Introduction

The hydroponic production of lettuce has revolutionised the salad industry worldwide. Crops can be produced year round, with the benefits of faster, cleaner production and a premium quality end-product. At the same time, newer varieties of lettuce, with improved colours and leaf shapes, have seen the market expand dramatically. This book is designed to provide essential information of a practical and scientific nature for current and prospective hydroponic lettuce growers. While hydroponic salad crops are often seen as being easier to produce than fruiting crops, such as tomatoes and cucumbers, the degree of skill required to produce a quality product and effectively utilise hydroponic technology is still high. The text explores everything from the background physiology of the lettuce plant, to the details of growing systems and management, raising seedlings, selecting cultivars, nutrition, pests and diseases, and harvesting. Hydroponic Lettuce Production represents an essential handbook for salad production in the 21st Century.

Contents

	Introduction
	Background and origin of the lettuce plant
	History
	New Zealand Industry
	Marketing of Fresh Lettuce in New Zealand
	Fresh Cut Produce 12 The Australian Industry

Chapter 2

	The Lettuce Plant - Germination & Media
	Lettuce Propagation - Seed
	Dormancy and Storage
	Seed Sowing
	Media and Seedling Propagation Containers
	Selection of a Seed Raising Media
	Oasis Blocks
	Rockwool or Growool
	Compressed Peat Blocks/Pellets
	Media and Types of Seedling Propagation Trays
	Composted Bark
	Perlite
	Vermiculite
	Pumice
	Sand
	Scoria
	Expanded Clay
	Germination and Seedling Development
	The Germination Process
	Seed Sowing - Water, Oxygen and Light
	Seedling Nutrition
	Planting Out
	Disease Control During Germination and Seedling Development
	Damping Off Diseases
	Treatment for Damping Off Diseases
	Germination Problems
	Crop Production Problems
	Leaf Colouration
	Temperature
	Lettuce Plant Spacing and Densities

Chapter 3

	Cultivars
	Introduction
	Lettuce Physiology
	Lettuce Types - The Main Groups
	Crisp Head (Iceberg) Types
	Butter Head (or Boston) Types
	Butter Head (or Boston) Cultivars
	Oak Leaf and Salad Bowl Types
	Oak Leaf and Salad Bowl Cultivars
	Lollo Rossa and Lollo Bionda (Red/Green Frill or Coral) Types
	Lollo Rossa and Lollo Bionda (Red/Green Frill or Coral) Cultivars
	Loose Leaf (or Leaf Lettuce) Types
	Loose Leaf (or Leaf Lettuce) Cultivars
	Cos (or Romaine) Types
	Cos (or Romaine) Cultivars
	Other Hydroponic Salad Crops
	Endive and Chicory
	Chicory and Endive Cultivars
	Chicory - Italian and Catalogna Types
	Endive
	Hydroponic Herbs
	Mesclun Mixes (Mesclun or Saldist)
	Grower Variety Trials

Chapter 4

	Hydroponic Systems
	Introduction to Hydroponic Systems
	NFT - Nutrient Film Technique
	Lettuce in NFT
	Types of NFT systems and Gullies
	NFT and Rockwool
	Short Run Hydroponics
	Other NFT Systems
	Movable Channels
	Mechanisation
	Pipe Systems
	Floating Hydroponics
	Aeroponics - Root Mist Technique
	Aggregate Hydroponic Systems
	Open Aggregate Systems
	Bag Culture
	Closed Systems - Flood and Drain
	Non Recirculating Capillary Systems

Chapter 5

	Hydroponic System Engineering
	Setting Up a System
	Gully Size and Slope
	Tank Size
	Pump Selection
	System Layout

Chapter 6

	System Maintenance
	Electrical Conductivity (EC or CF)
	Electrical Conductivity (EC) Measurement
	Solution pH levels
	The Effect of pH on the Availability of Essential Elements
	pH Adjustment
	pH Testing
	Water Supply
	Water Sterilisation
	Nutrient Sterilisation
	The Greenhouse Environment
	Nutrient Heating and Cooling
	Air Temperatures
	Relative Humidity Levels
	Algae
	Crop Timing
	CO2 Enrichment for Greenhouse Lettuce Crops
	Filters
	Automatic Dosing Systems

Chapter 7

	Lettuce Nutrition
	Lettuce Nutrition in Hydroponic Systems
	Major Elements Required by Lettuce Crops
	Tissue Analysis
	Functions of Macro, Micro and Beneficial Elements
	Carbon
	Hydrogen
	Oxygen
	Nitrogen
	Phosphorus
	Potassium
	Calcium
	Magnesium
	Sulphur
	Iron
	Maganese
	Boron
	Zinc
	Copper
	Molybdenum
	Chlorine
	Sodium
	Nickel
	Cobalt
	Silicon
	Mineral Disorders of Lettuce
	Specific Lettuce Mineral Deficiency Symptoms
	Lettuce Mineral Toxicity Symptoms
	Nutrient Solutions
	Lettuce Formulations and Nutrient Level Recommendations
	Addition of 'Beneficial Elements'
	Nutrient Conductivity (EC or CF) and pH Implications
	Hydroponic Solution Flow Rates
	Dissolved Oxygen

Chapter 8

	Pests, Diseases and Physiological Problems
	Pests and Diseases
	Pests - Identification and Control
	Aphids
	Caterpillars
	Slugs and Snails
	Whitefly
	Whitefly Control
	Fungas Gnats
	Birds
	Thrips
	Mites
	Leaf Miners
	Lettuce Diseases - Identification and Control
	Pythium
	Downy Mildew
	Sclerotinia
	Botrytis
	Internal Soft Rot
	Lettuce Ringspot
	Bacterial Infections
	Lettuce Viruses
	Lettuce Mosaic Virus
	Cucumber Mosaic Virus
	Big Vein Virus
	Physiological Disorders
	Tipburn of Lettuce Plants
	Calcium (Ca) and TipBurn
	Glassiness
	Wilting
	Spraying for Pest and Disease Control and Sanitation
	Alternative Pest and Disease Control

Chapter 9

	Harvesting and Shelf Life
	Harvesting of Lettuce Crops
	Post Harvest Handling
	Cooling and Refrigeration
	Modified Atmosphere Packaging for Fresh Cut Produce
	Packaging Films
	References