Back to the Basics
By Trevor Shields
Hop off of the fence, Green Thumb, as a hydroponic gardener you have a series of choices to make when you set up your own personal Eden. The first decision to make is which basic direction to go in with your garden. When you reach this first crossroads, you will see two directional signs pointing in opposite directions. To the left is “Water Culture Systems Boulevard” and to the right is “Aggregate Systems Avenue”. Both have the same destination in mind, but approach it in a uniquely different way.
The primary difference is obvious by definition: Water Culture Systems are identified as having constant nutrient solution delivery to your plants root systems through a variety of means, whereas Aggregate Systems generally operate by having their chosen substrates flushed with the nutrient solution at timed intervals. The aggregate, or substrate, is used as a receptacle to keep all that nutrient goodness handy until the plant determines it needs it, kind of like Heidi Fleiss living one block from Charlie Sheen’s house.
Water Culture Systems can further be divided into three classic types, and these types are identified by the way in which the nutrient solution is delivered to your plants. They are Nutrient Film Technique (of NFT for those that like acronyms), Aeroponics and Aeration Method.
Nutrient Film Technique uses a trough or tube to deliver the nutrients. The plants are then suspended through holes in the top of the trough, so that the roots have easy access to the active solution traveling below. These troughs are generally set up at a slight angle, so that gravity does the work of returning the solution back to the reservoir once it has completed its journey. This system is one of the most widely used hydroponic solutions, due to its effectiveness and low set up cost. Anyone handy enough with some power tools can make their own troughs with simple PVC pipe.
Aeroponics is a variation of the classic NFT garden, with its main difference being the method of nutrient delivery. Instead of a constantly flowing nutrient solution, the nutrient is misted onto the root system of your suspended plants. Again, the grower can get their hands dirty and build their own system if they have the time and the know-how. It may not look as snazzy as a commercial system, but generally function takes precedence over fashion every time. The most common method of building this system is accomplished by building an A-frame out of Styrofoam sheets. Then, by drilling or cutting holes through the Styrofoam sheets to match the size of your individual plant pots, you can suspend your plants. The delivery system is placed inside at the base of the A-frame, thus allowing it access to all of your plants’ roots. With Aeroponics, there are two methods of distributing the nutrient, and that is dependant on the type of delivery attachment. The attachment can be a drip system, or vaporizer, which directly focuses the nutrient on the root system, with the excess cascading down the inside of the A-frame into the reservoir to be recycled.
Aeration Method was one of the premier hydroponic gardens to be attempted. It uses an aquarium air pump to “bubble” oxygen to roots that are directly suspended in a static nutrient solution. The plants are supported about an inch above the actual solution in a mesh container, using some form of aggregate (rockwool, pea gravel, clay pebbles, vermiculite, etc.) for stability. The roots then extend through the mesh, and into the nutrient solution.
These are the main forms of Water Culture Systems, but with so many imaginative and technical minds becoming involved with hydroponics, effective variations on these methods are popping up everywhere. Water Culture Systems are very effective in their delivery of nutrient to the root systems of your plants due to their constant nature. Also, since the solution isn’t inert, build up of fungus and other problems with constant moisture are almost non-existent. While your pump system and gravity does the work of distributing your nutrient, your main job will be to keep adequate levels in your reservoir and ensure that the PH and PPM remain at optimum levels. A PH level out of optimum range can cause a toxic reaction with your plants, whereas allowing the PPM (Parts Per Million) level of your nutrient to drop too low simply means that your plants may not be receiving as much food as they need, or in contrast, too much. An overly rich nutrient solution can cause mineral buildup and other adverse effects. The key in this, and so many other parts of our lives, is balance.
Aggregate Systems are more closely related to conventional farming than Water Culture Systems. They generally rely on the timed delivery of nutrient solution to the substrate supporting your plants. The substrate itself becomes the conduit and receptacle of your plants three squares a day. Any substance can generally be used as the substrate for your plants with some considerations. Make sure the aggregate you choose to use is generally smooth. Rough edges can rub together during dispersal of your nutrient solution and cause tearing of your root systems. Also, make sure the substrate itself is clean of contaminants and PH balanced. You want to make sure that you are giving your plants the best possible foundation for their growth that you can. Some common materials used as substrates are rockwool, clay pebbles, pea gravel, vermiculite, perlite, sand or even foam packing chips. Another consideration for your substrate is to choose a material that is porous so that more than just the surface retains the nutrient when it is done cycling through your system. If you are using something dense such as pea gravel, try combining a porous material such as perlite or vermiculite with it. This will provide you with both stability and improved nutrient retention. Here comes the evil “B” word again. Balance here, again, is the key. If you choose a substrate which can retain too much nutrient, this stagnant moisture may cause problems such as root rot, mold and other effects. Monitor your circulation and the appearance of your substrate when you first set up your garden. If any adverse affects become noticeable, you may have to try something different. Roll up your sleeves and get dirty, this is gardening after-all.
One of the first and most commonly used methods of Aggregate System gardening is the Flood and Drain Method. This term, like so many others in hydroponics, is virtually defined by its name. A shallow container, such as a flood table, is filled with your chosen substrate and flooded with your nutrient solution at timed intervals. Then, after 20 or 30 minutes through the use of a timer or manual valve, the nutrient is drained back into the supplying reservoir. While nutrient is not continuously supplied to your plants as it is in the Water Culture Systems, the aggregate in your container retains enough nutrients to sustain your plants until the next scheduled flood.
Another form of Aggregate System is the Trickle Feed Method. It is similar in construction to Aeroponics, but of course relies on the substrate to harness and deliver the nutrient to your root system instead of accessing it directly. The nutrient solution is continuously pumped from the reservoir through 1/2 inch pipe. It is then split off to each individual plant pot using 1/8 inch, or spaghetti, tubing. The nutrient is distributed through this fine tubing to the base of the plant stalk in each container, and then allowed to filter through the substrate where it collects in the bottom of the pot, only to be recycled back into the reservoir.
There is an off-shoot of the Trickle Feed Method known as Tube Culture. This method is accomplished by filling a small bag or tube, generally measuring three to six inches in diameter, with lightweight aggregate, then suspending this container vertically. Holes are drilled down the sides of the tube or bag to allow placement of your plants. An irrigation tube is run from the reservoir to the top of this suspended tube, and nutrient is continuously fed through. Depending on the flow of the supplied nutrient, the solution may or may not be recycled back into the reservoir once it reaches the bottom of the tube.
Each and every one of these systems has its own limitations and benefits. Before deciding what system is best for you, consider the space you have available for your garden, the type of crop you are harvesting and the amount of money and time you can commit to your new enterprise. Once all of these considerations have been made, the best garden option for you should be evident. Weigh the alternatives, do a little research and order a pizza. It is always easier to come to a decision on a full stomach.