Hydroponics Made Easy
CHAPTER 3 GROWING SYSTEMS Many systems in the market The hydroponic market accounts for a great variety of systems. Let’s look at the main ones and some of their features. They all perform to a greater or lesser degree the basic function of hydroponic in that they deliver water and nutrient to the roots of plants and allow a degree of aeration. However the mechanics and the methods of this delivery are widely divergent. The following are listed in an order that carries no particular significance other than a possible order of complexity in either construction, operation or maintenance. Even this may be open to debate. We will attempt to show their main features, advantages and disadvantages.
System classification We have broadly classified each hydroponic growing system as a recyling or non-recycling system. The classification is useful as it allows us to differentiate whether the nutrient solution in each system has been reused or otherwise. It is important to note that the recycling system is far more difficult to manage than a non-recycling system. This is because of the constant need to overcome problems associated with fouling of the nutrient solution. solution.
1. MANUAL FEED AND DRAIN. A recycling system. This covers a very wide range of possibilities. At its simplest it consists of a single pot in a single location and can consist of as many pots in a wide variety of locations as the t he person controlling the system can maintain. The growing containers can vary widely, even in the one system and could be simple plastic bags with drain holes in the base, household utensils like saucers and plates, conventional plastic, ceramic, organic or other pots. The growing medium is most commonly perlite, vermiculite, a mixture of both or growool but could just as easily cover the full spectrum of media. Basically this system is simply a collection of containers that are generously watered once or twice a day by hand with the excess water/nutrient mix being allowed to run to waste. It is a system that depending on the conscientiousness of the person operating the system can give excellent results. It does however have quite a few disadvantages, disadvantages, as follows: •
it requires constant and careful attention
•
during hot weather and at times of peak growth, a twice daily watering will not be sufficient to produce optimum results
•
during the heat of the day the plants can wilt and suffer setback if they dry out for too long
•
if a 24 hour period goes by with no watering the results can be fatal to many plants for pumps, ponds, disposal and treatment. No running costs in fuel or power for pumping. pumping.
avoiding overhead watering problems. Plants that need sub irrigating to avoid damage to leaf of foliage f oliage love the Auto-pot System 1
Manual feed and drain drain system.
Hydroponics Made Easy •
growers who have have been hand watering watering will love the saving in la bour costs. Once under watering damage occurs the plants tend to yellow and can take a long time to recover
2. SELF-WATERING SELF-WATERING SYSTEMS. A SYSTEMS. A non-recycling system. There is also a variety of these. The most common and the simplest being the Decor style of pot. There are many others that come into the same category, many of them having reservoirs that are considerably larger in relation to the growing chamber to provide a longer period of supply. These semi automated systems are also very effective but they too also have problems. Normally they have some form of wicking arrangement to raise water from the reservoir to the root system. This fairly well limits the size of the reservoir to the root system. This fairly well limits the size of the reservoir, because the reservoir needs to be directly under the plant and once the size of the reservoir exceeds the size of the container, the system starts to look ridiculous. So it’s a semi-automated system but the reasonable period of storage is seldom more than about two or there days in times of peak usage. And it is still important to allow the plants to dry out a little every so often for peak performance so the system needs constant supervision. 3. DEEP WATER CULTURE. A CULTURE. A recycling system. The most common form of this is to have the plants suspended on some
Foam sheet
Air pump
Air stone to improve water circulation & aeration
Deep water culture system.
form of floating material such as foam sheeting which allows the root system to dangle into and grow in a nutrient solution. This is quite a good system, particularly for short term crops such as lettuce but because the plant supporting medium (foam sheet) usually covers the surface area, it has been found necessary to provide aeration to the nutrient solution, usually by pumping air through the solution or other circulating devices. Its not a system that is suited to growing long term or large plants and is not suited to many crops (potato and carrot spring to mind). Generally speaking it is hard to see how this sort of system would work in the house, office or display area. 4. DRIP TO WASTE SYSTEM. A non-recycling system. As the name suggests, this system allows a slow drip of nutrient to keep the growing medium damp and productive. It is a very simple and very effective system but also one that can be plagued by a lot of problems. For a start, you tend to be generous with the drip rather than miserly. You 2
Nutrient water drawn up the growing medium by capillary action.
A Self-Watering Unit Unit Problems with nutrient recyling. Fouling – caused by the anaerobic bacteria that feeds on soluble organic wastes in the nutrient solution. These cause the nutrient solution to become acidic. ∗ Fluctuating EC – – caused by the varying loss of moisture from the system. For example, on hot days, more moisture is lost through evaporation resulting in more concentrated nutrient solution. Nutrient inbalance – caused by ∗ by the selective uptake of nutrients by the plants. Root disease – the greatest ∗ greatest threat for commercial systems. Once the system is contaminated with a disease, it will be very difficult to eradicate. Even with the use of sophisticated sophisticated water sterilization equipment, equipment, there is no guarantee that the disease will not recur. ∗
Hydroponics Made Easy
use more nutrient than is really necessary, but that’s better than too l ittle. You need a means of running off the excess. Outside, that’s usually not a problem. Inside, it becomes becomes much more a consideration. Regulating the amount of drip is always a matter of trial and error, mostly error and by the time you have it just right, the temperature has risen or fallen and you need to start over. You need a large overhead reservoir reservoir or a pump primed header tank, and the drip at the end of a line is not always the same as the drip nearer the tank. But as a system, this is one that many people use to good effect. On a commercial scale, this system will require sophisticated computers to management the drip rate daily. 5. NUTRIENT FILM TECHNIQUE (NFT). A (NFT). A recycling system. This is a process where plants in media in a container or in medialess form are grown over a constant thin film of nutrient which flows down a gentle gradient usually in a form of a channel. It is considered a very Thin film of nutrient solution.
Troughs at an incline. Water pump running continuously.
An NFT system. good technique for both lettuce and tomatoes. It suffers many of the same problems as other systems in that it needs constant adjustment. It either runs to waste or the plants at the lower end of the system do not get enough. The system needs constant checking of its pH (potential hydrogen or acidity level) and its CF (Conductivity factor). It can be automated with the use of injectors to inject nutrient into the water as it is delivered but in general is not really a system for any other than full time professional growers. growers. 6. FLOOD AND DRAIN SYSTEM. A SYSTEM. A recycling system. Sometimes called Ebb and Flow. This system normally consists of potted plants or plants in cubes being placed on shallow self draining trays. The
Nutrient solution floods the tray above for about 15 minutes and allow it to drain back to the reservoir below.
Water pump running intermittently controlled by a timer.
A flood and drain drain system. trays are flooded intermittently or according to a program, the media saturated and the excess being permitted to either flow back to the bulk 3
A dripper
Excess water run-off
A Drip to Waste Unit Unit Managing nutrients recyling systems.
for
Nutrient solution monitoring – has to be done at least once a day for acidity and nutrient concentration. This monitoring allows the desired levels of acidity and nutrient concentration to be maintained. – nutrient ∗ Nutrient dumping – solution are usually usually dumped dumped once a week or fortnightly. fortnightl y. Dumping is necessary necessary because that will come a time when the nutrient solutions become too inbalanced. This is because corrective measures mentioned above (for acidity and EC) do not address the problems with nutrients becoming inbalanced. It is not advisable advisable to consider consider correcting the nutrient inbalances because the cost of nutrient analysis for its individual components such as N, P or K are just too high even the commercial growers.
∗
Hydroponics Made Easy
nutrient solution or t o wash away to waste. Normally coarse aggregates are used as a medium. Such systems are good but require all the controls and pumps used in items 4 and 5 above. They normally have relatively large nutrient tanks and have the problem that if corrupted or contaminated nutrient gets into the bulk solution the loss of the solution and possibly all the plants in the system can occur. 7. AEROPONICS. A recycling system. This is a technique that was developed initially for use in space where plants are grown with no media, sus pended in air and the root systems systems sprayed with a nutrient solution.
The water pump either runs continuously or intermittently at short inter-
An Aeroponic Unit.
Other than the manual system, all those listed need pumps to operate. Timers and computerised systems are common. The need for constant maintenance and monitoring of nutrient is a r egular routine. There is one other system that gives automation without the need for power, pumps, computers or timers, that is water efficient, ecologically unobtrusive, effective and suited to a wide range of uses. The Autopot System. *****
A Drip to Waste System.
Left– drip to sawdust.
An NFT system.
Bottom – drip to rockwool.
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