Table Of ContentB. LTlrich M. E. Sumner (Eds.)
Soil Acidity
With 76 Figures
Springer-Verlag
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Prof. Dr. B. ULRICH
Institut fUr Bodenkunde und Waldernahrung
der Universitat G6ttingen
Btisgenweg 2
W-3400 G6ttingen, FRG
Prof. Dr. M. E. SUMNER
Department of Agronomy
University of Georgia
Athens. GA 30602, USA
The figure on the cover page represents the emission of acidity due to
sulfur dioxide and nitrous oxides on the area of the Federal Republic of
Germany from 1850 to 1980, expressed as annual emission density (kmo\
acid equivalents per ha and year). The horizontal line represents the pre
industrial acid deposition.
ISBN-I3: 978-3-642-74444-0 e-ISBN-I3: 978-3-642-74442-6
DOl: 10.1 007/978-3-642-74442-6
Library of Congress Cataloging-in-Publication Data.
Soil acidity / B. Ulrich, M. E. Sumner, (eds.). P. cm. Includes bibliographical references and
index.
1. Soil acidity. I. Ulrich, B. (Bernhard), 1926- . II. Sumner M.E. (Malcolm E.), 1933-
S592.57.S65 1990 631.4'2-dc20 90-41845 CIP
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Preface
The acidification of soils is the consequence of natural processes occurring in
ecosystems. Usually soil acidification is a slow process. Acid soils are therefore
common in areas where ecosystem and soil development continued for long,
geological periods of time. Examples are the wet humic tropics and old land
surfaces. The driving force for the processes involved and the rate of soil
acidification remain unclear. With the advent of industrialization within the
last two centuries, enormous quantitites of acids have been mobilized and
released into the atmosphere, much of which have been deposited in terrestrial
ecosystems. In order to evaluate the importance of acid deposition for soil
acidification, the rate of natural and anthropogenically caused acid load in
soils had to be compared. In solving this problem, a new ecosystem-oriented
perspective on soil acidification was developed.
In some areas, the quantities of acid released and deposited have been large
enough to cause serious perturbations in the environment. Thus, many soils
throughout the world are or have become sufficiently acid to restrict the
growth and/or performance of roots of sensitive species at some locations in
the soil profile. As a result the productivity and longevity of both natural and
agricultural or other man-made ecosystems have been adversely affected. Un
doubtedly, soil acidity is one of the major factors regulating the species com
position of ecosystems and limiting crop production. As such it has attracted
the attention of soil scientists, plant scientists and ecologists since well before
the turn of the century. While the processes involved in soil acidification have
been relatively well understood for many years, there has been much debate
concerning the ecophysiological mechanisms by which soil acidity takes a toll
on plant growth. The involvement of hydrogen and aluminium as the prime
toxic agents has passed through more than a complete circle during this cen
tury. Today, it is generally accepted that aluminium is the main toxic factor in
acid soils. Considerable uncertainty exists, however, about the toxicity of dif
ferent species of aluminium in soil solution and the role played by other ca
tions and anions present in the soil solution in the detoxification of any
aluminium ions which may be present. Furthermore, in some soils, manganese
may also play an important role as a toxic agent.
In the voluminous literature on soil acidity, there have been a number of
books dealing with the topic and its consequences for plant growth. The pro
blem of acid deposition has created a new wave of research and new perspec
tives in the study of this important topic. In order to summarize the progress
VI Preface
made during the last decade, Commission II "Soil Chemistry" of the Interna
tional Society of Soil Science organized two Symposia at the XIIIth Interna
tional Congress in Hamburg in an attempt to remedy this situation. The first
Symposium dealt with Acid Sources and Acidification Processes while, in the
second, the Ecological Effects of Soil Acidification were discussed. As a result
of the great interest shown by the audience, it was decided to approach the
authors of the papers presented and to ask them to prepare full length reviews
with a view to publication in the form of a book. Most of the authors agreed
to cooperate, thus resulting in the completion and publication of this work.
The contents of the two Symposia have been re-arranged into a single volume
which deals with the subject matter in a logical sequence.
In the first Chapter, the processes of Soil Acidification and Alkalinization
are described and discussed as the backdrop against which the remainder of
the book is set. After defining the processes in terms of changes in the relevant
capacity factors, the sources of soil acidification are dealt with in a quan
titative manner. Thereafter, the Proton Sinks in Soil Controlling Soil Acidifica
tion are discussed in Chapter 2, mainly from the viewpoint of the reactions of
protons with inorganic compounds. The discussion focuses on what happens
when protons are added to a soil in terms of the equilibrium between the soil
solution and the solid phases involving adsorption, precipitation and dissolu
tion reactions. In the third Chapter, an Ecosystem Approach to Soil Acidifica
tion is presented as a scheme describing the phases in which an ecosystem ap
proaches stationary (stable) and non-stationary (aggradation or destabiliza
tion) states as a result of acid inputs which cause decoupling of the ion cycle.
Chapter 4 deals with the Influence of the Acid/Base Status on the Formation
and Interactions of Acids and Bases in Soils with respect to the occurrence of
simple and macromolecular organic acidic and basic substances. The base
status of the soil can influence the types and amounts of acids formed which,
in turn, affect the fertility status and some of the interactions which take place
in the soil. Knowledge of the Chemistry of Aluminium, Iron and Manganese
Oxides in Acid Soils is required for a clear understanding of the processes
which take place during acidification. This topic is discussed in detail in
Chapter 5, illustrating the important role which these poorly organized materi
als playas labile pools from which high concentrations of the elements can be
mobilized under appropriate conditions. The Solubility and Reaction Kinetics
of Aluminous Materials are assessed in Chapter 6. While much is known about
the thermodynamic aspects of these reactions, knowledge of the kinetics of
aluminium geochemistry remains primitive and there is a great need to in
tegrate solubility and kinetic models for a better understanding of natural
systems. Soil acidification results in changes in Nutrient Status and Toxicity
Problems which are discussed in Chapter 7. All the essential elements are con
sidered in relation to changes in soil pH and, in addition, a detailed discussion
of aluminium toxicity is presented. Thereafter, the Effects of Soil Acidity on
Plant Associations are discussed in Chapter 8. The adaptation of individual
plant species to acid soils conditions is explained on the basis of Ca/AI an
tagonism and the relative quantities of ammonium and nitrate in the system.
Preface VII
Finally, the mechanism by which the Transfer of Acidity from Soils to Surface
Waters is effected is discussed in Chapter 9. Acidity can only be transported
in the presence of anions such as sulphate, nitrate or chloride but can move
both as hydrogen ions or aluminium species.
Despite very busy schedules, the authors in this book willingly gave of their
time to prepare their contributions for which we as editors are most grateful.
In all cases, the manuscripts were examined by at least two reviewers con
sidered to be leaders in each particular field. We wish to thank all the reviewers
for their comments which have undoubtedly raised the quality of each con
tribution. We hope that this book will serve as a reference work and a point
of entry into the literature. For the most part, the contributions look forward
rather than backward and have focussed on many of the problems in the field
of soil acidity which still require further attention. In most cases, suggestions
for future research have been made and approaches for further advances have
been suggested.
In conclusion, we would like to thank all those who have made the suc
cessful completion of this book possible. In particular, we appreciate the will
ingness of the various authors, editors, publishers and secretaries of scientific
societies to grant permission to reproduce and use data and figures without
which the value of this volume would have been diminished. To our secretaries,
Fr. Hannelore Matzner and Mrs. Gail Jones and the Research Coordinator of
MES, Mrs. Nancy Barbour, who spent many hours helping with the prepara
tion of the manuscripts, thank you very much.
G6ttingen and Athens, June 1990 Bernhard Ulrich
Malcolm E. Sumner
Contents
Chapter 1 Soil Acidification and Alkalinization
N. van Breemen
1 Introduction
2 Definitions ............................................. . 1
3 Effects of Addition of Dissolved Strong Acid or Base ........ . 3
4 Internal Acid Production in Soils .......................... . 4
5 Assimilation of Minerals by Biota ......................... . 4
6 Redox Processes ......................................... . 5
7 Order of Magnitude of ~ANC by Various Groups of Processes 6
References .............................................. . 7
Chapter 2 Proton Sinks in Soil Controlling Soil Acidification
M. G. M. Bruggenwert, T. Hiemstra, and G. H. Bolt
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2 Survey of Proton Sinks in Soil ............................. 9
3 Adsorption of Protons by Soil Constituents .................. 12
4 Proton Consuming Dissolution Reactions .................... 16
5 Secondary Reactions ..................................... .21
5.1 Influence of Clay Minerals on AI-Speciation and Protonation
of AIOH-Groups ......................................... 21
5.2 AI-Saturation and pH Buffer Capacity of Clay Minerals. . . . . . . 25
References ............................................... 26
Chapter 3 An Ecosystem Approach to Soil Acidification
B. Ulrich
Implications of the Material Balance of the Ecosystem
for Soil Acidification ..................................... 28
2 Ecosystem Environment and Ecosystem Compartments ........ 29
3 Can Ecosystem Theory be Based on Thermodynamic Laws? ... 31
4 A Mathematical Model of Terrestrial Ecosystems ............. 32
5 Definitions of Acids and Bases in Soil ...................... 33
6 Inputs of Acids and Bases into Ecosystems .................. 35
x Contents
6.1 Deposition of Air Pollutants ............................... 35
6.2 The Role of Silicate Weathering ............................ 38
7 Input/Output Relations ................................... 38
8 Calculation of Proton Balances ............................ 46
9 State Variables of the Acid/Base Status of the Ecosystem ...... 50
9.1 Buffer Ranges in Soil ..................................... 50
9.2 Carbonate and Silicate Buffer Range. .. . . . . . . . . . . . .. . . . . . . . . 52
9.3 Cation Exchange Buffer Range ............................. 53
9.4 Aluminum and Iron Buffer Range .......................... 55
10 Assessment of Changes in Soil Acidity ...................... 56
11 The Temporal and Spatial Pattern of Soil Acidity ... . . . . . . . . . . 59
12 Interrelationship Between Ecosystem Functioning,
Changes in Acid/Base Status of Soil, and Soil Development ... 62
12.1 Stable Ecosystems Close to Steady State. . . . . . . . . . . .. . . . . . . . . 63
12.2 The Aggradation Phase ................................... 70
12.3 The Phase of Humus Disintegration ........................ 72
12.4 The Phase of Buildup of a Decomposer Refuge .............. 73
12.5 The Phase of Podzolization ................................ 73
12.6 Krypto-Podzolization ..................................... 74
12.7 Deacidification ........................................... 74
References ............................................... 75
Chapter 4 Influence of the Acid/Base Status on the Formation
and Interactions of Acids and Bases in Soils
M. H. B. Hayes
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
2 Small Organic Acids in Soils ............................... 80
3 Macromolecular Acids in Soils ............................. 84
3.1 Humic Substances ........................................ 85
4 Organic Bases in Soils .................................... 92
5 Influences of Organic Acids and Bases in Soils ............... 93
6 Summary and Conclusions ................................ 93
References ............................................... 95
Chapter 5 The Chemistry of Aluminium, Iron and Manganese
Oxides in Acid Soils
E. Paterson, B. A. Goodman, and V. C. Farmer
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
2 Aluminium Oxides ........................................ 98
2.1 Soil Species and Their Solubility ........................... 98
2.2 Reactivity of Allophane and Hydroxyaluminium Interlayers .... 104
3 Iron Oxides .............................................. 105
3.1 Forms and Occurrence .................................... 105
Contents XI
3.2 Solution Chemistry of Iron in Soils ......................... 107
3.3 Surface Chemistry of Metal Oxides ......................... 110
4 Manganese Oxides ........................................ 1 14
4.1 Mineralogy .............................................. 11 4
4.2 Solubility................................................ 116
4.3 Sorption................................................. 1 17
References ............................................... 120
Chapter 6 Assessing the Solubilities and Reaction Kinetics of
Aluminous Minerals in Soils
H. M. May and D. K. Nordstrom
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
2 Experimental Determination of the Stabilities
of Aluminous Minerals ........................ . . . . . . . . . . . . 126
2.1 The AlzOrHzO System: Aluminium Hydroxides
and Oxyhydroxides ....................................... 127
2.2 The AlzOrSOrHzO System: Aluminum Sulfate Minerals
in Acid Systems .......................................... 131
2.3 The Alz03-SiOz-HzO System:
The Aluminosilicate Clay Minerals .......................... 132
3 Kinetics of Aluminous Mineral Precipitation/Dissolution
Reactions ................................................ 135
3.1 Kinetics of Hydroxy-Aluminium Solids Formation
and Dissolution .......................................... 136
3.2 Kinetics of Aluminosilicate Mineral Formation and Dissolution 140
4 Interaction of Aluminous Mineral Stabilities
and Reaction Kinetics in Soils and Other Terrestrial Systems ... 141
4.1 Acidification Response in Natural Waters and Soils ........... 141
4.2 Watershed-Scale Weathering Phenomena, Rates and Models .... 143
References ............................................... 145
Chapter 7 Nutrient Status and Toxicity Problems in Acid Soils
M. E. Sumner, M. V. Fey, and A. D. Noble
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
2 Soil Acidity and Nutrient Status ............................ 150
2.1 Nitrogen ................................................ 152
2.2 Phosphorus.............................................. 153
2.3 Potassium ............................................... 155
2.4 Calcium................................................. 157
2.5 Magnesium .............................................. 158
2.6 Sulphur ................................................. 159
2.7 Copper.................................................. 161
2.8 Zinc .................................................... 161
XII Contents
2.9 Manganese .............................................. 161
2.10 Iron .................................................... 164
2.11 Boron ................................................... 164
2.12 Molybdenum ........................... . . . . . . . . . . . . . . . . . . 165
2.13 Silicon .................................................. 165
3 Toxicity Problems in Acid Soils ..... . . . . . . . . . . . . . . . . . . . . . . . . 167
3.1 Manganese Toxicity ....................................... 167
3.2 Al Toxicity in Relation to Ca Level and pH .................. 167
3.3 Al Toxicity and Soil Organic Matter ........................ 168
3.4 Al Toxicity, Soil Solution Ionic Strength, and the Effect
of Soil Drying Cycles ..................................... 169
4 Ion Activities in the Soil Solution: An Alternative Perspective
to Soil Acidity Problems .................................. 169
4.1 Relationship of Nutrient Uptake to Chemical Potentials ....... 171
4.2 Chemical Potentials and Root Response to Ca and Al .. . . . . . . . 173
5 Concluding Remarks ...................................... 175
References ............................................... 178
Chapter 8 Effects of Soil Acidity on Plant Associations
M. Runge and M. W. Rode
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
2 Effects of Single Factors ............................... . . . . 184
2.1 Concentration of Ca-Ions ................................. 184
2.2 Concentration of H-Ions .................................. 187
2.3 Concentration of AI-Ions .................................. 188
2.4 NH4/N03 Ratio .......................................... 191
3 Interactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 191
3.1 Interaction of Ca with H and Al ........................... 191
3.2 Interaction of the N-Form with Hand Al ................... 196
4 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
References ............................................... 199
Chapter 9 The Transfer of Acidity from Soils to Surface Waters
J.o.
Reuss
1 Introduction 203
2 Acid Neutralizing Capacity in Water ....................... . 203
3 Acid Neutralizing Capacity in Soil Solutions ................ . 207
4 Quantification of the Processes ............................ . 208
5 Other Processes ......................................... . 215
6 Conclusions ............................................. . 216
References .............................................. . 217
Subject Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 219
