Advances in agronomy volume 14

ADVANCES IN

AGRONOMY
VOLUME 14


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ADVANCES IN

AGRONOMY
Prepared under the Auspices of the
AMERICANSocm-ry OF AGRONOMY

VOLUME 14
Edited by A.

G. NORMAN

The Uniuetsity of Michigan, Ann Arbor, Michigan

ADVISORY BOARD
E. G. HEYNE
F. L. PATTERSON
R. W. PEARSON

W. H. h L A W A Y
W. H. F ~ T E
C. 0. G m m

1962

ACADEMIC PRESS

New York and London


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CONTRIBUTORS TO VOLUME 14
C. ROY ADAIR,Research Agronomist, Crops Research Division, Agricultural Research Service, United States Department of Agriculture,
Beltsville, Maryland

L. T. ALEXANDER,Chief, Soil Survey Laboratoy, Soil Conservation
Semice, United States Department of Agriculture, Plant Industy
Station, Beltsville, M aylund
H. M. BEACHELL,
Research Agronomist, Crops Research Di&on, Agricultural Research Service, United States Department of Agriculture,
Beaumont, Texas
R. L. BERNARD,
Research Geneticist, United States Regional Soybean
Laboratory, Crops Research Division, Agricultural Research Service,
United States Department of Agriculture, Urbana, Illinois
D. R. BOULDIN,Soil Chemist, Tennessee Valley Authority, Muscle Shoals,
Alabama

J. G. CADY,Soil Scientist, Soil Survey Laboratory, Soil Conservation
Service, United States Department of Agriculture, Plant Industry
Station, Beltsville, Maryland
J. L. CARTTER,Agronomist-in-charge, United States Regional Soybean
Laboratory, Crops Research Division, Agricultural Research Service,
United States Department of Agriculture, Urbana, Illinois

MARLIN G. CLINE,Professor of Soil Science, Department of Agronomy,
Cornell University, Ithaca, New York

E. E. HARTWIG,

Research Agronomist, United States Regional Soybean
Laboratoy, Crops Research Division, Agricultural Research Service,
United States Department of Agriculture, Stoneville, Mississippi
HERBERT
W. JOHNSON, Research Agronomist, Crops Research Division,
Agricultural Research Service, United States Department of Agriculture, Beltsville, Maryland
DONKIRKHAM, Curtiss Distinguished Professor of Agriculture and Professor of Soils and Physics, Iowa State University, Ames, Iowa

RAYMONDJ. KUNZE, Assistant Professor of Soils, Department of Agronm y , Iowa State University, Ames, Iowa
V


vi

CONTRIBmoRs

M . D. MILLER,Extension Agronomist, Agronomy Department, University
of California, Davis, CaZifornia
S. SNARAJASINGHAM,
Assistant Chemist, Soil Surceys, Department of
Agriculture, Peradeniya, Ceybn

DWIGHTD. SMJTH,Assistant Director for Water Management, Soil and
Water Conservation Research Division, Agricultural Research Service, United States Department of Agriculture, Beltsoilk, Maryland

GILBERT
L. TERMAN,
Agronomist, Tennessee Valley Authority, Muscle
Shoals, Alabama

FRANKG. VETS, JR., Chief Soil Scientist, Northern Plains Branch, Soil
and Water Conservation Research Division, Agricultural Research
Service, United States Department of Agriculture, Fort Collins,
Colorado
J. R. WEBB,
Associate Professor of Soils, Department of Agronomy, Iowa
State University, Ames, Iowa

WALTER
H . WISCHMEIER,
Research Investigations Leader for Water
Erosion, Corn Belt Branch, Soil and Water Conservation Research
Division, Agricultural Research Service, United States Department
of Agriculture, Purdue University, Lafayette, lndiana


PREFACE
The eight chapters in this volume fall into the general pattern
established for this series, which is to include reviews of research
progress in soil and crop science and developments in agronomic practice. The central theme is the soil-plant relationship. Some European
reviewers of this series have expressed the view that the range of subjects covered is far too wide to justify the implied suggestion that
they are all branches of one science and that the literature reviewed
is predominantly American. Essentially this criticism hinges on the
definition of the word “agronomy” which in European usage and particularly British usage does not have the same connotation as in the
U.S. Indeed one British reviewer states that “In England, little would
be left for agronomy when the claims of chemistry, entomology, plant
pathology and so on had been stated-perhaps the study of green
manuring, seed rates and sowing dates.” As understood in the United
States there is, however, a professional field of agronomy in which the
above and many other disciplines have a part. There is a professional

organization of agronomists with upwards of 4,000 members trained
in a variety of disciplines which they bring to bear on a great diversity
of problems relating to the soil, and its efficient use in the production
of economic crops. Much of the science involved is international; but
there are aspects that are regional and must be so. For example, in
this issue there are two extensive reviews dealing respectively with the
genetics of soybeans and the management of the soybean crop. Some
sixty percent of the world soybean production is located in the United
States. An even higher percentage of the total scientific work on this
fascinating crop plant is carried on in the United States, and it is inevitable, therefore, that the literature should be predominantly American. Much the same applies to the article on rice production in the
United States, where man hour per acre have been reduced to an
astonishingly low figure.
In contrast, attention should be drawn to the authoritative review on
the subject of laterite by Sivarajasingham, Alexander, Cady and Cline,
which reflects the world-wide distribution of the investigators of
laterites rather than the distribution of lateritic soils.
Greater fertilizer usage accounts in part for the steady yield increases recorded in most countries in recent years. In the development
of fertilizers considerable attention is being directed towards new and
unconventional materials, the evaluation of which presents challenging
problems. Some of these are discussed by Terman, Bouldin and Webb.
vii


viii

PmFACE

Viets, on the other hand, considers the involved relationships between
fertilizer usage and the water requirement of crops, a very important
issue in many areas of the world where rainfall is erratic and water

reserves inadequate.
The remaining articles deal directly with soil properties. Kirkham
and Kunze discuss some of the applications of the use of isotopes and
radiation to problems in soil physics, and Smith and Wischmeier the
physical principles of soil erosion by rain.
A. G . NORMAN
Ann Arbor, Michigan
July, 1962


CONTENTS

CONTRIBUTORS
TO VOLUME14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Puge
v

PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

vii

LATERITE
BY S. SIVARAJASJNGHAM. L. T. ALEXANDER.J . G . CADY.AND M. G. CLINE
I.
I1.
I11.
IV.
V
VI.

VII .

.

The Term “Laterite” ........................................
The Nature of Laterite ....................................
The Environment of Laterite ................................
Profiles Containing Laterite .................................
Formation of Laterite ......................................
Geomorphic Relationships ..................................
Softening of Laterite .......................................
References ...............................................

1
5

14
20
26
53
55
56

RICE IMPROVEMENT AND CULTURE IN THE UNITED STATES

.

BY c. ROY ADAIR. M. D. MILLER.AND H . M BEACHELL

I.

I1.
I11.
IV.
V.

Introduction ..............................................
Rice Culture in the United States ............................
Rice Field Pests ...........................................
Origin, Botany. and Genetics of Rice .........................
Rice Breeding and Improvement in the United States . . . . . . . . . . .
References ................................................

61
68
85

92
96
104

RAINFALL EROSION
BY DWIGHTD . SMITHAND WALTERH . WBCHMEIER
I.
I1.
I11
IV .

.

Introduction ..............................................

Mechanics of Rainfall Erosion ...............................
Basic Factors Affecting Field Soil Loss ........................
Soil Loss Prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ix

109
113
123
137
144


CONTENTS

X

SOYBEAN GENETICS A N D BREEDING
BY HERBERTW .
I.
I1 .
111.
IV .
V.

JOHNSON AND

RICHARDL . BERNARP

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reproduction .............................................
Genetics of Qualitative Characters ...........................
Genetics of Quantitative Characters ..........................
Breeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

149
152
157
172
199
218

FERTILIZERS AND THE EFFICIENT USE O F WATER

BY FRANK
G . VIETS. JR.
I.
I1.
I11.
IV .

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . .
.................
Definition of the Problem
.............................
...........
Validity of Evapotranspiration Data . . . . . . . . . . .
The Effects of Fertilizers on the Relationship of Evapotranspiration
and Yield ......................... .....................

V . Fertilizers and Water-Use Efficiency in Terms of Applied Water . .
VI . Fertilization and Water-Use Efficiency with Limited Moisture
Supply .................................................
....
VII . Fertilization and Moisture Extraction by Roots . . . . . . . .
VIII . Fertilizers and the Infiltration of Water ......................
IX . Fertilization. Crop Maturity. and Water Use . . . . . . . . . . . . . . . . . .
x . Other Practices for Increasing Water-Use Efficiency . . . . . . . . . . . .
XI . Is Maximum Water-Use Efficiency Desirable? . . . . . . . . . . . . . . . . . .
.....
XI1. Conclusions ..........................
References . . . . . . . . . .
........................

223
226
228
233
246
246
252
254
256
257
259
260
261

EVALUATION OF FERTILIZERS BY BIOLOGICAL METHODS

BY G. L TERMAN.D. R . BOULDIN.AND J . R . WEBB
I . Introduction ......................... . . . . . . . . . . . . . . . . . . . . .
11. Chemical and Physical Characteristics of Fertilizers . . . . . . . . . . . . .
I11. Concepts of Fertilizer Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV. Methods Used in Fertilizer Evaluation Tests . . . . . . . . . . . . . . . . .
V . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References

...............................................

265
266
280
295
316
317


xi

CONTENTS

ISOTOPES METHODS A N D USES I N SOIL PHYSICS RESEARCH
BY DONKIRKHAMAND RAYMONDJ . KUNZE

I.
I1.
I11.
IV.

V.
VI .
VII .
VIII .
IX .
X.

Introduction ..............................................
Soil Water ...............................................
Soil Density and Soil Structure ..............................
Soil Aeration .............................................
Soil Temperature ...........................................
Soil Particle Movement ....................................
Transformation of Soil Materials from One Form to Another .....
Soil Profile Formation and Dating ............................
Disposal of Radioactive Waste ..............................
Proposed Future Work .....................................
References ................................................

321
322
342
347
348
348
350
352
353
354
355

THE MANAGEMENT OF SOYBEANS
BY JACKSON
L . CARTTER
AND EDCARE . HARTWIG

.

1 Introduction ..............................................
I1. Soil and Climatic Adaptation .............
I11. Time of Planting and Varietal Adaptation ....................
IV Planting Methods and Equipment ............................
V Rotation Practices and Erosion Control ........................
.......
VI . Weed Control ....................
.......
VII. Seed Quality and Seed Treatment ...
VIII Nutrient Requirements .....................................
IX Water Requirements and Utilization ..........................
X. Growth-Regulating Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
XI . Harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
XI1 Seed Storage .............................................
XI11 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.
.
.
.

.

.

...................

360
365
372
378
383
386
389
390
401
403
404
406
407
. . . 408

AUTHOR INDEX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

413

SUBJECT INDEX
......................................................

427


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LATERITE
S. Sivarajasingham, L. T. Alexander, J. G. Cady,
and M. G. Cline
Department of Agriculture, Peradeniya, Ceylon, United States Department of Agriculture,
Belhville, Maryland, and Carnell University, Ithaca, New York

Page
I. The Term “Laterite” . .
......................
11. The Nature of Laterite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A. Physical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B. Chemical Characteristics ................................
C . Mineralogical Characteristics .
111. The Environment of Laterite . . . . .
A. Climate . . . . . . . . . . . . . . . . . .
.........
.........
.........................................
C. Parent Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D. Topography . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
E. Age . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
............
IV. Profiles Containing Laterite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A. Soil Material Overlying Laterite ..........................
B. Laterite within Soil Horizons ..............................
C. Horizons or Layers Beneath Laterite ......................
V. Formation of Laterite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A. Weathering as a Preconditioner of Material of Laterite . . . . . . . .

B. Development of Microstructures ..........................
C. Hardening of Laterite ....................................
D. Development of Laterite in Place without Enrichment from Outside Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
E. Enrichment from Outside Sources ........................
F. Principal Processes Involved .
..................
VI. Geomorphic Relationships . . . . . . .
......................
VII. Softening of Laterite .
............................
References . . . . . . . . . .
..................

1

5
5
7
14
15
16
20
20
21
22
24
26
28
38
39

45
45
53

55

1. The Term ”Laterite”

The term ‘laterite” was originally coined by Buchanan (1807) for a
ferruginous, vesicular, and apparently unsbatified material occurring in
immense masses over the country rock of Malabar in India. The freshly
1 This review constitutes Agronomy paper No. 542, Cornell University, Ithaca,
New York.

1


2

S . SIVARAJASINGHAM ET AL.

dug material, as described by Buchanan, was soft enough to be readily
cut into blocks by an iron instrument, but upon exposure to air it
quickly became as hard as brick and remarkably resistant to the action
of air and water. Since this material was used as building brick, and was
called “brickstone” in several of the indigenous languages, Buchanan
aptly called it ‘laterite” after later-the Latin for brick.
Prescott (1954, pp. 1-2) has reported that Buchanan did not use the
term “laterite” in his journals between 1807 and 1814 but used the term

“brickstone” and that Babington (1821) was the first to use ‘laterite” in
formal scientific literature. According to Prescott and Pendleton (1952,
p. I ) , Buchanan used the word “brickstone” only in his later travels
(1807-1813) through what is now Bihar to describe occurrences in the
Rajmahal hills: “He noted the similarity of the Bihar occurrences to
those of Malabar, but was puzzled by the fact that the former masses of
material while still in the ground and excluded from the air retained their
stony form.” At first in Malabar, he had used the terms ‘laterite” and
“brickstone” interchangeably in his descriptions of the soft materials that
harden; his later use of the term ‘8rickstone” in Malabar may have been
out of a desire to reserve the term “laterite” for the soft ferruginous
material that hardens.
Though some of Buchanan’s immediate successors ( Voysey, 1833;
Stirling, 1825) used “iron clay” as an alternative term, the word ‘laterite”
gradually came into wide use in India. Detailed morphological descriptions of laterite, still considered to be among the most vivid, were
given by Newbold (1844, 1846).
Interest in laterite was stimulated in other parts of the world by the
publication of a chapter by Blanford (1879) in the first Manual of the
Geology of India, with which the name laterite became finally confirmed
(Fox, 1936). Before the end of the nineteenth century, laterite as a
surficial or shallow formation was identified on the basis of physical
characteristics in many widely distributed areas of Australia, Africa, and
South America.
Fermor (1911) considered use of the term only for soft materials
that could be cut into bricks, a severe restriction, though such use
appears to conform with the intentions of Buchanan. Blanford (1859)
had mentioned that in some cases the lithomarge underlying laterite
becomes hard on exposure, and Harrison (1910) also recorded the
occurrence of mottled, creamy white and dark red sesquioxide-poor
deposits that harden on exposure. Thus, the property of hardening as a

criterion of laterite became controversial. Later this aspect was further
confused when Talbott in Australia (Prescott, 1931) extended the term


LATERITE

3

to include not only hard ferruginous surface formations, but also siliceous
and travertine crusts, designating them ferruginous, siliceous, and calcareous laterite, respectively. Prescott, however, confined “laterite” to the
ferruginous and aluminous forms and cited the earlier suggestion of
Woolnough (1927), who introduced the term “duricrust” to cover the
other kinds of crusts.
Though many earlier observers had suggested the ferruginous and
even the aluminous nature of laterite (Mallet, 1883), the fundamental
chemical character of laterite was first established by Bauer (1898). His
analyses revealed the low content of silica and the high contents of
alumina and iron oxide in samples collected from the Seychelles. Subsequent investigations of samples from many different parts of the
tropical region gave similar results (du Bois, 1903; Warth and Warth,
1903; Holland, 1903).
Great interest developed because of the possible use of laterite as an
ore for aluminum (Holland, 1905) and, in some cases, for manganese
(Fermor, 1909). Consequently, much of the early work was confined to
chemical analysis of bulk samples that were selected for high aluminum
content. This prompted a reviewer (Bull. Imp. Inst. 1909, vii, p. 133) of
Harrison’s work to suggest that the term laterite be restricted to products
of weathering containing free alumina. As a result, controversy developed
among geologists regarding the chemical properties of laterite.
Fermor (1911) finally abandoned the physical property of hardness
of a material in its natural state or on exposure as a criterion of laterite

and developed a comprehensive system of nomenclature of lateritic
materials on the basis of chemical composition, though he rejected the
presence or absence of alumina in large quantity suggested by Crook
(1909). He subscribed to the views of Evans (1910) that “though the
chemical composition of laterite varies within wide limits, . . . one feature
remains constant-the small amount of combined silica in proportion to
the alumina present. . . . It is in this respect that laterites differ from
clays, which also occur as tropical decomposition products.” Fermor, consequently, based his classification on arbitrary limits of the ‘lateritic”
constituents, which he defined as the oxides of iron, aluminum, titanium,
and manganese.
Meanwhile Walther ( 1889,1915,1916) had erroneously assumed that
the term “laterite” had been chosen to signify red color and “proposed
that the word should be used for all red-colored alluvia” (Prescott and
Pendleton, 1952, pp. 35-36). Ultimately, any tropical red earth came to
be called ‘laterite” or “lateritic.” As studies of tropical soil progressed,
attempts were made to standardize the use of these two terms on the


4

S. SIVhRAJASINGHAM ET AL.

basis of chemical composition. The silica-alumina ratio and, later, the
silica-sesquioxide ratio were used to classify soils into “laterite,” “lateritic,”
and “nonlateritic” (Martin and Doyne, 1921, 1930; Joachim and Kandiah,
1935). The terms received even wider connotation with the adoption
of “laterite” and “lateritic” as the names of Great Soil Groups by the
Lhited States Soil Survey Staff (Byers et al., 1938; Baldwin et al., 1938).
Pendleton (1936) strongly urged that the term “laterite” be restricted
to the original concepts of Buchanan, restated nearly 100 years later by

Oldham ( 1893). As a consequence of this rigorous definition of “laterite,”
Pendleton and Sharasuvana (1946, p. 434) defined a “laterite” soil as
“one in which a laterite horizon is found in the profile.” They considered
a “lateritic” soil to be “one in which there is an incipient or immaturely
developed laterite horizon, and in which it is believed a true laterite
horizon will develop if the prevailing conditions persist long enough.”
The definitions put fonvad by du Preez (1949) for ‘laterite soil” and
“lateritic soil” are essentially similar to those of Pendleton and Sharasuvana. His definition of laterite, like that of Pendleton and Sharasuvana,
fails to recognize the importance of alumina, and while he covered some
morphologicaI aspects of laterite comprehensively, he ignored the soft
variety that hardens on exposure. Mohr and van Baren (1954) defended
use of the terms ‘laterite” and “lateritic” for soil on grounds of similarity
of weathering products that produce soil as well as material that hardens.
Kellogg (1949, p. 79) confined the term ‘laterite” to four principal
forms of sesquioxide-rich material that either are hard or that harden
upon exposure: ( 1 ) soft mottled clays that change irreversibly to hardpans or crusts when exposed, ( 2 ) cellular and mottled hardpans and
crusts, ( 3 ) concretions or nodules in a matrix of unconsolidated material,
( 4 ) consolidated masses of such concretions or nodules. The Soil Survey
Staff of the United States Department of Agriculture (1960, p. 62)
proposed a new term, plinthite (Gk. plinthos, brick), for essentially the
same concept, defining it as “the sesquioxide rich, humus poor, highly
weathered mixture of clay with quartz and other diluents, which
commonly occurs as red mottles, usually in platy, polygonal, or reticulate
patterns; plinthite changes irreversibly to hardpans or irregular ( hard)
aggregates on repeated wetting and drying, or it is the hardened relicts
of the soft red mottles.” The term “plinthite” was introduced to avoid the
confusion arising from use of the word “laterite” without precise definition
for many widely divergent materials.
In this paper, the term laterite is retained as a term that would be
recognized by most readers, though its use is restricted to material that

conforms generally with the definitions of laterite by Kellogg (1919)
and of plinthite by the Soil Survey Staff (1960).


LATERITE

5

II. The Nature of Laterite

The term laterite is restricted in the remainder of this paper to
highly weathered material ( 1 ) rich in secondary forms of iron, aluminum,
or both; ( 2 ) poor in humus; ( 3 ) depleted of bases and combined silica;
( 4 ) with or without nondiagnostic substances such as quartz, limited
amounts of weatherable primary minerals, or silicate clays; and ( 5 )
either hard or subject to hardening upon exposure to alternate wetting
and drying. The term as used implies no restrictions, other than those
inherent in the properties defined, on size or shape of the masses, on
their internal organization, on the processes by which diagnostic properties have developed, or specific conditions of place or time as factors
essential to such development. In this sense it includes Buchanan’s
laterite and hardened equivalents of it. In addition, it includes certain
highly weathered material in sesquioxide-rich humus-poor nodules2 that
are hard or that harden upon exposure, though they may be surrounded
by earthy material that does not harden, as well as masses of such
nodules cemented together by sesquioxide-rich material. It excludes
( a ) sesquioxide-rich earthy material, which has been called “laterite”
or “lateritic soil,” that does not harden upon exposure; ( b ) ironrich masses or nodules with significant amounts of humus, which
are characteristic of certain podzols; ( c ) hard masses cemented by
silica, carbonates, or substances other than sesquioxides, though highly
weathered sesquioxide-rich fragments or nodules within such masses

might be included; and ( d ) certain hard pellets or “shot” found in
slightly weathered material.
A. PHYSICAL
CHARACTERISTICS
Laterite occurs in various morphological forms. Pendleton and Sharasuvana (1946, p. 438) recognized two distinct physical forms, vesicular
and pisolitic, with many types intermediate between the two. Du Preez
(1949, p. 57) has defined laterite as “a vesicular, concretionary, cellular,
vermicular, slaglike, pisolitic or concrete-like mass.” The description of a
vesicular laterite by Newbold (1844) is quoted in part here after Prescott
and Pendleton (1952, p. 5).
“The laterite . . . , generally speaking, is a purplish or brick red,
porous rock, passing into liver brown perforated by numerous sinuous
2 The term “nodule” is used not only in the sense defined by Bryan (1952) to
include “rounded lumps” of a variety of compositions whether formed by accretion
or by centripetal enrichment, but also to include rounded fragments of laterite
inherited from a laterite crust.


6

S. SIVARAJASINGHAM ET AL.

and tortuous tubular cavities either empty, filled, or partially filled with
a greyish-white clay passing into an ochreous, reddish and yellowish
brown dust; or with a lilac-tinted litheomargic earth. The sides of the
cavities are usually ferruginous and often of a deep brown or chocolate
color; though generally not more than a line or two in thickness, their
laminar structure may frequently be distinguished by the naked eye. . . .
The interior of the cavities has usually a smooth polished superficie, but
sometimes mammillary, and stalactiform on a minute scale . . . . The

surface masses of the softer kinds present a variegated appearance. The
clay and lithomarge exhibit lively colored patches of yellow, lilac, and
white, intersected by a network of red, purple, or brown. The softness
of this rock is such that it may be cut with a spade; hardening by
exposure to the sun and air, like the laterite of Malabar.” (Omissions are
by the present authors.) Vesicular laterite may be soft or of varying
hardness and commonly has earthy material in the cavities. It usually
occurs near the surface.
Cellular slag-like laterite is a scoriaceous mass. The many empty
cavities are separated by ferruginow material similar in appearance to
that which separates the earthy substance in vesicular laterite. Cellular
laterite is usually dark colored and may have a dull or lustrous surface.
It is of varying hardness and is brittle, being usually easily shattered
when struck a sharp blow with a hammer. According to Fox (1936),
cellular laterite is formed by removal of kaolin and other earthy material
from the cavities in vesicular laterite when the latter is exposed to
erosion and leaching at the surface. Falconer (1911), from his observations in nothern Nigeria gave a similar explanation, though he avoided
using the term laterite for “surface ironstone.”
Nodular laterite consists of individual concretions, pisolites or other
crudely round masses, usually the size of a pea but commonly larger or
smaller; it is generally ferruginous. The nodules may occur as a superficial covering or as a component in one or more horizons in the soil,
varying in concentration from low or insignificant amounts to very high
amounts. The nodules vary in hardness; some can be readily cut by a
knife but most are hard and brittle.
When the nodules of a layer are cemented together, hard “pisolitic”
or “concrete-like” laterite is formed. It occurs mainly at or near the
surface. The individual nodules may either be joined directly to one
another or be discrete entities in a cementing matrix of similar, but
usually less ferruginous, material.
Recent studies by Alexander and Cady ( 1962) present enlightening

detail on the physical arrangement of discrete components. Though
various specimens exhibit a great variety of micromorphological features,


7

LATERITE

certain structures are common to many, but not necessarily all, varieties.
Commonly under magnification in thin sections, tiny bodies ranging from
perfect spheres to oblong rounded forms may be seen embedded in a
matrix of fine particles; the matrix may be either very dense or spongelike. The rounded bodies may be individual units or, commonly, may be
aggregates of smaller spherical units closely packed. Such rounded bodies
may be widely spaced or closely packed in the matrix. Their boundaries
may be smooth and definite or irregular and indefinite in various specimens. The matrix may be unorganized, may have a gridlike rectangular
or reticulate network of oriented material, or may be largely oriented. Oriented material commonly lines pores and may appear as skins on the nodules. Crystalline oriented material is common as pseudomorphs after primary minerals, as porefillings, and as discrete bodies ranging from barely
visible units to relatively large homogeneous masses. Rock structure may
be preserved or may be entirely absent. Quartz particles may be
included, and in some specimens weatherable minerals encased in a
protective covering of weathered material have been observed.

B. CHENICAL
CHARACTERISTICS
Materials identified in the field as laterite have a wide range of
chemical characteristics. A prominent feature common to all laterites,
nevertheless, is a high content of either iron or aluminum or both
relative to other constituents (Alexander et al., 1956). This is clearly
illustrated by the following analyses, which are thought to be typical
examples (Table I ) .
Bases are almost completely absent. Combined silica is generally

TABLE I
Chemical Composition ( % ) of Selected Laterites
Constituent
Quartz
Feldspar
SiO,
A1203
Fe7.03
TiO,
CaO
H,O (loss on ignition)

Site:a

1

2

3

4

5

0.76
NDb
1.77
4.32
80.02
6.06

ND
ND
1.93
62.32
1.88
11.87

4.32
2.35
17.08
20.83
40.18
1.72

7.06

ND
ND
0.37
43.83
26.61
4.45
0.86
23.88

21.54

11.05

ND
ND
31.37
19.22
38.51
1.12
0.10
9.10

-

99.99

100.00

97.53

99.42

-

-

99.54

-

-

Site: 1, Coolgardie, Australia (Simpson, 1912). 2, Satara, Bombay, India

(Warth and Warth, 1903). 3, Bagru Hill, Bihar, India (Fox, 1936). 4, Cheruvannur,
India; Buchanan’s original site (Fox, 1936). 5, Djougou, Dahomey; laterite on
granite (Alexander and Cady, 1962).
0 ND, not determined.


8

S. SIVAFUJASINGHAM ET AL.

low (sites 1, 2, and 3, Table I ) , but some varieties, such as the original
laterite of Buchanan (site 4, Table I ) , may have significant amounts.
This is probably largely in the form of kaolin, which has been found in
recent work by Alexander and Cady (1!362) to be the principal or only
identifiable silicate clay mineral in samples from Africa. Alumina may
be the principal sesquioxide (site 3, Table I ) , but more commonly iron
oxide (site 1, Table I ) or iron oxide and alumina together (sites 2, 4,
and 5, Table I ) are the major constituents. Combined water, determined
by loss on ignition, is appreciable but is generally higher in aluminous
than in ferruginous varieties, as is shown in Table I. Titanium is also
common in significant amounts in most varieties and may be a major
constituent (site 3, Table I ) . Vanadium and chromium are found, but
rarely in appreciable quantities.
Quartz may be absent or present in only limited amounts, but on
rocks high in quartz it is commonly a significant or major component, as
on the granite of site 5 of Table I, for which petrographic studies showed
that much of the total silica was contributed by quartz. Quartz is also
common in laterite over nonquartzose rock, where it appears to be
derived mainly from wind-blown or detrital material from outside sources.
Ten samples of detrital laterite from various parts of India had an average

of ,2074 quartz (Warth and Warth, 1903). Pendleton and Sharasuvana
(1912, p. 10) have emphasized that differences in amount of quartz
commonly contribute to major variation in SiO, among samples, even
in the same profile.
The impoverishment in combined silica and bases and concentration
of sesquioxides during weathering and laterite formation on a dolerite
is illustrated in Table 11. The “primary laterite” of Harrison is not to be
confused with ‘laterite” as used in this review. It was a weathered earthy
product that lay between the surficial hard laterite crust and the unweathered dolerite rock. Major differences in proportions of iron and
aluminum and in amount of combined water between weathered material
and laterite presumed to have formed in similar material are common, as
in Table 11, but it is rarely possible to be certain that the laterite crust has
indeed formed in material like that of the underlying weathered product.
No consistent relationship seems to exist between the relative amounts
of silica, iron, and alumina and the degree to which the physical properties of laterite are developed. The shortcoming of any chemical classification was shown by Fox (1936) from the analyses of laterite samples
from Buchanan’s original sites (site 4, Table I ) . These would have been
called ‘lateritic lithomarge” in Fermor’s ( 1911) classifkation because of
the high content of combined silica, though the material was vermicular
and was being quarried for building purposes.


9

LATERITE

The analyses considered so far refer to bulk samples of massive
laterite without distinction between segregated nodular material and the
matrix. The nodular material is, however, found either to be similar in
composition to the matrix or to contain less combined silica and more
TABLE I1

Chemical Composition ( ”/o ) of Dolerite, “Primary Laterite,” and Associated Laterite
Ironstone at Eagle Mountain, British Guianaa
Constituent

Dolerite rock

“Primary
laterite”

Laterite
ironstone

2.40
49.60
17.29
2.90
8.26
0.35
0.53
0.05
6.95
8.80
0.18
2.81

2.86
0.50
46.80
23.64
2.50

22.96
0.69
Nil
Nil
Nil
Nil
Nil

0.14
0.62
10.54
74.43
0.65
9.60
3.91
Nil
Trace
0.02
Nil
Nil

99.95

99.91

H,O (loss on ignition)
TiO,
MnO
MgO
CaO

K,O
Na,O
a

-

-

100.12
From Harrison (1933).

TABLE I11
Selected Chemical Constituents (%) of Nodules of Laterite at 5 Sites and of the
Matrix in Which the Nodules Were Embedded at One of Them
5
Constituent Site:a
SiO,
A1203
Fe,%
TiO,
MnO,

1

2

3

4

Soft
nodules

Matrix

8.0
4.7
67.9

29.7
29.1
21.7
2.0
2.3

26.1
14.2
20.7
6.3
13.1

49.8
2.7
28.9
9.8
1.1

39.3
19.3
30.1

0.9
0.1

54.8
20.6
13.5
1.0
0.1

0.5
Nil

a Site: 1, Natal; ferruginous nodules (Beater, 1940). 2, Welimada, Ceylon;
aluminous and silicious nodules (Joachim and Kandiah, 1941). 3, Peradeniya,
Ceylon; manganiferous nodules (Joachim and Kandiah, 1941). 4, Hambantota,
Ceylon; titaniferous nodules (Joachim and Kandiah, 1941), 5, Congo; soft nodules
and matrix (Alexander and Cady, 1962).

ferric oxide. Site 5 of Table 111 illustrates the latter in soft nodules of a
ground-water laterite of the Congo. Prescott and Pendleton (1952, p. 21)
believed that nodules usually contain less free alumina than the more
massive forms and that they are low in manganese.


10

S. SIVARAJASINGHAM ET

AL.

Nodules studied by Alexander et al. (1956) were high in sesquioxides
and low in silica. Other workers have, however, reported appreciable
contents of both quartz and combined silica (Joachim and Kandiah, 1941;
Waegemans, 1954). The data in Table 111 illustrate the wide range of
silica, alumina, iron, titanium, and manganese in nodules from different
places. The work of Bennett and Allison (1928) also reveals variations in
the composition of nodules in different soils.

L
C. M W ~ L O G I C ACHARAC~ERISTLCS
Chemical analysis alone is not sufficient to reveal the nature and
origin of laterite ( Harrison, 1910; Campbell, 1917). Laterites having
similar physical properties, such as hardness or morphology, may differ
greatly in chemical composition, and, conversely, laterites having similar
chemical compositions may have greatly different physical properties.
Petrographic studies of thin sections ( Harrison, 1910, 1933), adsorption
of dyes (Hardy and Rodrigues, 1939), differential thermal analysis
(Humbert, 1948; Bonifas, 1959), and X-ray analysis (Alexander et al.,
1956; Bonifas, 1959) have been used to supplement chemical determinations.
Free alumina is mostly in the form of gibbsite (A1203.3H20),as
boehmite ( A1203.H20), or as an amorphous hydrated form which has
been called cliachite and a variety of other names (Hanlon, 1944;
Palache d aE., 1944). Iron is found in the form of goethite (FeO-OH),
hematite ( FeeOa),and as amorphous oxides or unidentifiable coatings on
other minerals (Alexander et al., 1956). Free silica is mostly inherited
quartz (Alexander et al., 1956),though Harrison ( 1933, p. 40) reported
PLATE 1
Photomicrographs illustrating features of weathering and laterite formation
A. Weathering diorite, North Carolina. Crossed Nicols. The lath-like forms are
gibbsite pseudomorphs after feldspar. Some dark areas are allophane and some are

iron oxide.
€3. Soft laterite from granite, Nigeria. Crossed Nicols. The light areas of the
crystal aggregate (upper left) and of the filled channel (lower right) are gibbsite
formed upon weathering of kaolinite. Dark areas are iron-impregnated clays and
iron oxides, which are isotropic or have a very low birefringence.
C. Hard laterite from granite, Nigeria. Plain light. The dark areas are impregnated with iron by local redistribution from the light areas. The higher population of quartz grains (white areas) in the part that has lost iron indicates that these
parts have collapsed.
D. Hard laterite from granite, Kigeria. Crossed Nicols. The yellow parts are
crystalline goethite which forms a continuous network, especially on the walls of
the small channel at the left. The dark streak through the center is a former channel
filled with fine-grained hematite. White spots are quartz grains.


A

C

B

D

PLATEI


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