CLASSEFECA'NON OF THE
SOILS OF GHANA

That: for “10 Degree 0:? M. 5.
MICHIGAN STATE UNlVERSETY
Go-dfried Kofi Asamoa

1961

THESIS

 

PPLEMV
SUMATET :3 VL-

LIBRARY

Michigan Stave
University

 

CLASSIFICATION OF THE SOILS OF GHANA

BY

Godfried Kofi Asamoa

AN ABSTRACT OF A THESIS

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

MASTER OF SCIENCE
Department of Soil Science

1961

ABSTRACT

CLASSIFICATION OF THE SOILS OF GHANA

by Godfried Kofi Asamoa

Many systems of soil classification are possible. In
fact there can be as many as there are objectives for classi-
fying soils. As a prelude to the discussion of the classi—
fication of the soils of Ghana past, present and proposed
systems of other countries are reviewed. This reveals some
changing concepts in soil classification. The early systems
of soil classification were based on the geology of the parent
material. Since Dokuchaiev's recognition of the soil forming
factors (climate, vegetation, parent material, topography and
time) as a function of the soil many systems based on these
were developed. Recent trends in soil classification are
toward the choice of soil properties, particularly morpholo-
gical characteristics which reflect soil genesis, as criteria.

Charter's proposed scheme for the classification of
the soils of Ghana is critically examined. Since the author
has not done any field studies on the soils of Ghana the
results of work so far completed by the Ghana Division of
Soil and Land-Use Surveys have been largely drawn upon. In
addition to current literature on the soils of Ghana profile
descriptions and laboratory data were supplied for ten repre-

sentative soil series. A, B, C, letter symbols and genetic

2
Godfried Kofi Asamoa
designations are proposed for the horizons of each of these
series. An attempt is made to place these soils within the
proposed system of the United States (the 7th Approximation).
While there was little difficulty with the placement of the
ground water podzol, tropical black and gray earths the place-
ment of the other series with the oxisols was difficult. This
is due to the lack of knowledge about the latosols. At present,
with the scanty descriptive and laboratory data, it appears
that Charter's system may be better than the 7th Approximation
for grOuping the latosols and latosolic soils of Ghana.
The soils of Ghana have been described according to
the major vegetation zones (forest, interior savannah and
coastal savannah) to which they are closely related. This
description and the classification of the soils of Ghana reveal

some general problems of soil classification in the tropics.

Knowledge about tropical soils is scanty and there is lack

of cooperation between workers of the various countries. The
soils are relatively featureless. This makes the choice of
properties for differentiation somewhat difficult. Some

unique processes of soil formation in the tropics make diffi-
cult the direct application of methods of temperate regions.
The need for careful morphological description and detailed

laboratory data has been emphasized for a sound classification

Godfried Kofi Asamoa
of soils of the tropics. The interrelationships of the soils
should be sought through the soil formation factors. The
major soil groups and their related land use have been dis-
cussed. Since Ghana is mainly an agricultural country, it
is recommended that agronomic investigations should go along
with the improvement of the classification of the soils.

For improving the classification of the soils of Ghana
the following suggestions were made: The nomenclature should
be improved to call to mind readily the important properties
of the soils. The possibility of using vernacular names
should be investigated. Morphological properties having some
genetic significance should be preferred as criteria for
differentiation. For this approach detailed description and
laboratory data are essential. Additional research involving
soil moisture determinations, soil texture, bulk density,
aggregation, porosity and other soil properties hitherto over—
looked, is recommended. Statistical approach should be
adopted for sampling in soil surveys and for other agricultural
research. It is recommended that soil survey data be used for
land capability classifications for various purposes.

The purpose for classifying the soils of Ghana is to
organize our knowledge about them so that their properties may

be remembered and their relationships easily understood for a

4

Godfried Kofi Asamoa

specific objective. The usefulness of the classification of
these soils, therefore, will depend on how well it serves this

purpose.

CLASSIFICATION OF THE SOILS OF GHANA

BY

Godfried Kofi Asamoa

A THESIS

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

MASTER OF SCIENCE

Department of Soil Science

1961

(915/?!
0/! 3”,. ’7’

ii

ACKNOWLEDGEMENTS

The author expresses his gratitude to Dr. E. P. Whiteside
for all the advice and encouragement received in the author's
program of studies at Michigan State University, particularly
during the preparation of this manuscript and to Dr. Louis
Wolfanger, for his advice during the absence of Dr. Whiteside.

He thanks Mr. H. B. Obeng, and the staff of the Soil
Survey Branch of the Ghana Division of Agriculture for providing
him with the data that made the preparation of this thesis
possible. The author also thanks Dr. G. D. Smith of U.S.D.A.
and Professor I. F. Schneider for providing him with copies
of the 6th and 7th Approximations respectively for early study.

Finally the author wishes to express his gratitude to
members of the Soil Science staff of Michigan State University,
and in particular to members of the committee, who have helped

in making his study at M.S.U. a success.

iii

TABLE OF CONTENTS

Page
I. INTRODUCTION . . . . . . . . . . . . . . . . . 1
II. REVIEW OF LITERATURE ON SYSTEMS OF SOIL
CLASSIFICATION . . . . . . . . . . . . . . . 3
Early Systems in Other Countries 3
Early and Present System in United States 9
Proposed Comprehensive System 12
Types of Classification Systems 20
Criteria of Soil Classification 23
III. SOILS OF GHANA: CLASSIFICATION AND SURVEY
EFFORTS . . . . . . . . . . . . . . . . . . 26
Charter's Proposed Scheme of Soil
Classification 27
Description of the Major Soils of Ghana 36
Soils of the Forest Zones 39
Soils of the Interior Savanna Zone 64
Soils of the Coastal Savanna Zone 68
IV. THE PLACEMENT OF SOME IMPORTANT SERIES OF
GHANA SOILS IN THE 7TH APPROXIMATION . . . . 92
Kumasi 93
Bekwai 94
Boi 94
Atuabo 95
Wacri 95
Mimi 96
erlesawga 96
Toje 97
Akuse 97
Agawtaw 98
V. DISCUSSION . . . . . . . . . . . . . . . . . . 99

Considerations on Some Problems of Soil
Classification in the Tropics 99

The Major Soéle flips}, and Their Relatde

Land Use rj%fi 3ifl;;
H
1K”! V?- L‘a1

102

VI.

VII.

Soils of the Forest Zones
Soils of the Interior Savannah Zone
Soils of the Coastal Savanna Zone

Suggestions for Improving the Classification

of the Soils of Ghana

Nomenclature
Choice of Criteria for the Classification
Description and Laboratory Data

Additional Research Needs

Conclusions

BIBLIOGRAPHY . . . . . . . . . . . . . . . .

APPENDICES . . . . . . . . . . . . . . . . . .

1.

2.

3.

Provisional Map of the Great Soil
Groups of Ghana

Diagrams Illustrating Some Typical
Ghana Soils

Texture Determination for the Soils
of Ghana

iv
Page
102
104
104
108
108
110
112
112
115

118

122

123

124

125

INTRODUCTION

The purpose of this study is threefold:

l. to acquaint the writer with work that has been done on
the soils of Ghana;

2. to help in correlating the most important soils of
Ghana with those of other countries;

3. to reveal some of the gaps in our knowledge about the
soils of Ghana, and suggest means of improving their

classification.

It was not possible for the writer to carry out any
field studies on the soils of Ghana. Hence the results of work
so far completed by the Ghana Division of Soil and Land-Use
Surveys, have been largely drawn upon in preparing this
manuscript. This handicap makes discussion of the classi-
fication of Ghana soils and their placement in the 7th Approxi-
mation a delicate undertaking. Besides the 7th Approximation
is only a proposed classification in its trial stages. How-
ever, these drawbacks will not defeat the purpose of this work.

Soil classification and survey work is comparatively
recent in the tropics. In Europe and in the United States
advanced systems of soil classification have been worked out
through many years of studies. Our limited knowledge about

tropical soils is revealed in the 7th Approximation (47);

the stage of approximation reached with tropical soils is
behind those for soils of other regions. It is pointed out
that the classification of tropical soils is the weakest part
of all systems of soil classification in Europe and in the
United States. Kellogg (27) emphasized the need for detailed
soil surveys in the tropics with classification according to
carefully defined units of lower categories. Efforts being
made to overcome these shortcomings are discussed in the
following pages. In order to properly evaluate soil survey
and classification efforts in Ghana it is necessary to review
various systems of soil classification, including the recently

proposed comprehensive system of the USDA (47).

II. REVIEW OF THE LITERATURE ON SYSTEMS OF SOIL

CLASSIFICATION (PAST, PRESENT AND PROPOSED)

Early Systems in Other Countries

 

In the seventeenth and eighteenth centuries the educated
class in Europe had little incentive for the study of soils or
agriculture. This was so because people looked down on
agriculture as dirty and menial. Early concepts of the soil
were therefore, developed in other fields such as botany,
chemistry and geology. According to the botanical concept (42)
soils were classified on the basis of the natural vegetation
or the crops they supported; e.g., wheat soils, oak soils, etc.

The work of early chemists and plant physiologists,
notably Joseph Priestley, Scheeka,IngenhouszamxiSenebier, paved
the way to the discovery that the soil furnishes a very small
but indespensable part of plant food (42). Traditionally the
soil has been looked upon as a medium for plant growth (47).
Today man's interest in the soil is chiefly centered around
this function.

In the early nineteenth century, interest in the study
of soils was aroused. At about this time the geologist's con-
cept was developing. The first attempt to study soils outdoors
was made by geologists (1). Notable among them were Fallou,
Sprengel and Thaer (2). They treated the soil as a function

of the parent material. Thaer classified soils on the basis

of texture. He recognized clayey soils, sandy soils, sandy
loam and humus. The classifications of Fallou and Sprengel

were genetic; i.e., based on the origin of weathered products

from rocks (2). They classified soils into:
1. nontransferred soils (essential original soils);
2. transferred soils (e.g., valley soils, lake soils).

Later, concepts involving zonality were developed by
Richthofen and Walther (2). These men were geographers or
geologists, who travelled widely and saw differences among
soils of great regions. Richthofen (1880) postulated that the
soil was a product of physical processes determined by climate,
topography and parent material. His classification consists

of the following major groups (2):

l. autogenous (residual) soils;
2. equilibrium soils;
3. soils of denudation;

4. soils of sedimentation.
Walther (1885-1890) was among the first to classify soils on
the basis of climate. He emphasized the effect of climate
on the nature of rock and on the process of rock weathering.
He classified soils into: boreal soils, temperate soils,
desert soils, and tropical soils.

At about this time the study of the soil as a science

began in Russia. Dokuchaiev (2), father of modern soil science,

5
laid the foundation. According to him soil is merely a function
of the five soil forming factors (climate, vegetation, parent
material, topography, and time). It is interesting to note
here that Jenny (23) put this idea into an equation but
emphasized the independent nature of each factor. The classifi-
cation scheme developed by Dokuchaiev is outlined in "Soils
and Men" (3) and lately it has been tabulated in the 7th
Approximation (46). (See Table l). Dokuchaiev classified
soils into: normal soils, transitional soils and abnormal
soils. The normal soils, similar to the zonal great soil groups
of today, express zonal effect. The abnormal soils represent
a young state of development and lack characteristics of zonal
soils. Further subdivisions of these groups may be seen in
the Table lb.

In 1900, Dokuchaiev's student, Sibirtsev classified soils
into three orders; zonal, intrazonal and azonal. The zonal
soils he said owed their properties mainly to the effect of
climate and vegetation; intrazonal soils were soils of which
the dominant factors of formation were topography and extremes
of parent material. The azonal soils were equivalent to
Dokuchaiev's abnormal soils.

It should be noted that the above two systems were
based on ideas of soil genesis. Glinka (1908-1925) asserted

that "the morphology of a soil is the result of internal soil

TABLE l.--1886 Classification of Soils by V. V. Dokuchaiev

 

According to

According to

According to According to

 

position (to origin climatical zeolite
presence of region (and clay
primary gene- to humus (each soil)
tical features) content)
I cl. Dry land 1. Light gray Sandy
vegetative soils northern soils sandy-loamy
Loamy
2. Gray tran- Clayey

sitional soils

3.

Chernozean

soil soils

4.

Chestnut tran-

sitional soils

A. Normal 5. Southern brown
alkaline soils
Primary
Secondary
Periodical
Eroded
Burrowed
II c1. Dry land 6. Soils of
moor soils swamped forests
7. Meadow soils
III c. Moor (bog) 8. Tundra soils
soils in potentia)9. Peats
10. Water logged
flood plains etc.
B. Transitional
IV. c1. Washed
soils
V. cl. Dryland
sedimentary soils
C. Abnormal VI cl. Sedimentary

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forming processes controlled by climate? He therefore set
up a classification system, which was based on morphology as
well as factors of soil genesis. He attributed the origin

of soil properties to two major changes (2):

1. changes in organic matter, and
2. decomposition of minerals.
Both changes are controlled by climate. His scheme reflects

the effect of climate and vegetation. He recognized five
major "types":

1. Laterite type,

2. Podzol type,

3. The Steppe type,

4. Alkaline type,

5. Bog type.

Gedroiz (1925) was among the first to emphasize morphological
properties of soils as criteria for classification. The
colloidal properties of soils (nature of exchangeable cations)
was the basis of his scheme. Although his major groups were
chernozem type, alkaline type, Podzol type and Laterite type,
it was his hope that a system which relates closely genetic
features to texture might be developed. It is not possible
to outline the schemes of all the important Russian workers
in this review. But a brief mention may be made of others:

Vilenskii, Zakharov, Vysotskii and Volobuev used essentially

Glinka's approach (7). Their classifications were based on
separate factors of pedogenesis. Kossovitch, flhmfixi and

Neustruev used pedogenic processes as a basis for their classifi—
cation (7) et. Neustreuv divided soils into automorphic and
hydromorphic groups. In 1925 Afanasiev put forth a classifi-
cation system modified after Dokuchaiev and Sibirtsev; he
recognized the regimes of climate, vegetation, water, geomorphology
and salt. Under each of these the normal, transitional and
abnormal soils were developed. These three men adopted the

"geographic-environmental" approach to soil classification (7).

Early and Present System in the United States
The Russian school of thought had great impact on soil

classification in the United States of America. Early workers
in the U.S., like their contemporaries in Europe, laid emphasis
on geology. In 1889 the USDA used soil type* as a fundamental
unit of classification (1). Hilgard (1860-1906) was notable
among the early workers because he recognized the importance
of soil formation factors including climate (22). In his
report on the soils and agriculture of Mississippi (21) he
showed how soils and their properties are related to the type

of vegetation. Coffey (1912) recognized the soil as an

 

*Soil type, as used here, is a subgroup or category
under the soil series based on the texture of the surface soil.

10
independent body (47). He stressed the need for using
morphological characteristics as criteria for soil classifi—
cation and classified soils into:

1. Acid soils,

2. Dark colored prairie soils,

3. Light colored timbered soils,

4. Black swamp soils,

5. Organic soils.

Each class was subdivided into series on the basis of parent
material and the series was further subdivided on the basis
of texture.

Marbut (1908-1935) greatly influenced thought in soil
classification in the United States. Being a geologist he
started with the ideas of the old school of geology. Later
he was influenced by the work of Glinka and following that
he greatly underemphasized the role of parent material (33).
Marbut developed the concept of the soil as an independent
natural body with three dimensions and profile characteristics.
The classification of normal soils was one of his major interests.
In his scheme of soil classification (3) he presented two
great divisions: (1) Pedocals (having a carbonate enriched
subsoil), and (2) Pedalfers (having a subsoil with concentrations
of iron and aluminum oxides). Further subdivisions are shown

in Table 2*.

 

*Table 2 adopted from Soils and Men (3, p. 938).

TABLE 2.-—Soi1 Categories

11

 

Category VI

Category V

Category IV

Category III

Category II

Category I

Pedalfers (VI-I)

Soils from mechanically
comminuted materials
Soils from siallitic
decomposition products
Soils from allitic
decomposition products

Tundra

Podzols

Gray-Brown Podzolic
soils

Red soils

Yellow soils

Prairie soils

Lateritic soils

Groups of mature but
related soil series

Swamp soils

Gley soils

Rendzinas

Alluvial soils

Immature soils on slopes
Salty soils

Alkali soils

Peat soils

Soil series

Soil units or types

Pedocals (VI-2)

Soils from mechanically
comminuted materials

Chernozems
Dark-brown soils
Brown soils

Gray soils

Pedocalic soils of
Arctic and Tropical
regions

Groups of mature but
but related soil series

Swamp soils

Gley soils

Rendzinas

Alluvial soils

Immature soils on slopes
Salty soils

Alkali soils

Peat soils

Soil series

Soil units or types

 

Baldwin, M., Kellogg, C. E. and Throp, J.
Classification. USDA Yearbook of

p. 938.

Agriculture,

1938 Soils and Men.

Soil

12

The year 1938 saw the revival and modification of
Sibirtsev's zonal, intrazonal and azonal concept by Baldwin,
Kellogg and Thorp (3). Their scheme of classification is
similar to Marbut's, but differs from it in one important
aspect: the azonal soils were raised to the level of zonal
and intrazonal soils. The detailed scheme presented in the
1938 classification was revised by Thorp and Smith in 1949 (46).
The three dimensional concept of the soil individual was
stressed. Since Marbut's time the trend in soil classification
in the United States has been toward an increasing recognition
of morphological characteristics with genetic significance as

criteria.

Proposed Comprehensive System

 

With the increase of knowledge, the need for developing
a new system was felt among the soil survey staff of USDA.
This led to the publication of the 7th Approximation of a
comprehensive system of soil clasSification. In this proposed
system some of the short-comings of the previous systems were
revealed (47). For example, definition of the classes were
vague, and the systems were based primarily on the factors of
soil genesis or properties of the virgin soil in the natural
landscapes. The new system takes into full consideration
changes taking place within the soil as a result of man's

influence. Certain assumptions that guided the development

13
of the system were outlined (47).

According to Cline (13), "The purpose of any classifi-
cation is so to organize our knowledge that the properties
of the objects may be remembered and their relationships may
be understood most easily for a specific objective." In
developing the nomenclature for the proposed system this
idea was brought up in the statement that "the most useful
names are those that are most easily remembered, suggest some
of the properties of the objects, and show the position of
the class in the system" (47), (see Table 3 for names of
higher categorical classes).

In the proposed system the following categories, starting
at the highest level of abstraction have been divised: VII,
Order: VI, Suborder; V, Great Soil Groups; IV, Subgroups;

III, Family; II, Soil Series; and I, Soil Type. It is stated,
moreover, that the type is to be eliminated as a category in
the proposed system.

There are ten orders and some of these correspond closely
to Coffey's major classes and Dokuchaiev's types (47). The
major kinds of differentia used for the soil order are presence
or absence, and nature of diagnostic horizons and their features;
major differences in soil moisture, and major differences in
kinds and amounts of organic matter. No attempt will be made

here to describe the various orders. However, attention is

TABLE 3.--Names of Proposed Orders,

and Great Groups of Soils

l4

Suborders,

 

 

Order Suborder Great group
1. Entisol ....... Aquent ..... 1.ll Cryaquent
1.12 Psammaquent*
1.13 Hydraquent
1.14 Haplaquent
Psamment.... 1.21 Quarzopsamment
1.22 Orthopsamment*
Ustent ..... 1.31 Psammustent*
1.32 Orthustent*
Udent ....... 1.41 Cryudent
1.42 Argudent
1.43 Hapludent
1.44 Plaggudent
2. Vertisol ....... Aquert ...... 2.11 Grumaquert
2.12 Mazaquert
Ustert ...... 2.21 Grumustert
2.22 Mazustert
3. Inceptisol .... Aquept ...... 3.11 Halaquept
3.12 Umbraquept*
3.13 Fragaquept
3.14 Cryaquept
3.15 Ochraquept*
Andept ...... 3.21 Cryandept
3.22 Durandept
3.23 Ochrandept*
3.24 Umbrandept*
3.25 Hydrandept
Umbrept ..... 3.31 Cryumbrept
3.32 Haplumbrept
3.34 Anthrumbrept
Ochrept ..... 3.41 Cryochrept
3.43 Eutrocherpt
3.44 Dystrochrept
3.45 Ustochrept
3.46 Fragochrept

TABLE 3 (Continued)

15

 

 

Order Suborder Great Group
4. Aridisol ....... Orthid ...... 4.11 Camborthid
4.12 Durorthid
4.13 Calcorthid
4.14 Salorthid
Argid ....... 4.21 Haplargid
4.22 Durargid
4.23 Natrargid
4.24 Nadurargid
5. Mollisol ...... Rendoll ..... 5.11 —--(Rendoll)
Alboll ..... 5.21 Argalboll
5.22 Natralboll
Aquoll ...... 5.31 Haplaquoll
5.32 Argaquoll
5.33 Calcaquoll
5.34 Duraquoll
5.35 Natraquoll
Altoll ..... 5.41 Vermaltoll
5.42 Haplaltoll
5.43 Argaltoll
5.44 Calcaltoll
5.45 Natraltoll
Udoll ...... 5.51 Vermudoll
5.52 Hapludoll
5.53 Argudoll
Ustoll ..... 5.61 Vermustoll
5.62 Haplustoll
5.63 Argustoll
5.64 Durustoll
5.65 Calcustoll
5.66 Natrustoll
6. Spodosol ...... Aquod ...... 6.11 Cryaquod
6.12 Humaquod*
6.13 Ferraquod
6.14 Placaquod
6.15 Thermaquod

TABLE 3 (Continued)

16

 

 

Order Suborder Great group
6.16 Duraquod
6.2 Humod ....... 6.21 Orthumod
6.22 Thermhumod
6.3 Orthod* ..... 6.31 Cryorthod
6.32 Placorthod
6.33 Typorthod
6.4 Ferrodd .....
7. Alfisol ....... 7.1 Aqualf ...... 7.11 Albaqualf
7.12 Glossaqualf
7.13 Ochraqualf
7.14 Umbraqualf
7.15 Fragaqualf
7.16 Natraqualf
7.2 Altalf ..... 7.21 Cryaltalf
7.22 Typaltalf
7.23 Natraltalf
7.24 Fragaltalf
7.3 Udalf ...... 7.31 Agrudalf
7.32 Typudalf
7.33 Fragudalf
7.34 Glossudalf
7.35 Fraglossudalf
7.4 Ustalf ..... 7.41 Durustalf
7.42 Natrustalf
7.43 Rhodustalf
7.44 U1tusta1f*
7.45 Typustalf
8. Ultisol ....... 8.1 Aquult ..... 8.11 Plintaquult
8.12 Ochraquu1t*
8.13 Umbraquu1t*
8.14 Fragaquult

TABLE 3 (Continued)

l7

 

 

 

Order Suborder Great group
8.1 Ochrult ..... 8.21 Plintochrult
8.22 Rhodochrult
8.23 Typochrult
8.24 Fragochrult
8.3 Umbrult ..... 8.31 Plintumbrult
8.32 Typumbrult
9. Oxisol ........
10. Histosol ......
*Used temporarily for want of a better name. The prior

formative element is duplicated in such a way that two different

subgroups may have identical names.

18
drawn to Table 5 in the 7th Approximation (47), which shows
their approximate equivalents in the revised classification of
Baldwin, Kellogg and Thorp. It should be noted that the humic
gley soils were redistributed among several orders. Subdivisions

of the orders into suborders is based primarily on chemical or

 

physiCal properties that reflect either the presence or absence
of water logging or moderate genetic differences due to climate
or vegetation, and minerological differences. The differentiating

characteristics used for the great groups were defined on the

 

basis of diagnostic horizons and their arrangement. Emphasis
is placed on properties least apt to be destroyed by tillage
oerrrosion. Dark red or dark brown surface colors, and major
differences in irreversible consistence changes of surface
layers, are also used as differentiae. At the subgroup level
we have the central concept of the great group (the orthic
group) and its intergrades. The differentiae for the families
are properties which are important to plant growth; i.e.,
properties affecting soil air, soil water, plant-root relation-
ships and nutrient supplying capacities for the major elements
other than nitrogen. The differentiae selected for horizons
below the plow layer are texture, thickness of horizon, mineralogy,
reaction, consistence, and permeability. The authors pointed
out that the families are not well defined and the subgroup

definitions are incomplete. The major properties used as

19
series differentiae are those of the solum below the plow
layer. "These properties should be observable or inferred with
reasonable assurance." They must have at least limited
singificance to soil genesis. The soil type has been dropped
as a category in this proposed system. If this proposed system
is to be used effectively the need for lower categories in
relation to land use cannot be overlooked.

The 7th Approximation has certain definite advantages.
It includes all known soils, and it has given due consideration
to changes taking place within virgin soils as a result of
man's influence. Morphological properties which have genetic
significance are used as differentiae. Temperature and moisture
conditions of soils are also used as differentiae at the great
group level. It should be noted that both temperature and
moisture can be regarded as genetic properties. Their use
as differentiae at this level is encouraging because it shows
that both genetical and morphological properties are closely
related.

As proposed the 7th Approximation has some draw-backs;
all the classes have not been studied in such detail as to
permit their classification to the same level. For example
the classification of tropical soils (Oxisols) and organic soils
(Histosols) lags behind the others. Definitions of classes

in the other subgroups and lower categories are not complete.

20

It is also likely that the nomenclature will not be easy to
manage at the initial stages. As new knowledge accumulates,
it is hoped, these shortcomings will be overcome. The proposed
system is now in its trial stages. It is, therefore, too
early to evaulate its usefulness.

From the above historical review of soil classification
efforts it is evident that repeated attempts have been made
to improve the systems as knowledge of the soils increased.
This is desirable since classification is conceptual and
reflects the knowledge of the period. The models of classifi-
cation we build up should be used to search for new facts,

which will in turn improve the classification.

Types of Classification Systems

Many types of classification of soils are possible.
In fact there can be as many systems as there are objectives
for classigying soils. However, each type may belong to one
of the following two groupings: (1) Technical system of
classification, or (2) Taxonomic systems of classification.
Technical systems are those based on one or more characteristic
features or properties which are important and of value for a
particular objective (51): an example is land-use capability
classification. The usefulness of such limited purpose
classification depends on the importance of properties chosen

for the objective. Cline (l3) refers to those systems which

21
assume that there is order in nature and attempt to organize
natural phenomena in the light of this concept as "taxonomic."
In the existing taxonomic systems soils are classified on the
basis of the operating soil forming processes as they are
inferred from the morphology of the soil profile.

Today, trends in the choice of criteria are toward
observable or inferred morphological properties which have
at least limited genetic significance. A point of contention
between some soil scientists is whether a system should be
called "natural" or "artificial." Kubiena (29) referred to
Leeper's system as artificial and Leeper (31) objected to the
use of the term natural for Kubiena's system. Such contentions
arise, because people accord different meanings to the same
term. The terms "technical" and "taxonomic" as used above are

to be preferred to "natural" and "artificial,' since the
latter lead to confusion. The types of classifications dis-
cussed above and in the following pages are taxonomic.

Methods of approach to soil classification differ from
country to country and for objectives. Manil (32) discussed
two broad methods of approach:

1. analytic and descending (genetic approach);
2. synthetic and ascending. [Kubiena (30) in the Soils of
of Europe refers to these as division and classification,

respectively.]

The descending and analytic types of classification start from

22
the highest categorical level. They may be based on genetic
factors per se or on pedogenetic processes or on properties
that reflect pedogenetic factors or processes. This type of
approach is used by European classificationists. The synthetic
and ascending type may be based on profile morphology with or
without genetic considerations. Manil (32) stated that the
synthetic and ascending classification is possible only when
a large body of knowledge has been accumulated at the lowest
categorical level.

In the United States the synthetic and ascending
approach is used with genetic considerations. The use of
morphological properties, which reflect soil genesis is be—
coming increasingly important in soil classification.

Basic principles guiding any natural classification
have been discussed by Cline (13). The principles of differen-
tiation as he outlined them are very important in soil classi-
fication. These principles are again seen in the assumptions
underlying the development of the 7th Approximation (47).
Here, only the criteria for soil classifiCation will be
considered.

In soil classification some properties must be chosen
as the basis of grouping. These are the differentiating
characteristics (13). According to Cline the differentiating

characteristics should be associated with the greatest possible

23
number of covarying properties. They should be such that the
most precise and meaningful statement can be made about the
soils. Properties of the soils themselves should be used.
Accidental characteristics which vary independently of these
differentiae are sometimes used with them in the lower categories.

Morphological characteristics are used as criteria in
the U. S. Genetical factors though not used as criteria serve
as indexes to properties of the soil that are criteria (13).
Genetical properties help in classifying at higher levels of
abstraction and in placing soil boundaries in the field.

Van Eck and Whiteside (48) point out that the making of accurate

soil maps requires an understanding of soil genetics.

Criteria of Soil Classification

Marbut (33) proposed ten important criteria used for
differentiating at the level of soil type: These are:
number of horizons in the profile, color of the various
horizons, texture, structure, relative arrangement of horizons,
chemical composition, thickness of horizon, thickness of the
true soil, character of the soil material and geology of the
soil material. Cline (13) reported that no one has since
then improved upon this list. But Whiteside (49) subsequently
outlined some changes in the criteria used since Marbut. He

grouped the criteria according to Whether they are properties

24

of the soil body or of its individual horizons as follows:

I. Prgperties of the soil body.

 

1. Number of horizons in the soil profile.
2. Relative arrangement of the horizons
3. The thickness of the true soil.
4. Mineralogical and chemical composition of the parent rock.
5. Texture of the parent rock.
6. Structure or fabric of the parent rock.
7. Shape.
8. Temperature.
9. Moisture.
10. Degree of development.
11. Age.
12. Air?
13. Biology?
II. 'Properties of the soil horizons.
14. Texture.
15. Structure.
16. Consistence.
17. Color.
18. Chemical composition.
19. Mineralogical composition.
20. Thickness.

These gave twice as many properties as originally pro.

posed by Marbut. Since then in the United States, the following

25
properties have been added to the second group: porosity,
nature of horizon boundaries, changes on wetting and drying,
ease of dispersion and N values. These new properties have
been used as criteria in the 7th Approximation. The N value
is not a completely new property since it is a combination of
a number of properties (moisture, texture, organic content,
and chemical composition) outlined above. However, moisture
content of soil horizons in the field, which is included in
the N value, is a new property.

It should be noted that the properties used are only
good as long as the objective of the classification remains
unchanged, and they maintain their original importance to
this objective. It may be necessary to further increase the
number of these properties as our knowledge of soils increases,
or drop some of them. However, there is a limit to the number
of properties that should be used. Although this limit is
not fixed, the number should not be so large as to unnecessarily

complicate the system or so small as to over-simplify it.

26
III. SOILS OF GHANA: CLASSIFICATION AND

SURVEY EFFORTS

Soil survey and soil classification in Ghana as in many
tropical areas, lags behind the development of other branches
of agricultural investigation (notably crop and animal husbandry).
An organized attempt to carry out a country-wide survey was
started in 1948 (8 and 9) with the formation of the Soil
Survey Division in the Department of Agriculture. The division
was headed by the late Hon. C. F. Charter. Mr. Charter
started work in Ghana as a soils specialist at the West African
Cocoa Research Institute, Tafo. It is interesting to note
that, in Ghana, the concern for a closer study of soils was

caused by "swollen shoot,’ a virus disease of cocoa. At the
initial stages of investigation research was directed toward
finding the cause of the disease. The soil as a medium of
growth for the cocoa plant constituted one of the areas of
search.

The Soils Division was faced with many initial problems:
there was the difficulty of recruiting qualified senior staff
and training locally recruited junior staff. Much effort was
expended during this period on the construction and equipping
of administrative and technical offices, laboratories, stores

and workshops (11). Charter (11) deserves credit for meeting

all these demands efficiently.

27

The initial survey and mapping of all the soils of the
country is still in progress. However, considerable data
have been accumulated to justify an attempt at developing a
scheme of classification and the making of a provisional map
of the soils of the country. Charter's (12) provisional scheme
of classification of soils so far discovered in Ghana is
discussed in the following section. This scheme was later
revised by Brammer (4 and 5). He made certain suggestions for
improving it. With the limited detailed descriptive data at

hand, this scheme of classification can be only provisional.

Charter's Proposed Scheme of Soil Classification

As stated by Brammer (4) the basis of Charter's interim
scheme for the classification of tropical soils is the formula:
soil = f (climate, vegetation, parent material, relief and
drainage, and age). The approach to this classification is,
therefore, genetic. Since detailed morphological descriptions
have not been made for most of the soils, this genetic approach
is to be expected.

The system as it is presented in outline includes
fomrsoil orders. The soil forming factors are used as criteria
for differentiating at this level. One or two of the factors
having predominant influence on the development of the soils

form the basis of the grouping:

28

Soil Orders Dominant Factor or Factors
Influencing Development

I Climatophytic earths Climate and vegetation
II Topoclimatic earths Relief and climate
III Topohydric earths Relief and drainage

IV Lithochronic earths Parent material and/age

At the level of the suborder different characteristics

were used to differentiate in each of the above order.

I The Climatophytic Earths
These are the normally well drained soils. They are
differentiated on the basis of depth of penetration of rain—

fall or thoroughness of leaching.

Suborders:
A. Hygropeds, soil profile through leached to groundwater

B. Xeropeds, soil profile not through leached.

II The Topoclimatic Earths

 

The Topoclimatic earths have not been further sub-

divided because they are not found in Ghana.

III Topohydric Earths

Topohydric earths are soils with poor drainage conditions.
It should be noted that at this level two different criteria
have been used for differentiation. The first four suborders
are differentiated on the basis of the nature of the topographic
site, while the fifth is characterized by accumulation of

peat at the surface.

29
Suborders
Planopeds: Poor drainage due to flat or very gentle
topography.
Clinopeds: Soils affected by water seeping from upslope
and precipitating chemical substances from solution.
Depressiopeds: Soils developed in poorly drained de—
pressions (receiving runoff or seepage waters from
adjoining areas).
Hydropeds: Soils developed under open water in shallow
lagoons, rice paddies, etc.
Cummulopeds: Soils developed in depressions with peat

accumulation.

IV Lithochronic Earths

Lithochronic earths are the soils with restricted profile

development. Differentiation into suborders is according to

the particular factor retarding development.

Suborders Factor Retarding Development

Lithopeds Resistant rock or erosion on steep slope

Regopeds Inert nature of loose sandy parent
material

Alluvioped Constant addition of fresh alluvium to

the surface.

The differentiating characteristic used for subdividing

30

the suborders into families of great soil groups is usually the

reaction of the profile.

Order I - Climatophytic earths

Suborder A — Hygropeds. These are subdivided into families

Family -

on the basis of mineral base supplying power
of the parent material.

1. Latasols. These are soils developed over
highly weathered parent material and in which
the clay fraction is predominantly iron and
aluminum sesquioxides and kaolinite.

2. Basisols. These are developed in parent
material relatively rich in bases and the
clay fraction has some montmorillonite to—
gether with kaolinite, and iron and aluminum

sesquioxides.

Suborder B - Xeropeds. The suborder Xeropeds are not

Order II -

Order III -

further subdivided since their presence in
Ghana is doubtful.

Topoclimatic earths are not further discussed
for the reason given above.

The great soil group families of the sub-
orders of Topohydric earths are differentiated
according to the nature of the reaction of the

groundwater influencing the soils. Very acid,

31
acid, neutral, calcium and sodium group families
are recognized. (See Table 4 for names.)

Order IV - Suborders of the Lithochronic earths, except
the Lithopeds are not further differentiated
into families of great soil groups. The
Lithopeds are simply divided into two family
groups: the Basimorphic Lithosols and Non-
basimorphic Lithosols, somewhat as are the
Hygropeds.

Within the families of the great soil groups are
differentiated on the basis of natural vegetation under which
they develop (forest or savanna) color, and trend of reaction
in the soil profile. Brammer (4) points out that the color
and reaction trends are used as criteria only in so far as they
serve as manifestations of other fundamental differences in
soil properties.

The great soil groups are further subdivided into
soil series mainly on the nature of the parent material in
which individual soils are developed. These have not been
listed in Table 4, except for the ten series for which placement
within the 7th Approximation was attempted.

The above scheme of classification is based on ideas
similar to those that guided some of the earlier European systems

of classification. It has the weakness of relying mainly on

32

TABLE 4.--Provisional Classification of Soils So Far

(ii)

(iii)

Discovered in Ghana, after Charter, and place—
ment of the Soil Series in Ghana in the 7th
Approximation.

The use of brackets around a term indicates that
the nomenclature is still provisional.

? before a term indicates that there is some doubt
as to the exact plans of the soil group or group
family in the classification.

? after a term indicates that there is some doubt
as to the classification of the soils examined
within the group indicated or of the soil group in
the family indicated.

 

ORDER SUBORDER
HYGROPEDS
O
cumuopmnc EARTHS
XEROPEDS
r' PLANOPEDS
CLINOPEDS

l

l DEPRESSIOPEDS

TOPOHYDRIC EARTHS

CUMULOPEDS

 

k HYDROPEDS

llTHOPEDS

LITHOCHRONIC EARTHS

REGOPEDS

ALLUVIOPEDS

(sou GROUP FAMILY)

Lotasol

Basisols

Very Acid Planosol?

Acid Planosol?

Calcium Planosol
Sodium Planosol?

Very Acid Gleisol
(Tropical Gray Earth)

Acid Gleisol

Neutral Gleisol

Calcium Vleisol
Sodium Vleisol
Cumulosol

Hydrosol

Basimorphic Lithsol

Non-Basimorphic lithosol

Alluviosol

l
l
l

l
{
i
l
l

GREAT SOIL GROUP

Forest Och rosol

Savannah Ochrosol

Forest Oxysol?

ForestRubrisol

Savannah Rubrisol

Forest Brunosol
Savannah Brunosol

(Reddish Prairie?)

(3 roundwater Podsol

G roundwater Lotarite

Tropical Black Earth
Tropical Brown Earth

(Savannah Gray Very Acid Gleisol)

(Savannah Black Acid Gleisol)
(Savannah Brawn Acid Gleisol)
(Forest Gray Acid Gleisol)
(Savannah Grey Acid Gleisol)

(Forest Black Neutral Gleisol)
(Savannah Brown Neutral Gleisol)
(Forest Gray Neutral Gleisol)
(Savannah Gray Neutral Gleisol)

(Black Vleisol)
(Brown Vleisol)
(Gray Vleisol)

Solonetz?
Solonchali

Very Acid 609?
Acid 800?
Saline Bog?

Neutral Hydrosol?
Saline Hydrosol

(Block Basimorphic Lithosol)
(Brown Basimorphic lithosol)
(Red Basimorphic Lithosol)

(Non-Basimorphic lithosol)

{

(Dune-sand Reoosol-with calcareous

pan—without calcareous pan)
(Other Regosols)

(Block Alluviosoll
(Brown Alluviosol)
(Gray Alluviosol)

GREAT SOIL SUBGROUP

Red Forest Ochrosol
Yellow Forest Ochrosol

Red Forest Oxysol
Yellow Forest Oxysol

Red Savannah Ochrosol
Yellow Savannah Ochrosol

Red Forest Rubrisol
YeIIOw Forest Rubrisol

Red Savannah Rubrisol
Yellow Savannah Rubrisol

(Yellow Basimorphic lithosol)

SERIES

Bekwai (9.43), Kurnasi (9.43)

Mimi (9.43), Toie (9.5:)

Boi (9. 32)

Atuabo (6.150)

erlesawgu (9.l l—9.l 2)

Akuse (2.] l)

Agawtaw (7.l 5)

Wacri‘fiZ)

34
the factors of soil genesis and processes of pedogenesis as
criteria. This is undesirable because in the choice of factors
of soil genesis as differentiating characteristics, theories
have been allowed to overrule observable facts. As Yalon (51)
stated elsewhere, the interdependence of soil forming factors
makes it difficult to relate soil properties to definite soil
forming factors with any certainty. If great care is not
exercised the classification becomes one of external soil
forming factors rather than of the soil. The analytic and
descending approach (32) adopted here indicates that detailed
knowledge about the morphology of the soils is lacking. At
this early stage of soil surveys in Ghana the authors could
not be blamed. They made the right approach.

The lack of morphological descriptions and the need
for precise observations was pointed out by Kellogg (27) in
his preliminary suggestions for the classification and nomen-
clature of the great soil groups in tropical and equatorial
regions. At least at the great soil group level and at lower
levels of abstraction adequate detailed description of morpho-
logical properties must precede the choice of important morpho-
logic characteristics as criteria. The trend today, particularly
in the U.S., is toward the choice of morphological properties
which are observable or can be inferred with some certainty

from morphology and limited experimental data. Those

35
morphological properties, which have some correlation with
genetic properties and the soil formation factors (genetical
properties) are preferable (48). Principles guiding such a
choice have been outlined by Cline (13).

In the above system the subdivision of the order Topo-
hydric earths is said to be based on the nature of topographic
sites. But the Cummulopeds are differentiated from the
Depressiopeds only on the basis of the peaty surface accumu-
lation. This is a violation of the principle that all classes
of the same category of a single population should be based
on the same characteristics. It is clear that presence of
peat accumulation is not used as criteria throughout the rest
of the suborders. Therefore, it would be better to consider
the separation of the cummulopeds from the depressiopeds at
a lower level of abstraction, if the peat soils are only found
in depressions, unless the peat horizon is morphologic evidence
of a topographic site. If, however, peaty soils occur at
sites other than in depressions then the raising of the peaty
(organic) soils to level of soil order as in the 7th
Approximation may be considered. Here again accurate observa-
tion and description of the nature of the peat (thickness, etc.)
are necessary before taking any step. (This principle is
sacrificed in order to avoid many additional categories in

the 7th Approximation).

36
The differentiation of the series, merely on the nature
of the parent material, is inadequate without properly correlated
morphology and may lead to gross errors. However, this is a
case where the genetical factors of soil formation are useful
as simplifying relationships among soils in a category based
on available information about the soils concerned. Obviously,
the parent material from which the soil is presumed to be
formed is no longer there to be seen. But, the nature of the
parent material may commonly be inferred beyond any reasonable
doubt from the properties of the parent rock and from the
remaining weathered material, as outlined by Marshall and
Haseman (35), and Whiteside (49). The morphological character-
istics of the soil horizons will serve as described criteria.
The use of type of vegetation (forest or savanna) at the
great soil group level has one serious disadvantage. The
type of farming practices adopted in Ghana (bush fires,
clearing of forest vegetation, etc.) are likely to change the
characteristics of a typical savanna or forest soil within a
matter of years. These should only be used as indicators to
certain morphological properties or to serve as a generalization

of the relationships involved in the morphological differences.

Description of the Major Soils of Ghana
Ghana has a tropical climate. The year is divided into

two seasons, a rainy and a dry season. The pattern of rainfall

37
distribution and intensity follow the major vegetational zones
to which the soils are very closely related.* The South-
western part of the country, with tropical rain forest, has
a mean annual rainfall of over 80 inches. The annual rainfall
in the other forest areas ranges from 60 to 70+ inches. In
the interior savannah zone the annual rainfall range is about
44 to 55 inches. There is a special coastal savannah area
with 25 to 35 inches of annual rainfall. In the forest zones
there are two peaks of rainfall; the lower peak occurs around
May to June and the high peak occurs in September to October.
November to February are relatively dry. Most of the interior
savannah areas experience one marked peak of rainfall (September
to October) with a pronounced dry season.

The mean annual temperature is about 80 to 850F. Tempera-
ture variation between the hottest and coldest months increases
as one goes inland (northwards), but there is only a few degrees
variation in temperature.

The landscape consists of plains, river basins, scarps

and mountain ranges. The northeast and northwest portions
have scarp regions. The Accra plains (Volta river plains)
occur in the southeast. The Kwahu range runs southeast to

 

*See map in Appendix 1 for distribution of great
soil groups.

38
northwest. Southeast of this range we have conspicuous
drainage patterns of rivers running north and south. In the
Accra plains the dissection is low with isolated hills of
Archean rocks (basic gneisses). Superficial deposits of talus
occur on steep slopes and on the bottom of the slopes. On
less steep ground a thicker soil mantle covers practically the
whole country. River alluvium in the deltaic region of the
Volta grade into lagoon deposits. These lagoons are a
possible origin of the black clays* found in these areas.

The Akwapim—Togo range runs from southeast to north-
east. Selective erosion and peneplaination are believed to have
played a major role in shaping the landscape.

As stated earlier all the soils of Ghana have not yet
been surveyed. The map in Appendix 1 shows the schematic
distribution of great soil groups. Brammer (4) made it clear
that this map has been greatly generalized and is only provisional.
Soil boundaries, in areas not yet surveyed, have been drawn
in by extrapolation using geological boundaries and isohyets
as a guide.

The soils differ, according to the three major vegetation
zones: forest, interior savanna, and coastal savanna. The

following general descriptions of soils under the different

 

*For a detailed petrographic description of these black
clays the reader is referred to Stephens discussion (45).

39
vegetation zones have been summarized from Brammer's (4)
report. Diagrams of soil profiles representative of each

group are shown in Appendix 2.

Forest Zones

 

The soils of the forest zones have greater accumulation
of organic matter in the surface horizon than soils of the
savanna zones. This is accounted for by more leaf fall and
less decomposition of organic matter under forest conditions.
Jenny (24), who studied two tropical forested soils of Colombia
and compared them with California forest soils, attributed the
higher level of nitrogen and organic matter in the tropical
forest soils to higher additions of nitrogen in rainwater and
higher non—symbiotic and symbiotic nitrogen fixation. He
stressed the latter possibility since large numbers of leguminous
trees occur in the tropical forest areas. He also observed
that several hundred years seem to be required to build soil
organic matter to a nearly steady state. Annual rainfall ranges
from 35 inches to over 80 inches in these zones. The soils
are developed over different types of rocks: igneous, meta-
morphic and sedimentary.

The major soils of the Forest Zones are Latosols. These
are subdivided into the great groups of Forest Ochrosols and

Forest Oxysols.

40

Forest Ochrosols are the most extensive and most
important soils of the forest zone. They are developed in the
weathering products of intermediate or moderately acidic
rocks in peneplain drifts and in terrace alluvium. These
soils, occupying the upland portions of gently undulating to
strongly rolling topography, are relatively well drained. Their
colors range from red through brown to yellow-brown. Color
differences are associated with slope and drainage conditions.
Associated with these are the poorly drained soils of the
bottoms. It has been noted that textural differences are
related to the nature of the parent materials (4). Detailed
descriptions of Kumasi and Bekwai series (model profiles from
a granite and a phyllite rock) are given below in Tables 5
and 6, respectively. Profile diagrams for these soils are
shown in Appendix 2.

Forest Oxysols are similar to the Ochrosols but have
paler colors. They have thinner surface horizons but thicker
subsoils than Ochrosols. The annual rainfall in areas of
the Oxysol is (60 to 70+") generally higher than in Forest
Ochrosol areas (35 to 65"). This higher rainfall accounts for
greater leaching of the soil, which gives rise to the paler
colors and lower pH values. A profile description for a model
Oxysol, the Boi series is given in Table 7. Since this profile
is also developed from phyllite it may be compared to the Bekwai

profile.

41

TABLE 5a.--Description of Kumasi Series, A
Representative Forest Ochrosol

 

 

SERIES: Kumasi Ref. PKR 299/1-14
LOCALITY: Central Agricultural Station Rainfall: 55"/yr.
Kumasi, Ashanti Altitude: 800-850 ft.
SITE: Upper slope/ gentle Soil group:
undulation Forest Ochrosol
SOURCE: Well
PARENT ROCK: Biotite Granite
VEGETATION: Bush Regrowth
Horizon
Proposed
Depth Proposed genetic
Ref.no. in A,B,C desig— Description***
inches system nation**
symb01*
299/1 0-4 Al Vh Moderate to dark yellowish

brown (lOYR 3/3 to 4/2); humic;
light loam, with occasional
fine quartz gravel; pH 7.2.

299/2 4-9 A2 Ei Moderate yellowish brown,
(lOYR 4/3), gritty loamy sand,
with rare subangular quartz
gravel; rare root fibers;
pH 6.8.

299/3 9-18 B2t1 II It Light brown (5YR 5/4); gritty
light clay, very frequent fine
and coarse gravel; occasional
ironstone concretions; pH 5.7;
many rootlets.

299/4 18-32 B2t2cn II Iti Light brown to brownish orange
(5YR 5/6): gritty light clay,
very frequent fine and coarse
quartz gravel, frequent sub-
angular small quartz stones;
frequent ironstone concretions:
pH 5.2; many rootlets.

42

TABLE 5a (Continued)

 

Ref.no.

Horizon

Proposed Proposed

Depth A,B,C
in system
inches symbol

genetic
desig-
nation

Description

 

299/5

299/6

299/7

299/8

299/9

32-55 B2t3

55-94 B2t4

94-133 B2t5

133-204 Cl

204-293 C21

II R1

IIR2

IIIRZ

IIIZml

IIIZmZ

Light brown to brownish orange
(5YR 5/6); slightly gritty
light loam, very frequent fine
and coarse quartz gravel; very
rare ironstone concretions;

pH 5.1; rare rootlets.

Light brown to brownish or-
ange (5YR 5/6); slightly

cloddy; light 10am, frequent
quartz gravel; occasional

ironstone concretions; occa-
sional patches of weathered
rock; pH 5.0; rare rootlets.

Light brown to brownish or-
ange (5YR 5/6) with strong
brown (2.5YR 3/6) mottles;
slightly cloddy; light 10am;
included frequent veins of
aplite; pH 4.9; rare rootlets.

Moderate reddish brown (10R
3/6 to 10R 4/4) with light
yellowish brown to moderate
orange (7.5YR 7/6) mottles;
structureless; light loam;
completely weathered coarse
grained biotite granite with
veins of aplite; pH 4.9;
some rootlets.

Moderate reddish brown (10R
3/4) with light grayish red
to light reddish brown (10R
6/3) and moderate orange

(5YR 6/8) mottles; light loam;
weathered coarse grained bio—
tite granite with veins of
weathered aplite; pH 4.0.

43

TABLE 5a (Continued)

 

Ref.no.

Horizon

Proposed Proposed

Depth A,B,C genetic
in system desig-
inches symbol nation

Description

 

299/10

299/11

299/12

299/13

293-342 C22 III Zm3

342-408 C23 III Zm3

408-444 C3 III Zm4

444-540 R III Zm5

Moderate reddish brown (10R
3/4) with pale yellowish

pink to brownish pink (7.5YR
8/2) and dark orange yellow
(7.5YR 6/8) mottles; light
loam; weathered coarse grained
biotite granite with included,
frequent aplite veins; pH 5.0.

Moderate reddish brown (10R
3/4) with pale yellowish pink
to brownish pink (7.5YR 8/2)
and pale to moderate orange
yellow (lOYR 8/6), mottles;
light loam; weathered coarse
grained biotite granite with
very frequent weathered
aplitic veins; pH 5.0.

Moderate reddish brown (10R

3/4) with light to moderate
orange yellow (lOYR 8/8) and
pinkish gray (5YR 8/l) mottles;
same textures as above; less
weathered aplitic veins; pH 5.0.

Moderate reddish brown (10R

3/4) with light to moderate
orange yellow (lOYR 8/6) and
light grayish red to light
reddisn brown (10R 6/3) mottles;
massive; weathered coarse
grained biotite granite with
very frequent thick veins of
aplite, pH 4.9.

44

TABLE 5a (Continued)

 

Horizon

Proposed Proposed
Depth A, B, C gene tic
Ref.no. in system desig- Description
inches symbol nation

7W

 

299/14 540-660 R III Zm6 Completely weathered coarse
grained biotite granite,
pH 4.9.

 

*See reference (47).
**See reference (50)-

***Color names according to: ISSC-NBS Method of
Designating Colors and a Dictionary of Color Names, 1955.
Nat. Bur. Standards Cir. 553, Gov't Printing Office,
‘Washington 25, D. C.

45

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SERIES:

48

TABLE 6a.--Description of Bekwai Series, a
Representative Forest Ochrosol

LOCALITY:

SITE:
SOURCE:

Bekawi

Near Manso Nkwanta,

Ref. PKR 74/1-7

Ashanti Rainfall: 55-60"/yr.

Upper slope/steeply rolling Altitude: 1,000 ft.

Profile Pit

Soil group:

 

 

PARENT ROCK: Phyllite Forest Ochrosol
VEGETATION: Cocoa
Horizon
Proposed Proposed
Ref. Depth A, B, C, genetic Description
no. in system desig-
inches symbol nation

74/1 0-2 Ap Vh Moderate brown (7.5YR 4/4);
humic; light loam, crumbly
and porous; pH 5.8+.

74/2 2-11 B2tl It Strong brown (5YR 4/7);
light clay; occasional irreg—
ular large and small iron-
stone concretions; rare fine
quartz gravel; cloddy and
slightly compact; pH 4.8.

74/3 ll—21 B2t20n1 II Iti Light brown to brownish
orange (5YR 5/6); light clay,
frequent irregular large and
small ironstone concretions;
frequent angular and sub-
angular coarse quartz gravel,
occasional-brash or fer-
ruginised phyllite; cloddy
and compact and gravelly;
pH 4.6.

74/4 21-33 B2t3cn2 II R Brownish orange (5YR 5/8);

heavy loam; frequent irreg-
ular large and small iron-
stone concretions, frequent
brash of ferruginised phyl-
lite frequent angular and
subangular quartz gravel,
rare cauliflower head, occa-
sional angular and subangular
quartz stones; cloddy and
compact and gravelly; pH 41L

49

TABLE 6a (Continued)

 

 

Horizon
Proposed Proposed
Depth A,B,C genetic
Ref.no. in system desig- Description
inches symbol nation

74/5 33-46 Cl III RZ Yellow red faintly mottled
yellow and red. Light loam,
occasional irregular large
and small ironstone concre-
tions, occasional angular
and sub-angular coarse quartz
gravel, occasional brash of
ferruginised phyllite.
Cloddy and compact; pH 5.0.

74/6 46-64 C21 III 21 Yellow green and yellow red
mottled: light loam of
decomposing phyllite;
schistose and friable;
pH 5.2.

74/7 64-79 C22 III Z2 Pale reddish brown gray

and yellow mottled;
light loam of decomposed
phyllite schistose and
friable; pH 5.2.

 

50

 

 

 

 

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53

TABLE 7a.-—Description of Boi Series, A
Representative Forest Oxysol

 

 

SERIES: Boi Ref. LTB 334/1-9
LOCALITY: . Approximately 10 miles Rainfall: 75"/yr.
North of Esiama, Western Altitude: c. 150 ft.
Region Soil group: Forest
SITE: Middle slope/steeply rolling Ochrosol
SOURCE: PP 3' X 6' x ll.5' Survey: Lower Tano
PARENT ROCK: Phyllite Basin
VEGETATION: Forb regrowth
Horizon
Proposed Proposed
Depth A,B,C genetic
Ref.no. in system desig- Description
inches symbol nation
334/1 0—3 Al Vh Grayish yellowish brown

(lOYR 5/2); humic; silty
light clay; crumbly and
slightly compact:

pH 4.6.

334/2 3-7 A2 Em Light grayish yellowish brown
to light yellowish brown
(lOYR 6/3): very slightly
humic; silty light clay;
Cloddy and compact: very
rare scattered ironstone
concretions, pH 4.8.

334/3 7-16 B2tcn Ril Strong yellowish brown
(lOYR 5/6); silty clay; very
rare quartz stones and
gravel; frequent ferruginised
rock brash; structureless
and very compact; very
frequent ironstone con-
cretions; pH 4.8+.

334/4 16-27 B2t Ri2 Strong yellowish brown (lOYR
5/6); silty light clay;
occasional quartz gravel;
very rare ferruginished
brash; structureless and
very compact, rare ironstone
concretions: pH 5.0.

54

TABLE 7a (Continued)

 

Ref.no.

Horizon

_ Proposed
Depth A,B,C
in system
inches symbol

Proposed

genetic

desig- Description
nation

 

334/5

334/6

334/7

334/8

334/9

27-42 C 1

42466 02

66-88 C3

88-114 C4

114-138 C5

RZ Orange brown, very slightly
mottled with red; silty
clay, occasional quartz
gravel; rare traces of
weathered rock; Cloddy
and compact; very rare
ironstone concretions: pH
5.2.

R22 Pale orange brown, mottled
hellow, red and olive;
silty light clay; rare
traces of decomposing rock;
slightly Cloddy and slightly
compact; pH 5.2+

Zil Pale yellowish brown,
mottled yellow and grey;
silty light clay; very
frequent patches of de—
composing rock; slightly
cloddy and compact; pH 5.4.

Zi2 Gray, yellow and red mottled:
silty light clay, abundant
patched of decomposing rock;
structureless and slightly
friable; pH 5.6.

Zi3 Silty light clay; decomposed
rock; structureless and
friable; pH 5.6+.

 

55

 

 

 

 

 

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58

Organic matter is generally lower in Oxysols than in
the Ochrosols and distributed to lower horizons. The clay
fraction of the Oxysols occurring at higher elevations,
associated with bauxite or bauxite-iron-pan cappings, contains
a high proportion of sesquioxides.

Forest Ochrosol-Oxysol intergrades occur between the
areas of Oxysols and Ochrosols. These are transitional soils
and have properties intermediate between the two groups.

Forest Rubrisols, as described by Bramman (4) p.

25, consist of dark red, firm or plastic, nutty or blocky
clays developed over basic rocks. The clay mineral fraction
has at least some montmorillonite. The profile contains large
amounts of bases. But, unfortunately such soils have limited

distribution in Ghana. They are developed, usually, over

small basic rock dikes. However, there are larger areas of
Rubrisol-Ochrosol intergrades. These are developed over horn—
blende and biotite granodiorites. (See map in Appendis l

for their distribution.) They have brighter colors, higher
exchange capacity, and better developed structure than the
forest ochrosols. The description of a typical profile,
the Wacri series, with analytical data is given below in Table
8.

Other groups of forest soils include Lithosols and

Regosols, which occur in limited areas (see map). Brammah (4)

59

TABLE 8a.--Description of Wacri Series, A
Representative Forest Ochrosol

 

 

SERIES: Wacri Ref: DB 174/1-7
LOCALITY: Block O, Wacri, New Tafo, Rainfall: 65"/yr.
Eastern Region Altitude: 700 ft.

SITE: Upper slope/gently rolling Soil group: Forest

SOURCE: Profile pit _ Rubrisol-Ochrosol

PARENT ROCK: Dark nornblende rock intergrade

VEGETATION: Good cocoa canopy

Horizon
Proposed Proposed
Depth A,B,C genetic

Ref. no. in system desig— Description*

inches symbol nation

174/l 0—1.5 Ap Vh Grayish brown (7.5YR 3/2);
fine sandy clay; crumbly;
pH 7.5; very frequent root
fibers.

174/2 1.5-8 Bll Iti Moderate brown (7.5YR 4/4);
sandy clay: occasional quartz
gravel and stones; loose;
pH 7.1. ‘”

l74/3 8-14 812 It2 Moderate brown (7.5YR 4/3);‘
sandy clay with occasional
quartz stones and dominant
quartz gravel; loose; pH
6.5.

174/4 14-20 BZt It3 Strong brown (5YR 4/6):
sandy clay, dominant quartz
gravel and fragments of
rotten rock; friable;
pH‘6.2.

174/5 20-39 BZtcnl IZl Strong brown (5YR 4/8);

' clay, with frequent quartz
gravel and frequent frag-
ments of ferruginis ed
rotten rock; friable; pH 6.1.

174/6 39-55 B2tcn2 122 Strong brown (5YR 4/8) with

gray, mottles; clay, with
frequent fragments of
ferrunginis ed rotten rock ;
friable; pH 5.6.

60

TABLE 8a (Continued)

 

 

Horizon
Proposed Proposed
Depth A,B,C genetic
Ref.no. in system desig- Description
inches symbol nation
l74-7 55-72 C Zi Dull brown, mottled gray

and red-brown; fine sandy
clay; dominant fragments
of ferruginised rotten
rock; pH 6.0.

 

*Munsell notations determined for another Wacri profile

Ref. No. 186/1-9.

61

 

 

 

 

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vnm .Q.z mm.m mH.o 0H.0 0H.0 wo.o mm.H mm.m Hflz om.© wa .m
me .Q.Z m>.h mH.o NH.o mH.o mm.a mm.m mm.oa HHZ oa.h m .m
0mm .Q.z om.m¢ mh.o mm.o mH.H m¢.h ma.¢m oo.m¢ mmm.o «m.h m.H .H
momma .CH Ca
. . . OH x >paommmu quUme CONHHOC
E.m m mmoEOmm Hmuoa mz M C2 m2 m0 mmCmCUxm mo m mm MD
A ADV >DH>HD hub Cm>o Coaumo U U Swamp
m IUCpCoo Cuumm mCHm .Em ooa\.m.E memEoo memsoxm “@304

 

 

 

 

Acmsqflucoov om mqm¢s

 

64
suggests that the Lithosols may be regarded as immature Forest
Rubrisols and Brunosols, and the Regosols as very weak Oxysols
or Regosol-Oxysol intergrades. These soils are associated
along the coast with dune sand, peaty clays in water—logged
areas and with Ground Water Podzols (Atuabo series). A
profile description and analytical data are given for the
Atuabo Series in Table 9 below. The Ground Water Podzol
is characterized by an organic subsoil pan 1 to 2 feet thick.

(See diagram in Appendix 2).

Soils of the Interior Savanna Zone

The interior savanna zone covers about two—thirds of
the country. Unfortunately, however, less is known about its
soils than about those of the other two zones. Soil boundaries
in this area are provisional. They follow more or less geolo-
gical boundaries.

The major soil groups recognized in this large area
may be seen on the accompanying provisional map in Appendix 1.
In general these soils have lower organic matter than forest
soils and they are also lower in nutrient content. This is
the reverse of conditions in temperate regions. The following
reasons may account for the lower organic matter content, of
the soils of the savannah grassland areas: (1) The grasses
and shrubs have less extensive root systems which are unable

to circulate baSes in the deeply leached soils and use them

 

65

TABLE 9a.--Description of Atuabo Series, a
Representative Ground Water Podzol

SERIES:
LOCALITY:

SITE:
SOURCE:

Atuabo
Atuabo, Western Nzima, Rainfall: c. 85"/yr

Western Region

Flat bottom
PP 3' x 6' x 5 1/12' water Podzol

PARENT ROCK:

Ref: LTB 443/1-6

Altitude: c. 5-10 ft.
Soil group: Ground-

 

 

VEGETATION: Short grass savanna
Horizon
Proposed Proposed
Depth .A,B,C genetic Description
Ref.no. in system desig—
inches symbol nation

443/1 0—2 Al VE Light brownish gray (2.5Y
6/1); slightly humic, silty
fine sand; structureless
and loose; pH 4.6

443/2 2—8 A21 EM 1 Yellowish gray (lOYR 7/1);
silty fine sand; structure-
less and loose; pH 5.0.

443/3 8-23 A22 Em 2 Yellowish gray (lOYR 8/1);
silty fine sand; structure-
less and loose; pH 4.8+.

443/4 23-31 Bhirl Ihi 1 Moderate olive brown (2.5Y
4/2); silty loamy fine sand;
slightly cloddy and slightly
compact; occasional lumps of
organic pan; pH 4.4; very
frequent rusty roots.

443/5 31-47 Bhir2m Ihi 2 Moderate yellowish brown
(lOYR 4/3); loamy sand;
cloddy and very compact;
organic pan; pH 4.6.

443/6 47-61 Bhir3 IP Yellowish gray to pale orange

yellow (lOYR 8/2); fine sand;
structureless and loose;
occasional fragments of or—
ganic pan; pH 5.0.

 

66

 

 

 

 

 

 

00.0 NN.o n©.HN 000.0 MH.o .Q.z .Q.z 0.00H HHZ HHz HHZ Ho .0
vh.m 0H.0 mo.o¢ mmo.o mm.m .Q.z .Q.Z 0.00H HHz HHZ HHZ sq .m
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CONHHOC
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. Suumm mCHm CH Cumwp
mudp qumHmm .Hmuume UHCmmHO
ImHQz A.EE CH mNHm mHUHuHmmv Hm3oq

 

 

quUHmm .mHthMCm HmoHCmComS

 

 

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67

 

 

 

 

 

 

 

M#M© 02 H .Q.Z
0.5 mm .mumumom ECHCOEEm .@ pCm mIH mCONHHom .H
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momma .CH CH
Muaommmu quUHmm CONHHOC
o omom 00.H x . .
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m IUCpCOU .Cuumm mCHH .Em OOH\.m.E XmHmEou mmCmnoxm HmBOH

 

AomscHucoov gm mamae

 

68

for growth (26). (2) There is less leaf fall under the
savannah conditions. (3) The rate of organic matter decomposition
is more rapid in the open savannah areas, and (4) Overgrazing
and bush fires in the savannah areas may also be important
factors. The moisture relation of these soils are poor owing
to unfavorable rainfall distribution. Most of the interior
savannah area has one peak of rainfall (August - October)
and a prolonged dry season (November - March), but the forest
areas have two peaks of rain.

Two important groups of soils in this area are described
below. The Mimi series (Table 10) represents a typical
Savanna Ochrosol whereas the erlesawgu series (Table 11)
represents a typical Groundwater Laterite. Besides these
Brammer (4) described the following less extensive soil groups
of this area: Savanna Lithosols, Brunosols, Tropical Black

Earths, and acid Gleisols (See appendixes 1 and 2).

Soils of the Coastal Savanna Zone

The soils of this zone have been influenced largely by
the geology of the area (4). It is believed that the old
weathered mantle was removed during quaternary fluctuations in
sea level. Rock weathering is, therefore, more recent and less
deep than in the previous areas (4).. The complex origin of the

soils is evidenced in the presence of a stone line within the

soil profile. It is postulated that the stone lines represent

69

TABLE 10a.—-Description of Mimi Series, A
Representative Savannah Ochrosol

Ref: PNB 139/1-7
Rainfall: 45"/yr.

SERIES: Mimi
LOCALITY: Approx. 25 miles W.S.W. of

 

 

Gambaga Altitude: 500 ft.

SITE: Upper slope/gently undulating Soil group: Savanna

SOURCE: Profile Pit Ochrosol

PARENT ROCK: Sandstone

VEGETATION: Cultivation

Horizon
Proposed ' Proposed
Depth A,B,C genetic

Ref.no. in system desig- Description

inches symbol nation

139/1 0-5 Ap Ep Moderate yellowish brown
(lOYR 4/3); humic; sandy
light loam; structureless
and loose; pH 6.0.

139/2 5-11 B2tl Iti 1 Moderate brown (5YR 4/4);
sandy clay; structureless;
loose; pH 5.6.

139/3 ll-l9 B2t2 Iti 2 Strong brown (2.5YR 4/6);
sandy clay; slightly cloddy;
and porous; pH 5.4+.

139/4 19-31 B2t3 Iti 3 Strong brown (2.5YR 4/6);
light clay, slightly cloddy
and porous; pH 5.6+.

139/5 31-41 B2tcn IZ Grayish reddish orange (2.5
YR 5/6); cloddy and slightly
compact; light clay; occasion~
al small and large iron con-
cretions; rare weathered
non-ferruginished sandstone
brash; pH 5.6+.

136/6 41-50 c2 Zm Grayish reddish orange (2.5YR
6/6); loamy sand: cloddy and
compact; decomposing non-
ferruginised slightly micaceous
sandstone; pH 5.0.

139/7 50-58 C P Underlying non-ferruginised

sandstone weathering pale
gray and orange; rock.

 

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mHo. HHo. me. wow. wow www.mH mm mm HoH moo m.H m .H
m CS 02 MD M C2 m2 m0 AmeCm mmCUCH
Immv CH
AMDHummmo HHOm Hmuou m z Hmuume M Hm mde
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mo =MuHHHQMHHm>m w>HHMHmM= hum ComH
IHOM
*.mmHumm HEHE mo ummm omuCB mommudm mCu CH muofi Mom mpCCom CH mquHHusz HOnMEtI.QOH mqmfia

 

71

 

 

 

 

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. pCmonm .mHthmCm HMUHCmCUQZ

 

 

 

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72

 

 

 

 

 

 

mumc 02 H .Q.Z
.Q.Z .Q.Z .Q.Z .Q.Z .Q.Z .Q.Z .Q.z .Q.Z om.o HHZ o¢.© mm .h
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mmH .o.z mo.H Hm.o mo.o No.0 mm.o mm.o mH.m Hflz m¢.o HH .m
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momma .CH CH
. . . OH x MuHommmo quuumm CONHHOH
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m IUCCCOU .Cyumm mCHH .Em OOH\.m.E memEou mmCmCUxm Hmon,

 

 

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73

TABLE lla.--Description of erlesawgu Series, A
Representative Ground-water Laterite

 

 

SERIES: erlesawgu Ref. DNB 239/1-7
LOCALITY: Approx. 10 mi. south of Rainfall: 40-45"/yr.
Bongo Da, Northern Region Altitude: 450 ft.

SITE: Middle slope/very gently Soil group: Ground-

undulating water Laterite

SOURCE: PP 5' x 3' and 5/46

PARENT ROCK: Mudstone

VEGETATION: Savanna regrowth

Horizon
Proposed) Proposed
Depth A,B,C genetic

Ref.no. in system desig- Description

inches symbol nation

239/1 0-4 Alcn Ei Light brown (7.5YR 5/4);
humic light loan containing
frequent ironstone concretions;
occasional manganese con-
cretions; granular, loose;
pH 6.6; occasional root
fibers.

239/2 4-11 B2cnl Ii 1 Light brown to dark orange
yellow (7.5YR 6/6); light
clay; abundant strongly
stained manganese dioxide
and irregular ironstone
concretions; structureless;
compact; pH 6.0.

239/3 11-20 B2cn2 Ii 2 Light brown to moderate
orange (5YR 6/5); light
clay; with concretions
similar to those in the
above horizon but with
slightly bigger concretions;
compact; pH 5.8.

239/4 20-32 Bch3 Ii 3 Light brown to dark orange

yellow (7.5YR 6/6); light
clay; tightly packed strong-
ly stained manganese dioxide
concretions; irregular iron-
stone concretions; occasional
cauliflower heads; concre-
tionary; very compact; pH
5.8.

74

TABLE lla (Continued)

 

 

Horizon
Proposed Proposed
Depth A,B,C genetic
Ref.no. in system desig- Description
inches symbol nation

239/5 32-41 B2cn4 Ii 4 Light yellowish brown (7.5
YR 7/4); light clay; slight-
ly stained manganese dioxide
concretions; irregular
spherical and small iron-
stone concretions; con-
cretionary; compact, pH 5.4.

239/6 41-45 C Zm Light brown (7.5YR 6/4)
mottled brownish-pink (7.5
YR 7/2); clay; decomposing
mudstone containing frequent
flakes of the rock; very
rare manganese stains pre-
sent; slightly cloddy;
slightly compact; pH 5.4.

239/7 45-58 R Pc Underlying rock of solid

mudstone containing manga-
nese patches along the
irregular planes; rock.

 

75

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.Qm mHHme OHOCHOOH mmmr

 

 

 

 

 

 

 

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IHom

 

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76

 

 

 

 

 

 

 

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77

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mumo oz

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OMN .Q.z mh.m .Q.z SH.O OH.O oo.H mm.N mm.o HHZ N.O HH .N
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momma .CH CH
. . . oOH x mvHommmu “CmUHmm CONHHOC
E.m m mCOEOmN Hmuoa mz M CE OS mo memCUxm moum mm mo
A Huv MuH>Hu MHO Cm>o COHumo U Swamp
m IUCUCOU .Cunmm mCHH .Em OOH\m.E wamEoo mmCmnoxm Hm3OH

 

 

AomscHucooo oHH mamas

 

 

 

78
old erosion surfaces. The nature and properties of these
coastal savannah soils have been largely influenced by termites
(Macrotermers) as a biotic factor. Macroternmmstransfer fine
soil material from below the surface and mix organic matter
with subsurface layers. These activities are carried out
through the building of termite mounds. The transfer of finer
material from below by the termites is another possible origin
of stone-lines within the solum (4).

Profile descriptions are given below for the three
major groups of soils in this area: Savannah,Ochrosol the
Toje series (Table 121 a Tropical Black Earth, the Akuse
series (Table 13) and a Tropical Gray Earth, the Agawtaw
series (Table 14). (Also see map and diagrams in Appendix
1 and 2). In addition to these series smaller amounts of
Regosolic Ground Water Laterites, acid Gleisols, sodium Vleisols,

Lithosols and Regosols also occur.

79

TABLE 12a.--Description of Toje Series, A
Representative Savannah Ochrosol

 

 

SERIES: Toje Ref: AP 405/1-5
LOCALITY: 1/2 mile west of Tema, Rainfall: 25-30"/yr.
Accra Plains Altitude: c. 100 ft.
SOURCE: Profile pit Site: Summit/gently
PARENT ROCK: undulating
VEGETATION: Savannah regrowth Soil group: Savannah
Ochrosol
Horizon
Proposed Proposed
Depth A,B,C genetic
Ref.no. in system desig- Description
inches symbol nation (50)
405/1 0-3 All EV 1 Grayish brown (5YR 3/2);

humic; fine sand; slightly
crumbly and loose; pH 7.0.

405/2 3-9 A12 Bi 1 Moderate brown (5YR 3/3);
less humic; fine sand with
plant root channels;
slightly crumbly and
loose; pH 6.8.

405/3 9-15 A13 Bi 2 Moderate brown (5YR 4/3);
fine sand, weak granular
and fairly compact; pH 6.2.

405/4 15-38 B21 Ii 1 Strong brown (2.5YR 3/6);
light loam; slightly granu-
lar and fairly compact;
pH 5.6.

405/5 38-76 B22 Ii 2 Strong brown (2.5YR 3/6);
light loam with frequent
fine quartz gravels; slightly
granular and compact; pH 5.6.

 

80

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Ovo. woo. OOH. NON. OomH mmmN OO0.0N HwO HO HOO NHmH O.H AHNV .w
mvo. OHO. OMN. mOm. mow OOO Ovmm.H OON ON OOm mmb O.H O .m
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OOO. NHO. NON. OHO. th mom «OF.HH OOH OH OOH mOO ¢.H m .H

m CE OS mo M O2 O2 mu AOGECm mmCUCH

Immv CH

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mo CoHuomum .m.HV momma Hmuoe Hmpoe UHCmOHO mwmmn mHQmmOCmCuxm COO IMUHHH
mo =>uHHHanHm>m m>HumHmm= mun cOWH
IHOM

 

 

 

 

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81

 

 

 

 

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NumN.O mN.OION

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prwMMQ MMHU uHHm wCHm mCHm mmumou mmCoum CONHHOC
H. AMHO Cm>ov Ho

MHOIHHM AMHO uHmV HHom Hmuou CH
Cunmm mCHm CH Cummo

mHCu qummHQ .HmemE UHCMOHO .

mac: . A.EE CH mNHm mHUHuummv Hm3OH

 

 

quonm

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82

 

 

 

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MuH>Hu MAO Cm>o . Spawn
m IUCOCOU .Cuumm mCHH .EO OOH\.m.E memEoo wOCmCUxm “0304

 

 

 

 

 

AcmsCHuCOUV UNH MHONB

 

83

TABLE 13a.-—Description of Akuse Series, A
Representative Tropical Black Earth

SERIES:
LOCALITY:

SOURCE:

PARENT ROCK:

Akuse

Kpong Pilot area,

Ref: APA 370/1-8

Traverse Rainfall: c. 45"/yr.

28/32 chains, Accra Plains Altitude: 60 ft.
PP 4' x 4' X 6'

Hornblende gneiss

Site: Middle slope/
very gently undu-

 

 

VEGETATION: Savannah lating
Soil Group: Tropical
Black Earth
Horizon
Proposed Proposed
Ref.no. Depth A,B,C genetic ' .
in system deSig— Description
inches symbol nation (50)

370/1 0-5.5 All VZ l Brownish gray (lOYR 3/1);
clay; slightly crumbly and
slightly tenacious; pH 6.4.

370/2 5.5-15 A12 VZ 2 Brownish gray (lOYR 3/1);
less humic; clay; occasional
patches of rock particles;
rare CaCO3 concretions;
cloddy and plastic; pH 8.0.

370/3 15-24 A13 Zt Olive gray (5Y 4/1); clay;
occasional CaCO concretions;
rare MnO3 concretions;
Cloddy and plastic; pH 8.4.

370/4 24-30 A14 Zt 2 Olive gray (5Y 4/1); clay;
occasional CaCO3 concretions;
cloddy and plastic; pH 8.4.

370/5 30-41 A15 Ztk 1 Light olive gray (5Y 5/1);
clay; frequent CaCO3 con-
cretions; occasional quartz
gravel and stones; cloddy and
fairly compact, pH 8.6+.

370/6 41—48 A16 Ztk 2 Light olive gray (5Y 5/1);

with faint light olive brown
(2.5Y 5/6 mottles; clay with
abundant CaCO3 concretions
and occasional quartz gravel;
slightly cloddy and compact;
pH 8.8+.

84

TABLE 13a (Continued)

 

 

Horizon
Proposed Proposed
Depth A,B,C genetic .
Ref.no. in system desig- Description
inches symbol nation
370/7 48-57 C Ztm Light olive gray (5Y 5/2):
V slightly mottled orange
brown and black; clay;
abundant patches of decom-
posed rock; slightly
cloddy and compact; pH 8.4+.
370/8 57-72 R Zm Light olive gray (5Y‘

5/1 - 5/2), with light
olive brown (2.5Y‘ 5/6)
mottles; decomposed rock

of hornblende gneiss; pH
8.2.

 

85

.Qm OHQOB muOCHOOM mmm*

 

 

 

OmON HNmm OON.OmH ¢m5 .Q.z OOOOH H¢50¢ .m mom Hmuoe

mOO. .Q.Z HHm. OOO. Omm mNH HOm.N mw .Q.Z NOmH moow ¢.H AOV .m

moo. .Q.z «Om. OOO. OOw vmm HNm.mH NOH .Q.Z mmmm OOOO ¢.H O .v

moo. .Q.z «Hm. ONO. OO5 HOHH NO0.0N OHN .Q.z O5Nv OOOOH ¢.H O .m

OOO. .D.Z HON. Omm. OO5 mO5H HON.N¢ OO .Q.Z H50¢ HVNNH ¢.H m.O .N

moo. moo. OHm. Ovm. mNm OO5H mOo.Hm HvH NO HOmN Omm5 ¢.H m.m .H

m CE OS mo M CE OS mo AOmEsm mmCUCH
Immv CH

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Ho CoHpumum .m.HV mmmmH Hmuoe Hmuoy UHCMOHO mmmmn mHQmmOCmCoxm MOO IMUHHH

mo .mpHHHnmaflm>m m>HhmHmm= Nun coNH.

IHOM

 

 

 

 

an

.mmHHmm mmCM< mo mem OOHCB

momuusm OCH CH

mno< Hmm mOCCOO CH mquHHusz Hohmzli.QmH MHOOB

 

86

 

 

 

 

 

 

 

 

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NO.m .Q.z .Q.z .n.z .Q.z N.5N O.HH H.OO 0.0 H.H HHz 5m .5
mm.5 OH.O .Q.z .Q.Z O0.0 0.00 0.0H H.mO O.N O.NH 5.H OO .O
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OO.5 55.0 O0.0H Nm0.0 m0.0 H.OO 0.0 O.NO O.m O.H O.N Om .O
mO.5 OO.H Nm.OH OO0.0 m0.0 O.NO 0.0 0.00 m.m m.O HHZ ON .m
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NImN.O ON.OION

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HCMMMMQ MMHU uHHO mCHm mCHm mmumoo mmCOHO CONHHOC

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Cuumm mCHm CH Cummc

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. quoqu .meMHMCm HMUHCmflomz

 

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87

mumo 02

Ill OQOZ

.Om5 mm .wnmumom ECHCOEEM .mCONHHOC OCHCHmEmH “OCHCmm3

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mmmH ONN O0.0m OO.N ON.O .Q 2 O0.0H O0.0H O0.0m OO.N 0.0 5m . .5
OOO OON Om.OO ON.m ON.O .Q 2 oo.mH OH.NN OO.HO OH.NH 0.0 OO .O
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OON mOH O5.HO ON.N ON.O .Q.z OH.mH ON.ON O5.HO ON.N. N.O ON .m
5mN mm 5m.mm OO.H 5H.O .n.z OO.HH O0.0N HN.Om O0.0 O.5 mH .N
OOm Om Oo.mm O0.0 HN.O mH.O OO.NH OO.HN O0.0m O0.0 .0.0 O.m. .H
mmme .CH CH
Muaummmo quoumm CONHHOC
. . . OOH x . .
E.m m mCOEOmN Hmuoe mz M CE O: we mOCmCUxm mo mm no
A Huv MUH>Hu MAO Cm>o COHumU Umu spawn
m IUCUCOU .Cpumm mCHH .EO OOH\.m.E memEoo mOCmColm Hm30H;

 

OOSCHHCOUV OOH mqmfifi

 

88

TABLE 14a.--Description of Agawtaw Series, A
Representative Tropicd.Gray Earth

SERIES: Agawta Ref: AP 509/1-5
LOCALITY: Junction on Tema Road Rainfall:25-30'/yr.
SOURCE: Profile pit Altitude: 100 ft.
PARENT ROCK: Site: Lower slope/
VEGETATION: Savanna gently undulating

Soil group: Tropical
gray earth

 

 

Horizon
Proposed Proposed
Depth A,B,C genetic
Ref.no. in system - desig- Description
inches symbol nation
509/1 0-2 All Eh 1 Dark grayish, yellowish brown
(lOYR 3/2); humic; fine sand;
structureless and coarse;
pH 6.6.
509/2 2-12 A12 Eh 2 Dark yellowish brown (10
YR 3/3); fine sand; structure-
less and loose; pH 6.0.
509/3 12-21 B21t Ith Grayish yellowish brown

(lOYR 4/2), with light
yellowish brown (lOYR
6/4) mottles; cloddy and
compact clay; pH 6.2.

509/4 21-60 B22t Itn 1 Light olive brown (2.5Y’
6/2), with light grayisn
yellowish brown and light
yellowish brown (lOYR 6/3)
mottling; cloddy and compact
clay; rare calcium carbonate
concretions; pH 7.0.

509/5 60-74 B23t Itn 2 Light olive brown (2.5Y'
6/2), with light greyish
olive to dark grayish
yellow (5Y 6/3) mottles;
clay; frequent calcium
carbonate concretions;
pH 7.2.

 

89

.nm mHQme cH mpocpoom mmm*

 

 

 

 

 

 

 

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50o. OOO. N5N. OOO. OHH HOHH OO0.0N OHm OH AHHm HOO O.H OH .N
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m CE OS mo M CE OS mu Aomasm mmCUCH

Immv CH
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mo COHuomum .w.Hv mmmmn HMHOB Hmuoe UHCMOHO mmmmn mHQmmOCmCoxm HOO IMUHCu
mo =>uHHHanHm>m m>HumHmm= who cowH
uHom
*.meumm

3mu3mm< mo ummm mmnflfi mommusm OCH CH mHU< Hmm mOCdom CH mquHHuCZ MOOMZII.QOH MHmOB

 

90

 

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5m.o O5.0 50.MH Hm0.0 m0.0 5H.m NO.m 0.00H HHZ HHZ HHZ m .H

 

 

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moo.v moo.umo. nunmm Hm>mum Hm>mum om A

 

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Mm H wCH mCH mmmmo mmCo .CH CH

quonm HU HH.O .m .m 0 pm . .
CONHHOC

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MHOIHHm Cuumm mCHH CH . . Ham
mus» qummum .Hmpume UHCmOHO C O
mHOz . A.EE CH mNHm MHUHuHmmV H030H

quUHmm .mHmMHmCm HmoHCmCUwz

 

 

 

 

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91

 

 

 

 

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O.5 mm .mumumum ECHCoEE< .H

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OO O.NON O0.0H OH.N m0.0 H0.0v Om.m N0.0H HO.5H HHZ m.O HN .m
Nm O.Nm mO.N 5m.O mN.O H0.0 N5.0 Nm.H OO.N HHZ N.O NH .N

Nm 5.05 OH.N H0.0 ON.O O0.0 50.o 55.0 mm.N mN0.0 H.O N .H
mmme .CH CH

. . . OH x MuHommmo quUHmm CONHHOC
E.m m mmoEOmN Hmuoe mz M CE OS mu wOCmCUxm mo m mm Ho
A Huv MuH>Hu MHO Cw>o COHumU U U CumwO
m IUCOCOU .Cpumm mCHH .EO OOH\m.E XmHmEoo mOCmCUxm Hm3OH

 

 

 

 

AnmsaHucooo OOH mqm<e

 

92

IV. THE PLACEMENT OF SOME IMPORTANT SERIES OF GHANA

SOILS IN THE 7TH APPROXIMATION

The author is aware of the danger of attempting to place
these soils, for which there is a scarcity of quantitative
data, with what is considered to be the most likely groups
described in the 7th Approximation. The attempt made here is
only tentative, and deserves further consideration in the
future. At present it is impossible to place all the known
soils of Ghana in the 7th Approximation since there are little
available data for most of them. However, there are enough
data for the ten representative series discussed below to
warrant an attempt at their placement. Most of these series
can be placed easily within Order 9: Oxisols. But further
subdivisions are difficult. This is partly due to the fact
that the Oxisols have not been classified in many details in
the 7th Approximation, and partly because of insufficient
data. For example, the presence of plinthite that has not
hardened, if any, has not been described. The series for
which a placement is suggested here are: Kumasi Series,
Bekwai, Boi, Atuabo, Wacri, Mimi, erlesawgu, Toje, Akuse
and Agawtaw Series. Profile descriptions and analytical data
for these soils were obtained from Obeng (37) and are shown

in Tables 5 through 14.

93

Munsell color readings were not made for the Agawtaw,
Toje and Kumasi series at the time they were sampled. The
readings recorded here were made from boxed profile samples
which have been kept in the museum for two to three years.
All color readings were made in the moist condition. The
color readings for the Wacri series were made on another
Wacri profile and not the same one as that for which the
description and data are given.(37).

The textures described have been determined by the
procedure described in Appendix 3.

The placement of these soils in the 7th Approximation
is indicated in Table 4. The reasons for these placements

are given for each soil below:

Kumasi Series

 

The Kumasi series belongs to the order of Oxisols
because it has an oxic horizon and plinthite. It may be
placed with the suborder Ustox because it occurs in a region
of a single pronounced dry season (November — February), and
it has less than 50% base saturation between depths of 20 and
50 inches from the surface. It belongs to the great group
9.43 because it has an ochric epipedon. It has some resemblance
to 9.32 (the base saturation of the oxic horizon is less than

25% between depths of 20 and 50 inches below the surface).

94

Bekwai Series

 

This soil is placed with the order Oxisol because of
the presence of an oxic horizon and plinthite. It belongs to
the suborder Ustox because the region in which it occurs
experiences a pronounced dry season (November - February),
and between depths of 20 and 50 inches below the surface the
base saturation is less than 50% in the oxic horizon. It is
placed with the great group 9.43 because it has an ochric

epipedon.

Boi Series

 

The Boi series, a Forest Oxysol, is placed with the

order Oxisols for the following reasons: it has an oxic

 

horizon and argillic horizons with plinthite. The parent

rock is basic. It belongs to the suborder Udox because of the

 

humid conditions giving rise to moisture in all the horizons
at all times and low base saturation in the oxic horizon. The
original native vegetation was tropical rain forest. It is

placed with the great group 9.32 for the following reasons:

 

it has moist color values of more than 3, and it occurs at
low elevation and the climate is warmer than for 9.31.
But the organic matter in the surface horizon is probably high

for this class.

95

Atuabo Series

 

The Atuabo series, a Ground Water podzol, is placed
with the Spodosols because of the presence of a spodic horizon,
thick enough to withstand the effect of cultivation. Since
it is saturated with water at some seasons, it belongs to the
suborder Aquod. It is a Thermaquod because the mean annual
temperature is greater than 60°F and it belongs to the orthic
subgroup for lack of an argillic horizon below the spodic

horizon.

Wacri Series

 

The Wacri series is placed with the order alfisol
because of the following reasons: it has an argillic horizon
with a base saturation (determined by sum of bases plus
exchange acidity) that is greater than 35%: it occurs in
a humid climate, and has an ochric epipedon.

It belongs to the suborder Udalf because it has a
mean annual temperature of more than 8.3OC (47oF); and it is
usually or always moist in some part of the solum; it lacks
the characteristics of wetness that are associated with the

aqualfs.
It is placed with the great group Typudalf because

it has no fragipan and no albic horizon that tongues
into the argillic horizon; the chroma between Ap and the
argillic horizon is 4; the ochric epipedon has a gradual

boundary with the argillic horizon. It is possible that this

96

great group intergrades to a great group of Ochrults, for exam—
ple Rhodochult because of the following reasons; it has moist
color values of 4 and chromas higher than 3; the argillic hori-
zonhasiahue as red or redder than 7.5YR.

Mimi Series

 

Mimi series, a representative Savanna Ochrosol from the
interior savanna zone, belongs to the order Oxisol because of
the presence of an oxic horizon and plinthite. Since it is found
in a region with a pronounced dry season (however, the horizons
remain relatively moist) and it has redder colors and higher
base saturation than the Udox it may be placed with the suborder
Ustox. It belongs to the great group 9.43.* The Mimi series is
placed in the same great group as the Kumasi and Bekwai soils.
In view of the fact that Charter's system does differentiate
among the ochrosols of the savanna and forest regions it may be
better than the 7th Approximation for classifying the Oxisols
at the present state of knowledge about these soils. It has an
ochric epipedon with color value more than 3 and organic carbon
less than 2% in the upper 10 inches.

erlesawgu Series
The erlsawgu series, a Ground Water Laterite, is placed

with the order Oxisol because of the presence of an oxic

 

*The Mimi series is placed in the same great group as the
Kumasi and Bekwai soils. In view of the fact that Charter's sys-
tem does differentiate among the ochrosols of the savanna and
forest regions it may be better than the 7th Approximation for
classifying the Oxisols at the present state of knowledge about
these soils.

97
horizon and plinthite. Because of evidence of wetness above
the shale horizon (presence of ironstone and manganese
concretions, stains of manganese dioxide and pale gray colors)
it is placed with the suborder Aquox. It belongs to the great
group 9.11 because it has some plinthite within 12 inches of
the surface that has not hardened. Since mottles of low

chromas are absent it is placed with the subgroup 911-9.3.

Tole Series

 

Toje series, a Coastal Savannah Ochrosol is placed
under the order Oxisol because of the presence of an oxic
horizon and plinthite. It belongs to the suborder Idox because
some of the horizons are dry in the dry season and there
is more than 50% base saturation in the oxic horizon, and it
belongs to the great group Haplidox because the oxic horizon
extends beyond 40 inches below the surface, and the plinthite

is hardened.

Akuse Series

 

The Akuse series, a Tropical Black Earth, is placed
with the order Vertisol because it has more than 25% clay and
more than 30 milli-equivalents of exchange capacity per 100
grams of soil in all horizons below the surface 2 inches; and
it develops deep vertical cracks in the dry season. It belongs

to the suborder Aquerts because it has chromas of less than

98
1.5 throughout the upper 12 inches and the hues are not redder
than 10YR; some concretions of manganese are present within
the surface 30 inches; it occurs on very gently undulating topo-
graphy. Because of the gray colors, self-mulching surface,
and seasonal saturation with drying and vertical cracking
in the alternate dry season, it is placed with the great group,

Grumaquert.

Agawtaw Series

The Agawtaw series, a Tropical Gray Earth, belongs to
the order Alfisol because of the presence of an argillic
horizon (12 to 74") with.base saturation more than 35% of
the sum of cation exchange. It experienced marked seasonal
variation in rainfall and the vegetation is grass with scattered
trees (Havannah).

It is placed with the suborder Aqualf because of the
presence of mottles, iron, and manganese concretions; the
chromas are l to 3 below the Al horizons, and the hues are
2.5Y or yellower.

Because it has more than 15% sodium saturation (in the

natric horizon with prismatic structure) it is placed with

the great group Natraqualf.

99
V. DISCUSSION
Considerations on Some Problems of Soil
Classification in the Tropics

The major problem of soil classification in the tropics
is the scanty knowledge of the soils. Research on tropical
soils has been hindered by several factors. As pointed out
elsewhere (47) workers in the tropics had their training in
temperate regions. There is, therefore, the tendency to inter-
pret observations with a bias dictated by their knowledge of
soils of temperate regions. This problem will be reduced if
these workers remain in the tropics long enough to make
detailed studies. Unfortunately, most of the competent
workers stay only for short periods. There is, therefore, a
growing need for training men on the spot. Soil studies
should be encouraged in the local institutions.

Another problem is the lack of cooperation among workers
in the variOus countries. According to Pendleton (38) some of
the able workers become isolated. This is particularly true
in Africa, where diverse countries work in colonies situated
in similar geographic regions. However, the inter-African
soils conference is an effort to remedy this situation.

The soils of the tropics are relatively featureless.
This makes the choice of properties for differentiation some-

what difficult.

100

Some unique processes of soil formation operate in
the tropics, which make difficult the direct application of
the A,B,C system of profile description. For example, Green
(17) pointed out that in the tropics topography plays an
important role in catenary association of soils; substances
leached from a higher member of a catena are deposited in lower
members. There is thus a kind of lateral movement of water
downhill. The A,B,C units, he said, recognize a vertical
movement of water. According to Pendleton (38) silica ses-
quioxide ratio determinations for colloidal clay by the
international method may lead to erroneous interpretations
for some tropical soils; because in some horizons iron Oxides
are precipitated in the form of concretions.

In the tropics the soils are relatively deep owing
to the intensity and time of weathering. Soil horizons in
general are not very distinct. Thus, there is a problem of
distinguishing some soil horizons from the parent material.
This was considered by Robinson (40) as an important distinction
that should be made.

A group of soils now known as latosols has been a source
of confusion in terminology. The confusion arose by applying
Buchanan's term laterite to some soils in the tropics. The
terms laterite and lateritic were thus used by various authors

to describe tropical soils with reddish colors.

101
Kellogg (26) suggested the term Latosol and used it for some
soil groups in the Belgian Congo. Sivarajasingham (44)
discussed the term laterite fully and clarified some of the
misunderstandings in the use of the term.

Laterite is not the only problem of terminology for
tropical soils. Color names have often been applied to soils
of different morphology. Costa (15) discussed some of the
problems of nomenclature of tropical soils. According to
him the chief source of difficulty is in the use of the term
laterite and some terms derived from it. The steps taken in
the nomenclature in the 7th Approximation will solve some of
these difficulties of confused terminology. However, there
is much to be studied about the Oxisols to enable coining of
suitable names for defined categories and classes below the
suborder level.

The above are only some of the problems of classifi—
cation of tropical soils. These and other difficulties can be
solved only through detailed studies of the soils and their
interrelationships through soil formation factors. There is
the need for careful morphological descriptions. Sufficient
laboratory data should be collected to enable a sound
classification to be made.

At the initial stages careful description of the soils,

mapping units, etc. is necessary. Concurrently, an attempt

102
should be made to classify them into known great soil groups
or to devise more useful ones showing the interrelationships
among these soils, relations to their environment, and relation-
ships to soils in other countries. This will also aid in
the correlation of the soils in the various countries and
permit interchange of basic knowledge concerning their use,
management and improvement.

The Major Soil Groups and Their
Related Land Use
In Ghana not much work has been done in classifying
soils according to land capability. However, the Soil Survey
Division has done much to relate the various soil groups to
their agricultural use. The following account is summarized

largely from Brammer's report (4).

Soils of the Forest Zones

These soils are used mainly for agricultural purposes.
However, forestry is becoming important in recent years.

Forest Ochrosols have good tilth, but under cultivation
they become susceptible to drought. Available plant nutrients
are concentrated in the top soil and at greater depths in the
zone of rock weathering. The distribution of nutrients within
the profile of typical forest ochrosols can be seen from
Tables 5b, 5c, 6b and 6c. There is rapid loss of organic

matter when the forest vegetation is cleared and the land is

103
cultivated. Maintenance of organic matter in the top soil
is, therefore, a problem in cultivating these soils. Brammer
recommends three crops for these soils. Cocoa and coffee are
the major crops on the upland soils, bananas, plantains, and
cocoyams are also grown, but these produce only moderate yields
for local consumption. Cocoa, which is the main cash crop of
the country, does well with adequate organic matter supply
and under moist conditions. Where these soils are droughty
yields of cocoa decrease after 20-30 years from planting (4).
C. F. Charter (10) stressed the need for manuring cocoa in
order to maintain and augment the level of production. Kola
grows well on the droughty soils.

The Forest Oxysols are suited to rubber and oil palms
owing to the high rainfall. Good yields of bananas are also
obtained on these soils. These soils are too acid to support
a good crop of cocoa. However, it has been noted that where
these acid soils contain appreciable amounts of exchangeable
manganese, cocoa does well on them. Brammer (4) pointed out
that there is some correlation between the distribution of
cocoa and soils with substantial amounts of exchangeable
manganese. The valley bottom soils are suited for rice pro—
duction.

Intergrade soils between forest ochrosols and oxysols

support satisfactory cocoa. Coffee on these soils requires

104
manuring. Brammer (4) recommends that forest lithosols
over the quartzites of the Akwapim-Togo range should be left
under forest. But those on more basic parent material can

be used for cocoa production.

Soils of the Interior Savanna Zone

 

These soils, like previous groups, have their nutrients
concentrated in the top soil. They are generally poor in
nutrients and low in organic matter. Droughty conditions
exist in the savanna areas. The major crop on the Savanna
Ochrosols are yams. Corn is grown in the south while guinea-
corn and millet are more important further north.’ The bottom
soils are suited for rice production. The Ground Water Laterites
and the Ochrosol-Ground Water Laterite intergrades are poor in
nutrients. The true Ground Water Laterites with pans are
little used for farming. Yams and cereal crops are grown
in some areas. These soils and their intergrades are generally
used for pasture and grazing, especially in the dry season.

This use needs to be investigated and improved.

Soils of the Coastal Savanna Zone

 

The Ochrosols of this region have good physical conditions
and good water relationships in the wet season. But the pro-
longed dry season is a problem in their better utilization.

They are generally low in organic matter and fertility.

105
However, local areas of termite mounds and earthworm activity
are relatively higher in fertility (35).

Drought resistant crops such as millet, guinea corn.
beans and various pulses are recommended (4). Tree crops
like mangoes are extensively grown in the Accra plains.
Coconuts are grown in the bottom soils, for which they are
most suited.

The Tropical Black Earths of the coastal region, like
those of the interior region, are almost uncultivated at
present. They are too "heavy" for hand cultivation. However,
they are suitable for continuous cultivation and the use of
machinery may be necessary. According to Brammer (4), rice,
vegetables, tobacco, sugar cane and fodder crops can be grown
on these soils. But fertilization and irrigation are necessary.
Cotton and sorghum is grown on similar soils in Tanganyika (40).
Investigations to discover suitable crops and methods of
cultivation are being carried out by the University College
Agricultural Research Station and the Kpong Irrigation Research
Station.

The Tropical Gray Earths are used mainly for grazing.
The presence of the clay pan presents a problem for the
cultivation of these soils. Drought resistant millets and
guinea corn are recommended. Cassava and groundnuts are grown

in the lighter soils.

106

From the above account it may be inferred that the
major factors controlling the distribution of crops between
the zonal soils of the savannah and those of the rain forest
regions are climatic and edaphic. But within an area occupied
by the same group of soils, soil characteristics determine
local land use patterns. Depth to parent rock, slope, and
degree of erosion are some of the important local factors that
control use.

The major problems of agricultural use of the soils
of the three regions are those of maintaining high organic
matter levels in the top soil, improving fertility, and
establishing good moisture relationships in the dry season.
The native systems of agriculture aim at solving these
problems. Unfortunately, however, some of the practices
adopted lead to soil deterioration. Shifting cultivation
under the native system cannot cope with increasing demands
of food by the expanding populations. Efforts are being made
to improve the system. In the Congo (26) the corridor
system of shifting cultivation has been experimented with to
reduce the length of fallow period. Mixed cultures of shallow
and deep rooted crops are some of the means adopted to cope
with the unfavorable vertical distribution of nutrients with-
in the solum.

In Ghana, as well as in other tropical regions, there

107
are systems for maintaining organic matter levels. Use of
farm-yard manure, crop residues, green manure and cover crops,
ridge and mound farming, and early burning of grasses are
practiced. Unfortunately, the practice of manuring and use
of cover crops is not widespread among native farmers. Since
there is no suitable leguminous cash crops like clover in
Europe and America, Crowther (16) suggested that leguminous
cash crops like groundnuts (peanuts) and beans be grown and the
land laid to rest with cultivated fodder crops.

Mulching or intercropping and shade crops may be
practiced to conserve moisture, for such crops as bananas and
coffee, in the dry season. This method is recommended else-
where (19) by Griffith.

Generally, fertilizer application is not practiced by
farmers in Ghana. However, some knowledge of fertilizer
response and placement has been gained at the experiment
stations. Green (18) reported work by Nye in Ghana. The
latter found that corn responded to nitrogen (ammonium sulphate)
and P205 (superphOSphate) but gave no response to potassium.
It has been found that soils of the coastal savanna region do
not respond to lime (18). In general, Nye (18) observed that
on the savannah region phosphorus and nitrogen are the main
needs for groundnuts, corn, sorghum, millet, rice and cotton.

Responses to calcium and potassium have been rare. Groundnuts

108

showed a need for sulphur but not for potassium.

Consideration should be given to a more extensive use
of the soils of the drier savanna areas for pasture and grazing.
Forestry, game and recreational uses of some of the less
productive latosolic soils should be given some consideration
in the development of the land resources. It is believed that
agronomic investigations should go along with the improve-
ment of the classification of the soils of Ghana.

Suggestions for Improving the Classification
of the Soils of Ghana

The author would like to point out here that the
following suggestions are being made, not in condemnation of
the outlined provisional system, but for general consideration
only. He is aware of the danger of undertaking to do this
without any personal experience with the soils. However, it

is hoped that some of these suggestions may be useful.

Nomenclature

The nomenclature used at the highest categorical level,
the soil order, in Charter's (5) provisional system is derived
from the names of the predominant soil forming factors. Since
these factors are only presumed to be the predominant ones
they may not form a valid basis for naming the soils. It
would be better if the names would be coined after the most

pronounced morphological properties of the soils. Some of

109
these properties may be hidden but can be revealed by chemical
or physical tests, e.g., the predominance of allophane in
certain soils derived from volcanic ash. Master horizons
and the nature of surface horizons may be suggestive for names
of the orders. In coining these names, their ease of remembrance
and the extent to which they reflect genetic characters and
show genetical relationships among the groups should be borne
in mind. A detailed study of the soils should be made with a
View to adopting some of the names proposed for the higher
categories in the 7th Approximation. At the great group level
in the 7th Approximation names reflect moisture relations
and temperatures of the soils. In Ghana, where catenary
associations are important the idea of drainage associated
with topographic site may be suggested in the names for sub-
orders. This attempt has been made in the present provisional
system and the 7th Approximation. The use of vegetative cover
names for the great soil groups (e.g., forest ochrosol, etc.)
may be misleading for reasons pointed out above. Color names
as pointed out elsewhere (15) may also cause confusion. For
names to be derived from diagnostic morphologic features
detailed field descriptions should be reinforced with laboratory
data.

The use of place names for the series is in accordance

with the practice in other countries. In the 7th Approximation

110
names for lower categories than the ones indicated in Table 3
have not been developed. For the soils of Ghana, the
possibility of using names that suggest distinguishing character-
istics of the series, or types may be investigated. In this
connection an attempt to use vernacular names that recall
some of these properties may be made. This is not an easy
job since there are about five principal languages. However,
Twi names may be used throughout most of the regions. These
vernacular names should be direct translations from English

which is used as the scientific language.

Choice of Criteria for the Classification

The use of soil forming factors as criteria for differ—
entiating the soil orders is objected to because these factors
are not easily observed or measured properties of the soils.
As already pointed out morphologic characteristics that are
the results of soil forming processes (soil genesis) or
reflect genetical relationships (soil genetics) should be used
as criteria. Properties of diagnostic horizons, as used in
the 7th Approximation, are recommended for trial. The assumed
predominance of the effect of a particular factor, say parent
material, may be complicated by the fact that other soil
forming factors are co-varying with it. Morphologic features
that are less sensitive to change in environment, but showing

recognizable changes with intensity of the effect of soil factors,

111
such as vegetative cover, slope, drainage, etc., should receive
correspondingly greater consideration. The soil formation
factors which are genetical or independently variable
properties aid in understanding the interrelationships among
the morphological or dependently variable soil properties.

The use of topographic site, or nature of parent
material to differentiate at the suborder level may also be
objected to. According to Krusekopf (28) slope may be an
important factor in land use, but it is not a soil forming
factor and cannot be used as a criterion in taxonomic soil
classification. This view is rather drastic. In my opinion,
slope or topography is actually a soil forming factor, as well
as a property of the soil body, and can be used together with
related soil profile properties as a criterion.

The use of soil reaction as a criterion for differenti-
ating soil group families should be re-examined. Soil reaction
or other dependently variable properties alone cannot be used
since two soils which are morphologically or genetically
different may have the same reaction. Recognizable morphological
differences which are associated with reaction may be used
together with it; e.g., calcium carbonate horizons, etc.

At lower categorical levels the properties of master
horizons and diagnostic surface horizons as suggested in the

7th Approximation may be used in addition to others. Soil

112
moisture, which is apparently quite important in Ghana, may also
be used. Owing to uniformity of temperature, this property
may not be very useful in differentiating at lower categories
in the tropics. Particular attention should be paid to the

nature of plinthite, and careful descriptions made.

Descriptions and Laboratory Data

 

If morphological characteristics are to be used as
criteria for the classification, then the need for detailed
descriptions and adequate laboratory data becomes paramount.
Detailed descriptions are fundamental to any sound system of
classification. Profile descriptions as well as mapping unit
descriptions should be systematic and in detail. Precise
descriptions of soil structure, consistency, boundaries between
horizons and their nature, plant roots and their distribution,
mottles on ped surfaces and in the interiors, etc., are now
commonly lacking. Detailed descriptions of geology, topography,
climate, vegetation and ages of landscapes are also necessary.
These should be helpful in conjunction with the soil profile
properties in discovering interrelationships among the soils
and their relationships to the landscape which permit more

accurate and rapid mapping of soils.

Additional Research Needs

 

Taking into consideration the many obstacles which the

soil survey staff has to meet, present research efforts are

113
praiseworthy. There has been an awareness of the need for
laboratory data for the most important soil groups described
above. These are being supplied. However, if we are to
correlate our soils with those of other countries, there is
need for more intensive research.

Some of the criteria used in the 7th Approximation
demand a careful analysis of the type of clay and the per-
centage present in each horizon. It is, therefore, necessary
that these determinations be made on representative samples of
all known soils in the country. Certain chemical analyses
such as the potassium content of clays and their silica and
sesquioxide ratios may be determined with a View to identifying
component minerals and studying the processes of soil genesis.

The N value (47) which is given by the formula

A - 2
N — L + 3H' where,
A = percentage of water in the soil under field conditions

(calculated on a dry soil basis),

L

percent clay, and

H percent organic matter (organic carbon X 1.724),

should be calculated for soils for which this may apply.
Investigation as to whether this N value has any significance
for land use or correlation with other soil properties needs
to be made in the tropics.

Moisture determinations are being made for air dry soils.

114
Research should be conducted on moisture tension determinations
at various moisture tensions of from 0.06 to 15. atmospheres.
At the low tensions these measurements should be on natural
structural aggregates or undisturbed core samples. The relation
of the moisture contents of the various tensions should be
related to field capacities of the soils, and the wilting
points of native plants or irrigated crops. If there are
other properties with which available moisture holding capacities
may be more closely correlated, than texture, these relationships
should be clarified and used in soil classification. The
textural classification of the soils needs re-examination and
correlations need to be made with those of other countries.

Bulk density determinations are desirable in investigating
soil air - soil water relationships. Other physical data on
soil aggregation and porosity need to be obtained.

Since Ghana is mainly an agricultural country soils
research should be geared towards land utilization and improved
crop production. Without this the National Soil Survey will
not achieve its purpose.

A statistical approach to sampling in soil surveys
and for other agricultural research purposes should not be
overlooked.

The above suggested needs for research are not exhaustive.

More problems will be discovered in the process of research and

115
the search for solutions will continue. In a country where
soils work is relatively new it will take some time to tackle
all these problems efficiently. To carry out these suggestions
there is need for strengthening the Soils Division of the
Department of Agriculture and the Soils Divisions of the local
university and technical colleges. It requires training of
soil scientists on the spot. Specialists in the various
branches of Soil Science are needed to carry out an effective
soils research. To meet these requirements effectively and
efficiently cooperation between the colleges and the govern-

ment department is necessary.

Conclusions

A review of the past, present, and proposed systems of
soil classification reveals the fact that each system is
directly related to the state of knowledge about soils at the
time of classification. Each system is an attempt to improve
upon the previous one. Thus with the increase of knowledge
new systems will be devised to replace old ones. As long as
knowledge about soils remains incomplete classifications will
continue to be approximations only. According to Simonson
(43) answers obtained today will sooner or later be superceded.

Soil classification has some continuing problems; there
are the problems of arriving at a clearer concept of the soil

individual, nomenclature and precise definition of terms to

116
meet universal acceptance, and the selection and weighing of
properties used in differentiating classes and categories.
With the growing desire to evolve a system that will be
applicable to soils of all regions of the world these problems
become more pronounced.

The concept of the soil individual has passed through a
series of changes. The definition of a "pedon" in the 7th
Approximation (47) is the most recent and precise. However,
the areal extent and lower depth limit are arbitrarily chosen.
Since the soil population, unlike those of plants and animals,
does not consist of discrete individuals this problem will
remain with us. Jones (25) questioned whether any form of
systematics is applicable to soils since classification must
necessarily involve systematic organization of individual
units. If we remember that classification is conceptual
there can be no doubt in our minds that the process of
individuation can be carried out. We are building up models
to fit our observations.

An effort is being made to overcome difficulties in
terminology. It remains to be seen what will result from
the trial being given to the proposals contained in the 7th
Approximation.

As descriptions become more precise, measurements more

quantitative and our understanding of soil genesis and soil

117
genetics becomes more complete, the choice of the most meaning—
ful morphologic characteristics as criteria will become relatively
easy.

The classification of the soils of Ghana is passing
through historical stages similar to those of other countries.
Hardy's (20) account of soil classification in the Caribbean
region showed that early workers there used the soil formation
factors as criteria. The trend toward the use of morphological
properties is well marked in the United States. This trend is
desirable in tropical areas for a sound system of soil classifi-
cation. There is a great need for detailed descriptions of
Ghana soils and detailed laboratory research. The classifica-
tion can improve only through the accumulation of knowledge
about our soils.

Although limited purpose classification is not the
subject here, attention may be drawn to the use of soil survey
data in land capability classifications for various purposes.
The purpose of any classification is to organize our knowledge
about the objects we classify so that their properties may be
remembered and their relationships easily comprehended for
specific purposes, including increased understanding of the
soils. This should be our goal in working out any system of
classification. The usefulness of the classification of the

soils of Ghana will depend on how well it serves this purpose.

10.

11.

118

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.122

APPENDIX 3

TEXTURE TEST

 

Equipment

A number of cash bowls, .
1 in. sq.

Wooden mortar and pestle,

 

Wooden board (see diagram), 8"
8" x 8" with a square 1"
each side, drawn in one
corner, a length of 6.5"
marked along one side, 1/3'
from the edge,

(Not to scale)

1/3"

r-———-—-6 l/4"-—————On

8" I

 

a 2 mm. sieve. J

 

 

 

 

Method

1. Place samples in cash bowls on table in order of horizon.

2. Pick out large concretions and nodules, gravels and stones.

3. Grind each sample separately in a wooden mortar with a
wooden pestle, to break clods and crumbs down into ultimate
particles. Coarse grit, sand and small concretions are
to be ground down.

4. Sieve with 2 mm. sieve into cash bowls again.

5. Add water and knead until sticky point is reached, i.e.,
the point where the samples just does not stick to the

fingers or other objects.

6. Try to form ball (1" in diameter) by rolling between the
hands.

7. Form roll 1/3" thick, 6 1/4" long by rolling with palm
of hand on board.

8. Bend roll, while lying on board, to form a circle 2" in
diameter.

9. Wash hands, board, mortar pestle and cash bowls between
each test.

 

123

Results

The test will stop at stage 6, 7, or 8. The texture is
then given as follows:

Form Texture Symbol
A. Sample will form a Sand (if smooth grains) A
cone, but not a ball Grit (if sharp grains)
B. Form a ball but not Loamy sand .

a roll

C. Forms a roll:

;(a) Ill formed Light loam ~—’-— -—-
(b) Well formed Loam
(c) Almost a circle Heavy loam //"\\
shoWing extent
of bending
. /\
D. Forms a Circle \\/
(a) Hardly Light clay
(b) Easily Clay <:>

Further subdivisions are given by visual inspection, e.g.:
A. Coarse sand (2.0 - 0.2 mm.)
Fine sand (0.2 - 0.02 mm.)
B. Loamy coarse sand
Loamy fine sand
Loamy micaceous sand
C. (a) Light fine sandy loam

Light coarse sandy loam
Light micaceous sandy loam

Similarly, (b) and (c)

D. Light micaceous clay

 

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