Nature and Properties of Soils, The

Dr. Raymond Weil, Professor, University of Maryland College ParkB.S. in Crop Science from Michigan State University, East Lansing, MI, 1970.M.S. in Soil Science from Purdue University, West Lafayette, IN, 1973.Ph.D. in Soil Ecology from Virginia Tech, Blacksburg, VA, 1977. Elected Fellow in 2003 of both the Soil Science Society of America and the American Society of Agronomy. Weil has been active in soil science research since 1972 and has made many contributions in the areas of nutrient cycling and management, environmental impact of soil management, and assessment of soil quality. His current research is focused on the assessment and improvement of soil quality and organic matter.  He has conducted research in several countries outside the United States, including Ethiopia, Chad, Brazil, Honduras, Sri Lanka, Zimbabwe, Malawi and Tanzania.  In addition to his teaching at the University of Maryland, he has conducted many training workshops for such agencies as the USDA, The World Bank, The Rodale Research Institute, and the International Food Policy Center. Dr. Weil has authored or coauthored more than 100 scientific publications in soil science and related areas.  Dr. Nyle BradyDr. Brady has, since 1947, worked in education, research and research administration, focusing on both international and U.S. issues. He is past president of the SSSA and served six years as Editor-in-Chief of the SSSA Proceedings and is Emeritus Professor at Cornell University. He has served in leadership positions with Cornell University, the International Rice Research Institute, USAID, the United Nations Development Programme and the World Bank. He is recognized around the world as author and co-author of eleven editions of the world's most widely used soil science textbook, The Nature and Properties of Soils.

• ContentsPreface xv  1The soils around us 11.1 What Ecosystem Services Do Soils Perform? 21.2 How Do Soils Support Plant Growth? 31.3 How Do Soils Regulate Water Supplies? 71.4 How Do Soils Recycle Raw Materials? 81.5 How Do Soils Modify the Atmosphere? 81.6 What Lives in the Soil Habitat? 81.7 Soil as an Engineering Medium 111.8 The Pedosphere and the Critical Zone? 121.9 Soils as Natural Bodies 122.5 How Do Living Organisms (Including People) Affect Soil Formation? 572.6 How Does Topography Affect Soil Formation? 62 2.7 How Does Time Affect Soil Formation 652.8 Four Basic Processes of Soil Formation 672.9 The Soil Profile 702.10 Urban Soils 772.11 Conclusion 81 Study Questions 81 References 821.10 The Soil Profile and Its Layers (Horizons) 15 31.11 Topsoil and Subsoil 181.12 Soil–Interface of Air, Minerals, Water, and Life 201.13 What are the Mineral (Inorganic) Constituents of Soils? 201.14 The Nature of Soil Organic Matter 231.15 Soil Water–Dynamic and Complex 251.16 Soil Air: A Changing Mixture of Gases 261.17 How Do Soil Components Interact to Supply Nutrients to Plants? 261.18 How Do Plant Roots Obtain Nutrients? 281.19 Soil Health, Degradation, and Resilience 301.20 Conclusions 31 Study Questions 32References 32  2 Information of soils from Parent Materials 332.1 Weathering of Rocks and Minerals 332.2 What Environmental Factors Influence Soil Formation? 412.3 Parent Materials 422.4 How Does Climate Affect Soil Formation? 55  3 Soil Classification 833.1 Concept of Individual Soils 833.2 Soil Taxonomy: A Comprehensive Classification System 853.3 Categories and Nomenclature of Soil Taxonomy 923.4 Soil Orders 943.5 Entisols (Recent: Little If Any Profile Development) 963.6 Inceptisols (Few Diagnostic Features: Inception of B Horizon) 993.7 Andisols (Volcanic Ash Soils) 1003.8 Gelisols (Permafrost and Frost Churning) 1023.9 Histosols (Organic Soils Without Permafrost) 1033.10 Aridisols (Dry Soils) 1073.11 Vertisols (Dark, Swelling, and Cracking Clays) 1093.12 Mollisols (Dark, Soft Soils of Grasslands) 1123.13 Alfisols (Argillic or Natric Horizon, Moderately Leached) 1143.14 Ultisols (Argillic Horizon, Highly Leached) 1153.15 Spodosols (Acid, Sandy, Forest Soils, Highly Leached) 1173.16 Oxisols (Oxic Horizon, Highly Weathered) 1183.17 Lower-Level Categories in Soil Taxonomy 121 3.18 Conclusion 128Study Questions 129References 129  4 Soil architecture and Physical Properties 1304.1 Soil Color 1304.2 Soil Texture (Size Distribution of Soil Particles) 1344.3 Soil Textural Classes 1394.4 Structure of Mineral Soils 1444.5 Formation and Stabilization of Soil Aggregates 1484.6 Tillage and Structural Management of Soils 1564.7 Soil Density 1614.8 Pore Space of Mineral Soils 1714.9 Soil Properties Relevant to Engineering Uses 1754.10 Conclusion 185 Study Questions 185 References 186  5 Soil Water: Characteristics and Behavior 1885.1 Structure and Related Properties of Water 1895.2 Capillary Fundamentals and Soil Water 1915.3 Soil Water Energy Concepts 1935.4 Soil Water Content and Soil Water Potential 1995.5 The Flow of Liquid Water in Soil 2075.6 Infiltration and Percolation 2135.7 Water Vapor Movement in Soils 2175.8 Qualitative Description of Soil Wetness 2185.9 Factors Affecting Amount of Plant-Available Soil Water 2225.10 Mechanisms by Which Plants are Supplied with Water 2285.11 Conclusion 230 Study Questions 230 References 232  6 Soil and the hydrologic Cycle 2336.1 The Global Hydrologic Cycle 2346.2 Fate of Incoming Water 2366.3 The Soil—Plant—Atmosphere Continuum (SPAC) 2446.4 Control of ET 2506.5 Liquid Losses of Water from the Soil 255 6.6 Percolation and Groundwater 2576.7 Enhancing Soil Drainage 2626.8 Septic Tank Drain Fields 2696.9 Irrigation Principles and Practices 2736.10 Conclusion 280 Study Questions 282 References 282  7 Soil aeration and Temperature 2847.1 Soil Aeration–The Process 2847.2 Means of Characterizing Soil Aeration 286 7.3 Oxidation—Reduction (Redox) Potential 288 7.4 Factors Affecting Soil Aeration and Eh 292 7.5 Ecological Effects of Soil Aeration 2947.6 Soil Aeration in Urban Landscapes 2987.7 Wetlands and Their Poorly Aerated Soils 301 7.8 Processes Affected by Soil Temperature 308 7.9 Absorption and Loss of Solar Energy 3147.10 Thermal Properties of Soils 316 7.11 Soil Temperature Control 321 7.12 Conclusion 324Study Questions 325References 325  8 The Colloidal fraction: seat of soil Chemical and Physical activity 3278.1 General Properties and Types of Soil Colloids 3288.2 Fundamentals of Layer Silicate Clay Structure 3328.3 Mineralogical Organization of Silicate Clays 3348.4 Structural Characteristics of Nonsilicate Colloids 3428.5 Genesis and Geographic Distribution of Soil Colloids 3448.6 Sources of Charges on Soil Colloids 3468.7 Adsorption of Cations and Anions 3488.8 Cation Exchange Reactions 3508.9 Cation Exchange Capacity (CEC) 3568.10 Exchangeable Cations in Field Soils 3628.11 Anion Exchange 3648.12 Sorption of Pesticides and Groundwater Contamination 3668.13 Binding of Biomolecules to Clay and Humus 369    9 Soil acidity 3749.1 What Processes Cause Soil Acidification? 3759.2 Role of Aluminum in Soil Acidity 3799.3 Pools of Soil Acidity 3809.4 Buffering of pH in Soils 3859.5 How Can We Measure Soil PH? 3869.6 Human-Influenced Soil Acidification 3909.7 Biological Effects of Soil pH 3979.8 Raising Soil pH by Liming 4049.9 Alternative Ways to Ameliorate the Ill Effects of Soil Acidity 4109.10 Lowering Soil pH 4149.11 Conclusion 415 Study Questions 417 References 417    10 Soils of dry regions: alkalinity, salinity, and sodicity 42010.1 Characteristics and Problems of Dry Region Soils 42110.2 Causes of High Soil pH (Alkalinity) 42910.3 Development of Salt-Affected Soils 43110.4 Measuring Salinity and Sodicity 43510.5 Classes of Salt-Affected Soils 43810.6 Physical Degradation of Soil by Sodic Chemical Conditions 44110.7 Biological Impacts of Salt-Affected Soils 444 10.8 Water-Quality Considerations for Irrigation 449 10.9 Reclamation of Saline Soils 45210.10 Reclamation of Saline—Sodic and Sodic Soils 456 10.11 Management of Reclaimed Soils 46110.12 Conclusion 461Study Questions 462References 463  11 Organisms and ecology of the soil 46411.1 The Diversity of Organisms in the Soil 46511.2 Organisms in Action 47011.3 Abundance, Biomass, and Metabolic Activity 475 11.4 Earthworms 47711.5 Ants and Termites 48211.6 Soil Microanimals 48611.7 Plant Roots 49011.8 Soil Algae 49411.9 Soil Fungi 49411.10 Soil Prokaryotes: Bacteria and Archaea 50211.11 Conditions Affecting the Growth and Activity of Soil Microorganisms 50911.12 Beneficial Effects of Soil Organisms on Plant Communities 51011.13 Soil Organisms and Plant Damage 51211.14 Ecological Relationships among Soil Organisms 51711.15 Conclusion 521 Study Questions 522 References 523  12 Soil organic Matter 52612.1 The Global Carbon Cycle 52612.2 Organic Decomposition in Soils 53012.3 Factors Controlling Rates of Residue Decomposition and Mineralization 53512.4 Genesis and Nature of Soil Organic Matter and Humus 54312.5 Influences of Organic Matter on Plant Growth and Soil Function 55012.6 Amounts and Quality of Organic Matter in Soils 55512.7 Carbon Balance in the Soil—Plant—Atmosphere System 55612.8 Environmental Factors Influencing Soil Organic Carbon Levels 56012.9 Soil Organic Matter Management 56412.10 Soils and Climate Change 568 12.11 Composts and Composting 575 12.12 Conclusion 579Study Questions 580 References 581  13 Nitrogen and sulfur economy of soils 58313.1 Influence of Nitrogen on Plant Growth and Development 58413.2 Distribution of Nitrogen and the Nitrogen Cycle 58513.3 Immobilization and Mineralization 58713.4 Dissolved Organic Nitrogen 59013.5 Ammonium Fixation by Clay Minerals 59113.6 Ammonia Volatilization 59113.7 Nitrification 59313.8 Gaseous Losses by Denitrification and Anammox 59613.9 Biological Nitrogen Fixation 60113.10 Symbiotic Fixation with Legumes 60313.11 Symbiotic Fixation with Nonlegumes 60813.12 Nonsymbiotic Nitrogen Fixation 61013.13 Nitrogen Deposition from the Atmosphere 61113.14 The Nitrate Leaching Problem 61313.15 Practical Management of Soil Nitrogen 61713.16 Importance of Sulfur 62513.17 Natural Sources of Sulfur 62613.18 The Sulfur Cycle 63113.19 Behavior of Sulfur Compounds in Soils 63113.20 Sulfur Oxidation and Reduction 634 13.21 Sulfur Retention and Exchange 637 13.22 Sulfur and Soil Fertility Maintenance 638 13.23 Conclusion 639Study Questions 639 References 640  14 Soil Phosphorus and Potassium 64314.1 Phosphorus in Plant Nutrition and Soil Fertility 64414.2 Effects of Phosphorus on Environmental Quality 64614.3 The Phosphorus Cycle 65214.4 Organic Phosphorus in Soils 65714.5 Inorganic Phosphorus in Soils 66114.6 Solubility of Inorganic Soil Phosphorus 66414.7 Phosphorus-Fixation Capacity of Soils 66714.8 Plant Strategies for Adequate Phosphorus Acquisition from Soils 67214.9 Practical Phosphorus Management 67414.10 Potassium: Nature and Ecological Roles 67714.11 Potassium in Plant and Animal Nutrition 67814.12 The Potassium Cycle 68114.13 The Potassium Problem in Soil Fertility 68314.14 Forms and Availability of Potassium in Soils 68514.15 Factors Affecting Potassium Fixation in Soils 68814.16 Practical Aspects of Potassium Management 68914.17 Conclusion 691 Study Questions 692 References 693  15 Calcium, Magnesium, silicon, and Trace elements 69615.1 Calcium as an Essential Nutrient 697 15.2 Magnesium as a Plant Nutrient 699 15.3 Silicon in Soil—Plant Ecology 703 15.4 Deficiency Versus Toxicity 70815.5 Micronutrient Roles in Plants 71015.6 Sources of Micronutrients 71515.7 Factors Influencing the Availability of the Trace Element Cations 71915.8 Organic Compounds as Chelates 72415.9 Factors Influencing the Availability of the Trace Element Anions 72815.10 Soil Management and Trace Element Needs 73415.11 Conclusion 741 Study Questions 742 References 743    16 Practical Nutrient Management 74516.1 Goals of Nutrient Management 74516.2 Nutrients as Pollutants 74916.3 Natural Ecosystem Nutrient Cycles 76216.4 Recycling Nutrients Through Animal Manures 76616.5 Industrial and Municipal By-Products 77516.6 Practical Utilization of Organic Nutrient Sources 77816.7 Inorganic Commercial Fertilizers 78216.8 Fertilizer Application Methods 78816.9 Timing of Fertilizer Application 79216.10 Diagnostic Tools and Methods 79316.11 Soil Analysis 79816.12 Site-Index Approach to Phosphorus Management 80416.13 Some Advances and Challenges in Fertilizer Management 80716.14 Conclusion 812 Study Questions 814 References 815  17 Soil erosion and its Control 81817.1 Significance of Soil Erosion and Land Degradation 81917.2 On-Site and Off-Site impacts of Accelerated Soil Erosion 82517.3 Mechanics of Water Erosion 82817.4 Models to Predict the Extent of Water-Induced Erosion 83117.5 Factors Affecting Interrill and Rill Erosion 83417.6 Conservation Tillage 84217.7 Vegetative Barriers 84917.8 Control of Gully Erosion and Mass Wasting 85017.9 Control of Accelerated Erosion on Range- and Forestland 85317.10 Erosion and Sediment Control on Construction Sites 85617.11 Wind Erosion: Importance and Factors Affecting It 86017.12 Predicting and Controlling Wind Erosion 86417.13 Tillage Erosion 86717.14 Land Capability Classification as a Guide to Conservation 87117.15 Progress in Soil Conservation 87317.16 Conclusion 875 Study Questions 876 References 877  18 Soils and Chemical Pollution 87918.1 Toxic Organic Chemicals 88018.2 Kinds of Organic Contaminants 88518.3 Behavior of Organic Chemicals in Soil 88718.4 Effects of Pesticides on Soil Organisms 89418.5 Remediation of Soils Contaminated with Organic Chemicals 89618.6 Soil Contamination with Toxic Inorganic Substances 90618.7 Potential Hazards of Chemicals in Sewage Sludge 91218.8 Prevention and Remediation of Inorganic Soil Contamination 91618.9 Landfills 91918.10 Radionuclides in Soil 925 18.11 Radon Gas from Soils 929 18.12 Conclusion 932Study Questions 932References 93319 Geographic soils information 93619.1 Soil Spatial Variability in the Field 93619.2 Techniques and Tools for Mapping Soils 941 19.3 Modern Technology for Soil Investigations 946 19.4 Remote Sensing in Soil Survey 95119.5 Making a Soil Survey 95919.6 Using Soil Surveys 96219.7 Geographic Information Systems (GIS) 968 19.8 Digital Soil Maps: Properties or Polygons? 971 19.9 GIS, GPS, and Precision Agriculture 97619.10 Conclusion 979 Study Questions 980 References 980  20 Prospects for soil health in the anthropocene 98220.1 The Concepts of Soil Health and Soil Quality 98320.2 Soil Resistance and Resilience 991 20.3 Soils and Global Ecosystem Services 99320.4 Using Plants to Improve Soil Health 99620.5 Feeding the Human Population 99920.6 Intensified Agriculture–the Green Revolution 100020.7 Impacts of Vastly Increased Ratios of People to Land 100520.8 Sustainable Agriculture in Developed Countries 101020.9 Biochar: Hype or Hope for Soil Quality? 101720.10 Organic Farming Systems 101920.11 Sustainable Agriculture Systems for Resource- Poor Farmers 102620.12 Conclusion 1037 Study Questions 1037 References 1038  appendix a World Reference Base, Canadian, and Australian Soil Classification Systems 1041appendix B SI Units, Conversion Factors, Periodic Table of the Elements, and Plant Names 1046Glossary of soil science Terms 1052 index 1071