Growing plants without soil has intrigued and challenged gardeners, hobbyists and commercial growers for many years. The terms – hydroponics, water culture, sand culture, gravel culture, solution culture, mist culture, soilless culture and more are often used describe a particular system of applying plant nutrients to the roots of the plant, and each, in its own way, is a method of substituting some other medium for soil.
In general the terms hydroponics has gained popular appeal, and is widely used to cover ‘all ways of growing plants without the use of soil’.
Hydroponics the word, is derived from two Greek words, hydro meaning water, and ponos meaning to work or labour.
It is reported that hydroponic production can yield around 25% more than ground grown crops and averages four times the number of crops per year. The economic benefit of this can be enormous, however set up costs can be very high due to the infrastructure required.
The Nature Of Hydroponics
Soil does four main things for the plants which grow in it. It provides support, supplies water and air to the roots, and provides nutrients. To be successful, hydroponics needs to cater for these four functions.
Types Of Systems
There are endless possibilities with hydroponics. The options open to you in creating a system are only limited by your imagination and your budget. Provided you can supply the plant with those things it needs achieve good growth, you can develop a system any way you wish. Systems can be very simple or very complex. They can be cheap or very expensive. On a farm it may be possible to utilise existing materials to some degree (e.g. plastic irrigation pipes, greenhouses). You might limit yourself to supplying enough product for you own use, perhaps later expanding as you gain more expertise into commercial production. If you have the expertise to grow plants commercially in the ground then it is likely that you could ‘convert’ to soilless production quite readily.
This is a key factor because it influences everything else. If the system is grown under cover (e.g. in a greenhouse) then the environmental conditions are more readily controlled. The temperature may fluctuate less than outside conditions. Wind problems will be reduced and so on, however natural rainfall can’t be readily utilised, unless it is captured (e.g. in tanks or a dam) for later use. If the system is outside it will be exposed to rain which may dilute the nutrient solution, and wind which can damage plants or blow debris into the system. Frost, hail, snow, etc. could also create problems. Temporary frost protection (e.g. removable covers) might be provided for outdoor systems at frost or hail danger times. Well designed windbreaks can help significantly reduce the likelihood of damage to both the plants and the hydroponic system itself.
Pest and disease problems can usually be reduced by keeping the hydroponic system isolated from those problems by growing indoors, by raising the system off ground (away from the soil which is a major reservoir of pest and disease problems), or locating your system in an isolated area away from other crops that may act as potential sources of pest and disease infestations. Outdoor systems will need to be securely fenced off from animals (e.g. cattle, sheep, in particular goats), otherwise plants may be eaten or trampled.
The plant roots, as well as the nutrient solution and medium, need to be contained by something, otherwise nutrient solutions, and any growing media would quickly run/fall away. You might, for example, have gravel, sand or perlite contained in plastic bags, in pots or in tubs. You might have rockwool fibre, sand, gravel or scoria contained in a raised bed built from timber, metal, concrete or plastic. You might use polystyrene boxes, fibreglass tanks, PVC pipes with slots in it, plastic roof guttering, square cross-sectioned PVC channel specifically designed for hydroponics, and so on. The list of possibilities is endless. The main criteria is that the container is large enough to support the particular plant/s you are growing, will contain the nutrient solution for long enough for the plant to utilise the nutrients in the solution, is stable so it won’t fall over, is durable enough to last at least until the crop, etc is harvested (it will preferably last much longer), and is chemically inert (i.e doesn’t release chemicals that might affect plant growth – some metal guttering, for example, corrodes over time).
Watering & Nutrients
Water quality is a critical factor in the success of hydroponic growing. Water should ideally be as pure as possible. Impurities such as sediments, salts, pathogens, etc. can block up dispensing systems (e.g. nozzles), cause toxicity problems, or affect the balance of nutrients in the solution, or rapidly spread disease. The water may need prior treatment before it is suitable for use (e.g. settling tanks to reduce sediments, filtering, disinfecting). The quality of any water you use should be regularly monitored. Reliability of supply also is critical, particularly if you are not recycling the water through the system.
Nutrient solutions may be applied automatically at predetermined times or as required. In the case of Nutrient Film Technique (NFT), a continuous thin, stream of nutrient solution flows through a channel which the plant roots sit in. The solution could be supplied at the bottom of the growing media (e.g. sand, gravel) and allowed to move upwards through the media by capillary action, or alternatively supplied at the top of the media (e.g. through drippers), and allowed to filter downwards.
It may be pumped onto the media, moved manually (e.g. from a watering can or bucket), or be gravity fed, such as from a tank up slope of the hydroponic system. The excess (runoff) might be collected and reused (this is known as a closed or recirculating system), which reduces waste of both water and nutrients, but needs careful management to control nutrient levels in the solution, and minimise the risk of recirculating and disease problems that may have arisen in the system (the reused water may need to be disinfected). Alternatively the nutrient solution may be lost after passing through the media (known as an open or run-to-waste system). This type of system uses more water and nutrients, but can reduce the likelihood of disease problems or salt build up in the system.
This is not always needed, but when growing tall or creeping plants, such as tomatoes, cucumbers, chrysanthemums, carnations, and roses, the medium may not be strong enough to support the plant. Trellising also helps control the direction of plant growth and better utilises space (more plants can be grown, with higher yields if they are grown upwards, rather than being allowed to sprawl). Trellising can be made from such things as wire (single strand or mesh), plastic mesh, strings, wooden posts or trellis, fishing line, etc.