Contents

Foreword xv

Preface and Acknowledgments xvii

1 Balancing Agriculture Between Development and Conservation 1

1.1 Agriculture: a Description 1

1.1.1 Scope of Activities 1

1.1.2 Description of Agricultural Systems 2

1.1.3 Characteristics of Agricultural Systems 4

1.2 Dynamics in Agriculture 4

1.2.1 Limiting Conditions for Agriculture 4

1.2.2 Improving the Limiting Conditions for Agriculture 7

1.2.3 Demand for Agricultural Products 8

1.2.4 Major Trends in World Agriculture 9

1.3 Agriculture and the Countryside 12

1.3.1 Description of the Countryside 12

1.3.2 Countryside Values 13

1.3.3 Countryside Values and Agriculture 14

1.4 Farming: a Balance 14

1.5 Sustainability in Farming and Countryside 15

2 Land- and Water-Use Planning 19

2.1 The Planning Issue 19

2.1.1 Why Land- and Water-Use Planning Are Important 19

2.1.2 Goals 22

2.1.3 The Planning Process 24

2.1.4 Levels of Planning 37

2.1.5 Knowledge Systems 38

2.2 Land-Use Planning for Farming 43

2.2.1 Land-Use Planning 43

2.2.2 Spatial Conditions 44

2.2.3 Biophysical Conditions 50

2.2.4 Socioeconomic Conditions 53

3 Rural Roads 59

3.1 Overview 59

3.2 Rural Road Development in a Wider Context 60

3.2.1 Introduction 60

3.2.2 Rural Road Networks and LTRs 62

3.2.3 Classification of (Rural) Roads 65

3.2.4 Rural Traffic Problems and the Need for Planning 70

3.3 Planning of Rural Road Networks 73

3.3.1 Planning for the Opening Up of Agricultural Areas 73

3.3.2 Planning for the Opening Up of Developing Rural Areas 75

3.3.3 Sustainable Planning for Multiple-Use Rural Areas 77

Contents

3.4 Construction of Rural Roads 86

3.4.1 Framework Conditions 87

3.4.2 Concepts 88

3.4.3 Substratum and Foundation 88

3.4.4 Frost Problems 91

3.4.5 Drainage 91

3.4.6 Road Body 94

3.4.7 Construction 95

3.4.8 Other Types of Road Construction 97

3.4.9 Road Safety 99

3.5 Maintenance of Rural Roads 101

3.5.1 Different Concepts 103

3.5.2 Causes of Damage 105

3.5.3 Planning and Execution of Work 106

3.5.4 Financing 108

4 Land Reclamation and Conservation 113

4.1 Soil Reclamation 113

4.1.1 Assessment of the Problem 113

4.1.2 Wet Soils 114

4.1.3 Saline Soils 122

4.1.4 Derelict and Degraded Soils 126

4.1.5 Tidal Soils 131

4.2 Soil Renegeration and Improvement 135

4.2.1 Soil Degradation 135

4.2.2 Soil Regeneration 143

4.3 Assessment of Soil Erosion 153

4.3.1 Types of Erosion and Its Assessment 153

4.3.2 Measurement of Soil Losses from Erosion 161

4.3.3 Estimation of Soil Losses from Erosion 170

4.3.4 Conclusions 176

4.4 Soil Conservation: Erosion Control 184

4.4.1 Mechanical Methods 184

4.4.2 Agrobiological Measures 194

4.4.3 Measures for Wind Erosion Control 206

5 Irrigation and Drainage 213 5.1 Crop Water Requirements 213

5.1.1 Main Concepts 213

5.1.2 Evapotranspiration: The Penman-Monteith Equation 214

5.1.3 Description of the Reference Evapotranspiration 220

5.1.4 Calculation of the Reference Evapotranspiration 224

5.1.5 Crop Evapotranspiration 236

5.1.6 Soil Water Balance and Irrigation Water Requirements 254

Contents xlll

5.2 Water Retention and Movement in Soil 262

5.2.1 Basic Concepts 262

5.2.2 Soil Water Content 263

5.2.3 Soil Water Potential 267

5.2.4 Soil Water Retention Characteristics 270

5.2.5 Flow Within the Soil 273

5.2.6 Water Flow in Saturated Soil 274

5.2.7 Water Flow in Unsaturated Soil 275

5.2.8 Indirect Estimation of Water-Retention and Hydraulic-Conductivity Functions 279

5.3 Irrigation Scheduling Techniques 284

5.3.1 Introduction 284

5.3.2 Methods 285

5.3.3 Water Balance 287

5.3.4 Irrigation Programming Under Adverse Conditions 288

5.3.5 Irrigation Advisory Systems 292

5.4 Irrigation Methods 297

5.4.1 Irrigation Systems and Irrigation Performance 297

5.4.2 Surface Irrigation 301

5.4.3 Sprinkler Irrigation 320

5.4.4 Microirrigation 346

5.4.5 System Selection 369

5.5 Crop Water Management 380

5.5.1 Introduction 380

5.5.2 Effects of Water Deficits 380

5.5.3 Effects of Water Excess on Plant Physiology 386

5.5.4 Water-Use Efficiency (WUE) 388

5.5.5 Water Yield Functions 393

5.5.6 Crop Water Models 400

5.5.7 Strategies for Water Conservation in Rainfed Agriculture 405

5.5.8 Water Management Under Specific Environmental Conditions 412

5.6 Land Drainage 430

5.6.1 Introduction 430

5.6.2 Drainage Investigations 431

5.6.3 Subsurface Drainage Systems 444

5.6.4 Surface Drainage Systems 462

5.6.5 Main Drainage Systems 468

5.6.6 Drainage and the Environment: Water-Quality Aspects 476

5.7 Off-Farm Conveyance and Distribution Systems 484

5.7.1 Irrigation Systems Definitions 484

5.7.2 Irrigation Areas 485

5.7.3 Objectives of a Conveyance and Distribution System 487

5.7.4 Types of Conveyance and Distribution Systems 487

Contents

5.7.5

Management of Conveyance and Distribution Systems

490

5.7.6

Water Delivery Policies

493

5.7.7

Flow Control Systems

498

5.7.8

Some Observations on Management Inputs

502

5.8 Water

Quality in Agriculture

507

5.8.1

Quality of Water for Agricultural Use:

Impacts on Agriculture

507

5.8.2

Effects of Agricultural Activities on Water Quality

518

5.8.3

Methods of Identification, Evaluation,

Management, and Control

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