Choosing a Hydroponics System
The word "hydroponics" is a word with Greek origins that literally means "working water". It is where (strictly speaking) plants are grown without soil and are fed via nutrients dissolved in water.
The origins of hydroponics, as legend has it, hark back as far as the ancient Hanging Gardens of Babylon, one of the seven wonders of the world. As the story goes, there were huge terraces of gardens which were watered from the river Euphrates via an Archimedes screw. The fact that the plants were grown in and drew their nutrients from soil means that, strictly speaking, this was really an automated watering system rather than hydroponics per se. However, for the era (a few hundred years BC), this was still quite the technical accomplishment.
It's all about Automation
The beauty of true hydroponics is that it allows the grower to continuously control and optimise the nutrients being fed to the plant. This gives the potential for incredibly fast growth and increased yields. It also means you don't have to hand water which can be quite time consuming if you have lots of plants.
There's 2 main types of real hydroponics - active and passive. An active hydroponics system is one where nutrient solution is pumped to plants roots. Passive hydroponics is where gravity is used to supply nutrient solution to the bottom of containers which contain an absorbent substrate, which then wicks it up to water and feed the plant.
There's a wide choice of types of hydroponics systems out there. For the beginner, it could seem a bit bewildering. However, with a bit of thought and planning, the choice can be whittled down to a small handful of contenders and eventually just one.
Types of Active Hydroponics Systems:
Flood and Drain (sometimes known as Ebb and Flow) systems involve a reservoir of nutrient solution which is periodically pumped into pots (usually from the bottom) filled with a medium with good drainage. The solution is usually left there for a short while to allow the medium to become wet and then it is either allowed to flow or pumped back to the reservoir ready for the next watering cycle. This is repeated periodically depending on the medium and the size of the plants.
One of the key reasons for the success of this system is the high oxygenation of the root-zone. Each time a feeding cycle begins, the pots fill with nutrient solution from the bottom. As they fill with the solution the air in the medium is pushed up and out. After that has happened, the solution drains back out and draws fresh air into the root-zone as it does so.
Suitable substrates for flood and drain systems are clay pebbles, coco coir, or a mixture of both. Rarely, you might find growers using small rockwool cubes but this substrate has fallen out of fashion since the advent of ready-to-buy mixtures of coco and clay pebbles. While purely clay pebbles are great for growing in, they don't really hold a lot of water. That means that if the watering system goes wrong the plants can suffer from drought damage very quickly. Coco holds a lot more water. A mixture of the 2 provides a much more reliable substrate to grow in.
Just like with Flood and Drain systems, dripper systems utilise a reservoir of nutrient solution. The plants are grown in pots containing a substrate with good drainage like clay pebbles or a coco/clay pebble mixture. However, with a dripper system, instead of the pots being filled periodically from the bottom, the nutrient solution is pumped into the top of the pots through feed-lines with dripper stakes driven into the medium. The nutrient solution wets the medium as it drains downwards through the pot. At the bottom the solution is collected and channelled back to the reservoir via drain lines and a pump or via gravity into a reservoir situated underneath the pots.
3) NFT
NFT, or Nutrient Film Technique, does not use pots. Instead, plants that have been started off in rockwool cubes are placed on a fibrous mat on a downwards sloping tray situated above a reservoir. A continuously running pump feeds nutrient solution up to the top of the sloping tray. As it runs down the tray, the mat becomes wetted and this provides a surface for roots to grow upon. When the nutrient solution reaches the bottom of the slope it drains back into the reservoir below. A cover above the tray prevents light getting to the roots and the nutrient solution below which might otherwise cause slow root growth and problems with algae.
The constantly flowing nutrient solution and the roots being in free-air means there is very high levels of oxygenation in the root-zone. Roots love this and they create a thick mat all along the top tray, sometimes an inch or two thick. NFT systems are low-profile and great for when height is at a premium as there are no pots to raise the height.
4) DWC System
DWC, or Deep Water Culture, is an unusual method of growing which involves nothing more than a small net pot of clay pebbles suspended in the lid of a container which contains nutrient solution and an air stone. The roots of the plant grow down into the bubbling nutrient solution below. Despite the simplicity, this system works remarkably well due to the high levels of oxygenation. It delivers fast plant growth and fantastic yields.
It is a wise precaution to keep a spare air pump handy in case of a failure. Also use a non-return (check) valve in the air line and place the air pump above the water level in the reservoir to prevent the solution back-siphoning into the air pump.
5) Aeroponics
Aeroponics is really in its own subset of hydroponics. It takes the concept of dwc and takes it a stage further. Like with DWC, a small net pot with clay pebbles in is suspended above a large, but this time empty, tank. The empty tank is situated above a reservoir with nutrient solution in the bottom. Periodically, nutrient solution in the reservoir is pumped up out of the reservoir and is then forced through tiny nozzles in the chamber above which turn it into a fine mist. The roots grow into the air space containing the mist. As the mist gradually condenses back into a liquid it then drains back into the reservoir below.
The roots literally grow in air meaning that they receive the absolute maximum oxygenation possible. Incredibly fast growth and big yields are almost guaranteed. In fact, it may be the type of system with the highest yield potential of them all. However, very regular maintenance with this type of system is critical. Should the pump fail, or the misting nozzles become blocked then it will only take a short time for the plants to really suffer. Daily (or even twice daily) checks to make sure everything is running properly is definitely recommended.
Many people who grow in aeroponics also love that there is no substrate to have to dispose of after the grow.
Passive Hydroponics Systems
Passive hydroponics systems are ones that do not use water pumps and do not recirculate the nutrient solution around like the active systems do. However, they are really the only type of hydroponics system that is suitable for growing in soil because using it in an active system will usually keep it too wet. There's also only 1 type of passive hydroponics system and that is bottom feeding.
As already mentioned, they work by supplying nutrient solution from a reservoir to a tray at the bottom of the pots via gravity alone. The soil "wicks" the solution up to feed the plants. This is done through a special type of valve which only allows a certain amount of solution to be in the plant saucer at a time.
Unfortunately, even though soil is probably the best substrate for this type of system, bottom-feeding is still not suitable for growing with organic feeds. This is because there are still feed-lines running from the reservoir to the bottom of the pots. Organic feeds will usually end up leaving residues in the pipes which eventually get blocked.
A little bit more about the different substrates
Soil - This is still the number one choice (and for many the only choice) for growing organically. It is the most natural substance in the world and plants have been growing in it for about 700 million years. Soil and beneficial microbes are what plants have become used to growing in. There's no getting around it - it is definitely the natural home of almost every plant in existence. However, there are advantages and disadvantages to growing in soil. For example, soil can hold a lot of water, and when it becomes saturated it can "clod" together which is not a good situation for plant roots. Roots need oxygen. Earth that has clodded together has no space for air to get to the roots. This makes soil prone to overwatering. One of the great things about hydroponics is that it involves automatic watering. But care needs to be taken not to overwater it.
Coco - Coco coir is a very natural substance made from the husks of coconuts. It is quite fibrous which means that water drains very well through it and it does not clod together like soil can. However, it is similar to soil in that the coir can be made home to beneficial microbes and there are organic feeds out there that can produce very high quality crops. Coco, or mixes that contain coco, are probably the most popular choice of medium in the UK at the moment. It can be purchased in dried, compressed blocks so that it is easy to transport. Once it is home it can be re-expanded by adding water to it. It will expand by roughly six times the volume so make sure you use a suitable size container.
Clay pebbles. Clay pebbles are most at home in dripper and flood & drain systems. Clay pebbles have lots of room between them for fresh air (and therefore oxygen) which means that fast root growth is entirely possible. However, they do not hold as much water as an equivalent volume of soil or coco. This means regular waterings (usually 2-3 times a day or more) are necessary. While clay pebbles have the potential to produce the biggest yields, things will go very wrong very quickly should drippers become blocked or a pump fails. Regular checks and maintenance is strongly advised when growing in just clay pebbles.
Clay Pebble and Coco Mix - Often referred to as 60/40 or 70/30 due to the ratio of clay pebbles to coco. It offers most of the advantages of both mediums. There's plenty of oxygen for the roots and great drainage. The coco gives the grower a bit of insurance because it holds on to water somewhat. It buys a bit of time should drippers become blocked or a pump fails. Growers who find it difficult to have reliably successful grows in just clay pebbles find a mix like this is excellent.
Rockwool has fallen out of fashion in recent years. It is still used in NFT and in vertical grow systems and there are still a few growers that use small rockwool cubes in dripper and flood & drain systems, but since the advent of 60/40 mixes and the like, these are the better choice.
If a beginner decides that they want to grow completely organically then they will probably have realised that it has to be hand-watering in soil. For others, they will be looking to create the biggest crops that they can with more convenience. This is where hydroponics really shines.
