Chapter 14

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 factors 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 too. 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 irrigations systems are typically open irrigation systems where the nutrient solution is allowed to pass through the root zone and out into the environment. Subirrigations 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 total water applied. For these reasons, 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., electric) 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 greenhouse production systems.

Topics Within This Chapter:

  • Soil Culture
  • Greenhouse Soils Amended with Compost or Manure
  • National Organic Program Standards for Compost
  • NOP Standards on Composts Used for Crop Production
  • Soilless Culture
  • Advantages and Disadvantages of Soiless Culture Systems
  • Advantages
  • Disadvantages
  • Hydroponic Systems
  • Nutrient Film Technique
  • Floating Raft System
  • Aeroponic System
  • Substrate Culture Systems
  • Capillary Mat System
  • Ebb-and-Flow System
  • Flooded Floor System
  • Trough Bench System
  • Trough Culture System
  • Floor Culture System
  • Lay-Flat Bag Container Culture System
  • Vertical Container Technique
  • Hanging Bag Technique
  • Deep Flow Technique
  • Hanging Basket System