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What is Hydroponics?

Posted by Roger Marshall on 6/18/2015

Hydroponics is the art and science of growing without soil. The term was first coined by William F. Gericke around 1940 who took the word from the Greek. Gericke was among the first to grow plants on what he called "litter" suspended above a tank of water containing a nutrient solution.

Since Gericke's time hydroponics has come a long way. Instead of Gericke's leaky wooden tanks, we now have leak-proof plastic tanks. Instead of Gericke's "litter," hydroponic growers have learned how to grow hydroponics using expanded clay ballsrockwoolperlite, sand or other support medium. In Gericke's day, he made his nutrient solution from manure with chemical additives, but today we can buy a concentrated nutrient solution optimized to suit the plants being grown.

Hydroponics, then is a way to grow plants using a nutrient solution and no soil. A hydroponic system can be as simple as a 4" water pipe with holes drilled in the top for growing lettuce plants or, in its most sophisticated form, a hydroponic grower might control the entire environment in which plants are grown. This might include nutrients, nutrient Ph, lights - even to the intensity and wavelength of the lights, temperature of both plants and nutrients, and air quality. For example, if you grow a head of lettuce in the ground outdoors, your plant might be subjected to frost, insect damage, being eaten by a deer or other animal and depending on the environment around your plant it might take 30 to 40 days to grow to harvestable size. By providing a totally managed environment, plant roots do not have to 'forage' for nutrients, nor do they have to put up with huge temperature fluctuations that may slow growth. Using hydroponics in an environmentally managed area, your plants will come out perfectly in as little as 15 to 20 days depending on the variety. In fact, it has been said that hydroponics can solve the problem of having to feed the billions of people on planet Earth as cities increase in size and agricultural areas become smaller

You can grow hydroponically, almost anywhere. Some growers use a greenhouse as small as 10' x 12' ( CropKing’s smallest greenhouse) while others have CropKing commercial systems in 100- to 200-foot long greenhouses. Some people grow plants in a warehouse under special lights. Some small-scale growers grow their own vegetables in their basement or attic space. A hydroponic system can be designed and built for almost any space, indoors or outdoors. The system can operate year round or seasonally. In short, hydroponic systems are adaptable, easy to use, easy to operate and can be as simple or as sophisticated as you want to make it.

But what is hydroponics? In hydroponic growing plants are grown with their roots in a nutrient solution using one of several methods. These methods might be as simple as placing the end of a cloth or rope "wick" in a tank of solution, and putting the other end of the wick under the plant roots. Unfortunately, this simple method can only grow a few plants at a time because the wick will not draw enough nutrient solution to the roots.

If you want to grow many more plants of the same type for sale to restaurants and markets, then you have to decide whether to grow using a deep or shallow tank which might be three or four feet wide or a small channel just four inches across. A deep tank might have nutrient solution running through it much like a slow running river. The plants sit in a styrofoam or wooden "raft" floating on the solution. This method is often used in aquaponic production (growing both fish and plants) and is known as "raft" growing.

If you do not have space for a deep tank, you might grow lettuce plants (or any other leafy green herbs and plants) in 4" wide channels only an inch or two deep and ten to twenty feet long. These channels typically sit on a steel framework at waist height (saves bending over and allows the nutrient solution to drain into the reservoir.) Each channel has holes spaced about 8" apart. Plants are set in the holes and a thin layer of nutrient solution runs down the slightly sloped channel under the plant roots. (This thin film of solution has given this system the name Nutrient Film Technique or NFT.) Because the channels are sloped slightly the solution drains out the bottom of the channel to a reservoir. A pump pushes the solution to the highest point of the channel. In some systems the pump runs continuously, while in others is it runs two or three times a day. The nutrient solution is recycled and the nutrients are refreshed as they are consumed by the plants based on computer. Periodically the tank is drained and cleaned.

falseLettuce in CropKing NFT System

Unfortunately, it is quite difficult to grow tall vining plants in small channels, so these are grown using a different technique. Beans, peppers, cucumbers and tomatoes are best grown in "Dutch" or "Bato" buckets. With this method, two tomato plants are placed in each bucket which has been filled with a support medium such as coconut coir, rockwool or perlite. Expanded clay balls may also be used, but they tend to be too expensive for commercial production. The best and most cost effective of these media is perlite or even sand (even though sand is heavy and does not absorb nutrients). The nutrient solution is delivered through a plastic feed line with pressure compensated emitters and two spaghetti feed lines in each bucket (one is a backup). This spaghetti tube drips nutrients to each plant. The extra or overflow solution drains out of the bottom of the bucket and down a drain line where it may be recycled. (At CropKing, we do not believe in recycling nutrient for long term plants such as tomatoes which may be in the greenhouse for almost a year. There is too much chance of passing diseases like botrytis from plant to plant. We drain the used nutrients with about a 10% overfeed.)

falseTomatoes in a CropKing Dutch Bucket System

The third method of growing hydroponically, is to grow in a large tank using a method known as "Flood and Drain" (or sometimes "Ebb and Flow.") In this method, the tank is filled with expanded clay balls or other support media (to hold the plant roots). The plants are set in the support media. At intervals (usually two or three times per day), nutrient solution is pumped into the tank, flooding it, and allowed to drain back to the reservoir. Ebb and Flow systems are considered to be hobby systems and not normally used for commercial growing.

Often, a commercial growing operation will use a combination of two or even three methods in a in a large structure. For example, NFT channels can be used to grow leafy green crops such as kale and lettuce at a low temperature of 55 to 60 degrees. (During a summer day, an 80-85 degree temperature in the greenhouse is acceptable. At CropKing, we lower the EC level when the plants are taking up more water. We have growers in Southern Louisiana who grow good lettuce at over 100 degrees in a greenhouse, much depends on humidity levels, EC levels and the lettuce variety.)

Dutch buckets are usually used for long term plants and are used to grow tall plants such as tomatoes and peppers at 70 to 80 degree temperatures. Each species of plant will have its own nutrient solution designed for best growth. For example, leafy green plants will use a solution containing higher levels of nitrogen, than will tomatoes and peppers. In a sophisticated system, the plants may be illuminated with high intensity lighting to keep them growing during winter months.

As you can see, there is no single hydroponic method of growing, no single size suits all. Hydroponics is a highly flexible growing method that can grow many crops with controlled nutrients and in a controlled environment. Why not take the first step and ask us to design your system? Contact us for help on how to grow hydroponics.

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