Chapter 17

Fertigation in Greenhouse Production

(draft 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.

Click on the following topics for more information on fertigation in greenhouse production.

Topics Within This Chapter:

  • Chemical Injectors for Fertigation Systems
  • Pressure Differential Tanks
  • Advantages and Disadvantages of Pressure Differential Tanks
  • Venturi Injectors
  • Advantages and Disadvantages of Venturi Injectors
  • Venturi Injector Configurations
  • Positive Displacement Pumps
  • Advantages and Disadvantages of Positive Displacement Pumps
  • Dosatron Injectors
  • DosMatic Injectors
  • Anderson Ratio:Feeder Injectors
  • Smith Measuremix Injectors
  • Gewa Injectors
  • Criteria for Selecting an Injector
  • Water Flow and Pressure
  • Injector Ratio
  • Types of Chemicals Injected
  • Multiple Injection Heads
  • Multiple Parallel Injectors
  • Portable of Injectors
  • Repair Costs and Reliability
  • Installing an Injector
  • Stock Tanks
  • Checking Water Flow Rate on Injectors
  • Calibrating an Injector
  • Volume Ratio Method
  • Electrical Conductivity Measurement
  • Fertigation Backflow Prevention
  • Irrigation Pipeline Check Valve
  • Low-Pressure Drains
  • Vacuum Relief Valve
  • Chemical Injection Line Check Valve
  • Containment Structures
  • Criteria for Selecting Fertilizers for Fertigation
  • Fertilizer Formulations
  • Liquid Fertilizers
  • Granular Fertilizers
  • Fertilizer Compatibility
  • Fertilizer Solubility
  • Jar Test
  • Application Techniques
  • Water Quality
  • Water Treatment
  • Fertilizers for Fertigation
  • Nitrogen Sources
  • Ammonium Nitrate (AN)
  • Ammonium Phosphate
  • Ammonium Sulfate (AS or AMS)
  • Ammonium Thiosulfate (ATS)
  • Anhydrous Ammonia or Aqua Ammonia
  • Calcium Ammonium Nitrate (CAN)
  • Calcium Nitrate (CN)
  • Urea Ammonium Nitrate (CAN)
  • Urea Sulfuric Acid
  • Phosphorus Sources
  • Ammonium Polyphosphate
  • Diammonium Phosphate (DAP)
  • Mono-Ammonium Phosphate (MAP)
  • Monobasic Potassium Phosphate
  • Phosphoric Acid
  • Urea Phosphate
  • Potassium Sources
  • Potassium Chloride
  • Potassium Nitrate
  • Potassium Sulfate
  • Potassium Thiosulfate (KTS)
  • Other Macronutrients
  • Micronutrients
  • Calculating Fertilizer Stock Solutions for Fertigation
  • Parts Per Million Basis
  • Weight Basis
  • Incomplete Fertilizer Calculations
  • References