Protected Culture Club Builds For Florida Growers
November 1, 2007 Vegetable greenhouse production systems include several options, including bag culture, trough culture, rockwool, nutrient film technique (NFT), and ground (in-soil) culture.
There are also several minor production systems, including container culture, ring culture, straw bale, and aeroponics. Aeroponics is a relatively new production system that involves growing plants in a trough or container in which the roots are suspended and sprayed with a nutrient mist.
These greenhouse production systems require the use of similar environmental controls, shade structures, support wires, and general production practices. The major differences would be in the irrigation and nutrient delivery methods and controls. In Florida, these production systems have comparable costs and produce good yields when managed properly. Research studies have shown that there was no significant difference in tomato yield among rockwool, bag, and hydroponic NFT systems. However, the study found that all of these systems produced higher yields than ground culture.
Here are some highlights of different greenhouse production systems:
Bag Culture
Trough Culture
• In the trough system, shallow wooden troughs contain the growing media. The troughs may vary from 6 to 8 inches deep and from 24 to 30 inches wide. The troughs can be plastic-lined to facilitate collection of excess nutrient solution.
• Drip systems used should consist of one of the systems that applies solution directly to the media via a drip emitter or ring. Growers should avoid the spray-stake types since they can wet the leaves and stems and promote disease.
• The major advantages of the trough system include ease of handling once the system is in place. Trough systems are flexible for various cropping decisions (e.g., vegetables, cut flowers, etc). The system is relatively inexpensive to maintain from one crop season to another.
Perlite And Rockwool Culture
• Rockwool is an inert, porous, sterile growing medium made from rocks that are heated at high temperatures and formed into thin fibers. The resulting fibers can be formed into slabs or bagged as a loose rockwool for bag culture.
• Perlite is a volcanic mineral that is expanded by heating at high temperature in a furnace. The resulting light-weight granular material makes a good media with high water-holding capacity.
• Rockwool perlite cultures are similar to bag culture in greenhouse layout and operation. Slabs are laid in twin-rows and are irrigated by microirrigation with one emitter per plant.
• Rockwool or perlite culture has many advantages over other production systems. Among these are the ease of handling, installation, and media removal. Rockwool and perlite have high-water holding capacities and allow for more precise control of nutrients. Each medium is inert and sterile and offers predictable performance. The media has very high air pore space, which provides for higher oxygen levels and thus better root growth.
Nutrient Film Technique
• Nutrient film technique (NFT) is a type of a “water culture” system in which roots are continually bathed in a flowing nutrient solution. True NFT consists of growing plants in a shallow plastic-lined trough through which a nutrient solution is continually flowed.
• In all NFT or modified NFT systems, channels and plants are arranged in the greenhouse similar to bag or rockwool culture (twin-rows, plant spacing, etc.).
• Crops adaptable to NFT include tomatoes, cucumbers, and lettuce. Lettuce is particularly adapted to NFT because it is a short-term crop and less subject to the damage from root rot.
• A major advantage of NFT is the one-time expense for the basic system. The major problem with the NFT systems is the high probability that disease organisms such as pythium could be recirculated quickly within the greenhouse.
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