaska 15.5 16.3 + .8 B22ir 39 Pewamo Ap 46.5 45.6 -1.0 50

and (5) summation of cations method. The CEC values ob­ tained by these methods will hereinafter be referred to as

CaEC, KEC, NH^EC, NaEC, and SumEC respectively, expressed in meq / 1 0 0 g of soil.

These five methods were compared with regard to their suitability in terms of accuracy, reliability, simplicity, reasonable quickness, and their proper significance in the following kinds of soil horizons:

(a) the surface horizons Ap and (13 samples),

(b) the illuvial spodic horizons B^, and B^r

(6 samples),

(c) the illuvial B. and B_ horizons (10 samples), t g (d) the leached A 2 horizon of Spodosols (2 samples),

the leached A 2 and A£ horizons of Alfisols or

Alfic intergrades (4 samples), and the parent

material or C^ horizon (3 samples).

The data obtained for A 2, a £ and C^ horizons were grouped together, (d) above, as they all contain essentially uncoated minerals possibly behaving similarly.

In Table 16 in the Appendix the CEC values obtained by five methods, the soil acidity components determined, and the estimation of vermiculite contents in these samples as determined by Alexiades and Jackson's (1965) procedure are s h o w n .

The vermiculite content in soils were calculated

(Alexiades and Jackson, 1965) assuming 154 meq/100 g as 51 the interlayer charge of vermiculite as follows:

, . ^ ^ (CaEC - KEC) X 100 percent vermiculite in Soil (B) « ------

B x 100 percent vermiculite in clay (C) - % cl-ay ln fche soil

The percent vermiculite in soil clay calculated from this procedure may be only a qualitative guide particularly for samples with low soil clay contents.

The depth functions of NaEC and CaEC of the soil horizons studied are shown in Figure 6 . The magnitude of the NaEC and CaEC values for specific profiles {Figure 6 ) showed consistently higher NaEC values on all horizons. The difference between these two CEC values was prominent in

Spodosols, particularly in spodic horizons as compared to

Alfisols or Mollisols. However, in Munising C^ horizon, a

Spodosol, there was less difference between NaEC and CaEC values.

The mean CEC values obtained by the five methods grouped according to soil horizons are shown in Table 6 .

The values in Table 6 indicate the general trend of

CEC values being equal or higher in the illuvial Bfc and Bg horizons as compared to the surface Ap or A^ horizons and lower CEC values in spodic horizons. However, the horizons in each vertical column are not all from the same profile .

Thus, the depth functions in Figure 6 are more truly indica­ tive of the situations in particular soil profiles. CEC meq/100 g of soil

10 20 10 20 10 20 10 20 10 20 10 20 *Tt> B 21t ig B 22g

A 2B3t a) Miami Loam Kalamazoo Spinks Loamy Ontonagon Volinia Loam Brookston Loam Loam Fine Sand Silty Clay c •H Ul to 10 20 10 20 10 20 g lO B a22 VAWV, 21h 20 B0 40 9 0 g Cx •0 Kalkaska Sand Onaway Loam Iron River Saugatuck Sand Silt Loam i Munising Loamy Sand

Figure 6. Depth functions of CaEC and NaEC in soils studied. CaEC NaEC TABLE 6.— The mean CEC values determined by five methods grouped according to the kinds of soil horizons.

Mean CEC meq/100 g of soil Ratio

Horizon KEC CaEC SumEC n h 4e c NaEC NaEC/CaEC

Ap and 6.4 8.4 11.8 12.4 18.2 2.2 Ui u> V Bhir and Bir 2'1 1.8 6.8 6.5 13.5 11.4

B. and B„ 7.3 9.4 11.7 12.9 17.2 1.8 t g

A j , A*2 and C^ 1.6 1.9 3.3 3.4 5.1 4.3 54

The decreasing order of the mean CEC values deter­ mined by five methods on the surface, the A 2 + A£ + C^, and the illuvial B. and horizons are; t g

NaEC > N H 4 EC >_ SumEC > CaEC > KEC

However, a slightly different pattern was observed for spodic horizons:

NaEC > SumEC _> NH^EC > KEC >_ CaEC

Under a given set of conditions, it may be possible to predict the CEC values among the five methods used in this study according to the prediction equations given in

Table 7 for the respective soil horizons of representative

Michigan soils. The prediction equations were highly sig­ nificant on all the soil horizon groupings except the spo­ dic horizons and correlation of the NaEC with the CaEC and

KEC on the A2, A£ and C^ horizons. For spodic horizons, however, only NH^EC vs NaEC and KEC vs CaEC could be highly significantly predicted while the SumEC vs NaEC and SumEC vs NH^EC were only significantly correlated and the others were correlated at the significance levels shown in the

Table 7, part B. These prediction equations can be inter­ preted as denoting the relative magnitudes of CEC values to each other with a positive or a negative constant. For 55

example, in the surface horizons, CaEC was .6 NaEC minus

2.43. There seems to be a 1:1 relationship between KEC

and CaEC in spodic horizons.

Variations in relative magnitudes among CEC values by a given method are due usually to the influence of clay

content and organic matter present in soils. Regression analyses were performed to know the extent of influence of clay and organic matter and the results are shown in Table 8 . To facilitate better interpretation of the regression equations presented in Table 8 , the relative magnitude of the charge contributions to each CEC value from clay and organic matter were listed in Table 9 and 10 respectively.

The charge contributions from organic matter (Table 10) were calculated on the basis of the conventional multipli­ cation factor 1.72 to convert percent carbon to percent organic matter present in the soil.

As seen from the results in Table 9, the charge con­ tribution from clay content of the soil amounted from as low as 11 meq/100 g for KEC in illuvial B^ and Bg horizons

(Significant at .11 level) to as high as 45 meq/100 g for

NH^EC in group D horizons of uncoated materials (significant at .01 level). The decrease in charge contribution by clay was consistent from surface to spodic to illuvial B^ and B^ horizons though in spodic horizons its contribution was 56

TABLE 7.— Regression equations and correlation coefficients among CEC values determined by five methods grouped according to the kinds of soil horizons.

A. Surface 1horizons Ap and A1 B. Illuvial spodic horizons Bh' Bhir and Bir r r CaEC .59 NaEC _ 2.43 .924** CaEC S .08 NaEC + .83 .420(.41) KEC - .41 NaEC - 1.11 .955** KEC = .09 NaEC + .86 .505(.31) n h 4ec = .63 NaEC + .95 .934** NH4EC = .46 NaEC + .25 .919** SumEC - .69 NaEC - .74 .918** SumEC - .34 NaEC + 2.21 .837* KEC - .66 CaEC + .82 .991** KEC 1.00 CaEC + .25 .988** n h 4ec => .98 CaEC + 4 .18 .937** n h 4ec **1.92 CaEC + 2.96 .677 ( .14) SumEC - 1.13 CaEC + 2.28 .973** SumEC = 1.06 CaEC +4. 89 .458 (. 36) NH4EC - 1.51 KEC + 2.78 .965** n h 4ec = 2.07 KEC + 2.18 .7 36 (.10) SumEC - 1.70 KEC + .92 .978** SumEC = 1.33 KEC +4 .07 .581(.23) SumEC - 1.06 n h 4ec - 1.40 .956** SumEC - .67 n h 4ec +2. 51 .821*

C. Illuvial B and :B horizons A C^ horizons 9 D * A2 ' 2 and

CaEC .70 NaEC - 2.54 .962** CaEC - .41 NaEC - .18 .711* KEC - .50 NaEC - 1.26 .977** KEC - .32 NaEC - .02 .743* n h 4ec - .74 NaEC + .21 .949** n h 4ec - .77 NaEC - .51 .882** SumEC - .80 NaEC - 2.12 .962** SumEC - .64 NaEC - .05 .839** KEC m .70 CaEC + .73 .989** KEC - .73 CaEC + .22 .973** n h 4ec - 1.03 CaEC + 3.21 .958** n h 4ec - 1.42 CaEC + .74 .929** SumEC - 1.15 CaEC - .89 .933** SumEC = 1.19 CaEC + 1.04 .896** n h 4ec - 1.49 XEC + 2.08 .972** NH4EC - 1.89 KEC + .39 .930** SumEC - 1.62 KEC - .11 .987** SumEC - 1.64 KEC + .68 .926** SumEC m 1.02 n h 4ec 1.49 .952** SumEC .81 n h 4ec .54 .927**

* Significant at .05 level ** Significant at .01 level ( ) Significant at level shown. TABLE 8.--Relationships between CEC values and clay and carbon contents, their partial and multiple correlation coefficients and levels of significance on soils grouped according to horizons.

A. The surface horizons A^ and A1 B. The Spodic horizons B^, ®h;IX And Bir

tClay ICarbon r2 IClay « Carbon r2 NaEC .37 + 12.14 -4.57 .811** NaEC m .31 + 6.11 + 5 + 58 .557{.3) a .66 .82 a .33 .74 b .02 .01 b .59 .15 CaEC .33 ♦ 4.07 -2.35 .637** CaEC ■ .22 + .24 + 0 + 38 .866* a • 57 .39 a .93 .41 b .05 .21 b .02 .49 KEC .24 + 3.01 -1.41 .737** KEC — .22 + .43 + 0 + 45 .853 (.06) a .65 .48 a .92 .60 b .02 .11 b .03 .28 NH.EC .44 + 3.92 ♦0.28 .832** nh4ec m .38 + 3.03 + 1.32 .724 (.15) a .79 .50 41 .73 .81 b .01 .10 b .16 .10 SumEC .41 ♦ 4.38 -0.58 .656** SumEC m .20 + 3.01 + 2.69 .832(.07> a .60 .37 a .66 .91 b .04 .23 b .22 .03

C. The: illuvial Bt and horizons 0. The , A’ and C^ horizons 9 A2 NaEC .24 ♦ 10.17 +7.34 .832** NaEC ■ .31 + 5.03 ♦ 2.28 .846** a .60 .77 a .78 .88 b .09 .02 b .02 .01 CaEC .14 + 7.93 +2.76 .805** CaEC ■ .34 + .90 ♦ .02 .972** a .48 .77 a .99 .81 b .19 .02 b .01 .01 KEC .11 5.60 +2.38 .855** KEC ■ .25 + .74 + .22 .929** a .57 .82 a .96 .69 b .11 .01 b .01 .06 nh4ec - .23 ♦ 6.75 ♦4.77 .827** NH4EC .45 + 2.68 + 53 .934** .67 .71 a .95 .87 b .05 .03 b .01 .01 SumEC .16 + 9.45 +3.73 .861** SumEC m .40 + 1.49 + 1.00 .798** a .56 .83 a .88 .54 b .12 .01 b .01 .17

a - partial correlation coefficients. * Significant at 0.05 level b « significance levels of the partial correlation coefficients *' Significant at 0.01 level ( ) ■ significance levels of multiple correlation coefficients TABLE 9.— Relative charge contributions from clay to CEC values grouped according to the kinds of soil horizons.

Horizon (Significance levels shown in parenthesis) Surface Illuvial spodic Illuvial CEC Values A2, A£ and C^ and A. B. and B„ P 1 V Bhir and Bir

meg per 100 g clay NaEC 37 (.02) 31 (.59) 24 (.09) 31 (.02)

CaEC 33 (.05) 22 (.02) 14 (.19) 34 (.01)

KEC 24 (.02) 22 (.03) 11 (.11) 25 (.01) n h 4e c 44 (.01) 38 (.16) 23 (.05) 45 (.01)

SumEC 41 (.04) 20 (.22) 16 (.12) 40 (.01) 59 significant only for CaEC and KEC. These charge contribu­ tions were in a fairly normal range for soil clays of mixed mineralogy, characteristic of many of the representative

Michigan soils used in this study.

Several workers (Cummings, 1959; Franzmeier, 1962;

Wurman et al. , 1959; Ross, 1965; Rieke, 1963; Reiman and

Mortland, 1969) have studied the mineralogical composition of the soil materials of horizons of soil types similar to those used in this study. The quantitative estimation of the clay minerals they reported are presented in Table 17 of the Appendix.

Since the horizon samples they studied were not the same, but similar to the ones used in this study, these data can only be a qualitative guide. On the basis of these data, the Ap, A^ and illuvial or horizons of the soils studied have dominantly a mixed mineralogy with kaolinite, illite, chlorite and vermiculite distributed approximately equally, with low amounts of smectites and

Al-intergrade minerals. In the illuvial spodic horizons

Bh , Bh^r and B^r , there is a predominance of Al-intergrade minerals. The C^ horizon of Kalamazoo loam has also a high amount of vermiculite (53.8%) in its clay fraction.

The results in Table 10 show that the charge contri­ butions from organic matter to NaEC was highest on all horizons and unreasonably high though highly significant in TABLE 10.— Relative charge contributions from organic matter to CEC values grouped according to the kinds of soil horizons.

Horizon (Significance levels shown in parenthesis) CEC values Surface Illuvial spodic Illuvial A,, A' 6 C1 Ap & Ax Bh, Bhir and Bir Bfc and Bg

meq per 100 g of organic matter

NaEC 706 (.01) 355 (.15) 599 (.02) 292 (.01)

CaEC 237 (.21) 14 (.49) 461 (.02) 52 (.01)

KEC 175 (.11) 25 (.28) 326 (.01) 43 (.06)

NH.EC 176 4 228 (.10) (.10) 392 (.03) 156 (.01)

SumEC 255 (.23) 175 (.03) 549 (.01) 87 (.17) surface horizons. For CaEC and KEC, they were unreasonably

low in both the illuvial spodic horizons and horizons of

uncoated materials and were least significant in spodic

horizons. The organic matter charge contribution was within

the normally expected range of a low of 87 to a high of 255

meq/100 g for all other CEC values on all horizons excluding

the illuvial B. and B horizons. t g The low charge contribution from organic matter to

KEC and CaEC in spodic horizons may be due to the fact that 3+ these unbuffered chloride salts do not dispalce Al com-

plexed by organic matter from the pH dependent sites at

pHs above that of the soil. Works of Thomas (1961) and

Rich and Thomas (1960) have indicated that the adsorbed

hydroxy Al ions are not extracted by neutral salt solutions

of 1 N concentration. However, in this study, NH^OAc method

gave higher values than the CaCl 2 or KC1 method. There was

a high charge contribution from organic matter to all CEC

values in the illuvial B. and B horizons (Table 10) where t g the organic matter content is normally expected to be the

lowest in the profile. This may be partially explained by

the fact that the conventional factor used for subsoil hori­

zons with low amount of organic matter should be more than

two as Broadbent (1953) and Ranney (1969) have discussed.

This increase charge contribution from organic matter to CEC values in the illuvial B. and B„ horizons as compared to t g surface or spodic horizons has a genetic significance in 62 that the organic exchange complex having more charge is evidently carried farther down in the natural leaching column, the soil profile in the course of its development.

Thus, the interpretations from regression equations presented in Table 8 show that the charge contributions from both clay and organic matter contents were fairly con­ sistent for NH^EC. The mean NH^EC values (Table 6 ), were intermediate between the CaEC and NaEC values. Also, they closely approximated the SumEC which includes the exchange­ able bases plus the exchange acidity measured by EA(BaCl2+

TEA) .

These facts lead one to conclude that for the Michi­ gan soil materials studied, the NH^OAc method is the best for CEC determination. However, the clay charge estimations were relatively more significant in spodic horizons for

CaEC and KEC values. Also, CaEC and KEC reasonably esti­ mated the relative charge contributions from both clay and organic matter on surface horizons.

In order to better understand the observed high NaEC values as compared to the other four methods used in this study on all horizons, particularly in the spodic horizons, the probable causes of their variations are discussed below. The four factors that may influence these varia­ tions a r e :

1. The position of the saturating cation Na+ in

relation to its replacing cation NH^+ within the

lyotropic series. 63

2. Anion retention by the amorphous positive edge

groups, of hydroxy aluminum layers or iron

oxides neutraiyzing their charge and thus reliev­

ing the net negative charge on the exchange sites

of the layer silicates for cation exchange.

3. Possible dissolution of the amorphous Fe 20^ p r e ­

sent in the spodic horizon by sodium acetate to

an unmeasured but significant extent and thus

exposing the blocked charges of the layer sili­

cate edges.

4. Possible mild dissolution of Al-interlayers

abundant in spodic horizons by the sodium ace­

tate solution and thus exposing blocked negative

charges of the clay minerals.

In the first cause mentioned above« due to the mass

action situation forcing the replacement to completion, the relative positions of cations in the lyotropic series are not relevant.

Concerning the second reason, i.e., anion retention possibility, aluminum interlajering is a natural pedogenic process according to Jackson (1960). As the degree of inter­

layering increase^ the degree of collapse from 14°A spacing

to 10°A decreases upon K+ saturation and air drying treat­ ment in the X-ray analysis. The resulting charged aluminum polymer is large and essentially unexchangeable resulting

in reduction of CEC. The reduction in CEC in excess of 64 that accounted for by oxidation of ferrous to ferric iron

(Raman and Jackson, 1966), results from protonation of hydroxyls at defects developed in the structure through removal of Al, Mg or Fe (Jackson, 1960, 1963a; Huang and

Jackson, 1966) according to the equation:

Layer - OH A1Q 33 + H+— >layer-OH2+ 0 .33 A l 3+

3+ The Al in the above equation can polymeryze as a positive hydroxy-Al coating on negative surfaces of clays

(Jackson, 1960, 1963a, 1965). Positive iron oxide coatings can form (Davidtz and Sumner, 1965). The resulting Al hy­ droxyl polymer, which is chlorite-like, has Al OH2+ edge groups that are pH dependent and are hydrolyzable as are silicate layer edges (Jackson, 1968) as follows:

-Al - OH - Al ----- > Al - O H _ 1 / 2

-Al - OH" 1 //2+H+--- > A 1 - O H 2+ 1 / 2

These polymers or colloidal particles containing positively charged edge groups can directly react with anions. When these occur on external surfaces, and in an acid environment, anions as well as cations may be retained by a reaction in which the positive charge is neutralized by the anion of a salt and the cation is then held by the released charges of the clay. As the pH is increased, 65 negative charge is released, but the edge groups of the polymer or colloid now take on OH*" ions.

It may be thought that when OH~ adsorption increases in preference to the solution anion, OAc", the OAc" remains in solution and the neutralization of the blocked charges by 0H~ may lift the blockage from exchange sites of the clay mineral similar to that hypothesized by Bartlett and

McIntosh (1969) in Sfc>odosols. In their studies of ion ex­ change in soils containing high amounts of amorphous con­ stituents, Birrelland Gradwell (1956), working with the clay fraction of a volcanic ash subsoil, found that after

NaOH dispersion but without the destruction of iron oxide coatings, the sample retained about 8 . 6 meq of OAc*" per

100 g of soil at pH 7.0 from BatOAc^ of 1.072 N concentra­ tion. The studies of Birrelland Gradwell (1956) also in­ dicated that Cl- ion retention was about 1/20 as great as

OAc” ion retention at pH 7.0 and that it was about 0.4 me q / 1 0 0 g soil.

Quirk (1960) found 3 meq of Cl” retained at pH 1 but less than 0.8 meq/100 g chloride was retained at pH

6 and above. Berg and Thomas (1959) studied the anion elution patterns from soils and soil clays and concluded that chloride ions though adsorbed get desorbed easily in the range of pH of soils under field conditions. deVilliers and Jackson (1967) also noted little or no retention of 66

Cl" ions by ligand exchange above pH 6.0. The increase

in chloride retention between pH 4 and 5 is attributed to

the development at pH 5 of an increased number of OH-

bridge sites between A1 atoms of the polymeric units by

continued polymerization or olation (Bailar, 1956). Since

Cl” retention increased with increasing pH value between

pH 4 and 5, whereas positive electrostatic charge of the

sesquioxide normally decreases with increased pH, owing to

deprotonation, the "anion exchange" measured here is con­

sistent with ligand exchange,

-Al Al- + Cl * -Al Al- + O H ”

OH

rather than electrostatic exchange of "swarm" anion. They

(de Villiers and Jackson, 1967) attributed the decrease in

the retention of Cl" above pH 5 to the increasing OH”/Cl”

ratio in solution, which favors hydroxyl retention in the

polymeric complexes in preference to the chloride.

Thus, it may seem that there may be a possibility of more acetate retention by the positively charged groups

compared to chloride releasing soil exchange sites for

cation exchange.

Possible dissolution of amorphous Fe 2 0^ or organic

iron complexes by sodium acetate solution thus making available the negative exchange sites of clay minerals 67 for cation adsorption and release, or, in other words, for exchange may be discussed as follows.

The relative abundance of amorphous material, A1 20 3 and F e 20 3 in the spodic horizons of Michigan Spodosols have been proved by studies of previous workers (Wurman et al. 1959; Franzmeier, 1962; Rieke, 1963; Lietzke, 1968;

Raman and Mortland, 1969).

For characterizing the mineral nature of the soil, the amorphous coatings and crystals of iron oxides such as hematite and goethite which mask the true nature of the clay components need to be removed. Mehra and Jackson

(1960) mentioned the importance of this removal for effec­ tive segregation into different particle size fractions and dispersion of silicate portions. For X-ray diffraction studies the removal of free iron oxides greatly enhances the parallel orientation of layer silicate clays and brings out some X-ray diffraction peaks that are otherwise dif­ ficult or impossible to detect. Differential and integral thermal analysis, electron micrographs and CEC are greatly improved after removal of free iron oxides. Aguilera and

Jackson (1953) compared the method employed by Deb (1950) who had proposed the use of sodium 'hydrosulfite' (Na2 S 2 0 ^, sodium dithionite or sodium hyposulfite) and a 0 . 2 N sodium tartrate , 1 N sodium acetate solution plus 2.0 grams of the reducing agent in pH ranges from 2.9 to 6.0 at 40°C.

But this procedure confronted a difficulty of FeS precipi­ tation. Their comparative studies (Aguilera and Jackson, 68

1953) with the use of 7.4% versene and acetic acid removed

88.9 percent of the Fe 2<)3 present in the sample but FeS

precipitated. Later Aguilera and Jackson (1953) proposed

the dithionite method and modified the same later to in­

clude NaHCO^ buffer to maintain the high oxidation poten­

tial of N a 2 & 2 0 ^ (Mehra and Jackson, 1960), wherein buffer

and chelating actions of sodium citrate and the reducing ability of Na 2 & 2 0 ^ were utilized advantageously at pH 7.3 not to destroy the iron layer silicate. Also, this in­ curred no FeS precipitation.

Thus, it is reasonable to conclude that under the congenial medium pH 8.2, Na acetate may remove some of the amorphous or coated Fe 2 0 ^, particularly their reduced forms when present, though not to the extent of citrate in the presence of ^ 2 8 2 0 ^, a reducing agent. This mechanism can expose the exchange sites for exchange with Na* and its replacement by NH^+ giving higher NaEC values.

In relation to the fourth cause, i.e., possible mild dissolution of Al interlayers, Frink (1965) used sodium citrate, an analogue of Na acetate, to extract Al inter­ layers in his studies for characterization of aluminum interlayers in soil clays known to be abundant in chloritized vermiculite.

Tamura (1958) used sodium citrate, being a mild re­ agent compared to fluoride or hydroxyl groups in Fe 20 ^ removal, to remove the interlayers to characterize the 69

clay mineral observed bo behave like a dioctahedral ver-

miculite. Therefore, it may be thought that Na acetate may

extract some of the interlayer-Al present especially in

spodic horizons to an undetermined but significant extent

and thus effect an increase in CEC due to release of

blocked exchange sites.

These reasons lead one to expect an additive effect

of the three factors particularly the latter two in obtain­

ing high NaEC values compared to other methods.

To ascertain whether the above mentioned mechanisms

operate effecting the dissolution of amorphous and free

Fe2°3 and a 1 2°3' or9anic iron complexes and Al-interlayers and their influence on CEC in 1 N NaOAc, the CaEC and KEC

values were obtained on the same 13 soil samples after

NaEC determination as described earlier. The results ob­

tained are shown in Table 11.

The results shown in Table 11 indicated an increase

in CaEC values after 1 N NaOAc treatment on seven of the 13

samples. This increase was particularly significant in

spodic horizons or Ap horizons of well developed Spodosols.

The six samples where the CEC values before and after 1 N

NaOAc treatment remained approximately the same were the Ap horizons of Miami and Onaway, illuvial of Brookston,

B22t Munising and Kalamazoo and C^ horizon of Kalamazoo. TABLE 11.— The effect of IN NaOAc on CEC of soil materials.

n h 4e c CaEC KEC Soil Soil SumEC NaEC Sample Horizon series Determination relative to IN NaOAc treatment no. before before before re-run before after before after

1 Ap Miami 9.0 9.7 12.3 10.9 7.5 7.6 5.4 6.4 14 Ap Onaway 13.5 13.1 20.4 19.4 11.8 10.9 7.7 11.5 19 Ap Iron River 13.5 12.2 26.5 24.6 6.6 12.0 6.2 14.8 11 Ap Saugatuck 4.2 4.8 7.4 6.7 1.2 3.3 1.3 3.8 27 4.4 9.4 9.0 2.5 4.8 2.2 4.8 A 2 Munising 5.3 28 Munising 4.4 .7.8 19.6 18.5 1.3 8.1 1.7 14.3 Bir *4 12 Saugatuck 10.6 9.8 22.4 20.3 1.8 9.1 2.2 10.0 O Bhir 13 Saugatuck 2.4 2.5 4.8 3.3 0.6 1.1 0.6 N.D. Bir 35 Kalkaska 5.5 6.3 15.4 13.9 1.2 6.0 1.5 6.7 Bhir 15 Brookston 23.9 26.0 33.0 32.6 21.8 21.2 15.6 21.5 ig 30 Munising 7.4 5.6 8.9 8.5 4.5 5.0 3.6 7.9 Bt 9 Kalamazoo 15.9 10.5 16.7 17.4 8.8 10.7 7.1 13.6 Bt 10 Kalamazoo 2.2 1.7 3.3 3.1 1.0 0.9 0.9 1.4 C1

N.D. ■ Not Determined. 71

The KEC values were all higher after 1 N NaOAc treat­ ment. They were even higher than the CaEC values and were comparable to the NH^EC values in all cases except for sam­ ple 28, the B^r horizon of Munising where it approached more nearly the NaEC values. These results clearly indicate that reactions such as the postulated dissolution and/or anion retention mechan­ isms do operate during the 1 N NaOAc treatment and effect a significant alteration of the CEC of soil materials. Also, it is plausible that there may be a significant change in the organic exchange complex of the soil materials.

The soil acidity components were also determined to know their influence on CEC values obtained by the five methods. These data included the exchange acidity deter­ mined by BaCl 2 +TEA, NH^OAc and KC1 methods. Hereinafter these will be referred to as EA(BaCl2+TEA), NH^EA, KEA re­ spectively. For the purposes of comparison and practical considerations, exchange acidity values were also obtained through the courtesy of the University Soil Testing Labora­ tory which employs the SMP buffer method (Shoemaker, McLean and Pratt, 1961) for lime recommendations of Michigan farms.

Those values will be referred to as EA(SMP) hereinafter. 3+ + The exchangeable Al and H determined by KC1 method will henceforth be referred to as Al^+ (KC1) and H+ (KC1). The data obtained are shown in Table 16 of the Appendix.

Several workers (Coleman e t a l ., 1959; Pratt and Bair, 1961) 72 have referred to the difference between EA(BaCl 2+TEA) and

KEA as the pH dependent CEC. To identify that difference, it has been called "potential acidity" in this study and referred to as PA hereinafter.

The EA depth functions are shown in Figure 7 for specific profiles. From Figure 7 it can be seen that only 3+ the Ontonagon and Saugatuck surface samples contained Al 3+ (KC1). But all spodic horizons contained Al (KC1) and 3+ only half of the Bt horizons had Al (KC1). Potential acidity component was present in all soil horizons except the A 2 2 of Kalkaska sand and A2x and B22t of Munising. Po­ tential acidity was comparatively high in spodic horizons and it was the only soil acidity component in all horizons of Spinks and Brookston studied.

The mean values of the acidity components determined by modified Chapman procedure (1965) and Shoemaker, McLean and Pratt buffer method (1961) are shown in Table 12. In general, the A1 3 + (KC1) content increased from surface to subsoil horizons (spodic or argillic), the highest being in the illuvial spodic horizons, as generally observed by other investigators (Coleman et al., 1959; Rich and Thomas,

1960) . It is to be noted, however, that these inferences are drawn from the groupings of similar horizons of differ­ ent soil types.

The decreasing order of the mean exchange acidity values in Table 12 are, by methods of measurement: Depth (in inches) 60 40 20 40 30 0 2 30 30 60 50 ,0 10 Figure 7: Depth functions of soil acidity components acidity soil of functions Depth 7: Figure ( * 2 2 ■ = P ®22ir P = ■ 2 2 * ( B21t3 N ■ B22i« □ “ ■ olaiiycmoet -mg10go soil of g meg/100 - components acidity Soil Miami Loam Miami Kalkaska Sand Onaway Loam Iron River Iron Loam Onaway Sand Kalkaska 4 8 6 4 2 nsis studied. soils in BT Kalamazoo Loam B'lt 4 ___ 8 Fine Sand Fine Spinks Loamy Loamy Spinks Silt Loam Silt - A2B3t 8 E Ontonagon Ontonagon Silty Clay Silty Munising Munising Loamy Sand Loamy Ap B It 8 H oii om Brookston Loam Volinia Saugatuck Sand Saugatuck + 0+1 ■ + l B 22t □ Potential acidity Potential □

|EA(BaCl2+TEA) I KEA (KC1) + |A13 (KC1) I H+ 21h l D» \ Loam IB B ig 22g t

TABLE 12.— The mean values of acidity components grouped according to the kinds of soil horizons

Exchange Acidity Components meq/100 g soil pA m Horizons EA(SMF) NH.EA EA(BaCl~ KEA Al3* H*(KCL) EA(BaCl?+ + TEA) (KC1) TEA)-KEA

Ap and A^ 4.2 2.8 2.7 0.4 0.2 0.2 2.3

Bh» Bhir and Bir 9.3 4.8 5.0 1.6 1.1 0.4 3.4 *

Bt and Bg 3.0 3.5 2.1 0.9 0.5 0.3 1.2

A2, A£ and Cx 1.7 1.2 1.0 0.5 0.3 0.3 0.5 E w , .

75

EA(SMP) > NH4EA >_ EA(BaCl 2+TEA) > KEA

for the surface Ap and A^ and A 2 # A£ and and the illuvial

B^, Bhir an<* Bir h0*^-20*18* The EA(SMP) in the Ap and A^ or

B^, Bhir an<^ Bir ^orizons were nearly double the NH^EA. The pattern of decrease for the B. and B horizons were: t 9

EA(SMP) >_ EA(BaCl 2 +TEA) > NH^EA > KEA

The regression equations presented in Table 13 could

be interpreted better by arranging the acidity contributions

from clay and organic matter according to kinds of horizons

as shown in Tables 14 and 15. Acidity contribution from

per cent carbon has been converted to that from percent

organic matter (Table 25) employing the conventional conver­

sion factor 1.72.

The acidity contribution from clay, Table 14, indi­

cated an unusually high negative contribution for EA(SMP) in

spodic horizons (-238 meq/100 g). All other values ranged

between a -10 meq (EA(SMP), in horizon of uncoated materials)

and +14 meq (for NH^EA in spodic horizons). However, the

partial correlation coefficients obtained for clay were

non-significant on all horizons for all acidity components

other than the PA in illuvial B. and B_ horizons. TABLE 13.— Relationships between soil acidity measurements and clay and organic matter grouped according to dominant soil horizons.

A. The surface horizons Ap and A^ B. The spodic horizons B^, B^ir and B^r %clay % carbon r2 % clay % carbon r2

FA - .03 + 1.50 + .58 .586** PA - .03 + 2.09 + 1.06 .685 (.18) a - .40 .75 a - .11 .82 b .20 .01 b .86 .09 EA(BaCl.+TEA) = - .02 + 1.45 + .82 .451* EA(BaCl,+TEA) * - .06 + 3.25 + 2.05 .848 (.06) a 2 - .16 .62 a 2 - .25 .91 b .63 .03 b .68 .03 KEA + .01 - .05 + .24 .065 (.72) KEA 0.0 + .74 + .75 .453 (.41) a .22 - .04 a - .02 .67 b .49 .90 b .97 .22 NH4EA + .07 + .80 + .57 .277 (.20) NH.EA * + .14 + 3.16 .86 .724 (.15) a .31 .19 a .40 .85 b .32 .56 b .50 .07 EA(SMP) - .05 + 2.87 + .77 .212 (.30) EA(SMP) -2.38 + 5.53 + 9.66 .699 (.55) a - .15 .43 a - .66 .84 b .65 .16 b .55 .37

C. The illuvial Bfc and Bg horizons D. The & 2’ a2 and ci horizons

PA + .03 + .72 + .35 .842** PA + .12 + .39 + .36 .156 (.60) a .75 .68 a .12 .37 b .02 .04 b .77 .37 EA(BaCl.+TEA) = + .03 + .38 + 1.27 .337 (.24) EA(BaCl.+TEA) * + .03 + 1.23 + .53 .380 (.24) a .38 .21 a .17 .60 b .32 .59 b .69 .12 KEA + .02 - .54 + .72 .068 (.78) KEA 0.0 + .76 + .32 .224 (.47) a .21 - .41 a .01 .47 b .59 .27 b .98 .24 - + + + NH.EA + .08 2.31 2.93 .185 (.49) NH.EA4 + .09 2.37 .09 .695* a4 .36 - .41 a .46 .81 b .34 .27 b .25 .02 EA(SMP) - .05 + 1.10 - 4.39 .097 (.77) EA(SMP) - .10 + 8.25 - .04 .933** a - .13 - .18 a - .44 .97 b .79 .70 b .28 .01

a = partial correlation coefficients * Significant at 0.05 level b = significance levels of the partial correlation coefficients ** Significant at 0.01 level ( } = significance levels of multiple correlation coefficients TABLE 14.— Relative acidity contributions from clay to the exchange acidities grouped according to the kind of soil horizons.

f a vain«o Surface Illuvial spodic Illuvial A~, Al Difference eji vaiues Ap and A ^ ^ and B^ and Bg and CJ (high-low)

PA -3 (.2) -3 (.86) +3 (.02) 12 (.77) 15

EA(BaCl2+TEA) -2 (.69) -6 (.68) +3 (.32) 3 (.69) 9

KEA +1 (.49) 0 (.97) +2 (.59) 0 (.98) 2

NH4EA +7 (.32) +14 (.50) +8 (.34) 9 (.25) 22

EA(SMP) -5 (.65) -238 (.55) -5 (.79) -10 (.28) 228 TABLE 15.— Relative acidity contributions from organic matter to exchange acidities grouped according to the kinds of soil horizons.

EA Values Surface Illuvial spodic Illuvial A2, A£ Difference Ap and Ax V and B.r Bt and Bg an

PA 87 (.01 122 (.09) 43 (.04) 23 (.37) 99

EA(BaCl2+TEA) 84 (.03) 189 (.03) 22 (.59) 72 (.12) 167

KEA -3 (.90) 43 (.22) -31 (.27) 44 (.24) 76

NH4EA 47 (.56) 184 (.07) -134 (.27) 138 (.02) 318

EA(SHP) 167 (.16) 322 (.37) 64 (.70) 480 (.01) 416 79

The results shown in Table 15 indicated a relatively strong significant acidity contribution from organic matter to EA(BaCl 2 +TEA) on surface and illuvial spodic horizons.

Both NH^EA and EA(SMP) were strongly and significantly in-

i fluenced by acidity contributions from organic matter on horizons of uncoated materials. Its EA contribution to PA was significant in both the surface and illuvial and Bg h o r i z o n s .

To see if the three acidity measurements EA(BaCl2+

TEA), NH^EA and EA(SMP) estimate similar acidity contribu­ tions from soil materials studied , prediction equations calculated among these variables when grouped according to kinds of horizons are shown below:

2 A. Surface Ap and A^ r

EA(SMP) =>2.38 EA(BaCl 2 +TEA) -2.13 .869 (.01)

EA(SMP) - 0.77 NH4EA +2.07 .557 (.05)

B. Illuvial spodio horizons

EA(SMP) = 1.41 EA(BaCl 2+TEA) +1.33 .926 (.07)

EA(SMP) « 1.05 NH4EA +4.25 .747 (.25)

C. Illuvial B.t and B g horizons EA(SMP) - 2.57 EA(BaCl 2 +TEA) -1.95 .676 (.07)

EA(SMP) - 2.30 NH4EA +6.11 .176 (.30)

D. Horizons of uncoated materials

EA(SMP) = 2.66 EA(BaCl 2 +TEA) 0.93 .651 (.06)

EA(SMP) = 1.91 NH4EA 48 .70 (.04) 80

The above prediction equations show a highly signifi­ cant relationship between EA (BaC^+TEA) and EA(SMP) on sur­ face horizons at at .07 and .06 significance levels in other horizons. The EA(SMP) was significantly (at .05 and .04 levels) correlated with NH^EA in surface horizons and hori­ zons of uncoated materials. However, the larger EA(SMP) values, Table 12, on all horizons indicated that there may be a proportional overestimation of the soil acidity by this method particularly in spodic horizons.

The results of the regression analysis of both the

CEC values and exchange acidities with clay and organic matter contents of these acid to near neutral representative

Michigan soils showed that both of them were relatively more influenced by organic matter as compared to clay. In addition to the dissolution effect of NaOAc on amorphous and clay materials, neutralization is another factor yield­ ing high NaEC values particularly in spodic horizons.

Similarly, the neutralization of soil acidity by BaC^+TEA at pH 8.0 was also responsible for comparatively high SumEC v a l u e s .

These reuslts raise a question as to the purpose of the CEC determination. If the purpose is to determine the net negative charge of only the clay mineral components, it is necessary to remove all the coatings of iron oxides and i amorphous materials including the organic matter with cer­ tainty before the CEC determination. 81

On the other hand, to be a realistic estimate of the net negative charge of the complex system such as the soil materials studied, the method should give results that should more resemble that system in its usual state as plants are grown on it. In the soil exchange complex, es­ sential and plant available cations are mostly present in divalent form, except for K+ and Cu+ . Calcium is a small O divalent cation of radius 0.99 A and is more representative of the common exchangeable ion population in the soil. In the CaCl2 method of CEC determination, the possibilities of chloride ion retention are negligible in the pH range of field conditions. However, in spodic horizons CaEC did not reflect the potential charge contributions from organic m a t t e r .

The NH^EC values were intermediate between those of

CaEC and NaEC. The CaEC values, determined after 1 N NaOAc treatment, (Table 11), approached the NH^EC values in most c a s e s . SUMMARY AND CONCLUSIONS

This study was initiated to gain a better under­

standing of and a more realistic measure of the cation ex­

change capacity of some representative acid to near neu­

tral mineral soils of Michigan. Cation exchange capacity

values obtained by the following more common methods on 38

horizon samples from 15 soil types were:

1. The CaCl 2 method or calcium saturation.

2. The KCl method or potassium saturation.

3. The NH^OAc method or ammonium saturation.

4. The summation of cations method.

5. The NaOAc method or sodium saturation.

The leaching procedures followed conventionally for

saturation, washing and replacement of cations were re­

placed by centrifugation after thorough mixing each time.

The efficient removal of the occluded salts in KEC and

CaEC procedures were achieved by the use of their respec­

tive solutions of 0.001 N and 0.0001 N concentration.

The exchange acidities of these soil materials were determined by: (1) the BaCl 2 + triethanolamine method, (2)

the KCl method,(3) the NH^OAc method, and (4) for practical considerations, the exchange acidity values were also ob­ tained through the courtesy of the University Soil Testing

Laboratory which routinely uses the Shoemaker, McLean and

Pratt buffer method for lime recommendations to Michigan f a r m s .

82 83

To facilitate meaningful interpretations of the re­

sults placing needed emphasis on the process of development

of soil profiles in general, the data obtained were grouped

according to the following kinds of horizons and subjected

to statistical analyses: (a) the surface horizons: Ap and

A^? (b) the illuvial spodic horizons: B^, Bhir and Bir*

(c) the illuvial B.c and B g horizons; (d) the leached A- r horizons of Spodosols, the leached A 2 and A£ horizon of

Alfisols and Alfic intergrades and the parent material or

the horizons. This last horizon grouping essentially was one of uncoated minerals and thus possibly behaving similarly.

From the discussions of the results obtained, these conclusions were drawn:

1. The predictive equations calculated, among CEC values grouped according to the kinds of soil horizons, showed highly significant relationships on all horizons other than spodic. In spodic horizons, however, only

NH^EC vs NaEC and KEC vs CaEC could be predicted highly significantly. The SumEC vs NH^EC and NaEC were but signif­ icantly related in spodic horizons and the other methods at significance levels ranging from 0.1 to 0.41. 84

2• The regression analyses performed -to know the relative magnitude of the charge contribution from clay and organic matter contents of soils to CEC values obtained by several methods grouped according to soil horizons showed the charge contribution from clay to be 11 to 45 meq per

1 0 0 g which was considered a normal range for soil mater- ials of dominantly a mixed clay mineralogy.

3. The charge contribution from organic matter was very high for NaEC particularly in surface (706 meq per

100 g) and illuvial and Bg (599 meq per 100 g) horizons whereas its contribution was too low for CaEC and KEC in spodic horizons (14 and 25 meq per 100 g respectively).

These may be due to non-exchangeability of hydroxy Al and 3+ Al complexed by organic matter. The organic matter con­ tributed to all CEC values relatively highly in B^ and Bg as compared to other horizons which may be associated with different kinds of organic matter accumulated in different horizons. For other CEC values on all horizons the charge contribution from organic matter amounted from 87 to 255 meq/ 1 0 0 g, a normal range observed.

4. To verify the hypothesis that the relatively high

NaEC compared to other CEC values have been caused by: (1) an anion retention possibility, (2 ) dissolution of amor­ phous and crystalline Fe 20 3 and A 1 20 3 or organic exchange complexes and (3) partial removal of Al-interlayers, the

CaEC and KEC were determined on the same soil samples after

IN NaOAc treatment in the NaEC determination. The results 85

showed an agreeable duplication of NaEC values but markedly

increased both the CaEC and KEC values on most samples.

This indicated that one or more of the above mentioned

mechanisms do operate to an undetermined but significant

e x t e n t .

5. Thus, the effect of IN NaOAc in altering the soil

material charge properties is of great significance and

involves the very question of the purpose of the CEC

determination. If the purpose is to determine the CEC

of the clay mineral components of soil materials, then the

extraneous materials such as organic matter and free ses-

quioxides should be removed without damaging the crystal­

line materials. If the purpose is to determine the net

negative charge of soil materials under field conditions,

their nature should be determined by a method approximating 2+ the conditions in nature. Though Ca is a small cation representing most of the divalent cation population pre­

sent in the soil exchange complex and though the CaEC es­ timated both the clay and organic matter charge contribu­ tions in surface horizons, it could assess only a very

low charge contribution from organic matter in spodic hor­ izons .

The NH^EC revealed a reasonable charge contribution from both clay and organic matter on all soil horizons and was intermediate in value between CaEC and NaEC. There­ fore, one may conclude that NH^OAc is the best method for CEC determination for Michigan soil materials. 86

6 . The predictive equations for the routinely mea­

sured exchange acidity, EA (SMP) , and EA(BaCl 2 + TEA) cor­ related highly significantly on surface horizons and at

0.05 to .07 level in other horizon groupings. However,

the larger EA(SMP) values indicated that there may be a proportional overestimation of the soil acidity by this method particularly in spodic horizons and thus resulting

in higher lime recommendations than required by other

standard methods. A separate determination of exchange acidity by the BaCl 2 + TEA or an adjustment of the EA(SMP) values based on their relationships, therefore may give a more realiable estimate of the lime requirements of common

Michigan soil materials. NEED FOR FURTHER RESEARCH

1 . It should be noted that the conclusions arrived

at from this study, though significant, are based on limited

data. Therefore, an extensive study of these CEC deter­ minations grouped according to soil horizons prevalent under Michigan conditions will be of great value. Also,

such studies should be done on alkaline and calcareous mineral soils and organic soils.

2. The postulated effect of 1 N NaOAc on amorphous materials, coatings of A ^ O ^ and Fe 2 0 ^ and Al-interlayers partially demonstrated in this study needs to be investi­ gated in detail before the actual mechanisms are known.

3. Understanding of the reasons for the differences in CEC by various methods in relation to their significance to growing plants are essential before the CEC of Michigan soil materials can be most meaningfully evaluated.

4. The observed low CaEC and KEC values in illuvial spodic horizons and the relatively high charge contribution from organic matter in the illuvial B.t and B_ g horizons seem to have genetic significance and deserve further ex­ ploration. During the course of profile development Al and Fe ions in soils may be held from moving down through that natural leaching column by complexing with relatively low charged organic complexes causing them to accumulate in

87 87a the spodic horizons, whereas the higher charged portion of the organic matter is moved further down in the profile.

5. With the study of CEC characteristics of spodic horizons by CaCl 2 and NH^OAc methods, it may be possible to define a certain range in their ratios where the spodic horizons can be identified. LITERATURE CITED LITERATURE CITED

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* 3 >* O + * u 2 V p* • e b E m •H H M 4 e-H Exchangeable Bases S 0 u 0 O > 0 H 4 4

! • • clay + 0 z a CM H j. i t h ick- Ln inches) vit e n n i c u i « c c c c b b H u • *» (j 0 S-l H e 4-1 u X u 0 U U u 4 u 1 H * e V u o u + + A 4 X 3 M b h b 41 b «• u V ■e i u U N nt 0 X e e e -h 4-1 4 4 u X 4 . 0< + i 3 H +"*

w u Horizoi ness sa t u r a t i o n Per Per cent b a s e a. a a i n SultiEC Q.M Z (J X z U Z X u 5 Exchang EA(SMP) X < X J 1 Group A: Ap and A^ horizons. meg per 100 g of soil 39 Pevaiso clay loan 0-6 6.1 31.0 2.5 6.0 19.4 46.4 28.5 19.2 28.8 33.8 23.5 6.0 . 29.9 3.9 4.0 0.3 0 .3 3.6 0 88.4 37 Blount clav loan 0-6 6.2 28.0 1.3 1.9 6.7 22.9 14.5 10.6 23.4 21.8 15.0 4.4 . 19.7 2.1 0.5 0 0 0 2.1 3.7 90.6 17 Ontonagon silty clay 0-5 4.9 44.0 2.1 1.3 3.0 30.2 12.4 10.4 20.7 16.6 8.5 4.4 . 13.3 3.8 9.0 1.5 .6 0.9 2.2 7.9 77.3 14 Onavay loan 0-6 6.9 14.9 1.7 2.7 17.8 20.4 11.8 7.7 13.5 14.4 9.5 2.2 . 12.0 1.1 0.3 0 0 0 1.1 1.6 91.4 6 Volinia loan 0-11 6.2 17.0 1.8 1.3 7.5 23.4 10.5 8.6 15.6 14.5 10.0 1.0 . 11.2 3.3 5.0 0 0 0 3.3 4.5 77.0 1 Miani loan 0-6 7.1 9.0 0.8 1.4 15.3 12.3 7.5 5.4 9.0 9.7 7.0 1.2 . 8.3 1.4 0.5 0 0 0 1.4 0.7 85.2 19 Iron River silt loan 0-5 5.4 11.5 2.4 0.3 2.2 26.5 6.6 6.2 13.5 12.2 6.5 1.2 . 7.9 4.3 8.0 0 0 0 4.3 5.6 64.8 8 Kalanazoo loan 0- 8 1/2 6.2 7.9 0.9 .9 11.1 9.5 5.0 3.7 7.0 7.9 6.0 .4 . 6.5 1.4 3.0 0 0 0 1.4 0.5 82.7 4 Plainfield loany sand 0-8 5.9 8.2 1.3 .2 2.2 10.3 4.0 3.7 8.0 6.9 4.0 .6 . 4.8 2.1 4.0 .5 0 .5 1.6 3.2 69.4 33 Munising loany sand 0-8 4.6 6.2 1.3 .3 4.5 11.3 2.9 2.5 6.5 9.0 3.0 1.4 . 4.5 4.5 10.0 1.7 1.0 .7 2.8 2.0 50.0 38 Hillsdale sandy laon 0-6 5.2 8.0 1.0 .1 1.4 9.3 2.3 2.0 7.6 6.0 3.0 0.6 . 3.7 2.3 4.0 0 0 0 2.3 3.8 62.2 24 Spinks loany fine sand 0-8 5.5 4.7 0.8 .1 2.3 7.2 2.2 1.8 3.9 5.3 2.5 .5 . 3.2 2.1 2.0 0 0 0 2.1 0.6 60.7 11 Saugatuck sand 0-7 5.4 4.0 1.0 0 0 7.4 1.2 1.3 4.2 4.8 2.0 .4 . 2.5 2.3 4.0 .9 .3 .7 1.5 1.7 52.1 Group B: Bh, Bhir and B^c horizons. 32 Onavay loan 9-12 5.5 13.7 0.7 0 0 14.5 3.5 3.6 8.8 7.3 3.0 0.6 .1 3.7 3.6 ND 1.2 0.9 .4 2.4 5.1 50.5 20 Iron River silt loan 6-12 5.9 7.5 .7 0 0 14.2 2.7 2.8 7.2 7.2 2.5 0.6 .1 3.2 4.0 ND 1.5 1.5 .0 2.5 4.9 44.4 12 Saugatuck sand 11-16 5.1 3.5 2.3 0 0 22.4 1.8 2.2 10.6 9.8 1.0 0.2 .1 1.3 8.6 12.0 2.1 1.4 .8 6.5 9.4 13.0 28 Munising loany sand 9-17 5.3 4.0 1.4 0 0 19.6 1.3 1.7 4.4 7.8 0.5 0.1 .2 0.8 7.1 11.0 2.1 1.4 .7 2.0 3.6 1.0 35 Kalkaska sand 15-19 4.7 1.3 .7 0 0 15.4 1.2 1.5 5.S 6.3 0.5 0.1 .0 0.6 5.7 12.0 2.1 1.7 .4 3.6 4.9 1.0 13 Saugatuck sand 19-25 5.6 2.8 .3 0 0 4.8 .6 .6 2.4 2.5 1.0 0.3 .1 1.4 1.2 2.0 0 0 0 1.2 1.1 53.2 TABLE 16. — Data on chemical analyses of the soil studied (continued). — B— ~i---- M ■ — a— + * •H fN e 0 • * «H a u •H C iH 9 • Exchangeable Bases u a 0 41 *> H • • + a c a c *» JJ eH V «-* n • H 0 I C -H c S* £ 3 e 3 H Ci >1 — U ^ 9 41-4 z & 0 “ e e c v u O X 5 1 C 44 H u u e a H -H • -K u X ♦ + +■ U k ■H •H k a k k k k k <1 u u N 3 n ■ — 5 3 0 0 0 • X • • ®'1 a u X e Cl + § .H < 5 k 4>

Exchan acidit (SMPEA X e a SumEC per per c« aoil varmic CD m * c a a IS a > u 2 CaEC X z u z X w 5 1 < +x O.H 2 & 10 Group C: B. and B„ horizons. meq per 100 g of soil t g IS Brookston loam 8-12 6.S 27.3 1.8 3.9 14.1 33.0 21.8 15.6 23.9 26.0 19.0 4.3 .3 23.6 2.5 1.0 0 0 0 2.5 .4 90.6 16 Brookston loam 18-36 6.9 31.0 .4 3.3 10.8 22.6 16.5 11.2 19.4 19.4 13.5 4.3 .3 18 .1 1.4 0.4 0 0 0 1.4 1.8 92.8 IB Ontonagon silty clay 5-15 4.8 54.4 1.0 1.8 3.3 25.7 14.7 11.5 20.5 18.7 9.0 5.5 .4 14 .9 3.8 ND 1.6 0.8 .6 3.1 5.7 79.8 33 Onaway loam 18-24 6.5 22.4 .3 1.2 5.4 21.4 10.0 8.3 12.3 12.2 e.o 2.4 .1 10 .5 1.7 0.5 0 0 0 1.7 1.8 85.9 9 Kalaatazoo loam 12-21 4.8 21.7 .3 1.1 4.9 16.7 8.8 7.1 15.9 10.5 6.5 1.7 .2 8 .4 3.1 7.0 2.1 1.1 .8 1.1 7.5 79.8 3 Miami loam 16 1/2-21 6.1 20.0 .3 1.6 8.0 16.3 7.4 4.9 9.6 9.2 6.0 1.7 .2 7.9 1.3 3.0 0 0 0 1.3 1.7 86.3

7 Volinia loam 21--28 1/2 4.9 14.0 .3 1.0 6.9 12.9 5.5 5.4 10.3 7.4 3.5 1.0 .2 4 .7 2.7 5.0 1.9 1.4 .5 .8 6.1 60.6 100 22 Iron River silt loam 20-30 4.8 10.1 .1 .4 3.6 12.1 4.7 4.2 8.3 6.6 3.0 .4 .2 3.6 3.1 7.0 1.9 1.3 .6 1.2 4.8 53.5 30 Munisinq loamy sand 48-62 4.9 13.1 0.0 .6 11.4 8.9 4.5 3.6 7.4 5.6 3.0 1.3 .1 4 .4 1.2 0 1.0 .5 .5 .2 4.1 73.2 26 Spinks loamy fine sand 48 6.4 3.1 .1 0 0 2.5 .9 .9 1.7 3.2 2.0 0.3 .1 2 .4 .8 0.3 0 0 0 .8 1.4 73.7

Croup D: Aj> A£ and Cj horizons 27 Munising loamy sand 1-9 4.5 3.8 1.2 0 0 9.4 2.5 2.2 5.3 4.4 2.0 .3 .1 2.4 2.1 10.0 1.2 .7 .5 .9 3.0 53.4 34 Kalkaska sand 4-13 4.3 0.6 0.0 0.1 20.0 2.6 0.5 0.3 0.6 .7 0.5 .1 .0 0.6 .1 0.2 .5 0.0 .5 0 0.0 85.7 2 Miami loam 7-11 6.5 12.0 0.4 .7 5.6 8.1 4.4 3.1 7.3 6.0 4.0 .8 .1 4.9 1.1 1.0 .5 0 .5 .6 2.5 81.3 21 Iron River silt loam 12-20 4.9 5.4 .2 0 0 7.1 2.0 2.1 4.6 5.1 2.0 .7 .1 2.8 2.3 2.0 1.5 0.9 .7 .8 1.8 54.5 25 Spinks loamy fine sand 14-25 5.6 4.5 .2 .2 3.6 4.6 1.6 1.3 2.6 3.2 1.5 .5 .2 2.2 1.1 0.4 0 0 0 1.1 .4 66.4 29 Munising loamy sand 29-40 5.2 4.7 .2 0 0 3.1 1.4 1.4 2.7 1.7 0.5 .3 .1 0.9 .9 1.0 1.0 .7 .3 0 1.9 47.1 31 Munising loamy sand 62-82 5.7 10.1 .0 .3 3.1 5.1 3.8 3.1 4.6 5.2 3.5 1.2 .1 4.8 .4 0.2 0 0 0 .4 0 92.4 10 Kalamazoo loam 34-41 1/2 5.7 1.8 .1 1.0 53.9 3.3 1.0 .9 2.2 1.7 1.0 .4 .1 1.5 .2 0 0 0 0 .2 .7 88.6 36 Kalkaska sand 37-63 5.4 .6 .1 0 0 2.9 .2 .3 1.0 1.9 1.0 .1 .0 1.1 .8 0.4 0 0 0 .8 0 59.1 ND - Not Determined. ‘Explanation follows on page 101. 101

Table 16 Explanation

* Samples 1 to 26 are from Dr. A. E. Erickson's un­ published data, Crop and Soil Sciences Department, Michigan State University, East Lansing, Michigan, where they are numbered as follows: 1*18, 2*19, 3*21, 4*64, 6*68, 7*70, 8*48, 9*50, 10*52, 11-203, 12*205, 13*207? 14*270, 15-303, 16*305, 17*328, 18-329, 19*337, 20*338, 21*339, 22-340, 23*356, 24*423, 25*425 and 26*427. The pHs, and clay and carbon percentages are from Dr. Erickson's data where available.

*Samples 27 to 36 are from the samples studied by Mr. D. A. Lietzke in his M.S. Thesis "Evaluation of spodic horizon criteria, and classification of some Michigan soils." Michigan State University, East Lansing, Michigan and the pHs, and clay and carbon percentages are from S.C.S. Beltsville Laboratory results.

♦Samples 37 * Blount Ap, 38 * Hillsdale No. 1 Ap and 39*Pewamo No 1, Ap are from the samples studied by Mr. J. B. Collins in his M.S. Thesis, "Seasonal variability of pH and lime requirements in several Southern Michigan soils when measured in different ways," Michigan State University, East Lansing, Michigan. The pH values used for these samples are from August readings on air dry samples in w a t e r . TABLE 17.--Estimation uf clay mineral* in the clay fraction of tha horltont of similar aoil type* aa used in chi* study.

Similar Al- Amor­ Clay Xaol- 111- Chlo­- V e m i ­ Smec­ phous to soil Horixon C-v intar- Quarts Soil typa inite ite rite culite* tite mater­ sanple par cent grada number ials* •

1 Miami loan *P 9.0 XX XX XX XXX(15.3) Mona X 8 Kalaaaioo loan Bp* 7.9 0000 0 00 000 (11.1)1 00 None 000 24 Spinks loany f:.ne sand Bp 4.7 XX xx xx XX (2.3) XX 15.7 17 Ontonagon silty clay Bp 44.0 XX xxx XX X (3.0) Nona X 14.4 « Volinia loan BP 17.0 XX XX X XX (7.5) XX X 19 Iron River silt loan Bp 11.5 XX XX XX XX (2.2) XX X 8,8 23 Munising loany sand Ap (.2 XX xxx XX XX (4.5) XX 14 Onavay sandy loan BP 13.5

20.0 XX XXXX X XX (8.0) Hone X 3 Miani loan Bm 21.7 0000 00 00 000 (4.9) 00 None 0 9 Kalanatoo loan B2l” 102 18 Ontonagon silty 54.4 00 0000 0 000 (3.3) 00 Nona 00 clay B71t* XX X XX (14.1) XX X 15 Brookston loan Blg 27.3 XX 31.0 XX XX XXX X (10.8) XX 1( Brookston loan B22g 22 Iron Rivar silt loan 10.0 000 00 000 0000(3.8) Nona Nona 000 "it* 30 Munising loany sand 13.1 XX XX xxx X (11.4) X B22t

35 Kalkaska sand 1.3 X B22ir X X '0.0) 28 Munising loany sand B22ir 4.0 000 oo 00 00 (0.0) 00 Nona 0000

2 Miani loan 12.0 000 00 00 000(5.4) 00 V Hone oo 21 Iron Rivar silt loan 5.4 000 0 V 000 0000(0.0) Nona Nona 000 27 Munising loany sand *2 3.8 0000 00 0 0 000 0 Nona None 14.0

10 Kalanesoo loan 1.8 XX X C1 XXX XXXXI54.0I XX X 19.3

X > 0-10 parctnt ■ 0; XX • 10-30 par cant • 00 and 000; XXX * 30-50 per cant ■ 0000; XXXX ■ 50 - 70 par cent

Note; Quantitative detemination* vara baaed on X-ray, apacific auriace and total X analyaea and by solving simultaneous aquations, Rosa, 1005; Transaaiar (1903); H u m a n atal. (1959); darnings (1959). * Quantitative estimations vara nade from X-ray tracinga (Rieka, 19(3). * values expressed in paranthases represent vemiculite in soil clay determined by Alexiadas and Jackson procedure (19(5). •* Data from Raaan and Mortland (19(9).