Diluvial Soils and Their Amelioration E-Book

Mukhtar Abduyev

• Herausgeber: Ithaca Press
• Kategorie: Fachliteratur
• Sprache: Englisch

Veröffentlichungsjahr: 2012

Beschreibung

Professor Mukhtar Abduyev's pioneering work was the result of ten years of study, field research and laboratory experimentation on salinized diluvial soils in the foothill plains and steppe of Azerbaijan. At a time of increased demand for agricultural land this work was a most timely contribution to bringing the country's foothill plains, a major soil reserve, into play. Important as the work was for Prof. Abduyev's native land, however, it had even wider implications. Because there are other forms of salinization in Azerbaijan, the work herein facilitated comparative analysis of their distinctive characteristics - common to the arid regions of many other countries. In Diluvial Soils and their Amelioration, as in his other works, Prof. Abduyev moves from rigorous scientific analysis of the problem and its origins to the development of techniques to return salinized land to productive efficiency; a true demonstration of science in practical action. In 1970, the original Russian edition of the work was nominated by the Academy of Sciences of the Azerbaijan SSR for the V.V. Dokuchayev Award for distinguished contributions to soil science.

Leseprobe

DILUVIAL SOILS AND THEIR AMELIORATION

MUKHTAR ABDUYEV

TRANSLATORS Angelika Dawson Amy Lesiewicz Ella Thomas

PROOFREADER Alisa Blokhina Alvares

ACKNOWLEDGEMENT TO TRANSLATION COMPANY Applied Language Solutions

The book was first published in 1968 in Russian

DILUVIAL SOILS AND THEIR AMELIORATION

Published by Ithaca Press 8 Southern Court South Street Reading RG1 4QS UK

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Copyright © Mukhtar Abduyev, 2012

All rights reserved. No part of this book may be reproduced in any form or by any electronic or mechanical means, including information storage and retrieval systems, without permission in writing from the publisher, except by a reviewer who may quote brief passages in a review.

First Edition 2012

ISBN: 9780863725036

British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library

Printed by TJ International, Padstow, Cornwall

CONTENTS

INTRODUCTION

PART I GENESIS AND MODE OF DILUVIAL SOIL SALINIZATION

CHAPTER I. GENERAL OVERVIEW OF THE CLASSIFICATION OF SALINE SOILS

1. Outline of the classification of saline soils

2. Genetic uniqueness of saline soils in Azerbaijan

3. Diluvial soils and their regions

CHAPTER II. CONDITIONS OF SOIL FORMATION IN THE REGIONS WITH DILUVIAL SALINIZATION

CHAPTER III. CHARACTERISTICS OF SOILS WITH DILUVIAL SALINIZATION AND THEIR GEOGRAPHY

1. Main genetic characteristics of soils

2. Soil alkalinity

3. Physical properties of soils

4. Soil salinity

CHAPTER IV. SOURCES OF SALT ACCUMULATION IN THE DILUVIAL SOILS

Salt accumulation in the soils of the arid region

I. Sources of ancient soil accumulation

II. Factors determining recent salt accumulation

1. weathering rocks of mountain structures

2. Eolian salt cycle

CHAPTER V. FACTORS OF SALT MIGRATION

I. Surface runoff

II. The role of biological agents in the migration and accumulation of salts in soil

1. Pattern of the root system distribution of halophytes

2. Reserves of vegetation mass

3. Annual growth of vegetation mass

4. Vegetation mass content and composition

5. Amount of salts involved in biological cycle

III. Diffusion of salts

IV. Influence of irrigation to the movement of salt masses

CHAPTER VI. SOIL WATER REGIME

Water regime of soils in diluvial plains of South-East Shirvan

Water regime of soils of the Siyazan-Sumgayit massif

Water regime of soils in the diluvial plain of Mil Steppe

CHAPTER VII. SOIL SALT REGIME

Salt regime of soils of diluvial plains of South-East Shirvan

Salt regime in soils of the Siyazan-Sumgayit massif

Salt regime in soils of the diluvial plain of the Mil Steppe

PART II DEVELOPMENT OF RECLAMATION REGIMES FOR SOILS WITH DILUVIAL SALINIZATION

CHAPTER VIII. THE GENERAL COURSE OF DEVELOPMENT AND THE CURRENT STATE OF SALINE SOIL RECLAMATION

CHAPTER IX. SOIL HYDROGEOLOGICAL CONDITIONS OF FIELD EXPERIMENT SITES FOR RECLAMATION OF SOILS WITH DILUVIAL SALINIZATION; METHODS OF RESEARCH

Selection and characteristics of the subjects of research

1. Soil conditions of pilot sites in the Siyazan-Sumgayit massif

2. Soil conditions of the pilot site in the Kyurovdagh massif

3. Soil conditions of the pilot sites on the Bozdagh diluvial slope

Methods of research

CHAPTER X. EXPERIMENTAL LEACHING OF SALINE SOILS UNDER DILUVIAL PLAINS CONDITIONS

Soil flushing in monoliths

Field leaching of soils (microplot trials)

1. Soil leaching without chemical soil amendments

2. Leaching of soils by applying sand

3. Soil leaching by applying acidifier

4. Soil leaching by applying gypsum

5. Leaching of soils with joint application of gypsum and manure

6. Intensity of salt mass leaching

7. Change in alkaline soil properties

8. Influence of reclamation on crop growth conditions

CHAPTER XI. EFFECTIVENESS OF FARM-SCALE RECLAMATION IN SOIL DESALINIZATION

Change in the level and mineralization of groundwaters

Dynamics of saline areas

CONCLUSION

BIBLIOGRAPHY

INTRODUCTION

Soil salinization develops on a wide scale under the conditions present in Azerbaijan. Saline soils are spread along nearly all the lowlands and the foothill plains of the Republic. within this territory, salinization develops under relatively varying natural conditions of salt migration, in particular, in alluvial-accumulative plains, alluvial river fans, and diluvial foothill plains. Salinization in the areas of alluvial-accumulative plains develops in still groundwater. Currently, this form of salinization is the most studied and a number of engineering amelioration projects applicable to this form of salinization have been developed. These measures have already been implemented in many areas and have a positive impact on the conditions of the indicated soils.

Saline soils of alluvial river fans formed under the impact of inter-colluvial groundwater are common within colluvial fans of rivers flowing from the Greater and Lesser Caucasus mountain range. There are many publications on the genesis, characteristics and conditions of amelioration of saline soils of alluvial river fans (V.V. Dokuchaev Soil Sciences Institute, Institute of Soil Science and Agricultural Chemistry of the Azerbaijan Academy of Sciences, Azgiprovodkhoz).

Saline diluvial and diluvial-proluvial soils within the territory of Azerbaijan also occupy relatively large areas, spreading along nearly the entire foothill zone of the Republic. These soils are a major reserve for the expansion of the cultivation area for cotton and other crops. Saline diluvial and diluvial-proluvial soils were discovered in Azerbaijan as early as 1928 by S.I. Turemnov. The presence of these soils was later confirmed by the research of V.R. Volobuev, V.A. Kovda, A.N. Rozanov, V.V. Egorov, A.S. Preobrazhensky and others who studied saline soils in the lowlands of Azerbaijan. Nevertheless, these soils remained unexplored as regards to soil amelioration. In the meantime, production companies in the Republic are increasingly reclaiming the land of the foothill plains due to the supply of irrigation water to this territory.

Irrigation farming has virtually no experience in the management of such land. Reclamation of such soils is difficult for many reasons: they are often extremely saline and alkalised; they mainly have heavy argilliferous texture and weak water impermeability. Precipitation and irrigation waters dwell on the surface, barely penetrating the subsurface. Thus, chemical, physical and physicochemical properties of saline diluvial soils of the foothill plains of Azerbaijan are highly unfavourable for crop cultivation.

Indeed, farms in this zone mainly have poor crop yield. At times, they do not even harvest the minimum that was sowed. Moreover, if irrigated within a short period of time, the soils are exposed to strong secondary salinization and quickly become unusable.

All this created the need for the accelerated development of amelioration measures to recover and bring these lands into cultivation. The situation was also exacerbated by the supply of irrigation water for lands on the foothill plains and the migration of many farms from the mountainous regions of the Republic to the lowlands.

No radical amelioration methods have been developed for the diluvial soils. The need for study of the soil genesis, the properties and the amelioration techniques was long underestimated and, until recently, we did not have any theories about the origins, seasonal dynamics and amelioration techniques of these soils based on direct field and experimental research.

The author of this work intended to study the properties of saline migration under the conditions of the foothill diluvial-proluvial plains of Azerbaijan. Our studies of the genetic form of soil salinization, with the goal of developing amelioration methods, were based on the data from our own extended research and the existing literature.

Perhaps, the field and static experimental research materials we have collected are not adequate for an exhaustive resolution of a complex problem of the origins and development of these soils. However, at this time, since their development has begun already, it appears to be useful to systemise the materials we have collected so far and to formulate the main theoretical concepts concerning the origins, properties and the main principles of amelioration and exploration of diluvial soils of the foothill plains of Azerbaijan. Such soils could seemingly serve as an analogy for soils with similar genesis explored in other regions of the Soviet Union and abroad.

Soil salinization related to the transport of salts by surface waters is highly common and found in many arid regions of the Soviet Union and other countries. Nonetheless, Azerbaijan is of particular interest in this regard, because this form of salinization is represented here along with other forms. This creates conditions for comparative analysis of the distinctive characteristics of salinization of various geneses.

For ten years (1955 to 1964), we studied diluvial soils in the foothill plains of the Siyazan-Sumgayit massif, in the Mil steppe and in the diluvial and diluvial-proluvial plains of the Bozdagh, Harami, Kyurovdagh and Babazanan mountain ranges. All work was conducted in the soil amelioration laboratory of the Institute of Soil Science and Agricultural Chemistry of the Academy of Sciences of Azerbaijan SSR, headed by Professor V.R. Volobuev, member of the Azerbaijan Academy of Sciences, Doctor of Agricultural Sciences.

All field research and laboratory experiments were conducted by the author personally. In field work, the author was assisted by A.M. Kadymov. Soil analyses were conducted mainly with the participation of S.E. Rzaeva and O.N. Kesareva.

After reading the draft of this book, member of the Academy of Sciences I.N. Antipov-Karataev, Prof. V.V. Egorov, Doctor of Sciences N.I. Bazilievich and Candidate of Sciences G.V. Zaharyina have made valuable comments and suggestions that have been taken into consideration by the author before final publication.

The author would like to express his utmost gratitude to these people.

This work consists of two parts: the first part is dedicated to the genesis and salinization conditions of the diluvial soils (Chapters I-VII) and the second part covers the development of amelioration techniques for these soils (Chapters VIII-XI).

PART I

GENESIS AND MODE OF DILUVIAL SOIL SALINIZATION

CHAPTER 1

General Overview of The Classification of Saline Soils

1. OUTLINE OF THE CLASSIFICATION OF SALINE SOILS

Despite the relatively long history of the first attempts to classify saline soils, this issue still cannot be considered fully settled.

To classify saline soils, it was needed primarily to take into consideration the content of easily soluble salts and their chemical properties. Based on these characteristics, some researchers (Knop, Cameron, 1899; Gilgrad, 1906) designated an individual group for saline soils and classified them based on their salt composition. V.V. Dokuchaev (1886) and N.M. Sibirtsev (1899) attributed saline soils to class A (or normal) type soils. Based on their geomorphologic-genetic characteristics, V.V. Dokuchaev sub-classified them into salt ponds, estuary formations, marshes, etc.

In the classification of P.S. Kosovich (1903), M.A. Dimo (1907), K.D. Glinka (1915, 1926), S.S. Neustruev (1926), saline soils were divided into solonchaks and solonetz. S.S. Neustruev classified solonetz soils as autogenic and saline soils as hydrogenous, sub-classifying them into solonchaks and solonchak-like alkali soils.

A new stage in the understanding of the nature of saline soils is connected with the name of K.K. Gedroits (1908-1917) who demonstrated the significance of the composition of absorbed bases in the development of solonetz soils and, at the same time, developed the ideas of evolution in the formation of saline and alkali soils. His ideas were widely used in further classification of saline soils.

Detailed classification of saline soils, with an allowance for a number of characteristics, has been suggested by D.G. Vilensky (1924) and S.I. Tyuremnov (1926). D.G. Vilensky considered saline soils to pertain to the halogenic soils class and sub-classified them based on morphology, salt composition, position within the soil profile, salt accumulation horizon and others. In his classification, S.I. Tyuremnov most consistently used such characteristics as the total quantity of salts in the soil, their chemical composition, and the morphology of salic horizons. He placed considerable importance on the factor of salt accumulation.

V.A. Kovda (1935, 1937) built his classification on the idea of saline soil development.

In their classification of saline soils, S.y. Sushko (1930), N.I. Usov (1937), E.N. Ivanova, A.P. Rozanov (1939), V.R. Volobuev (1948), V.A. Kovda, B.P. Stroganov, V.V. Egorov (1960) placed considerable importance on the total salt content in soil and their composition, along with the genesis of saline soils.

However, V.R. Volobuev (1964) found it necessary to consider three orders of soil division that constitute the known degrees of insight into the soil salinization phenomenon: 1) characteristics based on saline properties, or diagnostic description; 2) genetic division, or classification as such; 3) social divisions (division into agroecological categories).

Saline characteristics, according to V.R. Volobuev, should be specified in terms of their composition so that, overall, they could characterise all the significant properties of saline soils, including the content and composition of salts, morphological data, saline dynamics and conditions of saline soil formation. V.R. Volobuev believed that, in addition to the issues of crucial importance for the accurate explanation of the origins of saline soils and the justification of their classification in each specific case, it was important to consider the issues of how salt concentration actually occurs in nature and the factors and paths of salt migration, i.e., the entire process of salt salinization. Furthermore, V.R. Volobuev points out that the classification of saline soils should reflect the forms in which salt migration is manifested on the land surface, their interrelationship, i.e., the transition from one to the other, and the dependence of salt migration and concentration upon local conditions.

Thus, the origin of soil and groundwater salinization may be explained accurately only on the basis of general laws of element migration in nature and, in particular, on land surface, i.e., based on geochemical concepts.

A.E. Fersman (1939) specified two types of element migration: ion extraction from crystal lattices by transferring them into a solution and subsequent deposition of these substances from the solutions. After reviewing the procedure of ion extraction in the supergene zone A.E. Fersman (1937) came to the conclusion “that extraction takes place in accordance with maximum solubility, namely, from small to large energy coefficients, from small to high valances, from large to small ionic radii, from small to high lattice energy values. Absorption by soil and intake by living matter constitute the correction factors”.

According to A.E. Fersman (1935), the settlement of halophiles is also subject to the laws of energy and occurs inversely to their extraction from the crystal lattice. However, V.R. Volobuev (1948) believes that the dependence of the behaviour of halophiles on climatic conditions and geological history of the country is just as significant. This idea can be confirmed by the data obtained by G.A. Maksimov (1943). He determined that the subarctic tundra and tropical red earth zones have rivers that predominantly carry siliceous and hydrocarbonate-siliceous salts into the sea. At temperate latitudes, river waters carry hydrocarbonate-calciferous salts. In desert regions, river waters have chloride and sulphate salt composition.

These aspects in the distribution of geochemical facies of river waters on earth evidently reflect the stages of decay of the rocks that form the continents.

The distribution of the weathering stage on the earth’s surface in modern times of geological history is no doubt related to both geology and climatic conditions that determine, above all, the intensity of the individual weathering stages.

Based on the analysis of salt exchange in the soil-water system, I.P. Gerasimov and E.N. Ivanova (1936) established three main geophysical types of salt balance: arid, extra arid, and humid. Taking into account the geomorphologic and geological conditions, they distinguished the following subtypes of salt balance: endorheic and exorheic, continental and marine. Furthermore, the authors distinguished between the directions of flow: surface and infiltration. Each of the types and subtypes of salt balance differs significantly in the composition of salts that are deposited and carried away.

Thus, the nature of halophile migration is the main underlying characteristic for a geographical analysis of salt migration.

In determining the geography of soil salinization in Azerbaijan, V.R. Volobuev (1948) distinguished between the following 11 forms of salinization: eluvial, deflation-accumulative, diluvial, proluvial, colluvial, alluvial, valley, coastal, marshland, deep subartesian, and volcanic.

Indeed, salinization of soils in Azerbaijan is very different in its origins. Moreover, it is important to take into account the existence of saline soils that combine different forms of salinization.

2. GENETIC UNIQUENESS OF SALINE SOILS IN AZERBAIJAN

A review of the literature and library materials led us to conclude that alluvial soils, which occur due to the capillary rise of heavily mineralised groundwaters with nearly no drainage to the surface, are the most common soils in Azerbaijan. Alluvial soils are distinguished by the dynamics of the water-salt conditions and widespread occurrence of secondary salinization. Furthermore, the effects of anthropogenic activity (irrigation mode, etc.) have significant impact on their properties.

Colluvial soils are also widely common in the lowland areas of the Azerbaijan Republic. Inter-colluvial groundwaters with downward drainage along the slope, usually replenished substantially by irrigation waters, are a factor of salt migration in these soils. This form of salinization is characterized by increased soil salinization towards the periphery of the colluvial fans.

Large areas of the Azerbaijan Republic are occupied by eolian-marine soils, common mainly in the Caspian coastal zone, and related to the impact of the sea and eolian redistribution of the saline soil material.

Lacustrine and deflation-lacustrine soils are widespread in the regions with the developed processes of saline rock wash-out and eolian shifts of land waste. In particular, the lacustrine type includes salt accumulation in the Adjinaur basin that has a non-perennial salt lake surrounded by solonchaks.

The Absheron Peninsula commonly has deflation-lacustrine salinization that occurs due to the accumulation and subsequent evaporation of diluvial salt waters in the depressions developed by deflation and confined to salt-containing argillic deposits of productive strata. The latter are aggregated to a sand-like condition, while weathering and under the influence of salts contained in the rocks and, in some places, under the influence of evaporating strata waters. Then they are dispelled by wind. waters accumulated in the depressions increase this process by evaporation.

The Azerbaijan Republic also has saline soils related to volcanic activity. These soils are largely prevalent in the eastern regions. Volcanic and diluvial waters that leach mud outbursts expand on the periphery and cause solonchaks fed by groundwater, which develop under the influence of strong eolian activity and create shors (a type of solonchak) - wind-formed and hummocky zones - drifting zones.

Soils with perched groundwater salinization occur as a result of irrigation water salts concentration and are largely prevalent in the regions with irrigation farming.

Diluvial soils count among the widespread soils in Azerbaijan. This work is dedicated to the distinguishing characteristics of these soils.

3. DILUVIAL SOILS AND THEIR REGIONS

Diluvial soils imply soils that form under the impact of surface diluvial and diluvialproluvial stream flow1 under the conditions where there is no connection with groundwater.

Diluvial stream waters deposit a finely washed material on the surface of talus slopes, especially in their apron zones, causing uninterrupted rejuvenation of the top horizon of the soils. Moreover, salt concentration in the top soil layers is related, on the one hand, to the addition of salts from overlying sections and, on the other hand, with the redistribution of salts within the soil profile.

The largest area of these soils is confined within the Shirvan, Mil-Garabagh steppes, Ganja-Gazakh and Siyazan-Sumgayit massifs (Fig. 1)2. There are also considerable areas of diluvial soils in the south-west foothills of Gobustan, in Nakhchivan ASSR, within the boundaries of the jeyranchol massif and as far as the Lankaran Region. These soils are also common locally in mountainous regions.

Figure 1. Regions of diluvial soil occurrence:

1 - diluvial foothill upper quaternary plains; 2 - proluvial-diluvial foothill upper quaternary plains; 3 - abrasion-proluvial medium upper quaternary plains; 4 - abrasion-proluvial upper quaternary plains; 5 - abrasion-accumulative upper quaternary plains; 6 - profiles of experimental research; 7 - numbers of stationary and experimental research profiles.

According to our calculations, the area of the diluvial soils in lowlands of Azerbaijan amounts to more than one third (one million one hundred thousand ha) of the total plains area of the Republic.

In order to determine the characteristics of diluvial soils as comprehensibly as possible we will begin by examining the conditions under which they are formed.

____________________________

1 Regarding migration of salts with the surface diluvial flow and their accumulation in soils in areas of diffusion (evaporation) of such flow see the works of L.P. Rozov (1936), V.A. Kovda (1937, 1956), D.G. Vilensky (1938), I.A. Shulga (1938), N.A. Kachinsky (1938), V.R. Volobuev (1948), V.V. Egorov (1951), N.I. Bazilievich (1956), A.N. Rozanov (1959) and others. V.R. Volobuev (1948) determined and classified the position of the diluvial soils.

2 The map of diluvial soil distribution was prepared based on the soil data and in consideration of the geomorphologic map of Azerbaijan SSR.

CHAPTER 2

Conditions of Soil Formation In The Regions with Diluvial Salinization

Regions with diluvial soils, located within the plainlands of the Azerbaijan Republic, mainly occupy the peripheral submontane and foothill zones with an average altitude of 100-200 m or slightly less.

The geological structure of this part of the Azerbaijan Republic is closely related to the Kur-Araz lowlands and its surrounding mountain structures, and to a certain degree to the history of the Caspian Sea.

The formation of terrain in the Azerbaijan lowlands has a complex history. According to geological data, before the Baku Sea (present day Caspian Sea) era, the Mughan lowlands were a bay, which washed the slopes of Greater and Lesser Caucasus. The elevation of the Ajinour hills and the filling of the Kurin depression with the sediments of the Kur, Araz and other rivers flowing down the slopes of Greater and Lesser Caucasus occurred after Baku had already existed.

The sequence of terrain formation within the studied massif was examined in the works of V.E. Khain and A.N. Shardanov (1952). These authors observed that at the end of the Absheron and the beginning of the quaternary Period there were major marine regressions that caused the drainage of the significant areas of the Kurin bay. According to the data of some researchers (Shishkin, Rogovskaya, Popov, Gavrilov, Pobedonostsev, Aristov - 1950-1951), a foothill sloping plain began to form at that time by the southern slope of Greater Caucasus, where the low-hill areas of Ajinour are found today. As noted by V.I. Khain and A.N. Shardanov (1952), towards the end of the Pliocene Period and the early quaternary Period, the submontane plains turned into sloping plains. At the same time, the elevation of anticline folds in Ajinour and Harami-Salyan zone increased and the activity of mud volcanoes that began in the Middle Pliocene Period manifested itself widely.

In the middle of the quaternary Period there was a new and significant increase in the diastrophic activity. The Upper Pliocene sloping plains were broadened by the lower plains of the Lower Pliocene. This was particularly noticeable in the zone of the eastern margin of Lesser Caucasus, where the Garabagh-Mil sloping plain was formed.

According to these authors, a complete drainage of the Kurin depression took place in the period between the Gyurgan and Khazar transgressions along with the significant shrinkage of the sea within the territory of the present Caspian basin. The Absheron peninsula that occupied an area much greater than today and probably covered the Absheron archipelago and the North Absheron offshore area began to appear at the same time.

According to V.E. Khain and A.N. Shardanov, the last Early Khvalyn transgression caused flooding of the major part of the Lower Kurin depression. Thereafter, the sea no longer reached the eastward side of the Kur and Araz confluence. Active growth of anticline folds and corresponding hills of the Harami-Salyan strip continued in the Upper quaternary Period. Similar activity was observed at a slower pace along the southern margin of Ajinour (Gedakboz, Duzdagh, Bozdagh, Karaja and Karamaryan ridges) and, possibly, in East Absheron. This led to the preservation of the elements of a purely tectonic terrain in these regions until our time. The growth of some of these elevations continues in the modern age.

The second half of the quaternary Period was the time of intensive fragmentation of the sloping plains surrounding Greater and Lesser Caucasus with the formation of unique terrain that also includes modern day diluvial and diluvial-proluvial sloping foothill plains.

It is obvious that marine transgression and regression of the Caspian basin did not take place without impact on the territory exposed to the influence of these phenomena. Variations of the Caspian Sea level were accompanied by migration of perennial and ephemeral streams and their deltas, following the moving shoreline. Most of these streams no longer exist. They developed a system of dry deltas now blocked off by diluvial-proluvial sediments.

According to V.A. Kovda, N.I. Bazilievich and L.E. Rodin (1956), the process of formation of dry deltas of the Kopet Dagh foothill plains led to the deterioration of the conditions of the subsurface flow in their peripheral region, causing the evaporation of water solutions and the increase of mineral content of groundwaters due to the inflow of salts from the mountains. This phase was marked by the salinization of meadow and meadowswamp soils which formed under the impact of saline capillary solutions rising from relatively shallow groundwaters. The development of soil salinization and alleviation processes was reflected in the formation of numerous saline accumulations in the sedimentary rock mass.

New regression of the ancient Caspian region further led to the decrease of groundwater levels and the elimination of the impact of the capillary fringe on soil-forming processes. In consequence, dried and arid ancient alluvial-delta, proluvial and foothill plains lost their hydrophilic meadow and meadow-swamp vegetation and entered the desertification phase. Now these plains are entering a new cycle of their development: a certain fragmentation of the surface and desalination. However, desalination processes occur very slowly in dry climate conditions. According to the data given below, salic horizons commonly lie very close to the surface. In consequence, significant amounts of salts come to the surface even nowadays during the migration and evaporation of capillary-volatile moisture, which makes its way into the soil during rains and formations of diluvial streams and affects current soil-formation processes.

Salinization of the diluvial and diluvial-proluvial soils of the foothill plains of Azerbaijan is largely maintained due to the continuous inwash of salts from the mountains by effluent streams. All these phenomena will be analysed in detail below.

Geomorphology of the lowlands of Azerbaijan, including diluvial plains is described in a series of works (Geomorfologiia Azerbaidzhana, 1959; Volobuev, 1948, 1959; Kolopotovsky, 1949; Prikolonsky, 1932; Abduyev, 1956; etc.). These materials and our own direct observations show that the diluvial plains geomorphology of certain areas of the Azerbaijan Republic’s lowlands differs in a unique manner.

In the Shirvan Steppe, the diluvial-proluvial plain extends to the south-east from the Karamaryam ridges to the Hajigabul Lake. In the south, it is bordered by colluvial fans of rivers and an alluvial plain near Aghsu and by the Karasu metamorphic depression near Kazi Mahomed. The plain’s terrain is conditioned by the activity of the diluvial and proluvial agents, which created a varied surface presentation and conditioned the sorting and redistribution of drift material. The diluvial-proluvial plain of the Shirvan Steppe is characterized by the presence of rather numerous colluvial fans of temporary ravine streams, more pronounced in some places and less in others.

The elevated area of this plain contains a series of mud volcanoes. The most pronounced among them is the Akhtarma-Pashaly Volcano. The terrain they created has close genetic connection with the young anticline fold of the piercement type and its morphology is quite unique.

Products of mud volcanoes affect both the territory they occupy and the adjoining lowlands. This influence is conditioned by the chemistry of the products of mud eruptions in the form of mud volcano breccia (Fig. 3). The latter is salinized by easily soluble chlorine and sulphuric salts. The ancient marine terrace, which forms the upper layer of the ancient Caspian deposits, according to V.A. Klopotovsky (1949), is also well-defined here.

The outermost south-western part of the Kur-Araz lowlands is occupied by South-East Shirvan, a foothill region in the form of a sloping plain situated at the foothills of Gobustan.

The characteristic feature of South-East Shirvan is the presence of small hills called brachyanticlines (double plunging anticlines) with mud volcano outbursts that form mud fields and rather powerful streams of mud breccia on peaks and slopes. Such brachyanticline hills comprise the smooth slopes of the Kyurovdagh and Babazanan ridges, with absolute elevation of 40-150 m. These slopes were the direct object of our research. The core of these massifs was formed by Pliocene and quaternary deposits. The eastern slopes of these ridges are predominantly low gradient, while the western slopes are steep and scarred with ravines that form a typical look of badlands. Here, sharply dissected badland forms blend with argillic karst-like conical depressions, underground caves, passageways and galleries. Alkaline wind erosion pits are located along the axis of the hills in the exit points of saliferous tertiary rocks. In places, the foothill plain has completely isolated mud volcanoes (Kiursanga, Durovdagh and others), which reach 40-120 m in height. Their hills are steep and heavily scarred by ravines. Argillic karst-like forms are widely spread on these hills.

The diluvial-proluvial sloping plain of the Garabagh Steppe is characterized by a gently rugged topographic form. It occupies a large territory of the steppe. This terrain is dissected by pits and ravines in parts and also has flat ravine colluvial fans. According to F.P. Savarensky (1929) and V.A. Priklonsky (1932), the highest foothill zone of the Garabagh Steppe has ancient terraces, also highlighted on the map of B.F. Dobrynin (1948).

To the west, the Mughan lowlands transform into the Ganja-Gazakh plains. Based on geomorphology, geological structure and history, N.G. Minashina (1958) subdivided the Ganja-Gazakh plains into the following regions: 1) region of predominant erosion,2) region of ancient accumulation and predominant recent erosion, 3) region of predominant recent accumulation.

The region of predominant erosion constitutes the most ancient sections of the terrain that have undergone elevations and deformations as a result of tectonic, magmatic and erosive processes starting from the late Cretaceous Period. The region of ancient accumulation includes the upper part of the ancient Ganja-Gazakh sloping plains, composed of thick apron-pebbly mountain river deposits. The region of predominant recent accumulation is situated in the depression that formed between the Greater and Lesser Caucasus as a result of a downfold. In addition to river streams, the diluvial-proluvial streams flow here, bringing with them a lot of fine silt.

The foothill plain of the Mil Steppe lies at an elevation of 150-200 m and gradually descends to 0 m. It constitutes a sloping plain with a system of chiselly formations. The latter, acquires a radial configuration in some sections, tracing the following series of small colluvial fans. Each of these fans or their combination is connected to the arid valleys, located in the submontane and low mountain region of Garabagh, which gives reason to consider this sloping plain a diluvial-proluvial plain.V.R. Volobuev (1948), V.V. Egorov, V.S. Muratova and G.V. Zakharina (1951) distinguished a diluvial-proluvial plain in the Mil Steppe, excluding the colluvial fan of Araz and Karkarchay. They also noted four ancient Caspian terraces within its territory at 100-160 m, 50-100 m, 20-50 m and 0-20 m, which were for the most part subsequently covered by the diluvial-proluvial blanket.

The diluvial-proluvial plain in the Mughan Steppe occupies its southern and southwestern parts, situated along the mountain slopes (from 75 to 23 m of absolute elevation). The top part of the plain is characterized predominantly by steeper slopes and the lower part by small ones. A big role in the formation of the South Mughan terrain, just as with other foothill plains of the Kur-Araz lowlands, was played by the fluctuations of the Caspian Sea level, which were responsible for its multiple transgressions and repressions, accompanied by the formation of more or less clearly defined terraces and the accumulation of special coastal (lagoon) type sediments (Volobuev, 1959).

The genesis of the sloping plain of South Mughan is diluvial-proluvial. It is bordered by the Araz colluvial fan in the north and the Bolgarchay River colluvial fan in the south. The latter in particular consists of an alluvial fan and a diluvial trail. The 15 m horizontal plane may serve as the borderline between these two parts. The rupture in the surface slope is confined to this plane and it is steeper higher up and flattens down below. This rupture matches one of the new Caspian terraces. The clear cliff of the Novokhvalyn terrace, with a wave-cut dune levee running approximately at 0 m, clearly delimits the diluvial-proluvial section of the foothill plain from the alluvial plain located below.

The north-eastern territory of the Azerbaijan Republic contains lowlands that are a fragment of narrow foothill plains adjoining the Caspian Sea and encircling the foothills of the eastern end of the Great Caucasus. This flat, slightly sloping plain, hereafter referred to as the Siyazan-Sumgayit massif, stretches from the north-west to the southeast. The lowland coast of the Caspian Sea reaches a width of 4-6 km in its south-eastern part and runs as wide as 12 km to the north-west, forming the Gilaziskaia Spit. Genetically, the Siyazan-Sumgayit massif is closely related to the adjoining mountain system that surrounds the lowlands from the north-west. The terrain of the mountainous part of the massif is influenced predominantly by tectonics. In the region of Altiaghaj, the divides are synclinal in structure. In the lowlands of the mountainous part of the massif, aridity of the climate contributed to the development of arid erosion processes. Badlands and argillic karst-like rock are common on the slopes of these valleys. There are also widespread landslides and mud avalanches. Some valleys have unique terrain on fragmental talus deposits of slopes: the earth pyramids. The dividing areas of the ridges are smoothed out and constitute the remainders of abrasion and erosion suppression of denudation. The Beshbarmag Mountain has typical Dibrarsk calciferous cliffs. The river valley openings have a series of low, medium and, sometimes, high accumulative, accumulative-erosive and denudation terraces.

In fact, the Siyazan-Sumgayit massif was formed by quaternary deposits that have blocked the deeply submerged Tertiary and Mesozoic rock. The latter come out to the surface only in the anticline hills of the Gilaziskaia Spit in the form of flat abrasion ridges (Geomorfologiia Azerbaidzhana, 1959). The lowlands system is dominated by accumulation processes (alluvial-proluvial, diluvial, marine and Aeolian). It is a sloping terrace valley, formed by low accumulative-abrasion New Caspian and Upper Khvalyn terraces of the Caspian region. The lowlands are somewhat dissected by steep, but shallow intermittent and ravine-like river beds with one or two terraces. River (Valvalachay, Gilgilchay) sediments are formed from chalk deposits and are rich in carbonate rock. Therefore, the soil mantle becomes more calcareous from the north-west to the southeast. The interstream areas have shallow erosion dissection.

The Siyazan-Sumgayit massif is covered by loam on the surface. It is of alluvial-proluvial and diluvial origin in the foothill area. These sediments rest on the grit of extensive colluvial fans superimposed on marine terraces. This massif is distinguished by the presence of the remainders of numerous small and large lagoons. Large ancient lagoons are completely dry, for the most part, and constitute alkaline spaces nowadays. These depressions are now under water only during rain season, when they collect the waters of surface discharge. Such lagoons are found near Sovietabad village, between the Sitalchay and yashma stations and near the city of Sumgayit. The massif has low mud volcanoes with mud springs. Some of these volcanoes are active and their discharge flows to the surrounding areas. The mud volcanoes near the Zorat settlement (on the Beshbarmag parallel) and the Sitalchay village.

Thus, based on the foregoing it is clear that, in the foothill area of Azerbaijan, the diluvial-proluvial plains have their unique characteristics in each massif, along with the geomorphologic features that they share.

Groundwaters. The first general research on groundwaters of the lowlands of Azerbaijan, in particular the Kur-Araz lowland, was conducted by F.P. Savarensky (1929, 1931) and V.A. Priklonsky (1932, 1946). Most recently, the knowledge about groundwaters has been enhanced and detailed in the work of a series of scientists (Volobuev, 1946; Davydov, 1953; Suleymanov, 1955, 1961; Israfilov, 1956, 1961; Abduyev, 1958; Bibarsova, 1958; Tairov, 1958; Girkina, 1960; Gavrilov, 1961; Vaidov, 1961, Mamedyarov, 1961; Muratova, 1962 and others). Maps of the level, mineral content and composition of groundwaters were created based on the new research conducted by the staff of the Azerbaijan Geology Bureau (Azgeologoupravlenie) and the Institute of Geology at the Academy of Sciences of Azerbaijan SSR.

These maps show that groundwaters in the diluvial plains either do not exist or occur at such depth that their capillary fringe does not reach the soil layers. However, the occurrence of these waters has particular characteristics in some massifs.

In the diluvial plains of the Ganja-Gazakh massif, the permeability capacity of soils decreases progressively away from the foothills due to the transition from rudaceous rock to more argilliferous rock. This conditions the decreased sloping of the groundwater level in the same direction. In general, the massif is subdivided into eight hydrogeological subregions based on the depth of groundwater occurrence (Suleimanov and Musaev, 1961). In the diluvial-proluvial plains of the western part of the massif, groundwaters occur mainly at a depth of more than 10 m.

Extensive areas are characterized by groundwater occurrence at a depth of over 20 m. Deep groundwaters are relatively widespread in the central area of the massif. The characteristic of the outermost south-eastern part of the massif is that there are no groundwaters in quaternary deposits, where tertiary rock is directly covered by the diluvial-eluvial deposits mantle.

Groundwaters of the diluvial plains of the Ganja-Gazakh massif are nearly fresh waters. Their mineral content varies between 0.6-6 g/l. The waters are composed of calcium hydrocarbonate.

The surface of groundwaters in the diluvial plains of East Shirvan is of a specific nature. Here, in the area of the Padar depression, the groundwater contours form an internal drainage basin, locking at depths of 14 to 20 m. The hydrologic terrain is marked by a trough-shaped depression. Groundwater contours are extremely open. They expand towards the east, remaining open towards Lake Hajigabul (Suleimanov, Musaev, Israfilov, 1961).

Research of L.A. Girkina (1960) showed that there were no groundwaters found during drilling of up to 18-20 m in most of the diluvial plains of East Shirvan. Relatively shallow levels of groundwaters, approximately 9-16 m from the earth surface, were found only in the lowest part of the diluvial slopes. The mineralisation of these waters is high, varying within 21-50 g/l. In rare cases, waters have low mineral content of about 2-3 g/l. Salt composition of these waters: hydrocarbonate, sulphate, chloride, calcium and sodium.

Salinity of the groundwaters of this massif is conditioned by their recharge from the diluvial-proluvial streams, flowing down the slopes with heavily saline soils (Lengebiz, Big and Small Harami ridges).

Groundwaters of the diluvial plains of South-East Shirvan (regions of Durovdagh, Kyurovdagh, Babazanan ridges) occur at approximately the same level. The depth of groundwaters in the apron zone of diluvial plains usually reaches 8-10 m from the earth surface. Groundwaters delve in strongly towards the middle and upper zones of the diluvial slopes (as much as 15-20 m and more from the land surface). Their mineral content here is relatively high, fluctuating within 1.5-16.7 g/l. Overall mineralisation increases towards the centre of the steppe. Salt composition is dominated by sodium chloride, which constitutes up to 80% of the total salt in some places.

According to the data of V.A. Priklonsky (1932) and G.U. Israfilov (1956, 1961), the soil basin of the diluvial-proluvial plains of the Mil-Garabagh massif have a sloping surface profile with a common incline to the northeast towards the continuous incline of the land surface. Groundwaters of this massif occur below 10-20 m from the land surface. This zone of groundwaters runs along the borderline, where the sloping plain is transferred to a flat plain of the Mil-Garabagh massif.

S.I. Dolgov and G.V. Zakharina (1958) provided data for the groundwaters and soil moisture conditions for the diluvial plains of the Mil Steppe. In the well, located 500 m above the Orjonikidze Canal, the groundwaters occurred at 12.5 m in 1950. From july 1950 to December 1952 inclusively, the groundwaters rose by 1.5 m. According to G.V. Zakharina (1958), the rise in this section was conditioned by the backwater and the groundwater recharge from the Orjonikidze Canal in the canal area of the diluvial plain. Some rises and drops of the water levels in wells are conditioned by the rises and drops of water in the canal. Eluvial moisture conditions are formed in the soils of the upper part of the diluvial plains, with significant depth of groundwaters that exceeds 12 m. Precipitation percolation is mostly limited to the 50 cm thick upper layer (rarely reaching depths of 100-150 cm), where moisture is 12-15%. Relatively stable soil moisture of about 8-10% is detected lower in the profile. This corresponds to the value of film or even hygroscopic moisture in argilliferous soils.

V.S. Muratova (1962) summarised hydrological data, obtained as a result of the works of the expedition of the Azerbaijan Geology Bureau in 1946-1947 and Kur-Araz expedition of the Soil Institute of the Academy of Sciences of SSSR in 1949, and created diagrams of the depth of occurrence, mineral content and chemical composition types of groundwaters. Based on these materials, the diluvial plains of the Mil Steppe (above the Orjonikidze Canal) have groundwaters with less than 2 g/l of mineral content. According to their chemical composition, they are part of a mixed type with the predominance of sodium hydrocarbonate. According to V.S. Muratova, the capillary moisture does not reach soil horizons here and these soils develop unaffected by groundwaters.

Groundwaters of the lower part of the diluvial plains of the Mil Steppe occur at 4-7 m depths. In this case, capillary-pellicular water currents penetrate the lower section of the root habitable layer. There is no salt accumulation in the surface horizons; in deep horizons the salts accumulate due to subsoil evaporation and transpiration.

It is noteworthy that on the strip of land commanded by the Orjonikidze Canal, prior to its commissioning, groundwater occurrence was deep, at 14-15 m (Nojin, 1929). Upon commissioning of the canal, groundwater levels rose dramatically (up to 2-4 m from the surface), which led to salinization of a significant part of the territory, where the mineral content of groundwaters fluctuated within 2-5 g/l. Due to the fact that groundwaters of this part of the plain are currently (starting from 1952) regulated by a drainage network, they do not play any role in the process of salt accumulation (see part two of this book).

Groundwaters of the Siyazan-Sumgayit massif have not been studied much. Based on the depth level of groundwaters, N.S. Kuloshvili (1948) divided this massif into two very different sections. The first section, located closer to the sea, is a terrace of the ancient Caspian area. within the diluvial-proluvial plains of this section, groundwaters occurred at a depth of 6-10 m from the land surface. Groundwater exits composed of fractured limestone in form of springs are found along this high, steep Beshbarmag cliff near the apron of the slopes. This part of the diluvial-proluvial plains contains a relatively high stand of groundwaters. In the assumption of S.G. Aristov (1957), it is related to the intensive discharge of groundwaters that circulate in the original limestone of the Cretaceous Age. Due to the steep cliff of the original bedrock along the contact with the stream load, the waters from the limestone fractures get into the mantle deposits, forming a free horizon of groundwaters in the latter. To the southeast of the Zorat station, water occurred at a depth of 7.5 m; in the section adjacent to the middle zone of the diluvial-proluvial plains the groundwaters were found at a depth of 8-9 m.

In the region of the Gilazi sand and gravel quarry the underground water emerges in form of a concentrated spring. water is slightly mineral to the taste. To the southeast of the Gilazi quarry the depth of groundwaters in some sections of the coastline varies within 5-7 m. In other sections of the first area, groundwaters have not been found up to a depth of 7 m.

The second section is an elevated part of the diluvial-proluvial plains, which is characterized by the absence of groundwaters in the rock mass of the Upper Cretaceous and Tertiary age. In the area of the development of the indicated rocks, there is only isolated groundwater outflow in form of ascending springs, which resemble mud volcanoes. The yashmin section of the diluvial-proluvial plains is particularly typical in this regard. Active mud volcanoes are found at the top of a small hill.

Groundwaters lie deep in the Boghaz plain of the Siyazan-Sumgayit massif. In the southwest part of this plain the depth of their occurrence is 10-16 m. In the southern half of the north-eastern part of the plain, they are located closer to the land surface. In the section between Nasosny settlement and the coastline, groundwaters are found at a depth of 6-8 m. Annual fluctuation range is 1 m.

In his review of the influence of groundwaters on the soil formation process in the Boghaz plain N.A. Kachinsky (1937) concluded that, at present time, groundwaters do not play any role in the capillary supply of surface soil horizons with water and salts. He justified his conclusion, in particular, by soil moisture data. These data show that soil moisture in deep soil horizons (cross-section depth of 4 m) stays within the limits of one and a half of the maximum water-absorbing capacity.

Groundwaters of the Siyazan-Sumgayit massif are mineralised to various extents, whereby mineral content changes from north to south. Least mineral waters are found in the section near Beshbarmag cliff. Heavily mineralised waters are the subsurface waters of original bedrock. Groundwater mineral content varies within 1.8-5.6 g/l in the upper zone of the diluvial plains and within 6.8-9.2 g/l in the apron.

Thus, hydrogeological and hydrochemical properties of the diluvial plains of Azerbaijan are indicative of fairly deep groundwater occurrence here at present. It is known that the extent of the impact of groundwaters on soil depends on the depth of their occurrence. Salt accumulation in the upper soil horizons is affected by the groundwaters that reach ‘critical depth’. Based on the data of many researchers (Volobuev, 1946; Filosofov, 1948; Egorov and Zakharina, 1956; Bibarsova, 1958; Abduyev, 1958; Muratova, 1962), the depth of less than 1.75 - 2.5 m from the earth surface is the critical level of groundwaters for soils in Azerbaijan. Therefore, it is obvious that groundwaters everywhere in the diluvial plains occur below the critical level.

Taking into account that in regions where diluvial soils are common, groundwaters mostly occur at depths of more than 10 m (rarely rising to 5-8 m) below the earth surface with the annual fluctuation range of 1 m and a capillary fringe of about 60-100 cm, it may be said with surety that groundwaters do not play any role in recent soil salinization in the diluvial plains of Azerbaijan.

In addition to the terrain structure, the absence or very deep occurrence of groundwaters in the zone with the expansion of diluvial soils is also caused by the climatic conditions of the studied region. Here, the climate is subtropical, but very dry.

According to E.M. Shikhlinsky (1958), average annual temperature is 14-15 Co and average annual precipitation is 300-350 mm. Precipitation is distributed very unevenly throughout the year, with maximum precipitation in spring and autumn and minimum in summer (sometimes 0 mm per month). There is a lack of atmospheric moisture most of the year. Relative air humidity is rather high (average annual - 73%, summer - about 60%, winter - about 84%). But even this precipitation is far from being fully used to water the soils due to low permeability of the diluvial soils and the development of surface runoffs during rainfalls.

Our field research showed that wetting of soils of the diluvial slopes by rain rarely reaches 60-80 cm. The regular wetting of soils of the foothill plains and their subsequent significant dehydration promotes an intensive rise of salts with capillary current to the surface horizons. A salt migration horizon can always be observed in the profile of the studied soils above the salt accumulation layers.

Strong, predominantly northern winds are typical for the Siyazan-Sumgayit massif. Average speed of the north wind, which is rather cold, strong, dry and dusty in this region, is 6-7 m/sec. winds often reach 20-40 m/sec. North winds usually last two or three days and sometimes longer. Sharp drops in temperature in a short time are typical for north winds. These winds severely dry out the soil and have detrimental impact on vegetation.

In the coastal foreland, the average annual wind speed varies between 8.6-9.4 m/sec. winds cause the over-blowing of sand dunes, dispersion and depositing of sand and clay particles. Strong winds are typical also for other diluvial-proluvial sloping plains of Azerbaijan.

Therefore, the climatic conditions are one of the most significant factors that promote heavy salt accumulation in soils, the development of semiarid vegetation, etc. Among the variety of arid vegetation, Cargana, Cargana-Artemisia, Artemisia and ephemeral plant genera are most widespread in the majority of the regions we studied. Artemisia-Poa, Artemisia-Capparis and Capparis vegetation is widespread in the diluvial and diluvialproluvial plains of the Mil Steppe. Ephemers usually do not occupy a specific area and are found among sagebush and saltwort plants.

Sagebush, predominantly Artemisia Meyeriana and Artemisia maritima, usually cover higher areas of the terrain, but isolated spots of them can also be found in other areas, especially where solonetz-like soils are common. Sagebush is widespread and well developed in general in the foothill zone. There are many ephemers and various lichens in the Artemisia genus.

Most common among saltwort plants are Suaeda microphylla, Salsola dendroides, and Salsola ericoides. These plants are characterized by good development, open growth, and the ability to take root rather well and grow relatively fast.

Saltwort vegetation is common on the diluvial slopes of Azerbaijan. In some places it forms a continuous thick cover, but often it is found mixed with other plants, especially Artemisia and ephemers. These plants are common not only on the lower elements of the terrain, but also in relatively high sections. They are usually found in soils that are saline in general, but desalinated at the top.

A general characteristic of the plants on the diluvial slopes of the Azerbaijan Republic is their adaptiveness to dry conditions and salinization. This is reflected in the deep penetration of the root systems, relatively limited foliage, high osmotic pressure and heavy mineral content of cell sap (enchylema). Some types have the ability to excrete excess salts through their leaves. The participation of the vegetation of this massif in salt migration processes will be analysed in more detail in Chapter V.

An analysis of the natural conditions of the described massifs showed that the complex history of landscape formation in the diluvial-proluvial sloping planes of Azerbaijan resulted in a large variety of vegetation in the soil mantle. S.I. Tyuremnov (1927) and S.A. Zakharov (1932), who laid the foundation of the systematic study of soils in the Kur-Araz lowlands, identified all serozem (grey soil) soil formations as the zonal type. In recent times, research by several scientists (Aliyev, 1948; Volobuev, 1951, 1953; Salaev, Zeynalov, Sharifov, 1955, and others) confirmed this opinion. However, A.N. Rozanov (1956) named the grey-brown soil as the zonal soil of the Kur-Araz lowlands. According to V.R. Volobuev (1953), the distinctiveness of the serozem soils of the Kur-Araz lowlands, distinguished by A.N. Rozanov (as compared to Middle Asian), such as the relatively high clay content, brown colour, etc., is most likely the reason for the separation of the East Transcaucasia province of the serozem soils.

Soils with genuine alkaline characteristics, such as the foliage structure of the surface horizon and the prism-like, compactness and brownish colour of the second horizon, are common among serozem soils in the plains of Azerbaijan. In the studies of the history of the formation of soils with these characteristics, V.R. Volobuev (1953) found, that in the past, they underwent a rather lengthy stage of salt-meadow regime, replaced by the stage of dehydration and desalination. Alkaline properties in morphology evidently reflect the subsequent stage of alkalinisation. S.I. Tyuremnov (1926) called soils with these properties solonetz-like serozem. In his map of 1930, A.S. Zakharov showed grey (serozem) and grey-brown soils in the Kur-Araz lowlands. Moreover, in many cases he combined grey-brown soils with brown soils, considering them to be the further evolution of serozem soil. According to A.S. Zakharov, the morphologic and chemical differentiation of grey-brown soils is more complete than that of serozems.

In his description of the soil in the Boghaz plain of Azerbaijan SSR, I.A. Shulga (1938) noted that neither such typical soils as serozem, nor brown soils existed there, although the characteristics and the properties of both of those soils were found in the soils indicated by him.

Some of these soils, to a smaller or larger extent, have definitive properties that characterise them as grey-brown type soils (transitional between grey soils and serozem) with the tendency towards brown soils; others have the features of the same (grey-brown) soil type, but tending more towards the serozem type. According to I.A. Shulga, all features of both soil versions sufficiently comply with the properties specified for grey-brown soils in the literature, in particular taking into consideration the adjustment due to the relatively young age of the soils in the Boghaz plain. Grey-brown soils are characterized by known alkalinity (morphologically manifested in the relative density of the illuvial horizon and in the degree of profile differentiation).

According to V.R. Volobuev (1953), just as the soils of the Kur-Araz lowlands that most closely resemble the serozem type are called serozem-like soils, these soils, undergoing the process of formation into semiarid subtropical soils and currently in the alkaline stage, established in the specific morphological characteristics (somewhat leafy structure of horizon A, vaguely prism-like structure of horizon B1, somewhat brownish in horizon B and presence of illuvial-carbonate horizon C), may be called alkaline serozem (grey-brown) soils.

Solodization is another distinctive feature of the specified soil formations in the diluvial plains of Azerbaijan.

V.V. Akimtsev (1937), A.S. Preobrazhensky (1935) and V.R. Volobuev (1953) devoted much attention to the study of solodization in the soils of the Kur-Araz lowlands. while describing the phenomenon of solodization of these soils, V.V. Akimtsev took into consideration mainly the morphological properties, then the distribution along the profile of fine-grained textural elements, hummus and carbonates.

V.R. Volobuev also attributes the lightening of the upper soil horizon, observed in several places in the Kur-Araz lowlands, to solodization, and explained it by the destruction and desalination of organic matter from the upper part of the soil profile. V.R. Volobuev (1953) also noted the migration of fine-grained elements along the soil profile from the top horizons to the underlying horizons. In many cases, these fine-grained elements are enriched by silt of the layer, found at some depth. V.R. Volobuev (1953) believed that this phenomenon did not contradict the concept of K.K. Gedroits, who ruled out the destruction of the mineral part of the absorbing complex in carbonate soils, because mineral fine-grain particles migrate under the ‘protection’ of organic colloids, which are more likely to be destroyed during solodization. This is confirmed by the fact that there is a dark film on the surface of the structural elements of the illuvial horizon of somewhat solodized soils, which is more likely interpreted to be an organic-mineral substance.

According to V.V. Akimtsev (1937) and A.S. Preobrazhensky (1935), the relative share of absorbed magnesium in solodized soils increases in the composition of the absorbed bases.

According to V.V. Akimtsev and V.R. Volobuev, the reason for distinguishing the solodized soils in a number of zones of the Kur-Araz lowlands (dry forest steppe, brown-chestnut, serozem) was also the excess of silicon dioxide in alkaline extracts (5% KOH), as compared to that, calculated using the formula Al2O3x2SiO2. At the same time, according to the assumptions of V.R. Volobuev (1953), solodization must have gone further to the stage of complete removal of absorbed sodium from ancient elements of the terrain, both as a result of exchange reactions and its increase with the fine-grain particles that migrate deeper inside the soil profile.

Therefore, based on the above, it is evident that in most cases grey-brown and serozem soils, alkalised to a different extent and, sometimes, solodized are most common in the foothill plains and, especially, the diluvial plains of Azerbaijan. Nonetheless, these soils are not widespread on the whole territory of the diluvial plains. They mainly occupy more ancient and elevated elements of the terrain, i.e., the upper and middle part of the diluvial slopes where Artemisia, Cargana-Artemisia and ephemeral vegetation predominate. Their local components are younger in the lower parts of the diluvial slopes, i.e. in the apron zone.

In some cases, chestnut soils, developed mainly on higher and more ancient elements of the terrain, are typical for the diluvial plains of Azerbaijan.

As we will describe in detail hereafter, when surface discharge increases, the diluvial plains are characterized by extensive flooding of the areas that dry out relatively quickly and undergo a dewatering stage. Both the duration and the extent of rehydration of soils by this discharge are conditioned to a large extent by the geomorphologic conditions of the diluvial plains. The diluvial slopes of accumulative and sloping plains have a different hydrologic regime. Sloping plains are subject to less sustained and weaker wetting, whereas accumulative plains often stay flooded with large masses of water for a long time. Therefore, the horizontal migration by stratified surface discharge, which promotes the formation of mainly primitive and often takyr-like or takyric soils, is observed in addition to the vertical migration of substances during surface flooding in the accumulative plains. These soils occupy relatively large areas in the apron part of the diluvial plains of Azerbaijan.

Thus, data from the literature and the results of our own research demonstrate that the diluvial plains of Azerbaijan are characterized by grey-brown and serozem soils with various degrees of alkalinity and sometimes solodized with primitive varieties. Chestnut soils were identified in some diluvial plain massifs (in most ancient elements of the terrain).

CHAPTER 3

CHARACTERISTICS OF DILUVIAL SOILS AND THEIR GEOGRAPHY

In most cases, diluvial soils in Azerbaijan have a series of unfavourable properties due to the peculiarities of their genesis. Such properties as high salt content, high alkalinity, heavy texture, high density, relatively low degree of structure and porosity, water-retaining property of insignificant use for plants and relatively low permeability are typical for these soils. A rather significant and regular variation of these characteristics is observed within the diluvial hills and some massifs of the foothill plains. This enables us to specify the particular characteristics of a set of soil properties of clearly prominent local zones: upper (salt collection zone), middle (salt transit zone), lower (salt accumulation zone)3.

1. MAIN GENETIC CHARACTERISTICS OF SOILS