Hydroponics literally means water working however, in practical use, it means growing plants in a nutrient solution without soil. The hydroponic science had proved that soil isnt required for plant growth but the elements, minerals and nutrients that soil contains are. Soil is a place where the plant roots traditionally live and a base of support for the plant structure. Soil is simply the holder of the nutrients. By eliminating the soil, you eliminate soil borne disease and weeds and gain precise control over the plants nutritional diet. In a hydroponic solution, you provide the exact nutrients your plants need in precisely the correct ratios so they can develop stress-free mature faster and, at harvest, are the highest quality possible.
In commercial production, the two primary growing methods are NFT (Nutrient Film Technique) and drip (also known as substrate). There are a number of variations of these methods and also several others including the float system, ebb and flow system, Aeroponics and passive. The biggest difference between the NFT systems and drip systems is the use of a growing medium. In an NFT system, the plant roots are in a channel where a thin film of nutrient solution passes, keeping them moist but not water-logged. In a drip system, the plant roots are in a growing medium such as Perlite or Rockwool and the nutrient solution is dripped onto the medium to keep it moist.
NFT (Nutrient Film Technique)
With the NFT (also known Nutrient Film Technique) technique, the plants are grown in channels (also called gullies) in which the nutrient solution is pumped through. The plant roots are kept moist by the thin film of nutrient solution as it passes by. Ideally, the bottom of the roots is exposed to the nutrient solution while the top are kept moist but not water-logged.
With the development of on-demand dosing equipment, a nutrient reservoir can automatically be adjusted and, with proper aeration and pH adjustment, the system can effortlessly be kept fresh for weeks at a time. Most NFT channels are fed continuously at a rate of approximately 1 liter per minute. Since the plant roots are not in a growing medium, it is crucial that they are kept moist at all times. In most NFT systems, the nutrient solution is mixed in a primary reservoir, cycled through the channels and back to the reservoir.
NFT is ideal for short term crops like lettuce, leafy crops and herbs. In many locations around the world, Larger NFTchannels are used for long term crops such as tomatoes and cucumbers. One great benefit of NFT, especially for leafy crops, is that no washing is necessary since there no growing medium and no soil, and hence the crop is clean. Growers, chefs, grocers and consumers all appreciate this.
Most growers have found flat bottomed channels or gullies provide greater surface area for root development and oxygen uptake, resulting in better, faster plant development. NFT channels are usually set up on waist-high stands that slope slightly to allow the nutrient solution to drain to one end.
Aeroponics
Though Aeroponics is a unique way of growing; it is not a common means of commercial production. Aeroponics is the method of growing where the plant roots are constantly misted with a nutrient solution. Designs include an A-frame with boards on each side, plant plugs set in each side and a mister between the boards spraying the roots. A round, large diameter PVC pipe set vertically with plant plugs all they way around and a mister mounted inside is another way to set up an Aeroponic system.
Ebb and Flow
The Ebb and Flow method of hydroponics simply floods a growing area for 5 or 10 minutes and then the nutrient solution drains away. The nutrient solution is stored in a reservoir that can be located under the grow table. In an Ebb and Flow, the plant roots are usually grown in a medium of Perlite, Rockwool or expanded clay pebbles. Ebb and Flow is common in hobby systems but not often found in commercial production. This is also know as flood and drain.
Float
The float system can be an economical means of hydroponic crop production in areas where raw materials are limited and manufactured hydroponic systems and components are not availableFloat systems take advantage the surface of the nutrient solution. Most float systems are long, rectangular reservoirs built out of cement or wood and lined with a durable, poly liner. Holes are cut in a foam board which floats on the surface of the water and plants in net pots are set in the holes. The plant roots dangle in heavily aerated nutrient solution.
Passive
A passive system does not use timers or pumps to flood the root zone. The roots usually draw what they need by dangling into the nutrient solution. Being a slow growing system, passive system is not as productive as the other methods discussed. Passive hydroponic systems are sometimes used by hobbyists.
Drip (Substrate)
Long term crops like tomatoes, cucumbers and peppers are grown using the Drip system. In this system, the nutrient solution is delivered to the plants through drip emitters on a timed system. Depending on the stage of development of the plant and the amount of available light, the emitters are usually scheduled to run for approximately 10 minutes/hour. The drip cycle provides the plants with fresh nutrients, water and oxygen, thus flushes the growing medium.
Commercially, in a drip system, Perlite or Rockwool are the most common mediums for the plant growth. The biggest variables in a drip system are in the growing medium and the container that holds that medium. Perlite is often bagged in thin, plastic sleeves. Holes are cut in the bag and plants, usually 3-4, are set in with the roots growing down into the Perlite. Recently, a bucket system has been developed to contain Perlite for drip systems. Each bucket holds loose Perliteand one or two plants. In either of these methods, a slot or hole is cut in the container to allow excess nutrient solution to run out. A drain line below the bag or bucket collects the excess.
The Perlitetray is the another method of a drip system that is becoming popular for lettuce and herb production. Usually it is about 24 inches wide by 1014 feet long. An aluminum tray, coated with a non-toxic material, is filled with Perlite and set on a gentle slope of 1-inch to 10-feet. The nutrientsolution is continuously dripped in at the higher end of the tray and allows trickling through the Perlite to the other end. Basically, this system is a combination of drip and NFT techniques.
In this case, there is no need for a large nutrientreservoir tank or the periodic dumping of used nutrient. Injectors are used, in most drip systems, to add nutrient concentrates to water when the feed cycle starts.
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