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COMPARISONS OF THE CHEMICAL
PHYSICAL.AND NINERALOGICAL PROPERTIES OF
SOME IRAQI AND MICHIGAN SOILS

By

Tariq Barren

AN ABSTRACT OF A THESIS

Submitted to

Nichigan State University of Agriculture and

Approved:"'

Applied Science in
partial fulfillment of the requirements
for the degree of

EASTER OF SCIENCE ‘

Department of Soil Science
1961

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ABSTRACT

COMPARISONS OF THE CHEMICAL
PHYSICAL AND MINERALOGICAL PROPERTIES OF
SOME IRAQI AND MICHIGAN SOILS

by Tariq Harran

This study is a comparison of the chemical,
physical and mineralogical determinations of three pairs
of surface and subsoil samples from the Greater Mussayib
Project in Iraq with a sandy subsoil (Kalkaska-Bh) from
Ottawa County, Michigan and a clayey subsoil (Kent-3t)
sample from Newaygo County, Michigan.

The results of mechanical analyses show that the
Kent-3t is the finest textured sample studied. It con-
tained much.more water at the same tension than the
coarse textured Kalkaska-Bh. The Iraqi samples ranged
from silty clay to loam.

The soils from the arid region (Iraq) are alkaline
and the soils from the humid region (Michigan) are acid
in reaction. None of the Iraqi soil samples contain as
much organic matter as the subsoil samples from Michigan.

There is a great difference in carbonate, gypsum,
and chloride contents between soils studied. The Michigan
soil samples contained no carbonates and very little
gypsum or chloride. Electrical conductivity showed that
the Michigan soil samples and the Imam profile from Iraq
had negligible salinity. The yield of very sensitive crops
on the soils from Kharbana and Rashayid may be restricted

by the salt contents.

Tariq Harran

All Iraqi samples are higher in extractable
sodium, potassium, calcium, magnesium and phosphorus than
the Michigan samples, except the Kent-8t horizon which
showed a higher potassium content than the profile from
Rashayid.

A comparison of the X-ray diffraction patterns
of all clay samples studied shows that kaolinite, chlorite,
illite and montmorillonite are the main clay minerals
in the Iraqi samples. vermiculite, chlorite and
kaolinite are present in small amounts in the Kalkaska-Bh
horizon but much of the clay in that sample is non-
crystaline. Illite, kaolinite and vermiculite are the
main clay minerals in the Kent-8t horizon. The Iraqi
samples and the Kent-Bt horizon all contain some inter-
stratified clay minerals composed of montmorillonite and
chlorite layers.

The results of this study must lead to the con-
clusion that all three Iraqi soils are fairly well suited
for farming purposes. Nitrogen and phosphate fertilizers
may be required in large quantities. Their extractable K

contents are high. Lime will never be required.

COMPARISONS OF THE CHEMICAL
PHYSICAL AND MINERALOGICAL PROPERTIES OF
SOME IRAQI AND MICHIGAN SOILS

By

Tariq Harran

A THESIS

Submitted to
Michigan State University of Agriculture and
Applied Science in
partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Soil Science

1961

ACKNOWLEDGEMENTS

The author wishes to express his sincere apprecia-
tion to Dr. E. P. Whiteside for his guidance and assistance
throughout the work.

Acknowledgements are also due to Dr. A. E.

Erickson, Dr. M. M. Mortland, Dr. A. Wolcott, Dr. B. Ellis
and Professor I. F. Schneider of the Soil Science Department.

The author thanks Dr. L. T. Kedry, Mr. A. Sattar
Harran and A. S. Al..Said for providing him with the samples
from Iraq and some of the data that made the preparation
of this thesis possible. He is also indebted to Mr. J. E.
Lockwood of the Michigan State University Soil Testing
Laboratory for the measurements of the extractable nutrients
and many suggestions in the laboratory studies.

Finally the author wishes to express his gratitude
to the other members of the staff of Michigan State
University who have helped in making his study at M.S.U.

a. success e

TABLE OF CONTENTS

Page
INTRODUCTION . . . . . . . . . . . . . . . . . l
A. Historical 2
B. Location and Size of Iraq 2
C. Soil Formation Factors in Iraq 5
1. Physiography and Topography 5
2. Climate 5
3. Geology (primary material and age) 6
u. Vegetation 9
THE GREATER MUSSAYIB PROJECT . . . . . . . . . 1h
A. General Character of the Area 1h
B. Past Land Use 1%
C. Land Classification 15
l. Reconnaissance Survey 15
2. Grouping of Soils into Land Classes
for Semidetailed Mapping l9
3. Specification or Standards for
Semidetailed Mapping 21
D. Development of the Area 22
l. The Project Layout and Subdivision
into Farms 22
2. The Project Irrigation 22
3. The Project Drainage 23
E. Resettlement 23
1. Proposed Land Use and Farmers
Experiences 23
2. Problems and Solutions 2b
a. Saline and alkali soils 2h
b. Principles of reclamation 2h

iii

III. EXPERIMENTAL WORK . . . . . . . e . . e . . .

A. Description of the Soil Samples

B. Laboratory Studies

1. Physical Properties

8.
b.
Ce
d.

9.

Mechanical analyses
Bulk densities

Percent total pore space
Air dry moisture

Moisture retention studies

2. Chemical Preperties

a.
b.

Ce

d.

e.
f.

g.
h.

1.

je

pH measurements

Organic matter content

Total nitrogen determination
Carbonate content (lime)
Nitrate determination
Chloride determination
Gypsum determination
Electrical conductivity

Determination of extractable sodium,
potassium, calcium, and magnesium

(1) Extractable sodium
(2) Extractable potassium
(3) Extractable calcium
(h) Extractable magnesium

Available phosphorus

3. Mineralogical Composition

3.

Mineralogical analysis of non-clay
fractions

iv

55
56
58
59
59

59
61

61

b. Mineralogical analysis of clays

(1) X-ray determinations of
clay minerals

(2) Calcite contents

(3) Colors of clays beforg and
after ignition at 550 C

IV. SUMMARY AND CONCLUSIONS. . . . . . . .

V. BIBLIOGRAPHYeeeeeeieee

Page
62

62
66

66

73

Table

Table

Table

Table

Table

Table

Table

Table

Table

Table

Table

Table

Table

Table

1.

2e

3.

9.

10.

11.

12.

13.

1h.

LIST OF TABLES

Summary of the geology of Iraq, after
Buringh (1960).

Description of the soil samples from
Iraq and Michigan.

Analyses of Ananah series, after
Buringh (1960).

Mechanical analyses of the soil samples
from Iraq and Michigan.

Other physical properties of the soil
samples from Iraq and Michigan.

Moisture retained at various tensions
by the soil samples from Iraq and
Michigan. '

Available moisture estimates for the
soil samples from Iraq and Michigan.

Pdmntiometric pH measurements plus
H O loss, organic matter, nitrogen, and
car onate contents of samples.

Nitrate, chloride, gypsum content, and
electrical conductivity of samples
studied.

Pounds per acre of extractable nutrients
in soil samples studied.

Adequacy of potassium soil test levels
for mineral soils.

Fertility levels indicated by the
phosphorus soil tests for various crops.

Effex: of heating on lattice spacings
(in gstroms) of clay minerals

Clay minerals identified in the soil
samples from Iraq and Michigan.

Page
10
29
33
38

#0

#3

#6

#8

53
57
58
60
67

68

Figure

Figure

Figure

Figure

Figure

1.

2.

3.

5.

LIST OF FIGURES

Major physiographic features of Iraq
(Davies, 1957) and location of
Greater Mussayib Project.

Precipitation (Powers, l95h) and
vegetation (Davies, 1957) in Iraq.

Diagram comparing the textures of soils
of the Ananah series, with soils of
this study.‘

Soil moisture retention curves.

x-ray diffraction patterns of the
<2/Ifractions of the soil samples
from Iraq and Michigan.

Page

11

32

#3

63

I. INTRODUCTION

Iraq is basically an agricultural country. Enough
arable land and irrigation water are available to support
a prosperous farm population, but the actual condition of
farmers is far from being satisfactory. The needs are:
for improvement in agricultural practices; for better
organized marketing services; for irrigation, flood con-
trol and drainage projects: and for a more equitable land
tenure system. These should be provided for, to raise
the standard of living of the rural population and to
increase the national income.

The agricultural production in Iraq depends on
three quite different kinds of areas: the rainfed zone
of the northern hills and mountains, the irrigated plain
of the twin rivers Euphrates and Tigris, often referred
to as Mesopotamia, and the arid grazing lands of the
southwestern plateau.

It is known that the development of agriculture
in the Mesopotamian plain is seriously hindered in places
by the high salt content of the soil. Consequently crop
yields in irrigated areas are sometimes fractions of what
are considered as normal. Measures are being studied and
programs are being carried out to overcome salinity and
salinizatien by combined irrigation and drainage.

This study is concerned with a study of six sam-
ples from three soils on the Lower Mesopotamian plain
and comparisons of their physical, chemical and mineral-

\ogical properties with those of two soil samples from
1

Michigan.

A. Historical

The systematic scientific study of soils in Iraq
started only a few years ago. The main purpose is-to col-
lect basic information on soil conditions in various parts
of the country. The results are used in the planning and
execution of agricultural development schemes. Since the
success of these schemes mainly depends on the quality and
potential uses of the various kinds of soils, intensive
soil studies are being made - both in the field and in the
laboratory. In the field the soils are investigated and
classified. Their geographical distribution is shown on
soil maps. The work itself is termed soil survey and
classification.

During the field work, intensive studies are made
using the new technique of the systematic analysis of
aerial photographs (Buringh, 1960). In addition to the
use of the soil survey information in planning and develop-
ment of agricultural projects, it may also be important
for archanlogists and those who are conducting studies

of the ancient civilizations in the country.

B. Location and §_i_z_e_ 9__ Iraq
Iraq, as shown in Figure 1, covers an area of about
l7h,688,800 mesharas (about 168,000 square miles). It is
roughly triangular in shape, with the base running south-
west to northeast and the apex terminating at the Persian

Gulfe

Figure 1. Major physiographic features of Iraq (Davies,
1957) and location of Greater Mussayib Project.

I. Arabian massif or western plateau.

II. High fold mountain zone, (Disturbed mesozoic
' and tertiary sediments: limestone, marls and
sandstone.)

III. Alluvium, out-wash and loose deposits;

a. Miocene plain of upper Mescpotamia,
older deposits and higher level
alluvium.

b. Flood plain of lower Mesopotamia, younger
deposits and lower level alluvium.

c. Assyr foothills.

{t7 Greater Mussayib Project

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1. Physiography and Tepography

As indicated by the physiographic map of Iraq
(Figure l): rugged mountain terrain in the northeast, II;
adjoining foothills, IIIc; plateaus, I; and flat alluvial
plains, IIIb; feature the tapography of the Tigris and
Euphrates basins.

The area occupied by the headwaters of the rivers
is composed of the high mountains of the Pontian, Anatolian,
and Taurus ranges to the east in Iran and Turkey. The
upper basins of the Euphrates in Turkey (the Kara river
and the Murat river) are rugged with elevations varying
from 2,000 m. in the river gorges to 3,500 m. along the
interbasin divides. Below the junction with the Murat,
the Euphrates flows through the foothills of the Taurus.

In general, the topography is smooth. However, in
the western and southern portions, large salt and silt

drift dunes are present, (I and IIIb, Figure l).

2. Climate

The climate of the sourthern part of Iraq (I and.
IIIb, Figure l), is sub-tropical, continental, and arid
desert with.dry;hbt summers and cool winters, Figure 2.
Greater rainfall in the foothills of the northern part of
the country and adjoining countries supply water to the
Tigris and Euphrates rivers.

Due to the fact that Iraq has two big rivers and .

large flood plains, living in settlements is possible.

6

While the rainfall in northern Iraq is sufficient to sup-
port winter crops without irrigation, in all other parts
of the country cultivation is possible only by irrigation.
In Jezireh and the western and southern desert, no water
is available except in a few wells. Rainfall there is
very low and a large portion of the rainwater evaporates
immediately.. In reality the amount of water available
there for plant growth and soil formation is thus much
smaller than is indicated by precipitation data.

The influence of the Persian Gulf on the climate
of Iraq is very limited. However, near the Gulf the
relative humidity is higher than in other parts of the

country.

3. Geology (primary material and age)

The tectonic and paleographic events in the his-
itory of Iraq and the basins of the Tigris and Euphrates
,rivers can be summarised in broad outline as follows:

a. Marine conditions characterized by deposition of
estuarine,-and in some places continental sediments, pre-
vailed throughout the Cretaceous and Eocene periods.

b. The upper Eocene and the Oligocene were mainly peri-
ods‘of tectonic movements with erosion. Sedimentation
continued only in the central parts of the geosynclinal
tnough. c. During the early part of the Miocene period
the sea became more and more restricted and finally only
brackish waters with very small or no connections to the
cpen ocean were left. d. In the second half of the

Miocene and in the Pliocene periods the region was above

7

sea level and was covered by broad alluvial fans, which
are the deposits of detrital material encountered in the
Upper Fars and Bakhtiari formations. e. The end of

the Bakhtiari period was a generally turbulent time, with
earth movements and subsidence of great parts of the basin,
thus allowing the deposition in great thickness of sediments.
f. The soils of the Mussayib project have formed in
recent sediments. g. The position of the main geosyn-
clinal trough, situated east of the Tigris, was prac-
tically unchanged throughout the entire period under
consideration. Folding was possible in the unconsoli-
dated sediments of the sedimentation basin in eastern

Iraq, while only superficial movements and faulting were
possible on the rigid Arabian massif.

The main masses of the mountain ranges in which
the Euphrates and Tigris rivers rise are composed of
continental sediments which have been structurally altered
in varying degrees due to localized tectonic movements or
volcanic action. The detailed geology of large portions
of the area is not known.

The continental sediments forming the mountain
ranges (II, in Figure'l) consist of paleozoic schists,
slates and marls. Mesozoic strata of later origin over-
lie the older rocks in varying positions depending upon
the extent of geologic movement and volcanic action which
have occurred. The Cretaceous and Eocene sediments con-

sist of limestone, marls, marbles, schists, slates, flysch,*

 

v

*A thick conglomeratic series of rocks in southern
Europe, partly of Cretaceous and partly of Eocene age.

8

sandstones and conglomerates. Sediments of the Oligocene
period are characterized by sandstone and marls sometimes
associated with deposits of gypsum and rock salt. The
Miocene sediments are often lacustrine in nature, consist-
ing of porous limestone and white marls.

The foothills (III, in Figure 1) form a folded
tectonic zone of transition between the high mountains
rimming the basin and the vast central plains. The foot-
hills are broad and follow the outskirts of the northern
mountains in Iran to the Persian Gulf. The foothill zone
is a region of anticlines and synclines which are often
more intensively folded and faulted near the mountain
ranges. The sediments of the foothill zone vary from
cretaceous limestones, marls and slates and Eocene lime-
stone and shales to the more recent Miocene sediments such
as chalky limestone, gypsum, anhydrite, marly clays and
siltstones. In the valley of the Tigris river north
of Khabour river, effusive rocks, generally basaltic,
cover wide areas.

The broad plains (111a and b, Figure l) occupying
the central part of the sedimentation basins are under-
lain by Miocene formations represented by the sand, sand-
stones, silts, and silty clays of the Upper Fars formation,
and the sand and gravels of the Kuwait series. The
Pliocene age is represented by the marls, siltstones and
sandstones, gravels and conglomerates of the Bakhtiary
formation on top of the Fars formation. The recent

geological age is represented by deep alluvial deposits

9

of gravel, sand, silt and clays which are confined to the
broad alluvial plain of MesOpotamia and the delta plains
of the Tigris and Euphrates rivers on the Persian Gulf.
Table 1 (Buringh, 1960) summarizes the geology of
Iraq. Since soils in the Mesopotamian plain are formed
only in the recent sediments they are young soihs which

show little differential profile formation.

h. Vegetation

As a consequence of the arid climate, vegetation
is scarce in large parts of Iraq, Figure 2. Forest
vegetation occurs only in the Kurdish mountains. A
forest map of northeastern Iraq, scale 1:800,000, was
published in 195D by the Forest Department of the Ministry
of Agriculture. Nearly everywhere natural vegetation
has been destroyed. General studies on the vegetation
of Iraq have been published by: Guest (1932, 1933, 1953),
Zohary (1950) and Springfield (195a). Guest’s work is
still in progress; he is preparing a vegetation map of
Iraq and its complete flora. Smith (l9hb) and Chapman
(l9b9) have described the forests in northern Iraq. The
books of Hooker (1937) on Iran and of Zohary (19A0).on
the Syrian desert are also of general interest for Iraq.
The following general information is taken from the above
mentioned reports, in particular from Zohary (1950) and
Springfield (195“).

Due to its geographical position the flora of
Iraq is of a heterogeneous phytogeographical character.

According to Zohary (1950) three principal plant

10

 

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Figure 2. Precipitation (Powers, l95b) and
vegetation (Davies, 1957) in Iraq

12

geographical regions or elements are represented in this
country: a. The Mediterranean element is represented by
a number of Mediterranean weeds that occur in cultivated
fields. It is believed that these weeds are either the
easternmost representatives of the Mediterranean flora or
relics of the Tertiary Paleo - Mediterranean vegetation;
b. The Irano-Turanian element, which is the most impor-
tant, occurs in the vast areas of the Syrian Desert and
Jezira and in the hill and mountain region; and c. The
Saharo-Sindian element, occurs in the Southern Desert

and nearly the whole lower Me30potamian plain.

The vegetation is adapted to a climate with hot,
dry summers. It can survive in two ways: firstly, when
the growth cycle is completed in the cooler, rainy season,
the plant dies and the seeds survive, (e.g., cereal
grasses); or secondly, by structural adaptation (deep
roots, bulbs, rhyzomes).

The number of species of plants in Iraq is fairly
large. According to Fisher (1950), over 2,000 species
occur in the desert and its margins. The natural vegeta-
tion in the river plain has largely been destroyed, and
the principal vegetation is now hydrophytic, halophytic,
and crude (Springfield, 195k).

Leguminous species are exceptionally abundant as
weeds on cultivated land. They are significant from the
point of view of maintenance of soil fertility and

desalinization.

The influence of human activity on the natural

13

vegetation is very important (Buringh, 1957, 1961 and
Bennett, 1939). Human activity has caused the deterioa-
tion of natural conditions by: a. cultivation of land for
many thousands of years; b. shifting cultivation in the
steppe region; 0. grazing and overgrazing, particularly

in the semi-arid regions; d. using wood for fuel and house
construction; e. digging sub-shrubs for fuel; f. irrigation,
with resulting salinizatien and over-silting; and g, as

a result of mismanagement, wind and water erosion.

If the natural vegetation is destroyed, it is very
difficult and often nearly impossible to restore the natural
conditions, particularly in an arid and semi-arid climate
or in mountain regions. Under arid conditions soils are
blown and form desert pavements or lime and gypsum crusts,
which prevent the growth of grasses. In the mountains
the rather thin soil layers under natural forest are
eroded as soon as the trees are cut, and only bare rocks

remain.

15

alternately farmed and abandoned many times.

The present farming practice, in this and the
surrounding area, has possibly existed in the area for
centuries. Areas irrigated by large ditches from the
Tigris and Euphrates rivers are farmed to alternate
wheat or barley (planted in the late fall) and fallow,
until through salting up of the land or the silting of
ditches, they become uneconomical for further cultivation.
When this occurs, the peOple move to another piece of land.
There is evidence that in time many of these pieces of
worn out land heal themselves and the cycle begins over

again.

C. ngg.01assification

A reconnaissance land classification survey is
being conducted in the Tigris and Euphrates basins by the
Miri Sirf Land Development Committee under the direction
of H. Uautenpaugh. Technicians locate the areas suitable
for irrigation, and indicate their relative values for
development. Their reports designate which areas are
suitable for irrigation under a specific plan of development.

The work started in December, 1953, and is still
in progress. To date a broad reconnaissance land classifi-
cation (and drainage study) has been made over the whole
area and a semidetailed classification has been completed
for the Rashayid area which covers h0,000 mesharas,*
Figure 1.
l. Reconnaissance Survey

In making the reconnaissance survey, one step

 

*Meshara equals 0.6 acre.

II. THE GREATER MUSSAYIB PROJECT

A. General Character 2_f_‘_ 329.. Am

The Greater Mussayib Project, Figure l, is
situated between the Euphrates and Tigris rivers. This
can be called an alluvial desert area. The main part of
the project area is very dry.

One of the special features of this area is the
high amount of sand and especially pseudosand (clayey
aggregates with the "grainsize" of sand) which move with
every rather strong wind. In many places these materials
form complexes of many crescent-shaped dunes. This creates
a terrific problem in the establishment and maintenance of
irrigation or drainage canals and ditches.

Some of the pseudosand is deposited around Shnan"l
plants in smaller or bigger hammocks. These hummocks can
vary in height from 10-100 cm. The higher they are the
more they will create difficulties when leveling for

irrigation is attempted.

B. Past Land se

 

 

Ruins of ancient and recent irrigation ditches,
widely scattered broken pottery, trodden paths that wind
erosion has been unable to destroy, abandoned villages and
historic tales, give evidence that the area at one time or
aucther, over the centuries has all been farmed. It is
doubtful if all the area or even a majority of it was ever

farmed at any one time. Perhaps portions of it have been

 

‘Shnan is a kind of ChenoEodiaceae.
1h

16

was to open 18 pits, 2 meters deep. These pits were
located 5 kilometers apart throughout the project. In
digging the pits, a shelf was made on each soil horizon,
and percolation was studied on each bench.

An examination of the physical characteristics of
the horizons in the pit sampled in relation to their
percolation rates showed the following:

Rapid percolation -- Soils with >20.0centimeters
percolation per hour were: loose to slightly
compact, light brown to grey in color, slightly
granular in structure, and fine sands to coarser
in texture.

Moderately rapid perpolation -- Soils with 6.0

to 20.0 centimeters perco ation per hour were:
loose to compact, and loamy sands to silt loam
in texture. These soils were frequently full

or 5116115 e

Moderate percolation -- Soils with 2.0 to 6.0
centimeters percolation per hour were: loose
to compact, light-brown to coffee-brown to grey
in color, very thin platy or slightly vesicular
(full of tiny holes) in structure and sandy
loam to silty loam textures.

Moderately slow percolation -- Soils with 0.8

to 2.0 centimeters perco ation per hour were:
very compact, slightly rusty mottled or light
brown to grey in color, massive to nutty in
structure, usually somewhat sticky when wet and
were slightly vesicular in structure. They ranged
from silt loam to clay loam in texture.

Slow percolation -- Soils with O.“ to 0.8

centimeter percolation per hour were: compact,
reddish brown in color, massive in structure and
clay loam to clay in texture; or were soft, brown
to grey brown in color, very vesicular in structure,
and silt loam to clay in texture.

Verz slow percolation -- Soils with 0.1 to 0.h

centimeter perco ation per hour were: very
compact, often bluish-grey mottled, and steely
grey to grey, but more often brownish red in
color. They were not vesicular in structure,
and silty clay loams to clays in texture.

1?

Extremal: glpp.percolation -- Soils with less

than 0.1 centimeter percolation per hour were:

very compact, distinctly reddish brown in color

and usually massive, but sometimes platy in
structure. They were silty clay or clay in
texture.

The profiles were described, and soil samples
were taken of each horizon in the field. Analyses of the
salt content, and pH of the samples from each horizon, of
each hole have been made in the laboratory. Samples of
each horizon have also been sent to the Irrigation and
Drainage Laboratory for further analyses.

In addition to the above, at each location or pit
sample a deep boring was made to 21 feet. The soil was
described by horizons, from 2 meters to this depth and
determinations of salt and pH were made in the laboratory.
These samples have also been sent to the Irrigation and
Drainage Laboratory for further analyses. In each deep
hole a 1 1/8 inch pipe has been installed to serve as an
observation well.

In analyzing the (deep holes) for permeability in
accordance with the above findings it was found that, except
for two holes, extremely slowly permeable layers were
present in each case. Sometimes there were as many as
three separate horizons with this characteristic. At some
locations very permeable layers were found above the imper-
meable layers, but these location were not contiguous.

In two cases holes were dug in areas in which
irrigation has been practiced longer than one year. Perched

water tables were found in these soils. No water tables

were found on the unirrigated lands.

18

In the Latifiyah Project, which adjoins the
Mussayib to the north and which was inundated by a flood
6 or 7 years before, 18 deep holes revealed that perched
water tables were higher than on the presently unirrigated
land. The height of water table was greater with the
number of years under irrigation. Many of the lands
bordering the project, after irrigation for a number of
years, have a high water table and have gone out of
production.

An analysis of the pit samples and the deep holes
indicates that 10 of the locations now have sufficient salt
to seriously affect plant growth. Three more of the
locations, upon a rise of water table to within 1 meter
of the surface, will soon be effected with salt accumula-
tion. Only 5 of the 18 locations were free enough of
salt that salinity control would not be a serious considera-
tion. Tests of the pH, on the pastes at 1-5 dilution,
showed no indication that high alkalinity will be a serious
problem.

From the above facts it is seen that: under a
"full water supply without drainage" a water table will
soon be a problem to crop production; project drainage
will not fully solve the drainage problem, and farm drain-
age also will be necessary in places; drainage is not
feasible in some areas; salt accumulation is already a
problem, and strict salinity control is necessary if

continued farming is to be experienced in the area.

19

2. Grouping of Soils into Land Classes for Semidetailed
Mapping

The soils have been grouped into the following

land classes for mapping purposes:

Class 1

Class 2

These lands have no limitation, and are adapted
to intensive farming. No crop failure could be
expected. They contain no salinity and need
no drainage. The land is easily prepared for

farming, irrigation and management.

Land in this class has some deficiencies and is
of less value for farming purposes than Class 1.
The deficiencies may be the soil (5), salinity
(a), topography (t), or farm drainage (d).

§_s_ land is either m 22511 and needs irrigation
frequently, or requires fertilization, and
therefore increases cost of farming; or is £251
h_eg._v_'z pp}; increasing cost of farming or
decreasing yields due to difficulty of obtaining
good water percolation; or it may be shallow 22;;
incapable of high production without much fertili-
zation and requiring labor for frequent irriga-

tion and cultivation.

gg_is land on which salinitz, white alkali or
sabach, will be a problem. The amount of the
salts cuts down the production and limits crop
adaptability and increases cost of farming

practices.

Class 3

20

g§_land has a tapographic deficiency which if

not corrected by leveling, will lower yields
and increase farming costs, or if corrected will

involve considerable expense and labor.

2g.is land on which care must be exercised

in cropping practices and use of water so as

not to raise the water table to a dangerous
height and/or where some additional farm drainage
ditches pm pe_ construgted t_o_ remove excess

water.

Land classes with two deficiencies as 2sd or 2as
are slightly affected by these factors, but the
combination of the two are economically as

detrimental as land with only one deficiency.

This is the lowest class of land that can be farmed
successfully for a long period of time under

normal project management and farming practices.
Its limitations are more serious than those for
Class 2 for each subclass, e.g. 23, zgg, 239;,
25239" etc. In general, water control to prevent
high water tables and farm drainage, while
relatively costly, though not prohibitive, will

have to be rigidly observed in most cases.

Class h This land is so alkali or has such great drainage

problems that it cannot be economically maintained

under permanent irrigation. It will at present,

21

however, produce some craps for a limited
number of years under low water application and
a fallow system of farming. Family farms located

on this land are not expected to be permanent.

Class 5 These are lands that cannot be farmed at present
because of some limitation (usually high salinity)
but are believed good enough to be economically

reclaimed.

Class 6 These lands are characterized by such adverse
soil conditions (high salinity, irregularity of
topography, or poor drainage) as to make them
definitely uneconomical to reclaim. They are
too unproductive to support a farm family even

with excessive irrigation.

3. Specification or Standards for Semidetailed Mapping
This classification is best designated, according

to U. S. Bureau of Reclamation Standards, as semidetailed.

The land classes, outlined above, are shown on semidetailed

maps. They are made according to the following standards:

a. Delineations are made on a map 1:20.000 in size.

b. The accuracy of the delineation shows different classes

of land with at least 80 percent accuracy. 0. Each area,

of Class 6 lands of 20 mesharas or larger in size is

shown. d. Each delineation of arable land does not

contain more than no mesharas of another class within

the delineation. e. Each delineation has reCorded for

it not only the land class but also at least one typical

22

soil profile, the topography, the drainage, and the alkali
conditions. The procedure for recording this data is
similar to that used by the U. S. Bureau of Reclamation.
f. The land is examined to the depth of 2 meters. One
sample is taken for salt content determination, at a
minimum of each one-half kilometer or in each delineation,
whichever is smallest. g. At each kilometer distance,

a 3 meters hole is recorded and the samples are sent to

the Irrigation and Drainage Laboratory for analyses.

D. Developpent p_. he Area
1. The Project Layout and Subdivision into Farms

 

The project area was divided into townships of one
hundred square kilometers each. These townships were
further subdivided into 25 sections of 1,600 mesharas
each. Each section consists of 24 rectangular farm units,
500 by 333J5 meters dimensions (66.33 mesharas in area).

The project subroads, laterals and farm ditches
were laid out along the sections lines, all the project
subroads are connected to the main road running along the
Mussayib canal east to the Baghdad-Hilla highway.

Village sites have also been located in different

parts of the project as will be seen a little later.

2. The Project Irrigation

The completion of the Warrar inlet and the
Dhiban outlet canals connecting the Euphrates with the
Habbaniyah Lake, will make it possible to utilize the

stored flood water to augment the supply of the Euphrates

23

with.sufficient amount of water during late summer when
the river is low.

The Mussayib area is one of the projects that will
make use of this additional flow by bringing the water down
through the Mussayib canal. The canal, completed in l95h,
is almost 50 kilometers long and runs southwest from the
left bank of the Euphrates 10 kilometers below the

Hindiyah Barrage.

3. The Project Drainage
As the soils are similar to other silted up
river plain areas, it is clear that drainage will not
be feasible in some parts of the project, and it is expected
that approximately 25 percent of the reclaimed land will

be abandoned after some years of cultivation.

E. Rgggttlement
1. Proposed Land Use and Farmers Experiences

The Greater Mussayib Project is one of the concrete
efforts of the Government to help the small farmers of
Iraq to become land owners. It is a noble experiment
and will have the blessing of thoughtful people all over
the world.

The capacity of this project is about 3,000
families. Each family lives on its own land. Some of
them are using new methods of farming such as crop rota-
tions, treated seeds, and machinery, but most of them are
using primitive methods. Nothing is done to control the

weeds. No fertilizers or manure are being applied. Yields

2b

are low. Fifty percent of the cultivated land has a
winter cereal crap (mainly barley, sometimes wheat).
Water is applied every week to ten days during winter,

and two times a week during summer.

2. Problems and Solutions
a. Saline and alkali‘ soils

The principal soil formation process in the soils
of central and southern Iraq is salinization (Russel, 1957).
This is the accumulation of salts in the soil.

Iraqi farmers classify the saline soils into two
groups of soils that are salty. These are Sabach soils
and Shura soils.

Sabach soil generally implies a saline soil of
calcium chloride variety, or one which becomes wet at high
humidity (Booya, 1956). It is then much darker colored
than the dry non-sabach soils. The soils have a high
content of CaCl2 and MgCl2 which are deliquescent. Even
in the dry hot summers of Iraq these soils remain moist.

Shura soils are saline soils with white salt crusts.
The soils have a high content of NaZSOu or mixed NaZSOu
and Na01. They correspond to white alkali soils of the

United States.

b. Principles of reclamation

Crop rotation may be defined as a system of growing

 

I"The word alkali in English comes from Arabic,
a1 kali. The arabic etymology of it seems to be Kawi -
to burn or specifically the caustic derived from wood
ashes. Compare to the German, Kalium - potassium thich
occurs in wood ashes. '

 

25

different kinds of crops in recurrent succession on the
same land. A rotation may be good or bad as measured by
its effects on soil productivity or on the economic returns.
A good rotation provides for maintenance or improvement

of soil productivity. It usually includes a legume crop

to promote fixation of nitrogen, a grass or legume sod

crop for maintenance of humus and for soil structure,a
cultivated or intertilled crop for weed control and a
suitable sequence to avoid plant diseases or insect peSts.
A good rotation permits diversification of crops which
helps to promote a more reliable income for farmers and

a greater variety of food for their families. It furnishes
feed for livestock which brings added income to the farmer.
If the animal manure is returned to the land it decreases
the role of fertility depletion.

It has long been known that legume crops are
necessary in the rotation if yields are to be maintained
without nitrogen fertilization, and that the practices
which maintain a high content of soil organic matter will
also maintain high yields of clean tilled crops. If it is
more economical to grow alfalfa as a source of nitrogen
than to buy nitrogen, then alfalfa (which is the most
successful legume crOp in this area) should be grown in the
rotation. Farmers in Iraq harvest alfalfa two or three
times a year, then turn under the residues and find that
alfalfa is a profitable crop. The cotton or wheat crop
following the alfalfa is very favorably affected by the

legume residues.

26

In Greater Mussayib Project there has been little
effort to establish a crop rotation of any kind. Crap
rotations adapted to the economy of the project, and of
.the country need to be introduced and taught to the
farmers.

A In the Greater Mussayib Project, as in many other
places in Iraq (Burnell, 1955), it is the common practice
to fallow the land in alternate years. There are many
advantages in this system. It helps to control weeds.
Only deep rooted perennials and fast growing annuals are
able to survive in the fallow year. The deep rooted
perennials like shok (Prosopis Stephaniana) and agul
(Alhagi Maurorum) offer little competition to the winter
crops, since most of their growth is made in the summer.
Most of the annuals offer little competition to the winter
crops. The grain is usually mature enough in the spring
by the time the seeds of annuals germinate so that the
seedlings are shaded out until after the crop matures.
Both annual and perennial weeds are a serious problem in
the summer cr0ps, even under the fallow system.) However,
the deep rooted perennials dry out the substratum since
most of their growth is made on stored moisture. This
permits the salts to be washed down into the substratum
during the irrigation of the fallowing winter craps.
Shok, one of these deep rooted perennials, is a legume so
it may contribute some nitrogen to the soil which is an
additional advantage. There appears to be enough build

up of nitrogen with a one-year fallow to produce a moderate

27

yield without addition of fertilizers. But any effort
to increase yields must be accompanied by a fertility
program. Soil borne diseases are partially controlled by
fallowing. It is probable that some insect pests are
either partially or adequately controlled by fallowing.
There are also some disadvantages of the fallow
system. It is difficult to reclaim salty land where the
fallow system is used. A much more extensive canal system
is required, (however, the main canal would need to be
larger if it were to carry water for all the land every
year). The canal and ditch system usually supplies water
to 50 percent of the land in the winter and about 15 per-
cent in the summer. The principal winter crops are barley,
wheat, and broad beans. The principal summer crops are
sesame and green grass. Attempts made to grow cotton when
the project was first started were largely unsuccessful.
A.more extensive road system is required for a given amount

of production.

III. EXPERIMENTAL WORK

A. Description pgbthe Soil Samples

The six Iraqi samples studied have been brought
from three locations in Greater Mussayib Project. A sur-
face and a subsoil sample from each profile was collected
by A. S. Harran at the request of the author. These sam-
ples were sterilized in the United States before the
author started any experimental work on them. Two soil
samples from Michigan were also studied for comparisons
of all chemical, physical and mineralogical properties.

The locations, depth, texture, pH (by Soil Tex indicator
solution), and color of each of these samples are shown
in Table 2.

The classification of the soils from Iraq as
judged by their position on the general land classification
map of the project area, made under the direction of
Watempaugh is discussed below.

The soil from the Imam district was placed in land
class bad. This class is so saline (a) and has such great
drainage (d) problems that it cannot be economically main-
tained under permanent irrigation. It will at present,
however, produce some crops for a limited number of years
under low water application and a fallow system of farming.
Family farms located on this land are not expected to be
permanent. If these lands are given to farmers who have
little or no resources, they will need more than the usual
financial backing until these farms can be made productive.

The soil from the Kharbana district was classified

28

29

 

 

 

 

 

 

 

 

'Table 2. Description of the soil samples from Iraq and Michigan.
Location Depth Tex- pH Munsell Color ISCC-NBS
or soil in cm. ture Soil- Notations Color Names
32:26: agri- Tex Dry Moist Dry Moist
zon
Imam, 0-20 silty 8.0 101n7/1 10YR5/2 yellowish grayish
Iraq clay gray yellowish
brown
20-50 silty 8.5 lOYR7/2 lOYR5/2 yellowish grayish
clay gray to yellowish
light ‘brown
grayish
yellowish
brown
Kharbana, 0-20 silty 8.5 10136/3 10135/3 light grayish
Iraq clay grayish yellowish
yellowish brown to
brown to moderate
light yellowish
yellowish brown
brown.
20-50 silty 8.0 10137/3 10136/3 light light
clay grayish grayish
yellowish yellowish
brown to brown to
light light
yellowish yellowish
brown brown
Rashayid, 0-20 silty 7.5 lOYR7/2 _lOYR6/2 yellowish light
Iraq clay ' grayish to grayish
loam light yellowish
grayish brown
yellowish
brown
20-50 loam 8.0 2.5?6/2 2.575/2 light light
olive olive
brown brown
Kalkaska 3h sand 5.0 7.5YR3/2 5YR3/2 grayish grayish
(Ottawa brown brown
co.,
Mich.)
Kent Bt clay 6.0 5YR5/3- 7.5YRh/h light moderate
(Newaygo 5/4 brown brown
co.,

Mich.)

 

30

as class 6ad. These lands are so affected by high
salinity, and poor drainage as to make them definitely
uneconomical to reclaim. They are too poor to support a
farm family even with irrigation.

The soil from the Rashayid district was classified
as class 3ad. This is the lowest class of land that can
be farmed successfully for a long period of time under nor-
mal project management and farming practices. The limita-
tion of class 3 soils are more serious than those for
class 2 for each subclass e.g. 3s, 3sd, 3std, 3satd, etc.
In general, water control to prevent high water tables and
farm drainage are relatively costly but not prohibitive.
These limitations will have to be, in most cases, rigidly
observed.

Buringh (1960) has mentioned that the irrigation
depression soils in the Hilla-Nifl project are mapped in
the Ananah series. The author believes that the Iraqi
soils which were studied in this thesis are very closely
related to that soil series. The following is a description
of the Ananah silty clay, severely gullied phase, cited by
Buringh. (The color names have been changed to correspond
to the ISCC-NBS system (Kelley and Judd, 1955) and the
terms have been rearranged to give a more consistent arrange-

ment.)

0-25 cm. Light grayish yellowish brown to grayish
yellowish brown (lOYR5.5/2); silty clay; strong,
coarse, angular blocky to columnar structure;

extremely hard when dry, sticky and dispersed

25-35

35-50

50-100

100-120

120-130

130-150

150-170

170-200
200-250

0111.

cm.

cm.

cm.

CID.

cm.

CHI.

31

when wet; only a few wide pores.

Grayish yellowish brown (10YR5/2); silty
clay; moderate, medium, prismatic structure;

some wider pores; very firm; some shall fragments.

Grayish yellowish brown (lOYR5/2); silty clay;
moderate, medium, angular blocky to prismatic
structure; very firm; no macro pores; shell

fragments.

Similar to above, very firm or sticky, some

rust like mottling.

Grayish yellowish brown to moderate yellowish
brown (lOYR5/3); clay; sticky; some rust like

mottling.

Light grayish yellowish brown to light yellow?

ish brown (lOYR6/3); clay; sticky; rust and

gley.

Grayish yellowish brown to moderate yellowish

brown (lOYR5/3); clay; sticky; rust and more

gley.

Grayish yellowish brown (lOYRh/Z); silty clay

loam; rust and gley, more gley.
Grayish yellowish brown (lOYR5/2) clay, more gley.
Grayish yellowish brown to moderate yellowish

brown (lOYRh/2.5): clay; with abundant reduc-

tion (gley) spots.

32

Groundwater was found at 130 cm.; capillary water
occurred about 50 cm. above groundwater level. The soil
below 150 cm. represents an ancient soil, covered by
clay during floods and irrigation. When the Ananah silty
clay occurs in irrigation and basin depressions, Which are
often submerged by water, shell fragments occur indicating
lacustrine conditions during deposition. Soil texture

analyses of Ananah soils are shown in Figure 3 and Table 3.

100%
clay

100%
silt

 

 

‘ "I

100%
sand

Figure 3. Diagram comparing the textures of soils of the
Ananah series ff, , with soils of this study:

0- Imam 0-20 cm., 0- Imam 20-50 cm.;
I- Kharbana O-2O cm., I- Kharbana 20-50 cm.;
.A- Rashayid 0-20 cm., ,A- Rashayid 20-50 cm.‘

x. Kalkaska Bh hor. ; fix Kent Bt hor.

33

Table 3. Analyses of Ananah series*, after Buringh (1960)

 

. Total
Depth Lame soluble Gypsum

67
cm. Sand% Silt$ Clay% ” pH salt % me/lOO gms.

Texture

 

0-35 11 36 53 26 7.8 0.20 Nil

35-130 7 29 6b 28 7.9 0.30 1.h5
130-150 6 31 63 29 7.6 0.55 2.0
150-300 18 an 38 28 7.5 0.13 Nil

*The organic matter is less than 0.8%.

The Michigan soils from which samples were taken
by K. Pregitzer for this study were subsoils. One was from
a coarse textured soil series, Kalkaska, located in
Ottawa County, and the other was from a fine textured soil
series, Kent, located in Newaygo County, one mile west of
Brahman. The Kalkaska series includes well-drained Podzols
developed in sand glacial drift that contained little or no
calcareous material. The Kent series includes weakly
developed, well to moderately well-drained, Gray Wooded
soils deve10ped in light brown calcareous clay or silty
clay till. Profiles of these soil series are currently
described by the National CooPerative Soil Survey in the
United States as follows: (The color names have been

changed to correspond to the ISCC-NBS system (Kelley and

JUdd. 1955).)

 

Soil Profile:

A0 2.0“
A1 0-2"
A2 2-8"
Bzih . 8-1u"
B221r lu-zo“
'BZ3ir 20-30”

3h

Kalkaska series.
Partially decomposed leaves, and raw organic

matter. One to 3 inches thick.

Brownish gray (lOYR3/l) humus, mixed with
light brownish gray (10YR6/1); sand; numer-
ous fine roots; medium acid; abrupt smooth

boundary. One to 3 inches thick.

Brownish pink (7.5YR7/2) or light grayish
yellowish brown (10YR6/2); loamy sand or
sand; single grain; loose; medium to
strongly acid; abrupt wavy boundary.

Three to 12 inches thick.

Grayish brown - moderate brown (7.5YR3/2-h/h)
or grayish brown (5YR3/2); loamy sand or sand;
very weak medium granular structure; loose
to very friable; medium to strongly acid;

gradual irregular boundary. Four to 8 inches

thick.

Moderate brown (7.5YRh/h); sand; very
weak medium subangular blocky structure

to single grain; very friable to loose;
strongly to slightly acid; gradual irregu-

lar boundary. Six to 12 inches thick.

Light brown to strong yellowish brown
(7.5YR5/6) or moderate brown (7.5YRh/h);

BB

30-uo"

h0"+

Soil Profile:

AP

0-6"

6-8"

35

sand; single grain; loose; medium to
slightly acid; gradual irregular boundary.

Eight to 12 inches thick.

Light yellowish brown to dark orange yellow
(lOYR6/6) or moderate yellowish brown
(lOYR5/b); sand; single grain; loose;
medium to slightly acid; gradual wavy

boundary. Eight to 12 inches thick.

Light grayish yellowish brown to light
yellowish brown (lOYR6/3) or light yellow-
ish brown (lOYR6/h); sand; single grain;

loose; slightly acid to mildly alkaline.

Kent series.-

Grayish yellowish brown (lOYRh/2) or dark
grayish yellowish brown (lOYR3/2);.silt
loam; moderate, fine to medium, granular
structure; friable; slightly acid to mildly
alkaline; abrupt smooth boundary. Five to

8 inches thick.

Grayish yellowish brown (lOYR5/2), light
grayish yellowish brown to light yellowish
brown (lOYR7/3-7/h), or yellowish gray

to light grayish yellowish brown (lOYR7/2);
silt loam; weak medium platy, or weak fine
subangular blocky structure; friable to

slightly firm; slightly acid to mildly

A2B1

Bth

8-11"

11-20"

36

alkaline; clear wavy boundary. One to

h inches thick.

Grayish yellowish brown (lOYR5/2) or light
grayish yellowish brown to light yellowish
brown (lOYR7/3-7/h); silt loam, representing
the A2 horizon; and light grayish brown to
light brown (5YR5/3) or moderate brown
(7.5YRh/h); silty clay or clay, representing
the Bl horizon; A2 occurs as coatings on
pads and along cracks; Bl occasionally
occurs as isolated peds, surrounded or
nearly surrounded by A2; massive to weak
coarse granular (A2), and moderate fine angu-
blocky
lar/structure; friable (A2) to very firm
(Bl); slightly to medium acid; gradual

wavy boundary. Two to h inches thick.

Light grayish brown to light brown (5YR5/3-5/h)
or moderate brown (7.5YRh/h); silty clay

or clay; thin coatings and crack fillings

of yellowish gray to light grayish yellowish
brown (lOYR7/2) and grayish yellowish brown
(lOYR5/2); a few thin clay coatings of grayish
brown (SYRh/Z) and moderate brown (5YRh/h)

on some peds; moderate to strong, fine and
medium, angular blocky structure; very firm;
medium acid to neutral; clear wavy boundary.

Seven to 20 inches thick.

37

C 20"+ Moderate brown to light brown (7.5YRh/h-5/h),
or light brown (5YR6/h); silty clay or clay
till; weak, medium to fine, angular blocky

structure; very firm; calcareous.

B. Laboratory Studies
In the laboratory the samples described in Table 2
were crushed by a wooden rolling pin to pass through a
2mm sieve. All the laboratory studies were conducted on

subsamples from these crushed bulk samples.

1. Physical Properties
a. Mechanical analyses

The mechanical analyses were done according to
the method of Kilmer and Alexander (l9u9). Hydrogen perox-
ide was used to destroy organic matter and sodium hexameta-
phosphate was used as a dispersion agent. A 270-mesh sieve
was need to separate the sands from the silt and clay.

The results of the mechanical analyses were calcu-
lated on an oven dry, organic matter free basis. These
analyses are recorded in Table h.

The content of total clay is higher in the Iraqi
surface samples of all three profiles than in their subsoils,
but the content of total silt is higher in the subsoils
than in the surface. The clay contents of the samples
studied are lowest in the Kalkaska-Bh horizon and greatest
in the Kent-Bt horizon.

The results of mechanical analyses suggested that

no downward movement of clay has taken place in the three

38

 

 

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H.k ~.m o.o H.~ am.mm o~.wm om.oa oe.~ am «smasaau
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~.:m a.mm m.aa H.ma mm.” mo.o oa.o :H.o omuo eaaunmam
o.:a m.~: ~.HH o.m o~.o mo.c no.o mo.o onnom «assuage
m.w: :.n2 a.m a.H -.o ma.o mo.o Ho.o omuo «cannanu
o.ms o.mm n.oa m.s na.o no.o wo.o oH.o onuom aaaH
m.m: m.an o.m m.: :m.o ko.o mo.o No.0 omuc Beau
:ouanon 08¢:

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mocv «8:3. 33.53. amass. 1:3. 3...“. “:6.” c.7o.~ :3 5 Son .3

sedan caduceus

'V.’

.chHSoaz use dth Beam madman» Adam on» we aoahaond Heedcaaooz

.3 OHDKH

39

Iraqi profiles. The Kent-3t horizon is an horizon of
maximum clay accumulation in the Kent soil profile (t -
finer textured layer or ton for clay in German). The
Kalkaska-Bh horizon is a subsoil horizon in which humus
has accumulated and it contains little more clay than the

overlying or underlying horizons.

b. Bulk densities

The bulk densities of disturbed samples were measured
in this study by pouring the crushed fine earth into a
cylinder l-inch high and 3 inches in diameter. The sur-
face was then leveled with a spatula. The bulk density
was determined by dividing the oven dry weight of the soil
sample by the volume of the core. The results of these
measurements are shown in Table 5.

The bulk density of the subsoils of all Iraqi
samples are slightly lower than the bulk density of the
surface layers. The Kent-Bt horizon shows a lower bulk
density, and the Kalkaska-Bh horizon shows a greater bulk
density than do the Iraqi soils. The Kent-Bt horizon sample
has the highest clay content and the Kalkaska-Bh horizon
has the highest sand content of the samples studied. This
observed relationship between mechanical composition and
bulk density is in agreement with the observation of
Baver (19h8). The undisturbed bulk densities will

usually exceed those measured on crushed samples.

c. Percent total pore space

The percent total pore space was calculated in two

#0

 

 

 

Table 5. Other physical properties of the soil samples
from Iraq and Michigan
Location Depth in Bulk fi total pore % air
or soil cm. or density space dry
series horizon Based Based moisture
name on on content
bulk water by
density satura- weight
and tion
specific
+_ gravityg
Imam 0-20 1.30 50.5 73.6 “.39
" 20-50 1.28 .51.0 71.1 n.73
Kharbana 0-20 1.31 50.0 71.8 h.hl
" 20-50 1.23 53.0 68.1 “.00
" 20-50 1.25 52.0 66.b 3.23
Kalkaska Bh 1.63 36.6 51.6 0.60
Kent Bt 1.21 5h.0 70.h 0.20

bl
ways as shown in Table 5 (Richards, 195U). They are
based on bulk density and assumed Specific gravity, or water
content at saturation.

The results indicate that the percent pore space
based on water saturation is. higher than that determined
by the other method. This is due at least in part to the
swelling on wetting which gave a high amount of water held
by the particles and an actual volume when wet that is
greater than when dry.

The profile from Rashayid contains very much gypsum
which has a specific gravity 2.32. Use of an actual specif-
io gravity of this sample would give a lower porosity than
that calculated assuming a density of 2.60.

Generally speaking the method based on bulk density
and specific gravity is probably the more desirable method
for determining the percent pore space of disturbed samples.

A medium textured mineral soil that is in good
condition for plant growth will contain about 50 percent
total pore space on the basis of volume. This pore space
is important for gas exchange (02 and 002) between the

soil and atmosphere, water movement and water storage.

d. Air dry moisture
The results in Table 5 show that the coarse textured
Salkaska-Bh horizon has a low air dry moisture content.
Theflne textured Kent-8t horizon and the moderately fin;
textured Iraqi soil samples retain much more moisture when

air dry.

#2

e. Moisture retention studies

A modified method proposed by Richards (l95h)
for moisture retention studies was used in this study.
Tension tables were used for 0.01, 0.03, and 0.1 atmos-
phere measurements; pressure cookers were used for 0.3,
and one atmosphere determinations; and pressure membranes
were used at 3, and 6 atmosPheres. Cores 1-inch high
and 3 inches in diameter were used on the tension table
and in the pressure cooker studies.

The results of these measurements are shown in
Table 6. Curves showing the results of the moisture
determinations at different atmospheric tensions are
illustrated in Figure h. These data show that the coarse
textured Kalkaska-Bh horizon has a low moisture content,
while the fine textured Kent-Bt horizon and the Iraqi
soil samples contain much more water at the same tensions.
This is due to the larger number of contact points and
the greater surface area in the finer textured horizons.
The Kalkaska-Bh horizon had a moisture content of about
9.0 percent at 0.05 atmosphere's tension, while the Kent-Bt
had #3.0 percent at the same tension. The maximum water
holding capacity (M.W.H.C.) is at about 0.01 atmosphere
and the field capactiy (F.C.) is at abouto.05 atmosPhere;
tension, (Stolzy, 195k), when these measurements are made
on undisturbed samples. The permanent wilting percentage
(P.W.P.), as indicated in the review by Veihmeyer and
Hendrickson (l9h8), is generally accepted as being the

lower limit of water available for plant growth in non-saline

33

 

 

 

:.om :.Hm ~.nn H.mn m.mn w.ma a.mn um anon
:.m m.~ w.: n.ne m.m e.HH s.wm an namesaau
A.HH e.ma A.Hn o.sm n.2n a.mn s.n: onuom enhanuam
o.:H e.:a m.Hn m.mn c.2m a.mn m.m: omuo eaaanmum
:.om m.am o.H: n.a: :.m: m.wa m.an onuom «canuunu
a.c~ :.mm u.o= flea: a.a: a.k: m.an omuo acupuanu
n.ma a.ma a.an e.mn w.ca o.m: «.m: onuou swan
o.om n.am :.o: n.~: o.:: :.m: n.~n omno swan
.ave .aue .aad 980d .aao .aua .Bas coughed cad:
o.e o.n o.a m. H. no. no. to «canon

. _ . .50 ad Hdon.uo
unodanoMIusdboHHoh us vocddvon.aanwm03 haw ohunndoa uzoouom demon :ouadood

 

sundae“:.ucs UduH

acne nodule» Hue» one An nsodnnoa escape» as wondouou ousoufiom .m oHDdH

moisture tension in atmospheres

  
 
 
 
 
 
  
 
   
 
 
  

 

 

Imam.surface soil
Imam subsoil
Kharbana surface soil
Kharbana subsoil
Rashayid surface soil

Rashayid subsoil

Kalkaska Bh horizon

Kent Bt horizon

 

 

 

 

\
\

 

Figure

4.

Soil moisture retention curves

4 1 ‘~.fi I l ' I ‘
0 10 20 30 40 50
2.Mbisture

NANA-IL .

60

#5

soils. This corresponds to about 15 atmosPheres tension
on disturbed soil samples. Moisture commonly becomes a
limiting factor in the rate of plant growth before the 15
atmospheres percentage is reached (Shaw et.a1.. 1952).

One third (1/3) atmosphere's tension has commonly been
assumed to approximate field capactiy on disturbed samples
(Richards, 195“). One third (1/3) atmosphere values are
commonly below field capacities on sandy soils (Russells,
1950). The results of available moisture estimates made
in different ways are shown in Table 7.

The availability of soil moisture to the growing
plant has most commonly been assumed to be the water held
between 1/3 atmosphere and 15 atmospheres tension when the
measurements are made on disturbed samples. These values
are shown as the last column in Table 7 for the soil samples
in this study. For the sample of sand, the 1/3 atmosphere
tension probably underestimates the field capacity as the
Russells have indicated. The amount of water held.at
0.05-l5 atmospheres is probably a much better estimate of
the available water holding capacity of this sample.

These values are probably the best estimates of available
moisture under dry land conditions.

Since plant growth is usually inhibited before the
15 atmospheres percent is reached the 1/3 atmosphere to
6 atmosphere percentages in the next to the last column
of Table 7 may be better estimates of the available
moisture in the Iraqi and the Kent samples for irrigated

conditions. The values for the available water in the

#6

 

 

Table 7. Available-moisture estimates for the soil
' samples from Iraq and Michigan, in percent
moisture by weight. '

Location Depth in 005-600 005-15 003.6 003915

or cm. or atm. atm. atm. atm.

series horizon

names

Imam 0-20 26.5 33.0 22.5 29.6
" 20-50 2u.8 33.0 20.7 28.0

Kharbana 0-20 23.5 30.5 20.h 27.7
" 20-50 2h.0 32.0 21.1 28.3

Rashayid 0-20 22.0 25.2 18.9 22.8
” 20-50 26.0 29.5 22.3 25.8

Kalkaska Bh 6.5 8.0 3.1 h.6

Kent Bt 23.0 31.5 17.7 25.5

5?

Kalkaska-Bh horizon are probably too low in this column
and those in the third column .05-15 atmosPheres are
probably too high. For this sample the value in the first
column (.05-6 atmospheres) is probably the best estimate
of the available water in this sample for irrigated
conditions.

The effect of soil salinity on craps is also related
to the range over which the moisture content of the soil
varies. The concentration of the soil solution depends
both on the amount of soluble salt and the amount of water

present.

2. Chemical Preperties
The results of chemical studies of the soil sam-

ples from Iraq and Michigan are shown in Table 8 and 9.

a. pH measurements

pH measurements were made on 10 gm. of air dry
soil mixed with 20 cc. of distilled water in a 50 m1.
beaker and allowed to equflibrate for half an hour.
Measurements were made using a Beckman Zeromatic pH-
meter.

Except with two soil samples, the results obtained
with the pH-meter in Table 8 were about the same as
those obtained with the Soil-Tex indicator as reported
in Table 2. The Soil-Tex indicator is not as accurate
over the full range of pH values.

The pH values in Table 8 show that the soils

from Iraq are all mildly to moderately alkaline except

“8

Table 8. Potentiometric pH measurements plus H 02 loss,
organic matter, nitrogen, and carbonaée contents
of samples.

 

 

Location Depth H202
or soil in cm.
series or pH 1::s(-) 0.M Total N C/N Caco3
name horizon gain(+)

0% ii, %
Imam 0-20 7.9 0.00 0.5“ 0.018 17.“ 1“.1

Kharbana 0-20 8.3 +0.06 0.38 0.018 12.3 1“.5

Kharbana 20-50 8.2 +0.05 0.36 0.019 11.1 1“.1

Rashayid 0-20 7.“ 0.10 0.“1 0.017 1“.0 1“.9

Rashayid 20-50 7.u 0.1u 0.38 0.013 17.0 1u.3

[alkaska Bh “.7 0.08 0.69 0.017 23.6 0.0

Kent Bt 6.2 0.01 0.6“ 0.0“3 8.7 0.0

 

“9

the subsoil from Imam which is strongly alkaline.

The two soil samples from Michigan are acid in
reaction. The Kalkaska-Bh horizon has a medium acid reac-
tion and Kent-Bt horizon has a slightly acid reaction.

There is a distinct difference in reaction between
the soils from the arid (Iraq) and humid (Michigan)

regions.

b. Organic matter content

The wet combustion method of Walkley (Richards,
195“) was used to determine organic carbon. The results
were calculated as percent of organic matter by multiplying
the organic carbon content by 1.72.

As shown in Table 8 the organic matter content of
all the samples is very low. The surface horizons of
the soils from Iraq contain slightly more organic matter
than their subsoils, but none of the Iraqi soil samples
contain as much organic matter as the subsoil samples from
Michigan.

The H202 losses in Table 8 are less than the
organic matter in the samples. Indeed the profile from
Kharbana showed a gain on H202 treatment. These gains
are probably due to either higher oxidation or hydration.
Impurities in the H202 might also add a small amount to
the sample. Particularly in the Iraqi samples the gain if
due to oxidation, might indicate that these samples were
deficient in drainage as was indicated in the land classi-

fication of the areas sampled.

The smaller loss than anticipated from the organic

50

matter contents may be due either to some of the above
gains as well as some losses of organic matter or per-
haps the organic matter was not completely oxidized with
H202. The profile from Rashayid showed greater loss than
any other of the Iraqi samples;‘ This was probably due to
the abundanaaof gypsum, some of which was probably dis-

solved in the H202 treatments.

c. Total nitrogen determination

The modified Kjeldahl method was followed as
described by Jackson (1958), for total nitrogen determina-
tions. In general all the samples had a low total nitro-
gen content, Table 8. The Kent-Bt horizon had a higher N
content than the other samples. The subsoils of the Imam
and Kharbana samples have higher N content than the surface
horizons. This may be due to the denitrification in a
hot climate reducing the amount of nitrogen in the surface.
However, it may be due to the leaching process carrying
the nitrogen as NO; from the surface to the subsoils
and their accumulation deeper in the profile. The relative
N05 contents of the samples in these profiles are in agree-
ment with this idea, Tables 8 and 9. However, the amount
of nitrate is not enough to explain all the differences in
nitrogen.

In the Rashayid profile the total nitrogen percent
in the surface is higher than in the subsoil as would
commonly be expected. The N03 content of the surface

here is also higher than in the subsoil.

51

d. Carbonate content (lime)

A quantitative determination method of Williams and
Schellenberger (Richards. 195“) was used to determine
alkaline-earth.carbonates in these soils.

The alkaline-earth.carbonates that occur in signifi-
cant amounts in soils consist of calcite, dolemite. and
possibly magnesite. Owing to low rainfall and limited
leaching, alkaline-earth“carbonates are usually constituents
of soils of arid regions (Richards, 195“).

Alkaline-earth.carbonates influence the texture
of the soil when present in appreciable amounts. for the
particles commonly occur in the silt size fraction (Richards.
195“). Alkaline-earth carbonates, if present, areaimportant
constituents of alkali soils. They constitute a potential
source of soluble calcium and.magnesium for the replace-
ments of exchangeable sodium. .

All the Iraqi samples contained 1“-15 percent of

carbonates as 0e00 equivalents. Table 8. There is little

3
variation in carbonate content between layers within one
profile or between the three profiles.

There is a great difference in carbonate content
between Iraqi soils and.Michigan soils. Table 8. The.
Michigan soil samples contained no carbonates even though
they were both formed from materials containing some limestone.
This is due to the fact that free carbonates have been
removed by leaching in this humid climate as‘was'also
indicated by the pH values which are below 7.

e. Nitrate determination
The phenoldisulfonic acid.method.proposed by Jackson

52
(1958) was used to determine the N03 content of the soil
samples studied. The results of the determinations are
given in Table 9.

Valid interpretations of nitrate data in terms of
field conditions can only be made when samples are analyzed
in a moist condition directly out of the field. Even
with rapid drying some increases in nitrate will occur
before nitrification is completely suppressed.

There was no correSpondence between N03 levels and
total 3 in these soils. The fact that nitrate was found
in all soils in detectable quantities does indicate that
the appropriate organisms for nitrification were present

and active in all soils prior to air drying.

f. .Chloride determination

A method proposed by Reitemeier (Richards. 195“)
was used to determine the Cl'content of the soil samples
studied by titration with silver nitrate. The results of
these determinations are given in Table 9.

Chloride is known to be an essential plant nutrient
but its exact function in the plant is not known (Donahue.
1958). ~It is pertinent, at this point to point out that
it has been reported that high levels of chlorides (or
sulfate) may interfere with nitrogen, phosphorus. or sulfur
nutrition (Richards, 195“). However, the accumulation of the
dhloride ion in plant tissues may not manifest toxic symptoms.
Many plant species are no more sensitive to chloride salts
than they are to isosmotic concentrations of sulfate salts.

There is good evidence. however. for the specific toxicity

53

 

HH.o no.0 #:.o ado.o pm econ
no.o no.o aa.o :mo.e am sausages
e.n on.m: on.oa ano.o onuom easesmam
N.m oo.:e :w.m Hao.o omuo sameness
m.m ea.o n~.n nea.o_ onnom ecenueeu
k.m mH.o :m.m nso.o omuo sameness
n.H oo.n mm.H mno.o omuom seen
a.H om.o mm.m mmo.o omno sasH

Conanon

anon mo Mace no ado» no he

monxa0\ncaaa .am coH\.oE .Em ocH\.oa .Ew oon\.oa .80 ed
.o.m saunas use moz seem a., spoon Haom

 

pontoon nowmaon he
huflbfivosvnco Headhuoeao use .ucopnoo Ednnkm .ovduoano .oaohpfiz .m canoh

5).

of chloride to some tree and vine craps. Hayward and associates
and Brown and co-workers have found chloride salts to be

toxic to peaches and other stone fruits. Chloride burn

has also been reported for citrus by Reed and Haas.

The results in Table 9 indicate that some chloride
is present in all Iraqi samples but there is very little
in the Michigan samples. Imam and Kharbana samples show
lack of effective leaching of chloride through the profile,
since the surfaces contain higher chloride content than
the subsoils. While the soil from Rashayid had a higher
chloride content in the subsoil than in the surface, both

were higher than in the surface of the other Iraqi soils.

g. Gypsum determination (Quantitative)

The gypsum determination was done according to
the method of Bower and Huss (19“8) which involves its
precipitation with acetone.

Although gypsum is a salt which occurs in many
Iraqi soils. Table 9. it does not adversely influence
plant growth. The reason is that the solubility of gypsum.
in water is very low (1.8 g gypsum in one liter of water)
(Delver, 1960). Th?refore, the osmotic pressure of the
gypsum solution never increases beyond 0.5 atmospheres.
At low total salt concentrations the solubility of gypsum
increases if sodium chloride and magnesium chloride are
present in the solution. If the sodium chloride concen-

tration becomes too high (approximately 100 gm/l). the

55

gypsum solubility decreases. The presence of gypsum in
saline soils prevents these soils from becoming alkali soils
by supplying calcium to the soil solution for replacing
exchangeable Na from the soil.

Table 9 shows that soil from Rashayid has a high
gypsum content both in the surface and the subsoil. The
gypsum content of the subsoil is more than in the surface
in the profiles from Rashayid and Imam. The soil from
Kharbana has a low gypsum content. Michigan soils contain
a very low gypsum content compared with the Iraqi soils.

h. Electrical conductivity (Standard wheatstone

Bridge)

The electrical conductivity of 1:5 soil-water
extracts as suggested by Campbell and others (19“9), was
used in these studies.

It is very important to know when the concentra-
tion of soluble salts in a soil is so great as to injure
plants or prohibit their germination or growth.

Table 9 shows that Imam, Kalkaska-Bh horizon and
Kent-Bt horizon have negligible salinity. In the soils
from Kharbana and Rashayid, the yields of very sensitive
crops may be restricted by the salt contents. The study
in this thesis does not agree with the former land classi-
fication stating that these Iraqi samples are strongly
saline.

i. Determinations of extractable sodium, potassium,
calcium, and magnesium

The methods used for determining the extractable

56

nutrients are these used in the Soil Testing Laboratory

in Michigan State University. Extractable sodium, potassium,

calcium and magnesium were obtained by extracting the soil

with neutal normal ammonium acetate at a soil to extract

ratio of 1:10. The quantitative determination of Na, K

and Ca in the soil extract was carried out on a Coleman

flame photometer. Magnesium was determined on a Beckman

D. 0., with a flame attachment, at a wave length of 282.5 mu.
The results of these determinations are shown in

Table 10.

(1) Extractable sodium

Sodium in the soil may exert important secondary
effects on plant growth through adverse structural modifi-
cations of the soil. Thus, if the exchange complex
contains appreciable amounts of exchangeable sodium,

10-15 percent saturation, the soil may become dispersed
and puddled, thereby causing poor aeration and low water
permeability. In general increasing the exchangeable-
sodium percentage of the substrate results in a decreased
accumulation of calcium, magnesium and potassium in the
plants (Richard, 195“).

Laboratory experiments by Bower and Turk have shown
that the addition of calcium and sometimes magnesium, to
alkali soils can improve plant growth very markedly with
an associated increase in the uptake of the nutrients
by the plants.

As shown in Table 10, the amounts of sodium in

all the Iraqi samples are much greater than in the Michigan

57

Table 10. Pounds per acre of extractable nutrients in
soil samples studied.

 

 

Soil Depth Na K Ca Mg.‘ P
cm.

Imam 0-20 5,087 960 15,u56 1,050 32.5

Imam 20-50 3,285 8“0 15,792 98“ 37.5

Kharbana 0-20 10,500 8“0 12,800 912 “1.5

Kharbana 20-50 11,500 816 11,“80 896 “1.5

Rashayid 0-20 3,368 59h 31,800 1,568 53.0

Rashayid 20-50 3,368 “78 30,150 1,208 59.0

Kelkaska Bh “6 35 76 “ 28.0

Kent Bt 280 652 890 307 21.5

 

58

samples. The soil from Kharbana seems to contain a higher

amount of exchangeable sodium than the other Iraqi samples.

(2) Extractable potassium

All the samples except Kalkaska-Bh horizon contained
a very high amount of exchangeable potassium, Tables 10 and
11. The surface layers of the soils from Iraq contain
higher amounts than the subsoils. The soil from Rashayid
seems to contain a lower amount of exchangeable potassium
than the other Iraqi samples. The Kalkaska-Bh horizon is

low.in exchangeable potassium.

Table 11. Adequacy of potassium soil test levels
for mineral soils

 

 

 

 

Fertility Level Pounds per acre
Very low 0-50

Low 51-125
Medium 126-200
High 201-“00
Very High “01+

 

Among the soils studied, all Iraqi soils and the Kent-Bt
horizon from Michigan had very high levels of extractable
potassium. The Kalkaska-Bh horizon showed a very low level

of'potassium.

59

(3) Extractable calcium

Galoium like potassium is absorbed by plants as the
cation (Ca++). This may take place either from the soil
solution or by the process of contact exchange.

The calcium content of the soils from Iraq is high.
This is the result of calcium carbonates and/or calcium
sulfates in the primary material and a low rainfall with
little leaching. Many of the soils of the arid regions
actually have within their profile secondary deposits of

CaCO3 or CaSOh.

(“) Extractable magnesium

The Kalkaska-Bh horizon is very low in extractable
magnesium, Table 10. This might have been anticipated from
its acid reaction and sandy texture. Crops on this soil
would probably respond to additions of Mg fertilizers
such as dolomitic lime.

The Iraqi surface soils contain higher Mg than the
subsoils. All of these samples have more than 200 pounds
of Mg per acre and the calcium-magnesium ratio is usually
smaller than 20 to l, and their potassium-magnesium ratio
is smaller than 3 to 1. Consequently, none of these finer
textured samples are considered to need additions of

magnesium.

3. Available phosphorus
The available phosphorus was extracted with

0.025 E'HCI, containing 0.03 §.NHhF, at a soil to extract

ratio of 1:8. The phosphorus was determined by a colorimetric

 

60

method using the ammonium molybdate, hydrochloric acid
solution preposed by Dickman and Bray (19“0) and l-amino,
2-napthol, “-sulfuric acid reducing agent deve10ped by
Tiske and Subbarow (1925).

The results of these analyses in Table 10 indicate
that samples from Rashayid contain the highest amounts
of available phosphorus. Both Imam and Rashayid sub-
soils contain more available phosphorus than their surface
soils. The content of available phosphorus is higher in
Iraqi soils than in Michigan soils. But because crops
vary in their responses to phosphorus and also differ
greatly in cash value, the adequacy of the amounts present
have to be considered in the light of the fertility

levels indicated for different crops as shown in Table 12.

Table 12. Fertility levels indicated by the phosphorus
soil tests for various craps (those grown in
Greater Mussayib Project are underscored.)

 

Crops to be grown

 

 

Fertility , Pasture, Hay, Corn, Wheat, Sugar
level Barley, Oats, Field Beans, Beets.
Rye, Soy Alfalfa, Potatoes,
Beans Peas ' Most
Vegetables
Very low 0-10 0-15 0~20
Low‘ 11-20 16-30 21-“0
Medium 21-35 31-50 “1-70

 

High 36+ 51+ 71+

61

From Table 12, the following suggestions can be
made: the soil from the Rashayid district has a sufficient
amount of phosphorus for growing barley, wheat, and alfalfa,
but would require additional P for vegetables; soils from
Imam and Kharbana districts, showed a medium to high level
of P for only barley but require additional phosphorus for
wheat, alfalfa and vegetables. Michigan soils have a
medium level of P for barley, pasture, hay, oats, rye,

and soybeans but are low in phosphorus for other crops.

3. Mineralogical Composition
a. Mineralogical analyses of the non-clay fractions

The Rashayid sand fractions contained many shiny
platy grains. This is due to somewhat more mica in that
soil.

In the Imam sand samples black grains were noticed
which were probably due to the presence of magnetite.

The Kalkaska-Bh horizon sand fraction showed a
reddish color due to coatings on the sand grains.

Carbonate and gypsum: All the Iraqi samples
contained free carbonates as shown in Table 8, while the
Michigan samples contained no carbonates, even though these
soils were probably formed from materials containing lime-
stone. The Michigan samples also contained a very low
gypsum content compared with the Iraqi soils. The Rashayid
profile has a very high gypsum content. Much of the
carbonates and gypsum are probably present in the non-

clay fractions.

62

b. Mineralogical analysis of clays

(1) X-ray determinations of clay minerals

The clay fractions from the mechanical analyses
were carefully separated from the silt by repeated
decantations. In mineralogical studies of these clay
fractions, about five m1. of the suspension, containing
30-“0 mg. of clay were transferred to test tubes. Then
5 drops of glycerol were added. The suspension was shaken
and let stand overnight. In the morning a porous ceramic
plate was placed on a holder and attached to a vacuum.
The clay suspension was poured into the well of the
holder. When the clay was all deposited on the porous
plate it was leached with three increments of 0.1M CaCl2
containing 3 percent glycerol by volume. This was followed
by 3 percent, 10 percent and “0 percent glycerol solutions.
The plates were then removed and left overnight in a
desiccator containing CaClz. The plates were then mounted
on the Norelco x-ray spectrometer, using a 1/“” divergent
silt, 0.003” receiving slit and a l/“" scatter slit in the
beam collimating system. The diffraction unit was operated
at 20 milliamperes and 35 kilovolts using a capper target
tube. The recording unit circuit panel was set at time
constant four and multiplier one. A scale factor (SF) of
16 was used for the Iraqi samples and a scale factor of
8 was used for the Michigan samples. The clay samples
were scanned from two to thirty degrees 20. These
diffraction patterns are shown as curves numbered 1 in

Figure 5.

53

Figure 5. X-ray diffraction patterns of the <2Mfractions
of the soil samples from Iraq and Michigan.

Patterns No. l Correspond to Ca++ and glycerol

saturated samples.

Patterns N0. 2 Correspond to samples which were K+
saturated and heated to 110°C.

Patterns N0. 3 Correspond to samples which were K+
saturated and heated to 550°C.

6“

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

65

After irradiation, the ceramic plates were
replaced in the holders and the clay was leached three
times with 10-15 draps of 0.1M KCl then washed with dis-
tilled water, dried for four hours in the desiccator, and
then placed in an oven at 110°C for twenty-four hours, and
left to cool in the desiccator. The samples were then
scanned again in the X-ray diffraction unit. These diffrac«
tion patterns are shown as curves numbered 2 in Figure 5.

Finally, these samples were heated to 550°C for
twenty-four hours, cooled and scanned for the third time.
These diffraction patterns are shown as curves numbered 3
in Figure 5. .

The effect of the above treatments on the common
clay minerals, quartz, calcite and the ceramic plates
are listed in Table 13. The results of the different
methods used in the analysis of clay show, Table 1“, that
kaolinite, chlorite, illite, and vermiculite are the
main clay minerals in Kent-Bt horizon. Some montmorillonite
is also present in the Kent-Bt horizon but in a very low
percentage.

The Iraqi samples and the Kent-Bt horizon all con-
tain some interstratified clay minerals containing mont-
morillonite and chlorite. Much of the clay in the Kalkaska-
Bh sample was apparently amorphous since the intensity of
the clay mineral peaks were quite low for that sample. Only
about 15. percent of this clay sample was accounted_for

by the clay minerals present.

66

(2) Calcite contents

In the X—ray diffraction studies of the clay
fractions a 3.033 spacing appeared in all Iraqi samples.
This line disappeared on ignition of the samples. It
indicates the presence of calcite (Whiteside, 19“8)
in the clay fractions of those soil samples. This line
is absent in Michigan samples, so there is no calcite
present in the clay fraction from those horizons. If
we had gone farther, more than 300 20, in the X-ray
diffraction studies of Iraqi soils it would have been
possible to determine, on the basis of the presence or
absence of a diffraction line at 2.89a, whether or not
dolomite is present in those samples.

(3) Colorsoof clays before and after ignition

at 550 C -

All the clay samples reddened on ignition, Table 1“.
The clay from the soil profile near Imam, Iraq, became
darker in color on ignition as well as redder. Its color
changed on heating from light grayish yellowish brown
(lOYR6/3) to light grayish brown (7.5YR5/3-5/2). This
may be due to the presence of some organic matter that
charred on heating but did not decompose because of its
combination with the clayr' Another possibility might be
the presence of some manganese dioxide. The other Iraqi
clay samples became brighter on ignition as well as redder.
The Kent-Bt horizon became lighter and brighter as well
as redder on ignition. The clay from the Kalkaska-Bh

horizon became lighter in color as well as redder on

ignition.

57

Its grayish reddish orange (10R5/6) color after

ignition may be due to a higher content of iron oxide or

hydrated oxides than in the other samples.

 

 

Table 13. Effect of heating on lattice spacings (in
o
Angstroms) of clay minerals
Clay Glycerol K01 K01
minerals +CaC12 satgration satgration
110 C 550 C.
Kaolinite 7.1, 3.56 7.1, 3.56 Decomposed
Halloysite 10., 5.0 7.1, 3.56 Decomposed
Montmorillo-
nite 17.7, 10. 10.
Illite 10.. 5.0, 10., 5.0, 10., 5.0,
3.3 3.3 3.3
VermiCulite 1“.2, 7.1, 10., 5.0, 10., 5.0,.
“.7 3.3 3.3
Chlorite 1u.2, 7.1, 1“.2, 7.1, 1u.2, 7.1,
“.7 “.7 “.7
Quartz. “v.26, 3.35 l"e26, 3e35 “‘26, 3e35
Calcite 3.03 3.03 Decomposed
Ceramic Plate 5.“, “.2,

“.1. 3.35

 

68

 

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IV. SUMMARY AND CONCLUSIONS

In this study some physical, chemical and
mineralogical properties of a sandy subsoil (Kalkaska-Bh)
sample from Michigan and a clayey subsoil (Kent-Bt) sample
from Michigan were compared with three pairs of surface
and subsoil samples from the Greater Mussayib Project Area
in Iraq.

Mechanical analysis showed the sandy subsoil from
Michigan had a sand and the clayey subsoil had a clay
texture, four of the six samples from Iraq had silty clay
textures. The samples from the profile near Rashayid,
Iraq, had a silty clay loam texture in the surface and
a loam texture in the subsoil.

The results of mechanical analysis show that no
downward movement of clay has taken place in any of the
three Iraqi profiles. In contrast, from field studies the
Kent-Bt horizon is known to be an horizon of clay accumula-
tion in the Kent soil profile. The Kalkaska-Bh horizon is
a subsoil horizon in which humus has accumulated and it
contains little more clay than the overlying or underlying
horizons (Bailey, 1957).

The finer textured soil samples contained much
more water at the same tension than the coarse textured
Kalkaska.Bh. This is due to the larger number of contact
points and the larger area of particle surfaces in the finer
textured samples as well as differences in the clay minerals
present. The availability of soil moisture to the growing
plants is usually estimated by the differences in moisture

69

70

contents at field capacity and at the permanent wilting
point. In this study the amount of water held at 1/3 atm.
by the crushed finer textured samples is believed to be

the best estimate of field capacity. However, for the
Kalkaska-Bh sample a 0.05 atmosphere tension was used.

The first wilting point, beyond which we would not wish

to go when growing irrigated crops, is near 6.0 atmospheres
tension as Stolzy (195“) has indicated. The permanent
wilting point near 15 atmospheres would be a better measure
of the low available water range under dry land conditions.
On the basis of these premises the readily available and
available water content of these samples wereestimated for
irrigated and dry land conditions.

The Kalkaska-Bh horizon had a higher bulk density
than the fine textured disturbed samples. The finer
textured soils contained about 50-55 percent total pore
space and this is considered as a good condition for plant
growth. Perqent pore space based on bulk density and specific
gravity is probably the most desirable method among those
used for determining the pore space.

The chemical properties show that there is a
distinct difference in reaction between the soils from the
arid region (Iraq) which are alkaline and the soils from
the humid region (Michigan) which are acid. None of the
Iraqi soil samples contain as much organic matter as the
subsoil samples from Michigan, but in general the organic
matter content of all the samples is very low. .Two of the

Iraqi profiles contained slightly less nitrogen in the

71

surface than in the subsoil. It is suggested that this may
be due to denitrification and/or leaching of nitrate and
their deposition in the subsoil.

There is a great difference in carbonate, gypsum,
and chloride contents between Iraqi samples and Michigan
samples. The Michigan soil samples contained no carbonates
(and very little gypsum and chloride, even though they were
(probably formed from material containing limestone. This
is due to the fact that the free carbonates and more solu-
ble salts have been removed by leaching in this humid
climate as was also indicated by the pH values.

Electrical conductivity showed the Michigan soil
samples and the Imam profile from Iraq had negligible
salinity. 0n the soils from Kharbana and Rashayid, the
yield of very sensitive crops may be restricted by the salt
contents.

All Iraqi samples are higher in extractable sodium.
potassium, calcium, magnesium and phosphorus than the Michi-
gan samples, except the Kent-Bt horizon which showed higher
potassium content than the Rashayid profile. The general
idea is that for nearly all creps (except tobacco), and for
all Iraqi samples and the Kent-Bt horizon, the present
potassium content is sufficient. Lime fertilizers will
never be required. Buringh reports (1960) that ammonium-
sulfate and superphosphate are required in large quantities.
The level of phosphorus in Iraqi samples indicated a
level suitable for growing barley but additional P would

be needed for vegetables and occasionally also for wheat

 

72

.and alfalfa. The Michigan soil samples have a medium
level of phosphorus for barley, pasture, hay, oats, rye,
and soy beans but would require additional phosphorus
for other crops.

A comparison of the X-ray diffraction patterns of
all clay samples studied shows that, kaolinite, chlorite,
illite and montmorillonite are the main clay minerals in
the Iraqi samples. Vermiculite, chlorite and kaolinite
are present in small amounts in the Kalkaska-Bh horizon
but much of this clay seems to be amorphous or non-crystalline.
Illite, kaolinite and vermiculite are the main clay minerals
in the Kent-Bt horizon. The Iraqi samples and the Kent-Bt
horizon all contain some interstratified clay minerals
containing montmorillonite and chlorite layers.

The combination of all the results of this study
must lead to the conclusion that all of Greater Mussayib
Project soil samples studied are fairly well suited for
farming purposes unless they have some deficiency such as

‘drainage which is affecting the value of the land.

V. BIBLIOGRAPHY

Bailey, H. H., Whiteside, E. P. and Erickson, A. E., 1957.
Mineralogical composition of glacial materials as
a factor in the morphology and genesis of some
Podzol, Gray Wooded, Gray-Brown Podzolic, and

§¥$10-G%iz saggghia Michigan. Soil Sci. Soc. Amer.

Baver, L. D., l9h8. Soil Physics. John Wiley a Sons, Inc..
New York. 3rd. ed.

Bennett, H. H., 1939. Soil conservation. McGraw-Hill
Book Company, Inc. N.Y.

Booya, H. A., 1956. The nature of the saline (sabach) soils
of Iraq and their desalinization. Unpub. M.S.
Thesis, University of Arizona, Tuscon.

Bower, C. A., and Huss, R. B., l9h8. Rapid conductometric
method for estimating gypsum in soils. Soil Sci.
668 199-20“.

Buringh, P., 1957. Living conditions in the lower
Mesopotamian plain in ancient times. Dept. of Agr.,
Baghdad, Iraq.

Buringh, P., 1960. Soils and soil conditions in Iraq.
Printed in the H etherlands by H. Veenman a Zonen
N. V., Wageingen.

Burnell, G. W., 1955. Report of the soil survey and soil
classification Dujaila Project. Ministry of
Agriculture. Baghdad, Iraq.

Campbell, R. B., Bower, C. A., and Richards, L. A., l9h9.
Change of electrical conductivity with temperature
and the relation of osmotic pressure to E. C. and

ion concentration for soil extracts. Soil Sci.
Soc. Amer. Proc. (l9h8) 13: 66-69.

Chapman, G. 3., l9h9. Forestry in Iraq. Unasylva II,
53 251-2530

Davies, D. H., 1957. Observation on land use in Iraq.
Economic geography 33: 122-13h.

Delver, I. P., 1960. Saline soils in the lower Mesopotamian
plain. Minist. of Agri. of Iraq. Div. of Soils
c Agri. Chem.

Dickman, S. R. and Bray, R. 3., 19h0. Colorimetric deter-

mination of phosphate. Ind. Eng. Chem. Anal.
12: 665-668.

73

7h

Donahue, R. L., 1958. Soils an introduction to soils and
slant growth : 113-129. Prentice-Hall Inc.,
nglewood Cliffs, N. . ~

Fisher, V. E., 1950. The Middle East, a physical, social
and regional geography. London-New York. ed. 3,

1956.

Guest, E., 1932. Notes on trees and shrubs for lower Iraq.
Dept. of Agr., Bul. 26. Baghdad.

Guest, E., 1933. Notes on plants and plant products with
colloquial names in Iraq. Dept. of Agr., Bul. 27.
Baghdad.

Guest, E., 1953. The Rustam Herbarium, Iraq. Part VI.
Kew Bull. Ho. 3: 383-903.

Hooker, D., 1937. Useful plants and drugs of Iran and Iraq.
Publ. of the Field Mus. of Rat. Hist. Bot. Sec.
Vol. II, No. 3.

Jackson, M. L., 1958. Soil chemical analysis. Prentice-
Hall, Inc., Englewood Cliffs, N. J.

Kelly, K. L. and Judd, D. E., 1955. The ISCC-MBS method
of designating colors and a dictionary of color
names. National Bureau of Standards, Circular 553.

Kilmer, V. J. and Alexander, L. T., l9h9. Methods of
making mechanical analysis of soils. Soil Sci.
68: 15-2“.

Powers, V. L., l95h. Soil and land capabilities in Iraq,
Economic Geography. an: 373~380.

Richards, L. A. and United States Salinity Laboratory
Staff, 195”. Diagnosis and improvement of saline
and alkali soils. Agr. Handbook No. 60 U.S.D.A.

Russel, J. 0., 1957. Soil salinity in Iraq. (lecture)

Russell, E. J., and Russell, E. U., 1950. Soil conditions
and plant growth. New York, London, Longmans,
Green, and Co.

Shaw, B. T., 1952. Soil physical conditions and plant
growth. Academic Press Inc., Publisher, lbw York,
N.Y. pp 1514-158 . '

Smith, J., 19hh. Report on forests and forestry in the
Northern Liwas of Iraq. Baghdad.

Springfield, H. V., 195h. Eatural vegetation in Iraq.
Ministry of Agr., Tech. Bul. Baghdad.

75

Stolzy, L. H., l95h. The effect of mechanical composition
and clay mineral types on the moisture prOperties
of soils. Unpublished Ph.D. Thesis, Michigan State
University, 135 numbered leaves.

Tiske, C. H. and Subbarow, Y., 1925. The colorimetric
determination of phosphorus. Jour. Biol. Chem.

66: 375-300.

Veihmeyer, F. J., and Hendrickson, A. H., 19h8. The perma-
nent wilting percentage as a reference for the measure
of soil moisture. 'Trans. Am. Geophys. Union,

29: 887-896.

Whiteside, E. P., l9h8. Preliminary x-ray study of loess
deposits. Soil Sci. Soc. Am. Proc. 12: #15.

Zohary, M., 19h0. Gecbotanical analysis of the Syrian Desert,
Palest. Journ. Bot. Ser. J. #6.

Zohary, M., 1950. The flora of Iraq, and its phytogeo-
graphical subdivision. Iraq Dept. Agr. Bull. No. 31.

 

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