Soilless Culture: Theory and Practice,

List of Contributors

Preface

1 Significance of Soilless Culture in Agriculture

1.1 Historical Facets of Soilless Production

1.2 Hydroponics

1.3 Soilless Production Agriculture

References

2 Functions of the Root System

2.1 The Functions of the Root System

2.2 Depth of Root Penetration

2.3 Water Uptake

2.4 Response of Root Growth to Local Nutrient Concentrations

2.4.1 Nutrient Uptake

2.4.2 Root Elongation and P Uptake

2.4.3 Influence of N Form and Concentration

2.5 Interactions Between Environmental Conditions and Form of N Nutrition

2.5.1 Temperature and Root Growth

2.5.2 Role of Ca in Root Elongation

2.5.3 Light Intensity

2.5.4 pH

2.5.5 Urea

2.5.6 Mycorrhiza–Root Association

2.6 Roots as Source and Sink for Organic Compounds and Plant Hormones

2.6.1 Hormone Activity

References

Further Readings

3 Physical Characteristics of Soilless Media

3.1 Physical Properties of Soilless Media

3.1.1 Bulk Density

3.1.2 Particle Size Distribution

3.1.3 Porosity

3.1.4 Pore Distribution

3.2 Water Content and Water Potential in Soilless Media

3.2.1 Water Content

3.2.2 Capillarity, Water Potential and its Components

3.2.3 Water Retention Curve and Hysteresis

3.3 Water Movement in Soilless Media

3.3.1 Flow in Saturated Media

3.3.2 Flow in an Unsaturated Media

3.3.3 Richards Equation, Boundary and Initial Conditions

3.3.4 Wetting and Redistribution of Water in Soilless Media – Container Capacity

3.4 Uptake of Water by Plants in Soilless Media and Water Availability

3.4.1 Root Water Uptake

3.4.2 Modeling Root Water Uptake

3.4.3 Determining Momentary and Daily Water Uptake Rate

3.4.4 Roots Uptake Distribution Within Growing Containers

3.4.5 Water Availability vs. Atmospheric Demand

3.5 Solute Transport in Soilless Media

3.5.1 Transport Mechanisms – Diffusion, Dispersion, Convection

3.5.2 Convection–Dispersion Equation

3.5.3 Adsorption – Linear and Non-linear

3.5.4 Non-equilibrium Transport – Physical and Chemical Non-equilibria

3.5.5 Modeling Root Nutrient Uptake – Single-root and Root-system

3.6 Gas Transport in Soilless Media

3.6.1 General Concepts

3.6.2 Mechanisms of Gas Transport

3.6.3 Modeling Gas Transport in Soilless Media

References

4 Irrigation in Soilless Production

4.1 Introduction

4.1.1 Water Movement in Plants

4.1.2 Water Potential

4.1.3 The Root Zone

4.1.4 Water Quality

4.2 Root Zone Moisture Dynamics

4.2.1 During an Irrigation Event

4.2.2 Between Irrigation Events

4.2.3 Prior to an Irrigation Event

4.3 Irrigation Objectives and Design Characteristics

4.3.1 Capacity

4.3.2 Uniformity

4.4 Irrigation Delivery Systems

4.4.1 Overhead Systems

4.4.2 Surface Systems

4.4.3 Subsurface

4.5 Irrigation System Control Methods

4.5.1 Occasional Irrigation

4.5.2 Pulse Irrigation

4.5.3 High Frequency Irrigation

4.5.4 Continuous Irrigation

4.6 Irrigation Decisions

4.6.1 Irrigation Frequency

4.6.2 Duration of Irrigation Event

4.7 Approaches to Making Irrigation Decisions

4.7.1 ‘Look and Feel’ Method

4.7.2 Gravimetric Method

4.7.3 Time-based Method

4.7.4 Sensor-based Methods

4.7.5 Model-based Irrigation

4.8 Future Research Directions

References

5 Technical Equipment in Soilless Production Systems

5.1 Introduction

5.2 Water and Irrigation

5.2.1 Water Supply

5.2.2 Irrigation Approaches

5.2.3 Fertigation Hardware

5.3 Production Systems

5.3.1 Systems on the Ground

5.3.2 Above-ground Production Systems

5.4 Examples of Specific Soilless Crop Production Systems

5.4.1 Fruiting Vegetables

5.4.2 Single-harvest Leaf Vegetables

5.4.3 Single-harvest Sown Vegetables

5.4.4 Other Speciality Crops

5.4.5 Cut Flowers

5.4.6 Potted Plants

5.5 Discussion and Conclusion

References

6 Chemical Characteristics of Soilless Media

6.1 Charge Characteristics

6.1.1 Adsorption of Nutritional Elements to Exchange Sites

6.2 Specific Adsorption and Interactions Between Cations/Anions and Substrate Solids

6.2.1 Phosphorus

6.2.2 Zinc

6.2.3 Effects of P and Zn Addition on Solution Si Concentration

6.3 Plant-induced Changes in the Rhizosphere

6.3.1 Effects on Chemical Properties of Surfaces of Substrate Solids

6.3.2 Effects on Nutrients Availability

6.3.3 Assessing the Impact of Plants: The Effect of Citric Acid Addition on P Availability

6.4 Nutrient Release from Inorganic and Organic Substrates

References

7 Analytical Methods Used in Soilless Cultivation

7.1 Introduction

7.1.1 Why to Analyze Growing Media?

7.1.2 Variation

7.1.3 Interrelationships

7.2 Physical Analysis

7.2.1 Sample Preparation (Bulk Sampling and Sub-sampling)

7.2.2 Bulk Sampling Preformed Materials

7.2.3 Bulk Sampling Loose Material

7.2.4 Sub-sampling Pre-formed materials

7.2.5 Sub-sampling Loose Materials

7.3 Methods

7.3.1 Bulk Density

7.3.2 Porosity

7.3.3 Particle Size

7.3.4 Water Retention and Air Content

7.3.5 Rewetting

7.3.6 Rehydration Rate

7.3.7 Hydrophobicity (or Water Repellency)

7.3.8 Shrinkage

7.3.9 Saturated Hydraulic Conductivity

7.3.10 Unsaturated Hydraulic Conductivity

7.3.11 Oxygen Diffusion

7.3.12 Penetrability

7.3.13 Hardness, Stickiness

7.4 Chemical Analysis

7.4.1 Water-soluble Elements

7.4.2 Exchangeable, Semi- and Non-water Soluble Elements

7.4.3 The pH in Loose Media

7.4.4 Nitrogen Immobilization

7.4.5 Calcium Carbonate Content

7.5 Biological Analysis

7.5.1 Stability (and Rate of Biodegradation)

7.5.2 Potential Biodegradability

7.5.3 Heat Evolution (Dewar Test)

7.5.4 Solvita Test™

7.5.5 Respiration Rate by CO2 Production

7.5.6 Respiration Rate by O2 Consumption (The Potential Standard Method)

7.5.7 Weed Test

7.5.8 Growth Test

References

8 Nutrition of Substrate-grown Plants

8.1 General

8.2 Nutrient Requirements of Substrate-grown Plants

8.2.1 General

8.2.2 Consumption Curves of Crops

8.3 Impact of N Source

8.3.1 Modification of the Rhizosphere pH and Improvement of Nutrient Availability

8.3.2 Cation-anion Balance in Plant and Growth Disorders Induced by NH4+ Toxicity

8.4 Integrated Effect of Irrigation Frequency and Nutrients Level

8.4.1 Nutrient Availability and Uptake by Plants

8.4.2 Direct and Indirect Outcomes of Irrigation Frequency on Plant Growth

8.5 Salinity Effect on Crop Production

8.5.1 General

8.5.2 Salinity-nutrients Relationships

8.5.3 Yield Quality Induced by Salinity-nutrients8.6 Composition of Nutrient Solution

8.6.1 pH Manipulation

8.6.2 Salinity Control

References

9 Fertigation Management and Crops Response to Solution Recycling in Semi-closed Greenhouses

9.1 System Description

9.1.1 Essential Components

9.1.2 Processes and System Variables and Parameters

9.1.3 Substrate Considerations

9.1.4 Monitoring

9.1.5 Control

9.2 Management

9.2.1 Inorganic Ion Accumulation

9.2.2 Organic Carbon Accumulation

9.2.3 Microflora Accumulation

9.2.4 Discharge Strategies

9.2.5 Substrate and Solution Volume Per Plant

9.2.6 Effect of Substrate Type

9.2.7 Water and Nutrients Replenishment

9.2.8 Water Quality Aspects

9.2.9 Fertigation Frequency

9.2.10 pH Control: Nitrification and Protons and Carboxylates Excretion by Roots

9.2.11 Root Zone Temperature

9.2.12 Interrelationship Between Climate and Solution Recycling

9.2.13 Effect of N Sources and Concentration on Root Disease Incidence

9.3 Specific Crops Response to Recirculation

9.3.1 Vegetable Crops

9.3.2 Ornamental Crops

9.4 Modeling the Crop-Recirculation System

9.4.1 Review of Existing Models

9.4.2 Examples of Closed-loop Irrigation System Simulations

9.5 Outlook: Model-based Decision-support Tools for Semi-Closed Systems

Acknowledgment

Appendix

References

10 Pathogen Detection and Management Strategies in Soilless Plant Growing Systems

10.1 Introduction

10.1.1 Interaction Between Growing Systems and Plant Pathogens

10.1.2 Disease-Management Strategies

10.1.3 Overview of the Chapter

10.2 Detection of Pathogens

10.2.1 Disease Potential in Closed Systems

10.2.2 Biological and Detection Thresholds

10.2.3 Method Requirements for Detection and Monitoring

10.2.4 Detection Techniques

10.2.5 Possibilities and Drawbacks of Molecular Detection Methods for Practical Application

10.2.6 Future Developments

10.3 Microbial Balance

10.3.1 Microbiological Vacuum

10.3.2 Microbial Populations in Closed Soilless Systems

10.3.3 Plant as Driving Factor of the Microflora

10.3.4 Biological Control Agents

10.3.5 Disease-suppressive Substrate

10.3.6 Conclusions

10.4 Disinfestation of the Nutrient Solution

10.4.1 Recirculation of Drainage Water

10.4.2 Volume to be Disinfected

10.4.3 Filtration

10.4.4 Heat Treatment

10.4.5 Oxidation

10.4.6 Electromagnetic Radiation

10.4.7 Active Carbon Adsorption

10.4.8 Copper Ionization

10.4.9 Conclusions

10.5 Synthesis: Combined Strategies

10.5.1 Combining Strategies

10.5.2 Combining Biological Control Agents and Disinfestation

10.5.3 Non-pathogenic Microflora After Disinfestation

10.5.4 Addition of Beneficial Microbes to Sand Filters

10.5.5 Detection of Pathogenic and Beneficial Micro-organisms

10.5.6 Future

Acknowledgments

References

11 Organic Soilless Media Components

11.1 Introduction

11.2 Peat

11.2.1 Chemical Properties

11.2.2 Physical Properties

11.2.3 Nutrition in Peat

11.3 Coir

11.3.1 Production of Coir

11.3.2 Chemical Properties

11.3.3 Physical Properties

11.3.4 Plant Growth in Coir

11.4 Wood Fiber

11.4.1 Production of Wood Fiber

11.4.2 Chemical Properties

11.4.3 Physical Properties

11.4.4 Nitrogen Immobilization

11.4.5 Crop Production in Wood Fiber

11.4.6 The Composting Process

11.5 Bark

11.5.1 Chemical Properties

11.5.2 Nitrogen Immobilization

11.5.3 Physical Properties

11.5.4 Plant Growth

11.6 Sawdust

11.7 Composted Plant Waste

11.8 Other Materials

11.9 Stability of Growing Media

11.9.1 Physical and Biological Stability

11.9.2 Pathogen Survival in Compost

11.10 Disease Suppression by Organic Growing Media

11.10.1 The Phenomenon and its Description

11.10.2 Suggested Mechanisms for Suppressiveness of Compost Against Root Diseases

11.10.3 Horticultural Considerations of Use of Compost as Soilless Substrate

References

12 Inorganic and Synthetic Organic Components of Soilless Culture and Potting Mixes

12.1 Introduction

12.2 Most Commonly Used Inorganic Substrates in Soilless Culture

12.2.1 Natural Unmodified Materials

12.2.2 Processed Materials

12.2.3 Mineral Wool

12.3 Most Commonly Used Synthetic Organic Media in Soilless Culture

12.3.1 Polyurethane

12.3.2 Polystyrene

12.3.3 Polyester Fleece

12.4 Substrates Mixtures — Theory and Practice

12.4.1 Substrate Mixtures — Physical Properties

12.4.2 Substrate Mixtures — Chemical Properties

12.4.3 Substrate Mixtures — Practice

12.5 Concluding Remarks

Acknowledgments

References

13 Growing Plants in Soilless Culture: Operational Conclusions

13.1 Evolution of Soilless Production Systems

13.1.1 Major Limitation of Soilless - vs. Soil-growing Plants

13.1.2 The Effects of Restricted Root Volume on Crop Performance and Management

13.1.3 The Effects of Restricted Root Volume on Plant Nutrition

13.1.4 Root Confinement by Rigid Barriers and Other Contributing Factors

13.1.5 Root Exposure to Ambient Conditions

13.1.6 Root Zone Uniformity

13.2 Development and Change of Soilless Production Systems

13.2.1 How New Substrates and Growing Systems Emerge (and Disappear)

13.2.2 Environmental Restrictions and the Use of Closed Systems

13.2.3 Soilless ‘Organic’ Production Systems

13.2.4 Tailoring Plants for Soilless Culture: A Challenge for Plant Breeders

13.2.5 Choosing the Appropriate Medium, Root Volume and Growing System

13.3 Management of Soilless Production Systems

13.3.1 Interrelationships Among Various Operational Parameters

13.3.2 Dynamic Nature of the Soilless Root Zone

13.3.3 Sensing and Controlling Root-zone Major Parameters: Present and Future

References

Index of Organism Names

Subject Index