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Provides comprehensive coverage of the chemical interactions among organic and inorganic solids, air, water, microorganisms, and the plant roots in soil This book focuses on the species and reaction processes of chemicals in soils, with applications to environmental and agricultural issues. Topics range from discussion of fundamental chemical processes to review of properties and reactions of chemicals in the environment. This new edition contains more examples, more illustrations, more details of calculations, and reorganized material within the chapters, including nearly 100 new equations…mehr
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Provides comprehensive coverage of the chemical interactions among organic and inorganic solids, air, water, microorganisms, and the plant roots in soil This book focuses on the species and reaction processes of chemicals in soils, with applications to environmental and agricultural issues. Topics range from discussion of fundamental chemical processes to review of properties and reactions of chemicals in the environment. This new edition contains more examples, more illustrations, more details of calculations, and reorganized material within the chapters, including nearly 100 new equations and 51 new figures. Each section also ends with an important concepts overview as well as new questions for readers to answer. Starting with an introduction to the subject, Soil Chemistry, 5th Edition offers in-depth coverage of properties of elements and molecules; characteristics of chemicals in soils; soil water chemistry; redox reactions in soils; mineralogy and weathering processes in soils; and chemistry of soil clays. The book also provides chapters that examine production and chemistry of soil organic matter; surface properties of soil colloids; adsorption processes in soils; measuring and predicting sorption processes in soils; soil acidity; and salt-affected soils. * Provides a basic description of important research and fundamental knowledge in the field of soil chemistry * Contains more than 200 references provided in figure and table captions and at the end of the chapters * Extensively revised with updated figures and tables Soil Chemistry, 5th Edition is an excellent text for senior-level soil chemistry students.
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Hinweis: Dieser Artikel kann nur an eine deutsche Lieferadresse ausgeliefert werden.
Produktdetails
- Produktdetails
- Verlag: John Wiley and Sons Ltd
- 5 ed
- Seitenzahl: 384
- Erscheinungstermin: 30. Januar 2020
- Englisch
- Abmessung: 286mm x 221mm x 25mm
- Gewicht: 1236g
- ISBN-13: 9781119515180
- ISBN-10: 1119515181
- Artikelnr.: 58565432
- Verlag: John Wiley and Sons Ltd
- 5 ed
- Seitenzahl: 384
- Erscheinungstermin: 30. Januar 2020
- Englisch
- Abmessung: 286mm x 221mm x 25mm
- Gewicht: 1236g
- ISBN-13: 9781119515180
- ISBN-10: 1119515181
- Artikelnr.: 58565432
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 xii Preface to Fourth Edition xiii Acknowledgments xiv 1 Introduction to Soil Chemistry 1 1.1 The soil chemistry discipline 1 1.2 Historical background 3 1.3 The soil environment 6 1.3.1 Soil chemical and biological interfaces 6 1.3.2 Soil solids 10 1.3.3 Soil interaction with the hydrosphere 11 1.3.4 Interaction of soil and the atmosphere 12 1.4 Chemical reactions in soils 15 1.4.1 Flow of chemical energy in soils 17 1.4.2 Soil chemical speciation 18 1.4.3 Chemical reaction types in soils 19 1.5 Soil biogeochemical cycling 22 1.6 Soil chemical influences on food production 22 1.7 Soils and environmental health 23 1.7.1 Soil chemistry and environmental toxicology 24 1.8 Units in soil chemistry 26 1.8.1 Converting units 26 1.9 Summary of important concepts in soil chemistry 26 Questions 29 Bibliography 29 2 Properties of Elements and Molecules 31 2.1 Introduction 31 2.2 Ionization and ionic charge 33 2.3 Ionic radius 33 2.4 Molecular bonds 36 2.5 Nature of water and hydration of ions 37 2.6 Ligands and metal bonds 40 2.7 Summary of important concepts of elemental and molecular properties 42 Questions 42 Bibliography 42 3 Characteristics of Chemicals in Soils 43 3.1 Introduction 43 3.2 Occurrence of elements in soils 43 3.3 Essential elements 47 3.3.1 Plant deficiency 49 3.4 Inorganic contaminants in the environment 49 3.4.1 Assessing contamination status of soils 51 3.5 Anthropogenic organic chemicals in the soil environment 53 3.5.1 Pesticides in the environment 54 3.5.2 Chemicals of emerging concern in the environment 54 3.5.3 Chemical factors affecting organic chemical reactions in soil 57 3.6 Properties of the elements in soils 58 3.6.1 Alkali and alkaline earth cations 59 3.6.2 Major soluble anions in soils 61 3.6.3 Poorly soluble anions 63 3.6.4 Poorly soluble metal cations 67 3.6.5 Common toxic elements in soils 69 3.6.6 Major biogeochemical elements: carbon, nitrogen, and sulfur 71 3.7 Summary of important concepts for chemicals in the soil environment 75 Questions 75 Bibliography 76 4 Soil Water Chemistry 77 4.1 Introduction 77 4.2 Thermodynamic approach to aqueous soil chemistry 78 4.2.1 Example using thermodynamics to calculate gypsum solubility in soils 79 4.2.2 Types of equilibrium constants 82 4.3 Calculation of ion activity 83 4.3.1 Use of ionic strength to calculate activity coefficients 84 4.3.2 Example calculation of activity coefficient 86 4.4 Acids and bases 86 4.4.1 Bases 87 4.4.2 Weak acids 87 4.5 Gas dissolution 89 4.5.1 Predicting dissolution of ammonia in water 90 4.5.2 Predicting pH of water due to CO 2 dissolution 91 4.6 Precipitation and dissolution reactions 91 4.6.1 Solubility of minerals 92 4.6.2 Iron and aluminum dissolution from oxides and hydroxides 93 4.6.3 Calcite and carbon dioxide in soils 95 4.6.4 Solubility of minerals in soils 97 4.6.5 Solubility of contaminant metals from minerals 100 4.7 Cation hydrolysis 102 4.8 Complexation 105 4.8.1 Predicting equilibrium for complexation reactions 106 4.8.2 Chelate reactions with metals 106 4.8.3 Trends in cation ligand affinity 109 4.8.4 Predicting complexation using the hard and soft acid
base (HASB) concept 110 4.9 Using software to predict soil solution equilibrium 110 4.10 Kinetics of chemical reaction in soil solution 111 4.11 Summary of important concepts for soil solution chemistry 116 Questions 116 Bibliography 117 5 Redox Reactions in Soils 119 5.1 Introduction 119 5.2 Redox reactions in nature 121 5.2.1 Photosynthesis redox reactions 121 5.2.2 Electron donors in nature 122 5.2.3 Electron acceptors in nature 122 5.3 Basic approaches for characterizing soil redox processes 126 5.3.1 Using chemical species in soils to monitor redox status of soils 127 5.3.2 Predicting redox processes in soil using chemical reactions 128 5.3.3 Quantifying redox potential with a redox electrode 130 5.3.4 Relating Eh to pe 132 5.4 The role of protons in redox reactions 133 5.5 Redox potential limits in natural systems 133 5.6 pe-pH diagrams 135 5.7 Prediction of oxidation and reduction reactions in soils 137 5.7.1 Reduction reactions on the redox ladder 139 5.7.2 Oxidation reactions on the redox ladder 140 5.8 Redox measurement in soils 141 5.8.1 Other methods to assess redox status of soils 141 5.9 Soil redoximorphic features and iron reduction in wetlands 142 5.10 Nitrogen redox reactions in soils 144 5.10.1 Nitrogen assimilation 145 5.10.2 Ammonification 145 5.10.3 Nitrification 145 5.10.4 Denitrification 146 5.10.5 Biological nitrogen fixation 146 5.10.6 Anammox and dissimilatory nitrogen reduction to ammonium 147 5.10.7 Limitations to theoretical nitrogen redox reaction predictions 147 5.11 Summary of important concepts in soil redox reactions 147 Questions 148 Bibliography 148 6 Mineralogy and Weathering Processes in Soils 150 6.1 Introduction 150 6.2 Common soil minerals 152 6.3 Crystal chemistry of minerals 153 6.3.1 Bonds in minerals 154 6.3.2 Rules for assembling minerals 154 6.3.3 Isomorphic substitution 159 6.3.4 Mineral formulas 160 6.4 Common primary mineral silicates in soils 161 6.4.1 Nesosilicates 162 6.4.2 Inosilicates 162 6.4.3 Phyllosilicates 162 6.4.4 Tectosilicates 163 6.4.5 Cations in primary silicates 163 6.5 Minerals and elements in rocks 164 6.5.1 Elemental composition of rocks 164 6.6 Stability of silicates to weathering 165 6.7 Chemistry of soil weathering and mineral formation 167 6.7.1 Initial breakdown of primary minerals 167 6.7.2 Formation of soil minerals 167 6.7.3 Weathering effects on element composition in soils 169 6.8 Formation of secondary minerals in soils 170 6.8.1 Prediction of secondary mineral formation 172 6.9 Soil carbonates 174 6.10 Evaporites 176 6.11 Soil phosphate minerals 177 6.12 Sulfur minerals 177 6.13 Time sequence of mineral formation in soils 178 6.14 Measurement of soil mineralogy 180 6.14.1 Principles of X
Ray Diffraction (XRD) for clay mineralogy 180 6.14.2 Example calculation of d
spacing from a diffractogram 183 6.14.3 Selective extraction of iron oxides and amorphous aluminosilicates from soils 184 6.15 Important concepts in soil mineralogy 184 Questions 184 Bibliography 185 7 Chemistry of Soil Clays 186 7.1 Introduction 186 7.2 Structural characteristics of phyllosilicates 187 7.2.1 1:1 phyllosilicates 189 7.2.2 2:1 phyllosilicates 191 7.3 Relation of phyllosilicate structure to physical and chemical properties 193 7.3.1 Interlayer bond 193 7.3.2 Surface area 193 7.3.3 c
spacing 194 7.3.4 Cation adsorption and layer charge 194 7.3.5 Shrink and swell behavior and interlayer collapse 195 7.4 Detailed properties of phyllosilicates 199 7.4.1 Kaolins 199 7.4.2 Smectite 200 7.4.3 Vermiculite 200 7.4.4 Mica and Illite 201 7.4.5 Chlorite 204 7.5 Allophane and imogolite 204 7.6 Zeolite 205 7.7 Oxide minerals 205 7.7.1 Aluminum oxides 206 7.7.2 Iron oxides 207 7.7.3 Titanium oxides 208 7.7.4 Manganese oxides 210 7.8 Summary of soil clays 210 Questions 211 Bibliography 212 8 Production and Chemistry of Soil Organic Matter 214 8.1 Introduction 214 8.1.1 Components in SOM 215 8.1.2 Studying SOM 216 8.2 Ecosystem carbon storage and fluxes 217 8.3 Soil organic matter formation factors 219 8.3.1 Residence time of SOM 219 8.3.2 Climate effects on SOM 220 8.3.3 SOM in wetlands 220 8.3.4 Soil mineral effects on SOM 221 8.4 Organic chemistry of SOM 221 8.5 Plant and microbial compounds input into soil 223 8.6 SOM decay processes 225 8.7 SOM composition and structure 229 8.8 NaOH extraction of SOM 231 8.9 Function of organic matter in soil 233 8.9.1 Organic nitrogen, sulfur, and phosphorus 235 8.9.2 SOM influences on chemical processes 236 8.9.3 SOM influences on physical properties 237 8.9.4 Organic chemical partitioning 237 8.10 Summary of SOM 237 Questions 238 Bibliography 238 9 Surface Properties of Soil Colloids 240 9.1 Introduction 240 9.2 Permanent charge 240 9.3 pH
dependent charge 241 9.3.1 Balancing surface charge 243 9.3.2 Variable charge on phyllosilicates 243 9.3.3 pH
dependent charge on iron and aluminum oxides 245 9.4 Point of zero charge of variable charged surfaces 247 9.5 pH
dependent charge of SOM 250 9.6 Hydrophobic regions of soil organic matter 252 9.7 Summary of important concepts in soil surface charge 252 Questions 253 Bibliography 253 10 Adsorption Processes in Soils 255 10.1 Introduction 255 10.1.1 Outer
sphere adsorption 256 10.1.2 Inner
sphere adsorption 257 10.1.3 Adsorption of non
charged chemicals to soil particles 258 10.1.4 Desorption 258 10.2 Physical model of charged soil particle surfaces 260 10.2.1 Force of ion attraction to charged surfaces 260 10.2.2 The diffuse double layer 261 10.2.3 Surface potential on variable charged surfaces 263 10.2.4 Stern modification of the Gouy
Chapman DDL theory 264 10.2.5 Interacting diffuse double layers from adjacent particles 264 10.3 Cation exchange on soils 266 10.3.1 Cation exchange selectivity 267 10.3.2 Cation exchange equations 270 10.3.3 Measuring CEC 273 10.4 Inner
sphere adsorbed cations 273 10.4.1 Inner
sphere adsorption of cations on minerals 276 10.4.2 Metal adsorption selectivity on minerals 277 10.4.3 Inner
sphere metal adsorption on soil organic matter 278 10.4.4 Inner
sphere metal adsorption in soils 278 10.5 Anion adsorption 281 10.5.1 Outer
sphere adsorbed anions 282 10.5.2 Inner
sphere adsorption of anions 283 10.6 Adsorption of anthropogenic organic chemicals in soils 286 10.6.1 Mechanisms of organic chemical retention 286 10.6.2 Adsorption of charged pesticides 287 10.6.3 Retention of nonionic organic chemicals 289 10.6.4 Predicting organic chemical retention in soil 290 10.6.5 Aging effects on organic chemical adsorption 291 10.7 Summary of important concepts for adsorption and desorption reactions in soils 292 Questions 293 Bibliography 294 11 Measuring and Predicting Sorption Processes in Soils 296 11.1 Introduction 296 11.2 Adsorption experiments 296 11.3 Predicting adsorption using empirical models 297 11.3.1 Linear adsorption isotherms 298 11.3.2 Nonlinear adsorption isotherms 298 11.4 Predicting adsorption using mechanistic models 300 11.5 Rates of adsorption 304 11.5.1 Modeling adsorption kinetics 305 11.6 Reactive transport 306 11.7 Surface precipitation 309 11.8 Analytical methods for determining adsorption mechanisms 310 11.9 Summary of important concepts for modeling surface reactions in soils 311 Questions 312 Bibliography 312 12 Soil Acidity 314 12.1 Introduction 314 12.1.1 Measurement of soil acidity 314 12.2 History of soil acidity 317 12.3 The role of aluminum in soil pH 318 12.3.1 Creation of exchangeable aluminum 318 12.4 Base cations in soil solutions 319 12.4.1 Aqueous chemistry of base cations 319 12.4.2 Exchangeable base cations 320 12.4.3 Total exchangeable acidity 321 12.5 Soil acidification processes 321 12.5.1 Organic matter influences on pH 322 12.5.2 Acidity from the nitrogen cycle 323 12.5.3 Phosphate and sulfate fertilizer additions to soil acidity 325 12.5.4 Plant root influences on soil acidity 325 12.5.5 Protonation and deprotonation of mineral surfaces 325 12.5.6 Pollution sources of soil acidity 325 12.5.7 Redox reaction influence on soil acidity 326 12.6 Aluminum and manganese toxicity 326 12.7 Plant nutrients in acid soils 327 12.8 Managing acidic soils 327 12.8.1 Predicting lime requirement 327 12.8.2 Optimal management of soil pH 328 12.9 Summary of important concepts in soil acidity 329 Questions 329 Bibliography 330 13 Salt
affected Soils 331 13.1 Introduction 331 13.2 Distribution and origin of salt
affected soils 331 13.2.1 Mineral weathering sources of salts 332 13.2.2 Salinity from fossil salts 332 13.2.3 Atmospheric salt sources 332 13.2.4 Topographic influence on soil salt concentrations 332 13.2.5 Human sources of soil salinity 333 13.3 Characterization of salinity in soil and water 334 13.3.1 Total dissolved solids 334 13.3.2 Electrical conductivity 334 13.3.3 Sodium hazard 336 13.3.4 Exchangeable sodium percentage 337 13.3.5 Bicarbonate hazard 339 13.3.6 Other problematic solutes in irrigation water 340 13.4 Describing salt
affected soils 340 13.4.1 Saline soils 340 13.4.2 Saline
sodic soils 340 13.4.3 Sodic soils 341 13.5 Effects of salts on soils and plants 341 13.6 Salt balance and leaching requirement 343 13.7 Reclamation 344 13.8 Summary of important concepts in soil salinity 345 Questions 345 Bibliography 346 Index 347
base (HASB) concept 110 4.9 Using software to predict soil solution equilibrium 110 4.10 Kinetics of chemical reaction in soil solution 111 4.11 Summary of important concepts for soil solution chemistry 116 Questions 116 Bibliography 117 5 Redox Reactions in Soils 119 5.1 Introduction 119 5.2 Redox reactions in nature 121 5.2.1 Photosynthesis redox reactions 121 5.2.2 Electron donors in nature 122 5.2.3 Electron acceptors in nature 122 5.3 Basic approaches for characterizing soil redox processes 126 5.3.1 Using chemical species in soils to monitor redox status of soils 127 5.3.2 Predicting redox processes in soil using chemical reactions 128 5.3.3 Quantifying redox potential with a redox electrode 130 5.3.4 Relating Eh to pe 132 5.4 The role of protons in redox reactions 133 5.5 Redox potential limits in natural systems 133 5.6 pe-pH diagrams 135 5.7 Prediction of oxidation and reduction reactions in soils 137 5.7.1 Reduction reactions on the redox ladder 139 5.7.2 Oxidation reactions on the redox ladder 140 5.8 Redox measurement in soils 141 5.8.1 Other methods to assess redox status of soils 141 5.9 Soil redoximorphic features and iron reduction in wetlands 142 5.10 Nitrogen redox reactions in soils 144 5.10.1 Nitrogen assimilation 145 5.10.2 Ammonification 145 5.10.3 Nitrification 145 5.10.4 Denitrification 146 5.10.5 Biological nitrogen fixation 146 5.10.6 Anammox and dissimilatory nitrogen reduction to ammonium 147 5.10.7 Limitations to theoretical nitrogen redox reaction predictions 147 5.11 Summary of important concepts in soil redox reactions 147 Questions 148 Bibliography 148 6 Mineralogy and Weathering Processes in Soils 150 6.1 Introduction 150 6.2 Common soil minerals 152 6.3 Crystal chemistry of minerals 153 6.3.1 Bonds in minerals 154 6.3.2 Rules for assembling minerals 154 6.3.3 Isomorphic substitution 159 6.3.4 Mineral formulas 160 6.4 Common primary mineral silicates in soils 161 6.4.1 Nesosilicates 162 6.4.2 Inosilicates 162 6.4.3 Phyllosilicates 162 6.4.4 Tectosilicates 163 6.4.5 Cations in primary silicates 163 6.5 Minerals and elements in rocks 164 6.5.1 Elemental composition of rocks 164 6.6 Stability of silicates to weathering 165 6.7 Chemistry of soil weathering and mineral formation 167 6.7.1 Initial breakdown of primary minerals 167 6.7.2 Formation of soil minerals 167 6.7.3 Weathering effects on element composition in soils 169 6.8 Formation of secondary minerals in soils 170 6.8.1 Prediction of secondary mineral formation 172 6.9 Soil carbonates 174 6.10 Evaporites 176 6.11 Soil phosphate minerals 177 6.12 Sulfur minerals 177 6.13 Time sequence of mineral formation in soils 178 6.14 Measurement of soil mineralogy 180 6.14.1 Principles of X
Ray Diffraction (XRD) for clay mineralogy 180 6.14.2 Example calculation of d
spacing from a diffractogram 183 6.14.3 Selective extraction of iron oxides and amorphous aluminosilicates from soils 184 6.15 Important concepts in soil mineralogy 184 Questions 184 Bibliography 185 7 Chemistry of Soil Clays 186 7.1 Introduction 186 7.2 Structural characteristics of phyllosilicates 187 7.2.1 1:1 phyllosilicates 189 7.2.2 2:1 phyllosilicates 191 7.3 Relation of phyllosilicate structure to physical and chemical properties 193 7.3.1 Interlayer bond 193 7.3.2 Surface area 193 7.3.3 c
spacing 194 7.3.4 Cation adsorption and layer charge 194 7.3.5 Shrink and swell behavior and interlayer collapse 195 7.4 Detailed properties of phyllosilicates 199 7.4.1 Kaolins 199 7.4.2 Smectite 200 7.4.3 Vermiculite 200 7.4.4 Mica and Illite 201 7.4.5 Chlorite 204 7.5 Allophane and imogolite 204 7.6 Zeolite 205 7.7 Oxide minerals 205 7.7.1 Aluminum oxides 206 7.7.2 Iron oxides 207 7.7.3 Titanium oxides 208 7.7.4 Manganese oxides 210 7.8 Summary of soil clays 210 Questions 211 Bibliography 212 8 Production and Chemistry of Soil Organic Matter 214 8.1 Introduction 214 8.1.1 Components in SOM 215 8.1.2 Studying SOM 216 8.2 Ecosystem carbon storage and fluxes 217 8.3 Soil organic matter formation factors 219 8.3.1 Residence time of SOM 219 8.3.2 Climate effects on SOM 220 8.3.3 SOM in wetlands 220 8.3.4 Soil mineral effects on SOM 221 8.4 Organic chemistry of SOM 221 8.5 Plant and microbial compounds input into soil 223 8.6 SOM decay processes 225 8.7 SOM composition and structure 229 8.8 NaOH extraction of SOM 231 8.9 Function of organic matter in soil 233 8.9.1 Organic nitrogen, sulfur, and phosphorus 235 8.9.2 SOM influences on chemical processes 236 8.9.3 SOM influences on physical properties 237 8.9.4 Organic chemical partitioning 237 8.10 Summary of SOM 237 Questions 238 Bibliography 238 9 Surface Properties of Soil Colloids 240 9.1 Introduction 240 9.2 Permanent charge 240 9.3 pH
dependent charge 241 9.3.1 Balancing surface charge 243 9.3.2 Variable charge on phyllosilicates 243 9.3.3 pH
dependent charge on iron and aluminum oxides 245 9.4 Point of zero charge of variable charged surfaces 247 9.5 pH
dependent charge of SOM 250 9.6 Hydrophobic regions of soil organic matter 252 9.7 Summary of important concepts in soil surface charge 252 Questions 253 Bibliography 253 10 Adsorption Processes in Soils 255 10.1 Introduction 255 10.1.1 Outer
sphere adsorption 256 10.1.2 Inner
sphere adsorption 257 10.1.3 Adsorption of non
charged chemicals to soil particles 258 10.1.4 Desorption 258 10.2 Physical model of charged soil particle surfaces 260 10.2.1 Force of ion attraction to charged surfaces 260 10.2.2 The diffuse double layer 261 10.2.3 Surface potential on variable charged surfaces 263 10.2.4 Stern modification of the Gouy
Chapman DDL theory 264 10.2.5 Interacting diffuse double layers from adjacent particles 264 10.3 Cation exchange on soils 266 10.3.1 Cation exchange selectivity 267 10.3.2 Cation exchange equations 270 10.3.3 Measuring CEC 273 10.4 Inner
sphere adsorbed cations 273 10.4.1 Inner
sphere adsorption of cations on minerals 276 10.4.2 Metal adsorption selectivity on minerals 277 10.4.3 Inner
sphere metal adsorption on soil organic matter 278 10.4.4 Inner
sphere metal adsorption in soils 278 10.5 Anion adsorption 281 10.5.1 Outer
sphere adsorbed anions 282 10.5.2 Inner
sphere adsorption of anions 283 10.6 Adsorption of anthropogenic organic chemicals in soils 286 10.6.1 Mechanisms of organic chemical retention 286 10.6.2 Adsorption of charged pesticides 287 10.6.3 Retention of nonionic organic chemicals 289 10.6.4 Predicting organic chemical retention in soil 290 10.6.5 Aging effects on organic chemical adsorption 291 10.7 Summary of important concepts for adsorption and desorption reactions in soils 292 Questions 293 Bibliography 294 11 Measuring and Predicting Sorption Processes in Soils 296 11.1 Introduction 296 11.2 Adsorption experiments 296 11.3 Predicting adsorption using empirical models 297 11.3.1 Linear adsorption isotherms 298 11.3.2 Nonlinear adsorption isotherms 298 11.4 Predicting adsorption using mechanistic models 300 11.5 Rates of adsorption 304 11.5.1 Modeling adsorption kinetics 305 11.6 Reactive transport 306 11.7 Surface precipitation 309 11.8 Analytical methods for determining adsorption mechanisms 310 11.9 Summary of important concepts for modeling surface reactions in soils 311 Questions 312 Bibliography 312 12 Soil Acidity 314 12.1 Introduction 314 12.1.1 Measurement of soil acidity 314 12.2 History of soil acidity 317 12.3 The role of aluminum in soil pH 318 12.3.1 Creation of exchangeable aluminum 318 12.4 Base cations in soil solutions 319 12.4.1 Aqueous chemistry of base cations 319 12.4.2 Exchangeable base cations 320 12.4.3 Total exchangeable acidity 321 12.5 Soil acidification processes 321 12.5.1 Organic matter influences on pH 322 12.5.2 Acidity from the nitrogen cycle 323 12.5.3 Phosphate and sulfate fertilizer additions to soil acidity 325 12.5.4 Plant root influences on soil acidity 325 12.5.5 Protonation and deprotonation of mineral surfaces 325 12.5.6 Pollution sources of soil acidity 325 12.5.7 Redox reaction influence on soil acidity 326 12.6 Aluminum and manganese toxicity 326 12.7 Plant nutrients in acid soils 327 12.8 Managing acidic soils 327 12.8.1 Predicting lime requirement 327 12.8.2 Optimal management of soil pH 328 12.9 Summary of important concepts in soil acidity 329 Questions 329 Bibliography 330 13 Salt
affected Soils 331 13.1 Introduction 331 13.2 Distribution and origin of salt
affected soils 331 13.2.1 Mineral weathering sources of salts 332 13.2.2 Salinity from fossil salts 332 13.2.3 Atmospheric salt sources 332 13.2.4 Topographic influence on soil salt concentrations 332 13.2.5 Human sources of soil salinity 333 13.3 Characterization of salinity in soil and water 334 13.3.1 Total dissolved solids 334 13.3.2 Electrical conductivity 334 13.3.3 Sodium hazard 336 13.3.4 Exchangeable sodium percentage 337 13.3.5 Bicarbonate hazard 339 13.3.6 Other problematic solutes in irrigation water 340 13.4 Describing salt
affected soils 340 13.4.1 Saline soils 340 13.4.2 Saline
sodic soils 340 13.4.3 Sodic soils 341 13.5 Effects of salts on soils and plants 341 13.6 Salt balance and leaching requirement 343 13.7 Reclamation 344 13.8 Summary of important concepts in soil salinity 345 Questions 345 Bibliography 346 Index 347
Preface to Fifth Edition xii Preface to Fourth Edition xiii Acknowledgments xiv 1 Introduction to Soil Chemistry 1 1.1 The soil chemistry discipline 1 1.2 Historical background 3 1.3 The soil environment 6 1.3.1 Soil chemical and biological interfaces 6 1.3.2 Soil solids 10 1.3.3 Soil interaction with the hydrosphere 11 1.3.4 Interaction of soil and the atmosphere 12 1.4 Chemical reactions in soils 15 1.4.1 Flow of chemical energy in soils 17 1.4.2 Soil chemical speciation 18 1.4.3 Chemical reaction types in soils 19 1.5 Soil biogeochemical cycling 22 1.6 Soil chemical influences on food production 22 1.7 Soils and environmental health 23 1.7.1 Soil chemistry and environmental toxicology 24 1.8 Units in soil chemistry 26 1.8.1 Converting units 26 1.9 Summary of important concepts in soil chemistry 26 Questions 29 Bibliography 29 2 Properties of Elements and Molecules 31 2.1 Introduction 31 2.2 Ionization and ionic charge 33 2.3 Ionic radius 33 2.4 Molecular bonds 36 2.5 Nature of water and hydration of ions 37 2.6 Ligands and metal bonds 40 2.7 Summary of important concepts of elemental and molecular properties 42 Questions 42 Bibliography 42 3 Characteristics of Chemicals in Soils 43 3.1 Introduction 43 3.2 Occurrence of elements in soils 43 3.3 Essential elements 47 3.3.1 Plant deficiency 49 3.4 Inorganic contaminants in the environment 49 3.4.1 Assessing contamination status of soils 51 3.5 Anthropogenic organic chemicals in the soil environment 53 3.5.1 Pesticides in the environment 54 3.5.2 Chemicals of emerging concern in the environment 54 3.5.3 Chemical factors affecting organic chemical reactions in soil 57 3.6 Properties of the elements in soils 58 3.6.1 Alkali and alkaline earth cations 59 3.6.2 Major soluble anions in soils 61 3.6.3 Poorly soluble anions 63 3.6.4 Poorly soluble metal cations 67 3.6.5 Common toxic elements in soils 69 3.6.6 Major biogeochemical elements: carbon, nitrogen, and sulfur 71 3.7 Summary of important concepts for chemicals in the soil environment 75 Questions 75 Bibliography 76 4 Soil Water Chemistry 77 4.1 Introduction 77 4.2 Thermodynamic approach to aqueous soil chemistry 78 4.2.1 Example using thermodynamics to calculate gypsum solubility in soils 79 4.2.2 Types of equilibrium constants 82 4.3 Calculation of ion activity 83 4.3.1 Use of ionic strength to calculate activity coefficients 84 4.3.2 Example calculation of activity coefficient 86 4.4 Acids and bases 86 4.4.1 Bases 87 4.4.2 Weak acids 87 4.5 Gas dissolution 89 4.5.1 Predicting dissolution of ammonia in water 90 4.5.2 Predicting pH of water due to CO 2 dissolution 91 4.6 Precipitation and dissolution reactions 91 4.6.1 Solubility of minerals 92 4.6.2 Iron and aluminum dissolution from oxides and hydroxides 93 4.6.3 Calcite and carbon dioxide in soils 95 4.6.4 Solubility of minerals in soils 97 4.6.5 Solubility of contaminant metals from minerals 100 4.7 Cation hydrolysis 102 4.8 Complexation 105 4.8.1 Predicting equilibrium for complexation reactions 106 4.8.2 Chelate reactions with metals 106 4.8.3 Trends in cation ligand affinity 109 4.8.4 Predicting complexation using the hard and soft acid
base (HASB) concept 110 4.9 Using software to predict soil solution equilibrium 110 4.10 Kinetics of chemical reaction in soil solution 111 4.11 Summary of important concepts for soil solution chemistry 116 Questions 116 Bibliography 117 5 Redox Reactions in Soils 119 5.1 Introduction 119 5.2 Redox reactions in nature 121 5.2.1 Photosynthesis redox reactions 121 5.2.2 Electron donors in nature 122 5.2.3 Electron acceptors in nature 122 5.3 Basic approaches for characterizing soil redox processes 126 5.3.1 Using chemical species in soils to monitor redox status of soils 127 5.3.2 Predicting redox processes in soil using chemical reactions 128 5.3.3 Quantifying redox potential with a redox electrode 130 5.3.4 Relating Eh to pe 132 5.4 The role of protons in redox reactions 133 5.5 Redox potential limits in natural systems 133 5.6 pe-pH diagrams 135 5.7 Prediction of oxidation and reduction reactions in soils 137 5.7.1 Reduction reactions on the redox ladder 139 5.7.2 Oxidation reactions on the redox ladder 140 5.8 Redox measurement in soils 141 5.8.1 Other methods to assess redox status of soils 141 5.9 Soil redoximorphic features and iron reduction in wetlands 142 5.10 Nitrogen redox reactions in soils 144 5.10.1 Nitrogen assimilation 145 5.10.2 Ammonification 145 5.10.3 Nitrification 145 5.10.4 Denitrification 146 5.10.5 Biological nitrogen fixation 146 5.10.6 Anammox and dissimilatory nitrogen reduction to ammonium 147 5.10.7 Limitations to theoretical nitrogen redox reaction predictions 147 5.11 Summary of important concepts in soil redox reactions 147 Questions 148 Bibliography 148 6 Mineralogy and Weathering Processes in Soils 150 6.1 Introduction 150 6.2 Common soil minerals 152 6.3 Crystal chemistry of minerals 153 6.3.1 Bonds in minerals 154 6.3.2 Rules for assembling minerals 154 6.3.3 Isomorphic substitution 159 6.3.4 Mineral formulas 160 6.4 Common primary mineral silicates in soils 161 6.4.1 Nesosilicates 162 6.4.2 Inosilicates 162 6.4.3 Phyllosilicates 162 6.4.4 Tectosilicates 163 6.4.5 Cations in primary silicates 163 6.5 Minerals and elements in rocks 164 6.5.1 Elemental composition of rocks 164 6.6 Stability of silicates to weathering 165 6.7 Chemistry of soil weathering and mineral formation 167 6.7.1 Initial breakdown of primary minerals 167 6.7.2 Formation of soil minerals 167 6.7.3 Weathering effects on element composition in soils 169 6.8 Formation of secondary minerals in soils 170 6.8.1 Prediction of secondary mineral formation 172 6.9 Soil carbonates 174 6.10 Evaporites 176 6.11 Soil phosphate minerals 177 6.12 Sulfur minerals 177 6.13 Time sequence of mineral formation in soils 178 6.14 Measurement of soil mineralogy 180 6.14.1 Principles of X
Ray Diffraction (XRD) for clay mineralogy 180 6.14.2 Example calculation of d
spacing from a diffractogram 183 6.14.3 Selective extraction of iron oxides and amorphous aluminosilicates from soils 184 6.15 Important concepts in soil mineralogy 184 Questions 184 Bibliography 185 7 Chemistry of Soil Clays 186 7.1 Introduction 186 7.2 Structural characteristics of phyllosilicates 187 7.2.1 1:1 phyllosilicates 189 7.2.2 2:1 phyllosilicates 191 7.3 Relation of phyllosilicate structure to physical and chemical properties 193 7.3.1 Interlayer bond 193 7.3.2 Surface area 193 7.3.3 c
spacing 194 7.3.4 Cation adsorption and layer charge 194 7.3.5 Shrink and swell behavior and interlayer collapse 195 7.4 Detailed properties of phyllosilicates 199 7.4.1 Kaolins 199 7.4.2 Smectite 200 7.4.3 Vermiculite 200 7.4.4 Mica and Illite 201 7.4.5 Chlorite 204 7.5 Allophane and imogolite 204 7.6 Zeolite 205 7.7 Oxide minerals 205 7.7.1 Aluminum oxides 206 7.7.2 Iron oxides 207 7.7.3 Titanium oxides 208 7.7.4 Manganese oxides 210 7.8 Summary of soil clays 210 Questions 211 Bibliography 212 8 Production and Chemistry of Soil Organic Matter 214 8.1 Introduction 214 8.1.1 Components in SOM 215 8.1.2 Studying SOM 216 8.2 Ecosystem carbon storage and fluxes 217 8.3 Soil organic matter formation factors 219 8.3.1 Residence time of SOM 219 8.3.2 Climate effects on SOM 220 8.3.3 SOM in wetlands 220 8.3.4 Soil mineral effects on SOM 221 8.4 Organic chemistry of SOM 221 8.5 Plant and microbial compounds input into soil 223 8.6 SOM decay processes 225 8.7 SOM composition and structure 229 8.8 NaOH extraction of SOM 231 8.9 Function of organic matter in soil 233 8.9.1 Organic nitrogen, sulfur, and phosphorus 235 8.9.2 SOM influences on chemical processes 236 8.9.3 SOM influences on physical properties 237 8.9.4 Organic chemical partitioning 237 8.10 Summary of SOM 237 Questions 238 Bibliography 238 9 Surface Properties of Soil Colloids 240 9.1 Introduction 240 9.2 Permanent charge 240 9.3 pH
dependent charge 241 9.3.1 Balancing surface charge 243 9.3.2 Variable charge on phyllosilicates 243 9.3.3 pH
dependent charge on iron and aluminum oxides 245 9.4 Point of zero charge of variable charged surfaces 247 9.5 pH
dependent charge of SOM 250 9.6 Hydrophobic regions of soil organic matter 252 9.7 Summary of important concepts in soil surface charge 252 Questions 253 Bibliography 253 10 Adsorption Processes in Soils 255 10.1 Introduction 255 10.1.1 Outer
sphere adsorption 256 10.1.2 Inner
sphere adsorption 257 10.1.3 Adsorption of non
charged chemicals to soil particles 258 10.1.4 Desorption 258 10.2 Physical model of charged soil particle surfaces 260 10.2.1 Force of ion attraction to charged surfaces 260 10.2.2 The diffuse double layer 261 10.2.3 Surface potential on variable charged surfaces 263 10.2.4 Stern modification of the Gouy
Chapman DDL theory 264 10.2.5 Interacting diffuse double layers from adjacent particles 264 10.3 Cation exchange on soils 266 10.3.1 Cation exchange selectivity 267 10.3.2 Cation exchange equations 270 10.3.3 Measuring CEC 273 10.4 Inner
sphere adsorbed cations 273 10.4.1 Inner
sphere adsorption of cations on minerals 276 10.4.2 Metal adsorption selectivity on minerals 277 10.4.3 Inner
sphere metal adsorption on soil organic matter 278 10.4.4 Inner
sphere metal adsorption in soils 278 10.5 Anion adsorption 281 10.5.1 Outer
sphere adsorbed anions 282 10.5.2 Inner
sphere adsorption of anions 283 10.6 Adsorption of anthropogenic organic chemicals in soils 286 10.6.1 Mechanisms of organic chemical retention 286 10.6.2 Adsorption of charged pesticides 287 10.6.3 Retention of nonionic organic chemicals 289 10.6.4 Predicting organic chemical retention in soil 290 10.6.5 Aging effects on organic chemical adsorption 291 10.7 Summary of important concepts for adsorption and desorption reactions in soils 292 Questions 293 Bibliography 294 11 Measuring and Predicting Sorption Processes in Soils 296 11.1 Introduction 296 11.2 Adsorption experiments 296 11.3 Predicting adsorption using empirical models 297 11.3.1 Linear adsorption isotherms 298 11.3.2 Nonlinear adsorption isotherms 298 11.4 Predicting adsorption using mechanistic models 300 11.5 Rates of adsorption 304 11.5.1 Modeling adsorption kinetics 305 11.6 Reactive transport 306 11.7 Surface precipitation 309 11.8 Analytical methods for determining adsorption mechanisms 310 11.9 Summary of important concepts for modeling surface reactions in soils 311 Questions 312 Bibliography 312 12 Soil Acidity 314 12.1 Introduction 314 12.1.1 Measurement of soil acidity 314 12.2 History of soil acidity 317 12.3 The role of aluminum in soil pH 318 12.3.1 Creation of exchangeable aluminum 318 12.4 Base cations in soil solutions 319 12.4.1 Aqueous chemistry of base cations 319 12.4.2 Exchangeable base cations 320 12.4.3 Total exchangeable acidity 321 12.5 Soil acidification processes 321 12.5.1 Organic matter influences on pH 322 12.5.2 Acidity from the nitrogen cycle 323 12.5.3 Phosphate and sulfate fertilizer additions to soil acidity 325 12.5.4 Plant root influences on soil acidity 325 12.5.5 Protonation and deprotonation of mineral surfaces 325 12.5.6 Pollution sources of soil acidity 325 12.5.7 Redox reaction influence on soil acidity 326 12.6 Aluminum and manganese toxicity 326 12.7 Plant nutrients in acid soils 327 12.8 Managing acidic soils 327 12.8.1 Predicting lime requirement 327 12.8.2 Optimal management of soil pH 328 12.9 Summary of important concepts in soil acidity 329 Questions 329 Bibliography 330 13 Salt
affected Soils 331 13.1 Introduction 331 13.2 Distribution and origin of salt
affected soils 331 13.2.1 Mineral weathering sources of salts 332 13.2.2 Salinity from fossil salts 332 13.2.3 Atmospheric salt sources 332 13.2.4 Topographic influence on soil salt concentrations 332 13.2.5 Human sources of soil salinity 333 13.3 Characterization of salinity in soil and water 334 13.3.1 Total dissolved solids 334 13.3.2 Electrical conductivity 334 13.3.3 Sodium hazard 336 13.3.4 Exchangeable sodium percentage 337 13.3.5 Bicarbonate hazard 339 13.3.6 Other problematic solutes in irrigation water 340 13.4 Describing salt
affected soils 340 13.4.1 Saline soils 340 13.4.2 Saline
sodic soils 340 13.4.3 Sodic soils 341 13.5 Effects of salts on soils and plants 341 13.6 Salt balance and leaching requirement 343 13.7 Reclamation 344 13.8 Summary of important concepts in soil salinity 345 Questions 345 Bibliography 346 Index 347
base (HASB) concept 110 4.9 Using software to predict soil solution equilibrium 110 4.10 Kinetics of chemical reaction in soil solution 111 4.11 Summary of important concepts for soil solution chemistry 116 Questions 116 Bibliography 117 5 Redox Reactions in Soils 119 5.1 Introduction 119 5.2 Redox reactions in nature 121 5.2.1 Photosynthesis redox reactions 121 5.2.2 Electron donors in nature 122 5.2.3 Electron acceptors in nature 122 5.3 Basic approaches for characterizing soil redox processes 126 5.3.1 Using chemical species in soils to monitor redox status of soils 127 5.3.2 Predicting redox processes in soil using chemical reactions 128 5.3.3 Quantifying redox potential with a redox electrode 130 5.3.4 Relating Eh to pe 132 5.4 The role of protons in redox reactions 133 5.5 Redox potential limits in natural systems 133 5.6 pe-pH diagrams 135 5.7 Prediction of oxidation and reduction reactions in soils 137 5.7.1 Reduction reactions on the redox ladder 139 5.7.2 Oxidation reactions on the redox ladder 140 5.8 Redox measurement in soils 141 5.8.1 Other methods to assess redox status of soils 141 5.9 Soil redoximorphic features and iron reduction in wetlands 142 5.10 Nitrogen redox reactions in soils 144 5.10.1 Nitrogen assimilation 145 5.10.2 Ammonification 145 5.10.3 Nitrification 145 5.10.4 Denitrification 146 5.10.5 Biological nitrogen fixation 146 5.10.6 Anammox and dissimilatory nitrogen reduction to ammonium 147 5.10.7 Limitations to theoretical nitrogen redox reaction predictions 147 5.11 Summary of important concepts in soil redox reactions 147 Questions 148 Bibliography 148 6 Mineralogy and Weathering Processes in Soils 150 6.1 Introduction 150 6.2 Common soil minerals 152 6.3 Crystal chemistry of minerals 153 6.3.1 Bonds in minerals 154 6.3.2 Rules for assembling minerals 154 6.3.3 Isomorphic substitution 159 6.3.4 Mineral formulas 160 6.4 Common primary mineral silicates in soils 161 6.4.1 Nesosilicates 162 6.4.2 Inosilicates 162 6.4.3 Phyllosilicates 162 6.4.4 Tectosilicates 163 6.4.5 Cations in primary silicates 163 6.5 Minerals and elements in rocks 164 6.5.1 Elemental composition of rocks 164 6.6 Stability of silicates to weathering 165 6.7 Chemistry of soil weathering and mineral formation 167 6.7.1 Initial breakdown of primary minerals 167 6.7.2 Formation of soil minerals 167 6.7.3 Weathering effects on element composition in soils 169 6.8 Formation of secondary minerals in soils 170 6.8.1 Prediction of secondary mineral formation 172 6.9 Soil carbonates 174 6.10 Evaporites 176 6.11 Soil phosphate minerals 177 6.12 Sulfur minerals 177 6.13 Time sequence of mineral formation in soils 178 6.14 Measurement of soil mineralogy 180 6.14.1 Principles of X
Ray Diffraction (XRD) for clay mineralogy 180 6.14.2 Example calculation of d
spacing from a diffractogram 183 6.14.3 Selective extraction of iron oxides and amorphous aluminosilicates from soils 184 6.15 Important concepts in soil mineralogy 184 Questions 184 Bibliography 185 7 Chemistry of Soil Clays 186 7.1 Introduction 186 7.2 Structural characteristics of phyllosilicates 187 7.2.1 1:1 phyllosilicates 189 7.2.2 2:1 phyllosilicates 191 7.3 Relation of phyllosilicate structure to physical and chemical properties 193 7.3.1 Interlayer bond 193 7.3.2 Surface area 193 7.3.3 c
spacing 194 7.3.4 Cation adsorption and layer charge 194 7.3.5 Shrink and swell behavior and interlayer collapse 195 7.4 Detailed properties of phyllosilicates 199 7.4.1 Kaolins 199 7.4.2 Smectite 200 7.4.3 Vermiculite 200 7.4.4 Mica and Illite 201 7.4.5 Chlorite 204 7.5 Allophane and imogolite 204 7.6 Zeolite 205 7.7 Oxide minerals 205 7.7.1 Aluminum oxides 206 7.7.2 Iron oxides 207 7.7.3 Titanium oxides 208 7.7.4 Manganese oxides 210 7.8 Summary of soil clays 210 Questions 211 Bibliography 212 8 Production and Chemistry of Soil Organic Matter 214 8.1 Introduction 214 8.1.1 Components in SOM 215 8.1.2 Studying SOM 216 8.2 Ecosystem carbon storage and fluxes 217 8.3 Soil organic matter formation factors 219 8.3.1 Residence time of SOM 219 8.3.2 Climate effects on SOM 220 8.3.3 SOM in wetlands 220 8.3.4 Soil mineral effects on SOM 221 8.4 Organic chemistry of SOM 221 8.5 Plant and microbial compounds input into soil 223 8.6 SOM decay processes 225 8.7 SOM composition and structure 229 8.8 NaOH extraction of SOM 231 8.9 Function of organic matter in soil 233 8.9.1 Organic nitrogen, sulfur, and phosphorus 235 8.9.2 SOM influences on chemical processes 236 8.9.3 SOM influences on physical properties 237 8.9.4 Organic chemical partitioning 237 8.10 Summary of SOM 237 Questions 238 Bibliography 238 9 Surface Properties of Soil Colloids 240 9.1 Introduction 240 9.2 Permanent charge 240 9.3 pH
dependent charge 241 9.3.1 Balancing surface charge 243 9.3.2 Variable charge on phyllosilicates 243 9.3.3 pH
dependent charge on iron and aluminum oxides 245 9.4 Point of zero charge of variable charged surfaces 247 9.5 pH
dependent charge of SOM 250 9.6 Hydrophobic regions of soil organic matter 252 9.7 Summary of important concepts in soil surface charge 252 Questions 253 Bibliography 253 10 Adsorption Processes in Soils 255 10.1 Introduction 255 10.1.1 Outer
sphere adsorption 256 10.1.2 Inner
sphere adsorption 257 10.1.3 Adsorption of non
charged chemicals to soil particles 258 10.1.4 Desorption 258 10.2 Physical model of charged soil particle surfaces 260 10.2.1 Force of ion attraction to charged surfaces 260 10.2.2 The diffuse double layer 261 10.2.3 Surface potential on variable charged surfaces 263 10.2.4 Stern modification of the Gouy
Chapman DDL theory 264 10.2.5 Interacting diffuse double layers from adjacent particles 264 10.3 Cation exchange on soils 266 10.3.1 Cation exchange selectivity 267 10.3.2 Cation exchange equations 270 10.3.3 Measuring CEC 273 10.4 Inner
sphere adsorbed cations 273 10.4.1 Inner
sphere adsorption of cations on minerals 276 10.4.2 Metal adsorption selectivity on minerals 277 10.4.3 Inner
sphere metal adsorption on soil organic matter 278 10.4.4 Inner
sphere metal adsorption in soils 278 10.5 Anion adsorption 281 10.5.1 Outer
sphere adsorbed anions 282 10.5.2 Inner
sphere adsorption of anions 283 10.6 Adsorption of anthropogenic organic chemicals in soils 286 10.6.1 Mechanisms of organic chemical retention 286 10.6.2 Adsorption of charged pesticides 287 10.6.3 Retention of nonionic organic chemicals 289 10.6.4 Predicting organic chemical retention in soil 290 10.6.5 Aging effects on organic chemical adsorption 291 10.7 Summary of important concepts for adsorption and desorption reactions in soils 292 Questions 293 Bibliography 294 11 Measuring and Predicting Sorption Processes in Soils 296 11.1 Introduction 296 11.2 Adsorption experiments 296 11.3 Predicting adsorption using empirical models 297 11.3.1 Linear adsorption isotherms 298 11.3.2 Nonlinear adsorption isotherms 298 11.4 Predicting adsorption using mechanistic models 300 11.5 Rates of adsorption 304 11.5.1 Modeling adsorption kinetics 305 11.6 Reactive transport 306 11.7 Surface precipitation 309 11.8 Analytical methods for determining adsorption mechanisms 310 11.9 Summary of important concepts for modeling surface reactions in soils 311 Questions 312 Bibliography 312 12 Soil Acidity 314 12.1 Introduction 314 12.1.1 Measurement of soil acidity 314 12.2 History of soil acidity 317 12.3 The role of aluminum in soil pH 318 12.3.1 Creation of exchangeable aluminum 318 12.4 Base cations in soil solutions 319 12.4.1 Aqueous chemistry of base cations 319 12.4.2 Exchangeable base cations 320 12.4.3 Total exchangeable acidity 321 12.5 Soil acidification processes 321 12.5.1 Organic matter influences on pH 322 12.5.2 Acidity from the nitrogen cycle 323 12.5.3 Phosphate and sulfate fertilizer additions to soil acidity 325 12.5.4 Plant root influences on soil acidity 325 12.5.5 Protonation and deprotonation of mineral surfaces 325 12.5.6 Pollution sources of soil acidity 325 12.5.7 Redox reaction influence on soil acidity 326 12.6 Aluminum and manganese toxicity 326 12.7 Plant nutrients in acid soils 327 12.8 Managing acidic soils 327 12.8.1 Predicting lime requirement 327 12.8.2 Optimal management of soil pH 328 12.9 Summary of important concepts in soil acidity 329 Questions 329 Bibliography 330 13 Salt
affected Soils 331 13.1 Introduction 331 13.2 Distribution and origin of salt
affected soils 331 13.2.1 Mineral weathering sources of salts 332 13.2.2 Salinity from fossil salts 332 13.2.3 Atmospheric salt sources 332 13.2.4 Topographic influence on soil salt concentrations 332 13.2.5 Human sources of soil salinity 333 13.3 Characterization of salinity in soil and water 334 13.3.1 Total dissolved solids 334 13.3.2 Electrical conductivity 334 13.3.3 Sodium hazard 336 13.3.4 Exchangeable sodium percentage 337 13.3.5 Bicarbonate hazard 339 13.3.6 Other problematic solutes in irrigation water 340 13.4 Describing salt
affected soils 340 13.4.1 Saline soils 340 13.4.2 Saline
sodic soils 340 13.4.3 Sodic soils 341 13.5 Effects of salts on soils and plants 341 13.6 Salt balance and leaching requirement 343 13.7 Reclamation 344 13.8 Summary of important concepts in soil salinity 345 Questions 345 Bibliography 346 Index 347