Saline and sodic soils. Principles-dynamics-modeling.

1 Diagnosis and Properties.- 1.1 Sources of Salts.- 1.1.1 Rainfall.- 1.1.2 Mineral Weathering.- 1.1.3 Fossil Salts.- 1.1.4 Man's Activities.- 1.2 Some Water Quality and Soil Solution Parameters.- 1.2.1 Common Water Quality Parameters.- 1.2.1.1 Total Salt Concentration.- 1.2.1.2 Electrical Conductivity (EC).- 1.2.1.3 Chemical Analyses.- 1.2.1.4 Sodium Adsorption Ratio (SAR).- 1.2.1.5 Langelier Index (pHc).- 1.2.1.6 Specific Ion Hazards.- 1.2.2 Physical Characterization of Soil Water.- 1.2.2.1 Soil Water Potential.- 1.2.2.2 Pressure and Head Equivalents of Soil Water Potential.- 1.2.2.3 Water (Solution) Retentivity Curve.- 1.2.2.4 Modeling of the Soil-Water-Salt Retentivity Function h(? C, R).- 1.2.3 Simplified Interactions of Irrigation Waters and Rainfall with Soils.- 1.2.3.1 Basic Concentration and Displacement Processes.- 1.2.3.2 Ion Exchange Phenomena.- 1.2.3.3 Dissolving and Precipitation of Minerals.- 1.3 Surface Phenomena of Salt-Affected Soils.- 1.3.1 Soil Minerals and Their Properties.- 1.3.1.1 Common Soil Minerals.- 1.3.1.2 Some Relevant Surface Properties of Soils.- 1.3.1.3 Water Retention and Swelling.- 1.3.1.4 Effects of Salts on Soil Hydraulic Parameters..- 1.3.1.5 Modeling of Hydraulic Conductivity K (?, R, C) Based upon Soil Water Retentivity.- 1.3.2 Ion Exchange and Exclusion.- 1.3.2.1 Mass Action Approaches.- 1.3.2.2 Diffuse Double Layer Approach.- 1.3.2.3 The Gapon Equation.- 1.3.2.4 Modeling of Na-Ca Exchange Equilibria.- 1.3.2.5 Anion Exclusion.- 1.3.2.6 Modeling of Anion Exclusion.- 1.3.2.7 Estimating the Osmotic Efficiency Coefficient Function ? (?,c).- 1.3.3 Retention of Uncharged Solutes.- 1.4 Salt Dissolution and Precipitation.- 1.4.1 Primary Minerals.- 1.4.2 Carbonate Minerals.- 1.4.3 Evaporite Minerals.- 1.5 Diagnosis of Salinity Problems.- 1.5.1 Diagnostic Parameters.- 1.5.2 Saline Conditions.- 1.5.3 Sodic Conditions.- 1.5.4 Other Salinity Problems.- 2 Transportation and Distribution of Salts.- 2.1 Water Movement Processes.- 2.1.1 Flow of Viscous Fluid.- 2.1.2 Darcy's Equation.- 2.1.3 Unsteady (Transient) Water Flow.- 2.1.4 Vapor Flow.- 2.1.5 Infiltration of Water into Soils.- 2.1.6 Redistribution of Soil Water.- 2.2 Salt Transport in Soils.- 2.2.1 Transport by Diffusion Without Solution Flow.- 2.2.2 Transport of Salt by Convection.- 2.2.3 Combined Effects of Diffusion and Convection on Salt Transport.- 2.2.4 Miscible Displacement in Soils.- 2.2.5 Solute Reflection During Water Flow.- 2.2.6 Solute Chromatography in Soils.- 2.2.6.1 Qualitative Description.- 2.2.6.2 Quantitative Description of Chromatographic Processes.- 2.2.6.3 Application of Chromatographic Theories to Soil Systems.- 2.2.7 Effects of Salinity on Soil Water Transmission Rates.- 2.2.7.1 Effects of Salt Concentration Gradients.- 2.2.7.2 Modified Solution Flux Equation.- 2.3 Modeling of Salt-Flow Phenomena.- 2.3.1 Mathematical and Numerical Models.- 2.3.2 Mathematical Modeling of Transport Phenomena in Soils.- 2.3.3 Numerical Methods Applied to Transient Flow Problems.- 2.3.3.1 Finite-Difference Methods.- 2.3.3.2 Finite Element Method.- 2.3.4 Salt Dynamics and Distribution in Fallow Soils.- 2.3.4.1 Noninteractive Solute.- 2.3.4.2 Solute Interacting with Soil.- 2.3.5 Modeling of Salt Dynamics and Distribution in Soils Under Crop Growing Conditions.- 2.3.5.1 Models for Water Extraction by Crop Roots.- 2.3.5.2 Computed Salt Distribution Profiles and Measured Data.- 2.3.6 Solute Dispersion and Distribution in Heterogeneous Field Soils.- 2.3.6.1 Piston Flow Profiles.- 2.3.6.2 Dispersive Profiles.- 3 Management.- 3.1 Crop Salt Tolerance.- 3.1.1 Osmotic Effects.- 3.1.2 Specific-Ion Effects.- 3.1.3 Plant Sensitivity.- 3.1.4 Crop Selection.- 3.2 Irrigation Practice.- 3.2.1 Irrigation Water Quality.- 3.2.2 Water Quality Classifications.- 3.2.3 Leaching Requirement.- 3.2.4 Drainage Water Quality.- 3.2.5 Salt Balance.- 3.3 Reclamation of Saline and Sodic Soils.- 3.3.1 Reclaiming Saline Soils by Leaching.- 3.3.2 The Use of Mulches and Other Surface Management to Enhance Salt Leaching.- 3.3.3 Gypsum Use for Reclaiming Sodic Soils.- 3.3.4 High Salt Water Leaching.- 3.3.5 Deep Mixing Sodic Soils for Reclamation.- 3.3.6 Sulfuric Acid for Reclaiming Sodic Soils.- 3.4 Solute Flow Models Applied to Irrigation Management Optimization.- 3.4.1 Reclamation of Saline Soils by Leaching.- 3.4.2 Quantity-Quality Substitutions of Water During the Irrigation Season.- 3.4.2.1 Modeling of Crop Response to Soil Salinity..- 3.4.2.2 Optimizing the Quantity-Quality Combination of the Irrigation Water.- 3.4.3 Models for the Economic Evaluation of Salinity in Irrigation Water Management.- 3.4.3.1 Least Cost Quantity-Quality Combinations Based on the Critical-Threshold Concept.- 3.4.3.2 Optimal Irrigation Management Based on the Total Potential Approach.- 3.4.3.3 Modeling of Optimal Irrigation Scheduling.- 3.5 Specialized Management Practices.- References.