Fertigation in Greenhouse Production
(book excerpts)Fertigation consists of applying simultaneously water and fertilizers through the irrigation system, supplying the nutrients required by the greenhouse crops. Most commonly this is done through a drip irrigation system but it can also be done with ebbb and flow and trough bench systems. Using a fertigation system, a grower can apply the nutrients exactly and uniformly only to the wetted root volume, where the active roots are concentrated. With fertigation, plants can receive small amounts of fertilizer early in the crop’s season when plants are vegetative. The dosage is increased as nutrient demands grow and then decreased as plants approach the end of the crop’s cycle. Fertigation increases the efficiency in the application of the fertilizer, which allows reducing the amount of applied fertilizer. Nutrient characteristics such as solubility and mobility are important and irrigation water quality factors such as pH, mineral content, salinity, and nutrient solubility must be considered. The macronutrients nitrogen, potassium, phosphorus, and magnesium are the most common nutrients applied by fertigation, but micronutrients such as boron, zinc, iron, calcium manganese, and copper can also be applied through the irrigation system. In addition, to fertilizers other chemicals can be injected through the irrigation system, including chlorine, acid, herbicides, nematicides, and fungicides.
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Topics Within This Chapter:
- Fertilizer Delivery Systems
- Pressure Differential Tank Injection
- In-Line Injection
- Venturi Injectors
- Positive Displacement Injectors
- Criteria for Selecting a Fertigation Injector
- Water Flow
- Checking Water Flow Rate
- Multiple Parallel Injectors
- Injection Ratio
- Types of Chemicals Injected
- Multiple Injection Heads
- Water Quality
- Portable Injectors
- Repair Costs and Reliability
- Design and Management Considerations
- Injection Point
- Stock Tanks
- Fertigation Dosing Systems
- Batch Method
- In-Line Injection Method
- Calibrating an Injector
- Input/Output Method
- Electrical Conductivity Method
- Scheduling Fertigation
- Criteria for Selecting Fertilizers for Fertigation
- Fertilizer Formulations
- Liquid Fertilizers
- Granular Fertilizers
- Fertilizer Compatibility
- Fertilizer Solubility
- Fertilizer Solubility Considerations
- Jar Test
- Scheduling Fertigation
- Fertilizer Calculations for Greenhouse Crops
- Rates of Fertilization
- Stock Solution Calculations
