Advances in agronomy. V.94 /

Front Cover 1
Advances in Agronomy 4
Copyright Page 5
Contents 6
Contributors 12
Preface 14
Chapter 1: Soil Redox Potential: Importance, Field Measurements, and Observations 15
I. Introduction 16
A. Redox and Wetland Issues 16
B. Relevance of Redox Measurements in Soil Science 19
II. Potentiometric Measuring Techniques 25
A. Reference Cell 27
B. Working Redox Electrodes 29
C. Problems of Soil Redox Measurements 34
D. Testing Electrodes Prior to Installation 38
III. Data Interpretation 39
A. Correction of Field Data 39
B. Variability 41
C. Pooling of Long-Term Data Sets 44
IV. Alternative Methods for Assessing Reduction in the Field 46
A. Iron-Coated (IRIS) Tubes 46
B. Dyes 48
C. Zero Valence Iron Rods 49
V. Field Installation and Procedures for Redox Potential Measurements 50
A. Number of Electrodes to Install 50
B. Installing Pt Electrodes 52
C. Reading the Electrodes 55
D. Common Field Problems 55
E. Field pH Measurements 56
F. Interpreting Redox Potential 57
VI. Summary 58
References 58
Chapter 2: Increasing Rice Production in Sub-Saharan Africa: Challenges and Opportunities 69
I. Introduction 71
II. Rice Demand and Supply 72
III. Wetlands: The Potential Resource for Rice Production in SSA 77
A. Definition, Area and Distribution of Wetlands 78
B. Types and Characteristics of Wetlands 78
IV. Rice Soil Resources 81
A. Dryland Soils and Their Characteristics 81
B. Wetland Soils and Their Characteristics 82
V. Agroclimatic Zones and Rice Ecosystems 85
A. Dryland Rice Ecosystems 86
B. Wetland Rice Ecosystems 91
VI. Rice Production Constraints in SSA 99
A. Physical, Biological, and Management Constraints 99
B. Human Resource Constraints 99
C. Socioeconomic and Policy Constraints 100
VII. Rice Research and Technology Development During the Past 20 Years 100
A. Rice Germplasm, Breeding, and Variety Development 101
B. Rice Seed Production and Distribution Services 111
C. Crop Establishment 113
D. Nutrient Management 113
E. Water Management for Rainfed and Irrigated Areas 121
F. Weeds, Insect Pests, and Diseases and Their Management 125
G. Grain Quality Management: From Breeding to Milling 128
H. Diversification of Rice Farming Systems 129
I. ICM for Rice 129
VIII. Rice Intensification Issues and Thoughts for the Future 131
A. Rice Intensification in Relation to Vector-Borne Human Diseases 131
B. Environmental Issues Related to Rice Intensification in SSA 134
C. Preparing for the Impact of Climate Change 135
D. Technology Delivery and Deployment Issues 136
E. Policy Support for Rice Intensification in SSA 137
IX. Conclusions: Challenges to and Opportunities for Enhancing Rice Production in SSA 138
Acknowledgments 139
References 140
Chapter 3: Phosphate Reaction Dynamics in Soils and Soil Components: A Multiscale Approach 149
I. Introduction 150
II. P Chemistry 151
III. Phosphate Adsorption on Soil Components 152
A. Phosphate Adsorption on Soils (Empirical Approaches) 152
B. Phosphate Retention as Affected by Physicochemical Properties of Soils 153
C. pH Effects on Phosphate Adsorption on Variable Charge Minerals 154
D. Phosphate Adsorption on Metal Oxides 155
E. Phosphate Adsorption on Phyllosilicate Minerals 156
F. Temperature Effects on P Adsorption on Soil Components 157
G. I Effects on P Surface Complexation 159
IV. Phosphate Surface Complexation on Soil Components 160
A. Surface Complexation-Modeling Approaches 160
B. Electrophoretic Mobility Measurement Studies 161
C. Ex Situ Spectroscopic Studies 162
D. In Situ Spectroscopic Studies 163
V. Residence Time Effects on Phosphate Adsorption and Desorption in Soils and Soil Components 173
A. Residence Time Effects Theory 173
B. Slow Adsorption 174
C. Slow Desorption Process and Hysteresis 175
D. Solid-State, Inter-, and Intraparticle Diffusion 179
E. Surface Precipitation 181
F. Higher Energy Binding Through Chemical Reconfiguration 184
VI. Future Research Needs 185
References 185
Chapter 4: Ecological Agriculture in China: Principles and Applications 195
I. Introduction 196
A. Alternative Agriculture 197
B. Ecological Agriculture in the West 197
C. International Sustainable Agriculture 198
II. Chinese Ecological Agriculture 199
A. Environmental Problems in China 199
B. Researches on SA in China 200
C. Characteristics of CEA 201
D. Basic Principles of CEA 202
III. Development and Achievements of CEA 205
IV. Practical Aspects of CEA 207
A. Vertically Distributed Farming 207
B. Multilevel Organic Substance Utilization 207
C. Energy Exploitation 208
D. Integrated Control Techniques 208
E. Introducing New Varieties 208
F. Comprehensive Management of the Agricultural Environment 209
V. Case Studies of CEA 209
A. Ecological Agriculture in Mountainous Regions 209
B. Water-Collecting Ecological Agriculture in Western China 211
C. From Ecological Agriculture to Ecological Industry 213
VI. Problems 216
A. From Theory to Practice 216
B. Poverty 216
C. Lack of Systematic Theoretical Research 217
D. Samll Production Scale 217
E. Lack of Funds 217
F. Education of Farmers 217
G. Lack of Market Competiveness 218
VII. Concluding Remarks 218
A. Further Studies on Theories of CEA 218
B. Modern Techniques Application 218
C. Organic Food: Filling a Gap in the Market 219
D. Ecological Agriculture and Township Enterprise 219
E. International Cooperation in Ecological Agriculture 219
Acknowledgments 220
References 220
Chapter 5: Cotton Leaf Photosynthesis and Carbon Metabolism 223
I. Introduction 224
II. Genetic Variability 224
A. CO2 Exchange Rate and Stomatal Conductance 224
B. Chlorophyll Fluorescence 228
C. Photosynthetic Enzymes 229
D. A:Ci Curves 230
E. 13C Discrimination 231
III. Management and Environmental Effects 233
A. Plant Growth Regulators 233
B. Plant Nutrition and Soil Fertility 235
C. Moisture Stress 237
D. Temperature 239
IV. Conclusions 243
V. Summary 243
References 243
Chapter 6: The Impacts of Grazing Animals on the Quality of Soils, Vegetation, and Surface Waters in Intensively Managed Grasslands 251
I. Introduction 252
II. Impact of Treading by Grazing Animals on Grassland Soils 254
III. Factors Influencing the Amount and Form of Soil Structural Alteration 255
A. Animal Species and Age 255
B. Stocking Density 256
C. Soil Moisture 257
D. Vegetation Cover 258
IV. Forms of Soil Structural Alteration Resulting from Treading by Grazing Animals 259
A. Soil Compaction 259
B. Soil Pugging 260
C. Soil Poaching 261
V. The Impacts of Soil Structural Alteration by Grazing Animals 263
A. Treading and Soil Physical Properties 263
B. Treading and Soil Hydrology 265
C. Treading and Vegetation Growth 266
D. Treading and Soil Fauna 268
VI. The Impact of Defoliation by Grazing Animals on Grassland Vegetation 268
A. Animal Species and Age 269
B. Stocking Density 270
C. Vegetation Response 271
VII. Impact of Excretion by Grazing Animals on Vegetation, Soils, and Surface Waters in Intensively Managed Grasslands 272
A. Livestock Wastes as a Source of Nutrients 272
B. Livestock Wastes as a Source of Pathogens 273
VIII. Impacts of Grazing Animals on the Water Quality of Surface Waters in Intensively Managed Grasslands 274
A. Soil Erosion and Sedimentation Problems 276
B. Eutrophication 277
C. Pathogenic Contamination 279
IX. Environmental Degradation by Grazing Animals: Recovery and Remediation 280
A. Natural Recovery of Soil Physical Condition Following Treading Damage 280
B. Mitigation and Damage Reduction Methods 280
X. Future Research 286
Acknowledgments 287
References 287
Index 295