Soil Acidity

1 Soil Acidification and Alkalinization.- 1 Introduction.- 2 Definitions.- 3 Effects of Addition of Dissolved Strong Acid or Base.- 4 Internal Acid Production in Soils.- 5 Assimilation of Minerals by Biota.- 6 Redox Processes.- 7 Order of Magnitude of ?ANC by Various Groups of Processes.- References.- 2 Proton Sinks in Soil Controlling Soil Acidification.- 1 Introduction.- 2 Survey of Proton Sinks in Soil.- 3 Adsorption of Protons by Soil Constituents.- 4 Proton Consuming Dissolution Reactions.- 5 Secondary Reactions.- 5.1 Influence of Clay Minerals on Al-Speciation and Protonation of AlOH-Groups.- 5.2 Al-Saturation and pH Buffer Capacity of Clay Minerals.- References.- 3 An Ecosystem Approach to Soil Acidification.- 1 Implications of the Material Balance of the Ecosystem for Soil Acidification.- 2 Ecosystem Environment and Ecosystem Compartments.- 3 Can Ecosystem Theory be Based on Thermodynamic Laws?.- 4 A Mathematical Model of Terrestrial Ecosystems.- 5 Definitions of Acids and Bases in Soil.- 6 Inputs of Acids and Bases into Ecosystems.- 6.1 Deposition of Air Pollutants.- 6.2 The Role of Silicate Weathering.- 7 Input/Output Relations.- 8 Calculation of Proton Balances.- 9 State Variables of the Acid/Base Status of the Ecosystem.- 9.1 Buffer Ranges in Soil.- 9.2 Carbonate and Silicate Buffer Range.- 9.3 Cation Exchange Buffer Range.- 9.4 Aluminum and Iron Buffer Range.- 10 Assessment of Changes in Soil Acidity.- 11 The Temporal and Spatial Pattern of Soil Acidity.- 12 Interrelationship Between Ecosystem Functioning, Changes in Acid/Base Status of Soil, and Soil Development.- 12.1 Stable Ecosystems Close to Steady State.- 12.2 The Aggradation Phase.- 12.3 The Phase of Humus Disintegration.- 12.4 The Phase of Buildup of a Decomposer Refuge.- 12.5 The Phase of Podzolization.- 12.6 Krypto-Podzolization.- 12.7 Deacidification.- References.- 4 Influence of the Acid/Base Status on the Formation and Interactions of Acids and Bases in Soils.- 1 Introduction.- 2 Small Organic Acids in Soils.- 3 Macromolecular Acids in Soils.- 3.1 Humic Substances.- 4 Organic Bases in Soils.- 5 Influences of Organic Acids and Bases in Soils.- 6 Summary and Conclusions.- References.- 5 The Chemistry of Aluminium, Iron and Manganese Oxides in Acid Soils.- 1 Introduction.- 2 Aluminium Oxides.- 2.1 Soil Species and Their Solubility.- 2.2 Reactivity of Allophane and Hydroxyaluminium Interlayers.- 3 Iron Oxides.- 3.1 Forms and Occurrence.- 3.2 Solution Chemistry of Iron in Soils.- 3.3 Surface Chemistry of Metal Oxides.- 4 Manganese Oxides.- 4.1 Mineralogy.- 4.2 Solubility.- 4.3 Sorption.- References.- 6 Assessing the Solubilities and Reaction Kinetics of Aluminous Minerals in Soils.- 1 Introduction.- 2 Experimental Determination of the Stabilities of Aluminous Minerals.- 2.1 The Al2O3-H2O System: Aluminium Hydroxides and Oxyhydroxides.- 2.2 The Al2O3-SO3-H2O System: Aluminum Sulfate Minerals in Acid Systems.- 2.3 The Al2O3-SiO2-H2O System: The Aluminosilicate Clay Minerals.- 3 Kinetics of Aluminous Mineral Precipitation/Dissolution Reactions.- 3.1 Kinetics of Hydroxy-Aluminium Solids Formation and Dissolution.- 3.2 Kinetics of Aluminosilicate Mineral Formation and Dissolution.- 4 Interaction of Aluminous Mineral Stabilities and Reaction Kinetics in Soils and Other Terrestrial Systems.- 4.1 Acidification Response in Natural Waters and Soils.- 4.2 Watershed-Scale Weathering Phenomena, Rates and Models.- References.- 7 Nutrient Status and Toxicity Problems in Acid Soils.- 1 Introduction.- 2 Soil Acidity and Nutrient Status.- 2.1 Nitrogen.- 2.2 Phosphorus.- 2.3 Potassium.- 2.4 Calcium.- 2.5 Magnesium.- 2.6 Sulphur.- 2.7 Copper.- 2.8 Zinc.- 2.9 Manganese.- 2.10 Iron.- 2.11 Boron.- 2.12 Molybdenum.- 2.13 Silicon.- 3 Toxicity Problems in Acid Soils.- 3.1 Manganese Toxicity.- 3.2 Al Toxicity in Relation to Ca Level and pH.- 3.3 Al Toxicity and Soil Organic Matter.- 3.4 Al Toxicity, Soil Solution Ionic Strength, and the Effect of Soil Drying Cycles.- 4 Ion Activities in the Soil Solution: An Alternative Perspective to Soil Acidity Problems.- 4.1 Relationship of Nutrient Uptake to Chemical Potentials.- 4.2 Chemical Potentials and Root Response to Ca and Al.- 5 Concluding Remarks.- References.- 8 Effects of Soil Acidity on Plant Associations.- 1 Introduction.- 2 Effects of Single Factors.- 2.1 Concentration of Ca-Ions.- 2.2 Concentration of H-Ions.- 2.3 Concentration of Al-Ions.- 2.4 NH4/NO3 Ratio.- 3 Interactions.- 3.1 Interaction of Ca with H and Al.- 3.2 Interaction of the N-Form with H and Al.- 4 Conclusions.- References.- 9 The Transfer of Acidity from Soils to Surface Waters.- 1 Introduction.- 2 Acid Neutralizing Capacity in Water.- 3 Acid Neutralizing Capacity in Soil Solutions.- 4 Quantification of the Processes.- 5 Other Processes.- 6 Conclusions.- References.