Chapter 9

Greenhouse Plant Growing Systems

Hydroponic Systems

Hydroponics is a technology for growing plants in nutrient solutions (water and fertilizers), with or without the use of an artificial substrate (e.g. sand, gravel, vermiculite, rockwool, peat moss, sawdust) to provide mechanical support. Sometimes hydroponics is referred to as soilless culture because soil is not used. Liquid hydroponic systems have no other supporting substrate for the plant roots; aggregate systems have a solid substrate of support. Hydroponic systems are further categorized as open (i.e., once the nutrient solution is delivered to the plant roots, it is not reused) or closed (i.e., surplus solution is recovered, replenished, and recycled). Hydroponics has been recognized as a viable method of producing vegetables (tomatoes, lettuce, eggplant, spinach, melons, cucumbers, and peppers) as well as ornamental crops such as herbs, roses, freesia, and foliage plants. Some fruit crops—for example, strawberries and raspberries—are also well-suited to hydroponics. Hydroponic culture of greenhouse vegetables involves the production of crops in sand, gravel, or artificial soil-less mixes in bags, tubes, tubs, tanks, or troughs designed to allow the circulation of nutrient media needed for crop growth. Unlike conventional soil culture, hydroponic culture of greenhouse vegetables is less forgiving and requires intense management. Although present automation systems can minimize fertilization and irrigation labor inputs, continuous monitoring of the system is important. Growers must be highly knowledgeable about plant growth, nutrient balances, cultural media characteristics, and plant physiology.


Hydroponic production has a number of advantages:

  • Because hydroponics does not use soil, soil-borne diseases and pests that live in soil cannot damage hydroponic crops.
  • Hydroponic systems do not have weed seeds that might germinate and compete with crops for water, nutrients, and light. Soil contains dormant weed seeds that germinate when given the right conditions.
  • Hydroponic systems allow for every plant’s optimal nutrient needs to be addressed. The plants do not have to compete for available nutrients and can therefore be placed closer together. The amount of nutrients needed by the plants are adjusted accordingly during the plant’s life cycle. As plants mature, the type and amount of nutrients can be easily adjusted in a hydroponic system.

Hydroponic production has a number of disadvantages:

  • Despite of many advantages, hydroponics culture has some limitations. Application on commercial scale requires technical knowledge and higher initial capital expenditure.  High degree of management skills is necessary for solution preparation, maintenance of pH and Ec, nutrient deficiency judgment and correction, ensuring aeration; maintenance of favorable condition inside protected structures, etc.
  • Some diseases like Fusarium and Verticillium can spread quickly through a hydroponic system.
  • Finally energy inputs are necessary to run the system. Considering the significantly high cost, hydroponics is limited to high value crops of the area of cultivation.

Liquid Hydroponic Systems

In liquid hydroponic systems, no solid substrate is used except at the time of sowing, such as the case of vegetables where urethane sponges are used to raise seedlings. The roots of the plant are continuously or intermittently immersed in nutrient solution.

Aggregate Hydroponic Systems

In aggregate hydroponic systems involve the use of aggregate or substrate materials that help support plants. Such materials allow the plants to take root. Common substrates include sand, perlite, vermiculite, gravel, peat moss, and rock wool. All these materials are considered inert. They do not provide nutrients to the plants. Solutions provide the plants with essential nutrients. Aggregate systems may similarly be either open or closed, depending on whether, once delivered, surplus amounts of the solution are recovered and reused. Open systems do not recycle the nutrient solution. Closed systems do. Different containers characterize the different production systems within this category. The fertigation and drainage of these systems are all somewhat similar. Differences in the media will require minor adjustments in the frequency and amounts of solution to be applied.

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