Irrigating Greenhouse Crops
(book excerpts)The irrigation of greenhouse crops is one of the most critical of all production practices. And yet it is frequently overlooked and taken for granted. To provide conditions for optimum plant growth, it is essential to become familiar with the conditions that influence soil moisture. In most cases, water is applied to the upper surface of the media. This water may be applied by means of an overhead sprinkler, micro-irrigation, by hand using a hose or similar device, or some combination of these delivery systems. Overhead sprinklers and hand watering tend to waste water and also wet the foliage, which increases the potential for diseases and injury. Micro-irrigation systems are the most efficient and provide greater control over the amount of water applied. Also, since the foliage does not become wet, there is a reduced potential for diseases and injury. Water may also be applied to greenhouse crops using subirrigation systems. In subirrigation systems, water and nutrient solution provided at the base of the container rises by capillary action through holes in the bottom and is absorbed by the growing media. Overhead irrigation systems are typically open irrigation systems where the nutrient solution is allowed to pass through the root zone and out into the environment. Subirrigation systems are typically closed irrigation systems where the nutrient solution is recirculated and not allowed to leach into the ground. The goal of irrigation scheduling is to provide plants with the quantity of water they need when they need it. The physical properties of the substrate or soil, along with container size, determine how much of the applied water is retained (water holding capacity) and how much is available to the plant. As crops grow, the portion of water that is taken up by plants rapidly increases to almost 100 percent of the total water applied. For these reasons, knowing when to irrigate and how much to apply is very important. Maximizing the efficiency of crop water application is a practical way to extend finite water supplies in a greenhouse. This also reduces energy consumption (i.e., electricity) and other inputs used to move, filter, and treat irrigation water before use or reapplication, thus increasing the profitability of your operation.
Click on the following topics for more information on irrigating greenhouse crops.
Topics Within This Chapter:
- Greenhouse Irrigation Systems
- Overhead Irrigation Systems
- Micro-Irrigation Systems
- Boom Irrigation Systems
- Sprinkler Irrigation Systems
- Subirrigation Systems
- Advantages and Disadvantages
- Media
- Water Storage Tanks
- Irrigation Scheduling
- Types of Containers
- Closed Irrigation Systems
- Hydroponics Systems
- Advantages and Disadvantages
- Crops Suitable for Hydroponics Systems
- Irrigation Efficiency
- Improving Irrigation Efficiency
- Crop Water Needs
- Irrigation Design
- Maintenance of Irrigation Systems
- Pulse Irrigations
- Irrigation Zones
- Group Plants with Similar Water Needs
- Avoid Irrigating Where No Plants Are Present
- Automation
- Monitoring Leaching Fraction
- Measuring the Amount of Water Used for Greenhouse Irrigation
- Propeller Flowmeters
- Magnetic Flowmeters
- Ultrasonic Flowmeters
- Turbine Flowmeters
- Irrigation Scheduling
- Irrigation Scheduling Methods
- Visual and Tactile Assessment
- Monitoring Container Weights
- Monitoring Evapotranspiration Rates
- Substrate Moisture Sensor Technologies
- Monitoring Leaching Fraction
- Measuring LF and Adjusting Irrigation
- Using LF in an Irrigation Program
- Conditions Affecting the Frequency and Volume of Irrigation
- Irrigation System
- Weather
- Water Quality
- Available Water Holding Capacity of Substrate
- Crop Type
- Irrigation System Controllers
- Basic Control Strategies
- Open Control Loop Systems
- Closed Control Loop Systems
- Timers
- Electromechanical Controllers
- Electronic Controllers
- Computer-Based Control Systems
- Key Features and Functionality
- Fuzzy Logic Control for Irrigation
- Water Delivery Systems
- Groundwater Wells
- Backflow Prevention
- Pressure Tanks
- Pumps
- Centrifugal Pumps
- Deep-Well Vertical Turbine Pumps
- Submersible Pumps
- Power Units for Pumping Water
- Electric Motors
- Internal Combustion Engines
- Selecting a Well Pump
- Estimating Total Irrigation Flow Rate
- Total Dynamic Head
- Total Static Head
- Well Drawdown
- Operating Head
- Friction Loss
- Velocity Head
- Suction Head
- Pump Power Requirements
- Pump Efficiency
- Reading a Pump Curve
- Friction Loss
