DANIEL G. STRAWN, PHD, is a professor at the University of Idaho. HINRICH L. BOHN, PHD, is Professor Emeritus, at the University of Arizona. GEORGE A. O'CONNOR, PHD, is Professor Emeritus, at the University of Florida.

• Preface to Fifth Edition xiiPreface to Fourth Edition xiiiAcknowledgments xiv1 Introduction to Soil Chemistry 11.1 The soil chemistry discipline 11.2 Historical background 31.3 The soil environment 61.4 Chemical reactions in soils 151.5 Soil biogeochemical cycling 221.6 Soil chemical influences on food production 221.7 Soils and environmental health 231.8 Units in soil chemistry 261.9 Summary of important concepts in soil chemistry 262 Properties of Elements and Molecules 312.1 Introduction 312.2 Ionization and ionic charge 332.3 Ionic radius 332.4 Molecular bonds 362.5 Nature of water and hydration of ions 372.6 Ligands and metal bonds 402.7 Summary of important concepts of elemental and molecular properties 423 Characteristics of Chemicals in Soils 433.1 Introduction 433.2 Occurrence of elements in soils 433.3 Essential elements 473.4 Inorganic contaminants in the environment 493.5 Anthropogenic organic chemicals in the soil environment 533.6 Properties of the elements in soils 583.7 Summary of important concepts for chemicals in the soil environment 754 Soil Water Chemistry 774.1 Introduction 774.2 Thermodynamic approach to aqueous soil chemistry 784.3 Calculation of ion activity 834.4 Acids and bases 864.5 Gas dissolution 894.6 Precipitation and dissolution reactions 914.7 Cation hydrolysis 1024.8 Complexation 1054.9 Using software to predict soil solution equilibrium 1104.10 Kinetics of chemical reaction in soil solution 1114.11 Summary of important concepts for soil solution chemistry 1165 Redox Reactions in Soils 1195.1 Introduction 1195.2 Redox reactions in nature 1215.3 Basic approaches for characterizing soil redox processes 1265.4 The role of protons in redox reactions 1335.5 Redox potential limits in natural systems 1335.6 pe–pH diagrams 1355.7 Prediction of oxidation and reduction reactions in soils 1375.8 Redox measurement in soils 1415.9 Soil redoximorphic features and iron reduction in wetlands 1425.10 Nitrogen redox reactions in soils 1445.11 Summary of important concepts in soil redox reactions 1476 Mineralogy and Weathering Processes in Soils 1506.1 Introduction 1506.2 Common soil minerals 1526.3 Crystal chemistry of minerals 1536.4 Common primary mineral silicates in soils 1616.5 Minerals and elements in rocks 1646.6 Stability of silicates to weathering 1656.7 Chemistry of soil weathering and mineral formation 1676.8 Formation of secondary minerals in soils 1706.9 Soil carbonates 1746.10 Evaporites 1766.11 Soil phosphate minerals 1776.12 Sulfur minerals 1776.13 Time sequence of mineral formation in soils 1786.14 Measurement of soil mineralogy 1806.15 Important concepts in soil mineralogy 1847 Chemistry of Soil Clays 1867.1 Introduction 1867.2 Structural characteristics of phyllosilicates 1877.3 Relation of phyllosilicate structure to physical and chemical properties 1937.4 Detailed properties of phyllosilicates 1997.5 Allophane and imogolite 2047.6 Zeolite 2057.7 Oxide minerals 2057.8 Summary of soil clays 2108 Production and Chemistry of Soil Organic Matter 2148.1 Introduction 2148.2 Ecosystem carbon storage and fluxes 2178.3 Soil organic matter formation factors 2198.4 Organic chemistry of SOM 2218.5 Plant and microbial compounds input into soil 2238.6 SOM decay processes 2258.7 SOM composition and structure 2298.8 NaOH extraction of SOM 2318.9 Function of organic matter in soil 2338.10 Summary of SOM 2379 Surface Properties of Soil Colloids 2409.1 Introduction 2409.2 Permanent charge 2409.3 pH-dependent charge 2419.4 Point of zero charge of variable charged surfaces 2479.5 pH-dependent charge of SOM 2509.6 Hydrophobic regions of soil organic matter 2529.7 Summary of important concepts in soil surface charge 25210 Adsorption Processes in Soils 25510.1 Introduction 25510.2 Physical model of charged soil particle surfaces 26010.3 Cation exchange on soils 26610.4 Inner-sphere adsorbed cations 27310.5 Anion adsorption 28110.6 Adsorption of anthropogenic organic chemicals in soils 28610.7 Summary of important concepts for adsorption and desorption reactions in soils 29211 Measuring and Predicting Sorption Processes in Soils 29611.1 Introduction 29611.2 Adsorption experiments 29611.3 Predicting adsorption using empirical models 29711.4 Predicting adsorption using mechanistic models 30011.5 Rates of adsorption 30411.6 Reactive transport 30611.7 Surface precipitation 30911.8 Analytical methods for determining adsorption mechanisms 31011.9 Summary of important concepts for modeling surface reactions in soils 31112 Soil Acidity 31412.1 Introduction 31412.2 History of soil acidity 31712.3 The role of aluminum in soil pH 31812.4 Base cations in soil solutions 31912.5 Soil acidification processes 32112.6 Aluminum and manganese toxicity 32612.7 Plant nutrients in acid soils 32712.8 Managing acidic soils 32712.9 Summary of important concepts in soil acidity 32913 Salt-affected Soils 33113.1 Introduction 33113.2 Distribution and origin of salt-affected soils 33113.3 Characterization of salinity in soil and water 33413.4 Describing salt-affected soils 34013.5 Effects of salts on soils and plants 34113.6 Salt balance and leaching requirement 34313.7 Reclamation 34413.8 Summary of important concepts in soil salinity 345Questions 345Bibliography 346Index 347

DANIEL G. STRAWN, PHD, is a professor at the University of Idaho. HINRICH L. BOHN, PHD, is Professor Emeritus, at the University of Arizona. GEORGE A. O'CONNOR, PHD, is Professor Emeritus, at the University of Florida.

• Preface to Fifth Edition xiiPreface to Fourth Edition xiiiAcknowledgments xiv1 Introduction to Soil Chemistry 11.1 The soil chemistry discipline 11.2 Historical background 31.3 The soil environment 61.4 Chemical reactions in soils 151.5 Soil biogeochemical cycling 221.6 Soil chemical influences on food production 221.7 Soils and environmental health 231.8 Units in soil chemistry 261.9 Summary of important concepts in soil chemistry 262 Properties of Elements and Molecules 312.1 Introduction 312.2 Ionization and ionic charge 332.3 Ionic radius 332.4 Molecular bonds 362.5 Nature of water and hydration of ions 372.6 Ligands and metal bonds 402.7 Summary of important concepts of elemental and molecular properties 423 Characteristics of Chemicals in Soils 433.1 Introduction 433.2 Occurrence of elements in soils 433.3 Essential elements 473.4 Inorganic contaminants in the environment 493.5 Anthropogenic organic chemicals in the soil environment 533.6 Properties of the elements in soils 583.7 Summary of important concepts for chemicals in the soil environment 754 Soil Water Chemistry 774.1 Introduction 774.2 Thermodynamic approach to aqueous soil chemistry 784.3 Calculation of ion activity 834.4 Acids and bases 864.5 Gas dissolution 894.6 Precipitation and dissolution reactions 914.7 Cation hydrolysis 1024.8 Complexation 1054.9 Using software to predict soil solution equilibrium 1104.10 Kinetics of chemical reaction in soil solution 1114.11 Summary of important concepts for soil solution chemistry 1165 Redox Reactions in Soils 1195.1 Introduction 1195.2 Redox reactions in nature 1215.3 Basic approaches for characterizing soil redox processes 1265.4 The role of protons in redox reactions 1335.5 Redox potential limits in natural systems 1335.6 pe–pH diagrams 1355.7 Prediction of oxidation and reduction reactions in soils 1375.8 Redox measurement in soils 1415.9 Soil redoximorphic features and iron reduction in wetlands 1425.10 Nitrogen redox reactions in soils 1445.11 Summary of important concepts in soil redox reactions 1476 Mineralogy and Weathering Processes in Soils 1506.1 Introduction 1506.2 Common soil minerals 1526.3 Crystal chemistry of minerals 1536.4 Common primary mineral silicates in soils 1616.5 Minerals and elements in rocks 1646.6 Stability of silicates to weathering 1656.7 Chemistry of soil weathering and mineral formation 1676.8 Formation of secondary minerals in soils 1706.9 Soil carbonates 1746.10 Evaporites 1766.11 Soil phosphate minerals 1776.12 Sulfur minerals 1776.13 Time sequence of mineral formation in soils 1786.14 Measurement of soil mineralogy 1806.15 Important concepts in soil mineralogy 1847 Chemistry of Soil Clays 1867.1 Introduction 1867.2 Structural characteristics of phyllosilicates 1877.3 Relation of phyllosilicate structure to physical and chemical properties 1937.4 Detailed properties of phyllosilicates 1997.5 Allophane and imogolite 2047.6 Zeolite 2057.7 Oxide minerals 2057.8 Summary of soil clays 2108 Production and Chemistry of Soil Organic Matter 2148.1 Introduction 2148.2 Ecosystem carbon storage and fluxes 2178.3 Soil organic matter formation factors 2198.4 Organic chemistry of SOM 2218.5 Plant and microbial compounds input into soil 2238.6 SOM decay processes 2258.7 SOM composition and structure 2298.8 NaOH extraction of SOM 2318.9 Function of organic matter in soil 2338.10 Summary of SOM 2379 Surface Properties of Soil Colloids 2409.1 Introduction 2409.2 Permanent charge 2409.3 pH-dependent charge 2419.4 Point of zero charge of variable charged surfaces 2479.5 pH-dependent charge of SOM 2509.6 Hydrophobic regions of soil organic matter 2529.7 Summary of important concepts in soil surface charge 25210 Adsorption Processes in Soils 25510.1 Introduction 25510.2 Physical model of charged soil particle surfaces 26010.3 Cation exchange on soils 26610.4 Inner-sphere adsorbed cations 27310.5 Anion adsorption 28110.6 Adsorption of anthropogenic organic chemicals in soils 28610.7 Summary of important concepts for adsorption and desorption reactions in soils 29211 Measuring and Predicting Sorption Processes in Soils 29611.1 Introduction 29611.2 Adsorption experiments 29611.3 Predicting adsorption using empirical models 29711.4 Predicting adsorption using mechanistic models 30011.5 Rates of adsorption 30411.6 Reactive transport 30611.7 Surface precipitation 30911.8 Analytical methods for determining adsorption mechanisms 31011.9 Summary of important concepts for modeling surface reactions in soils 31112 Soil Acidity 31412.1 Introduction 31412.2 History of soil acidity 31712.3 The role of aluminum in soil pH 31812.4 Base cations in soil solutions 31912.5 Soil acidification processes 32112.6 Aluminum and manganese toxicity 32612.7 Plant nutrients in acid soils 32712.8 Managing acidic soils 32712.9 Summary of important concepts in soil acidity 32913 Salt-affected Soils 33113.1 Introduction 33113.2 Distribution and origin of salt-affected soils 33113.3 Characterization of salinity in soil and water 33413.4 Describing salt-affected soils 34013.5 Effects of salts on soils and plants 34113.6 Salt balance and leaching requirement 34313.7 Reclamation 34413.8 Summary of important concepts in soil salinity 345Questions 345Bibliography 346Index 347

DANIEL G. STRAWN, PHD, is a professor at the University of Idaho. HINRICH L. BOHN, PHD, is Professor Emeritus, at the University of Arizona. GEORGE A. O'CONNOR, PHD, is Professor Emeritus, at the University of Florida.

• Preface to Fifth Edition xiiPreface to Fourth Edition xiiiAcknowledgments xiv1 Introduction to Soil Chemistry 11.1 The soil chemistry discipline 11.2 Historical background 31.3 The soil environment 61.4 Chemical reactions in soils 151.5 Soil biogeochemical cycling 221.6 Soil chemical influences on food production 221.7 Soils and environmental health 231.8 Units in soil chemistry 261.9 Summary of important concepts in soil chemistry 262 Properties of Elements and Molecules 312.1 Introduction 312.2 Ionization and ionic charge 332.3 Ionic radius 332.4 Molecular bonds 362.5 Nature of water and hydration of ions 372.6 Ligands and metal bonds 402.7 Summary of important concepts of elemental and molecular properties 423 Characteristics of Chemicals in Soils 433.1 Introduction 433.2 Occurrence of elements in soils 433.3 Essential elements 473.4 Inorganic contaminants in the environment 493.5 Anthropogenic organic chemicals in the soil environment 533.6 Properties of the elements in soils 583.7 Summary of important concepts for chemicals in the soil environment 754 Soil Water Chemistry 774.1 Introduction 774.2 Thermodynamic approach to aqueous soil chemistry 784.3 Calculation of ion activity 834.4 Acids and bases 864.5 Gas dissolution 894.6 Precipitation and dissolution reactions 914.7 Cation hydrolysis 1024.8 Complexation 1054.9 Using software to predict soil solution equilibrium 1104.10 Kinetics of chemical reaction in soil solution 1114.11 Summary of important concepts for soil solution chemistry 1165 Redox Reactions in Soils 1195.1 Introduction 1195.2 Redox reactions in nature 1215.3 Basic approaches for characterizing soil redox processes 1265.4 The role of protons in redox reactions 1335.5 Redox potential limits in natural systems 1335.6 pe–pH diagrams 1355.7 Prediction of oxidation and reduction reactions in soils 1375.8 Redox measurement in soils 1415.9 Soil redoximorphic features and iron reduction in wetlands 1425.10 Nitrogen redox reactions in soils 1445.11 Summary of important concepts in soil redox reactions 1476 Mineralogy and Weathering Processes in Soils 1506.1 Introduction 1506.2 Common soil minerals 1526.3 Crystal chemistry of minerals 1536.4 Common primary mineral silicates in soils 1616.5 Minerals and elements in rocks 1646.6 Stability of silicates to weathering 1656.7 Chemistry of soil weathering and mineral formation 1676.8 Formation of secondary minerals in soils 1706.9 Soil carbonates 1746.10 Evaporites 1766.11 Soil phosphate minerals 1776.12 Sulfur minerals 1776.13 Time sequence of mineral formation in soils 1786.14 Measurement of soil mineralogy 1806.15 Important concepts in soil mineralogy 1847 Chemistry of Soil Clays 1867.1 Introduction 1867.2 Structural characteristics of phyllosilicates 1877.3 Relation of phyllosilicate structure to physical and chemical properties 1937.4 Detailed properties of phyllosilicates 1997.5 Allophane and imogolite 2047.6 Zeolite 2057.7 Oxide minerals 2057.8 Summary of soil clays 2108 Production and Chemistry of Soil Organic Matter 2148.1 Introduction 2148.2 Ecosystem carbon storage and fluxes 2178.3 Soil organic matter formation factors 2198.4 Organic chemistry of SOM 2218.5 Plant and microbial compounds input into soil 2238.6 SOM decay processes 2258.7 SOM composition and structure 2298.8 NaOH extraction of SOM 2318.9 Function of organic matter in soil 2338.10 Summary of SOM 2379 Surface Properties of Soil Colloids 2409.1 Introduction 2409.2 Permanent charge 2409.3 pH-dependent charge 2419.4 Point of zero charge of variable charged surfaces 2479.5 pH-dependent charge of SOM 2509.6 Hydrophobic regions of soil organic matter 2529.7 Summary of important concepts in soil surface charge 25210 Adsorption Processes in Soils 25510.1 Introduction 25510.2 Physical model of charged soil particle surfaces 26010.3 Cation exchange on soils 26610.4 Inner-sphere adsorbed cations 27310.5 Anion adsorption 28110.6 Adsorption of anthropogenic organic chemicals in soils 28610.7 Summary of important concepts for adsorption and desorption reactions in soils 29211 Measuring and Predicting Sorption Processes in Soils 29611.1 Introduction 29611.2 Adsorption experiments 29611.3 Predicting adsorption using empirical models 29711.4 Predicting adsorption using mechanistic models 30011.5 Rates of adsorption 30411.6 Reactive transport 30611.7 Surface precipitation 30911.8 Analytical methods for determining adsorption mechanisms 31011.9 Summary of important concepts for modeling surface reactions in soils 31112 Soil Acidity 31412.1 Introduction 31412.2 History of soil acidity 31712.3 The role of aluminum in soil pH 31812.4 Base cations in soil solutions 31912.5 Soil acidification processes 32112.6 Aluminum and manganese toxicity 32612.7 Plant nutrients in acid soils 32712.8 Managing acidic soils 32712.9 Summary of important concepts in soil acidity 32913 Salt-affected Soils 33113.1 Introduction 33113.2 Distribution and origin of salt-affected soils 33113.3 Characterization of salinity in soil and water 33413.4 Describing salt-affected soils 34013.5 Effects of salts on soils and plants 34113.6 Salt balance and leaching requirement 34313.7 Reclamation 34413.8 Summary of important concepts in soil salinity 345Questions 345Bibliography 346Index 347