Grow Systems

“ cannaquack ” grow units utilise simple basic NFT systems which is a proven technology for being the favourite system in commercial growing. Enabling full control over root temperature, nutrient supply, removable of unwanted gasses and supplying oxygen promoting optimum growing..

NFT has many advantages over other systems of crop production. It has been designed for simplicity, low cost, and dependability. In particular, it gives absolute control of the root environment; it greatly simplifies watering, and ensures a uniform nutrient supply across the whole crop. Root temperature can be raised or lowered easily whenever required merely by warming the nutrient solution or cooling of the nutrient solution, which can be circulated either continuously or intermittently to further conserve energy and to control the growth of plants.

Other advantages include a rapid turnaround between successive crops, the potential for more efficient use of space because of the possibility of plant mobility, and the potential for more efficient use of water. NFT's high degree of control over nutrition, water availability, and root environment makes it the most sophisticated of all commercial plant-culture systems in practice today. Theoretically it offers the highest yield potential.

Plant variety will be the same no matter how it is grown provided there is adequate care and fertilisation during growth and is not dependent on the growing method

The root system of a plant basically supplies only water and mineral nutrients to the plant. It’s the upper part of the plant, through photosynthesis, that provides all the other types of compounds to the plant and its fruit regardless of where the plant’s roots are growing.

Nutrient uptake is generally proportional to the concentration of nutrients around the roots but in flowing solutions plants are able to grow better over a wide range of concentrations.

Environmental factors also have a profound effect on nutrition.

Hydroponics produce does have healthy benefits compared to other growing methods, provided that the fertilizer program is well managed.

Hydroponically grown produce has more of a chance of being good for consumers’ health because there is no contact with the ground. This reduces the risk of getting disease organisms from soil and manure in the produce.

The major health problems from vegetables have been associated with the external contamination of produce, rather than what’s inside them.

To produce a good product requires good horticultural practice and hydroponics is no different. It’s not technology, but a more sophisticated, horticultural technique.

Hydroponic producers have been trying very hard to align with the organic growers, particularly since hydroponics is becoming more and more organically based.

Hydroponics has the opportunity to fill the gap between traditionally grown produce and organics. It’s the low chemical alternative to traditional field cropping and uses IPM (integrated pest management) to its maximum.”

Hydroponic growers must have a good knowledge of their crop if they are to grow successfully. Hydroponics plants are often less stressed than in other systems which means that produce quality is more likely to be maintained consistently, especially in adverse conditions.

But there is NO conclusive evidence to suggest that organically grown produce is nutritionally better or has less chemical residue.

The main feature of NFT, is a 'film' of nutrient approximately 1 - 2.5 litre per minute passing by the roots of the plant and therefore the design of the gully is a major consideration when planning for a commercial system. The channel should be designed in such a way as to provide for gas exchange and to ensure the nutrient runs down the centre of the channel. The depth of the channel should have sufficient space between the roots of the plant and the top of the channel. This space is to allow for oxygen, entering through the holes provided for the plants, (round holes for square grow medium and square holes for round medium thus providing a gap around the grow medium and lid ) this is to facilitate the removal of waste gases. The roots are in contact with this film of nutrients not the grow medium the roots then can take up nutrients while others not covered by nutrient are able to take up oxygen. There is a fairly critical balance between the right amount of moisture and air required in the rooting envelope. The gases that are produced are generally heavier than air; flow out with the nutrient solution returning to the feeder tank. The use of flat bottom channel should be avoided, as it is nigh impossible to ensure the nutrient will flow down the centre of the channel. The use of round pipes negates the 'film' technique, which is the basis of this method of growing. In round pipe, the nutrient flow is a lot deeper, as the roots cause damming between each plant. That is, as the plant matures and the root mass grows bigger, the nutrient level rises in the pipe and the space necessary to carry out the waste gases removal and provide appropriate oxygen uptake is markedly reduced. In addition to this, set up costs can also be greater as the round base does not readily apply itself to the standard flat stands.

If the film is too deep, then the plants will suffer from oxygen deficiency that can lead to root disease.

Allowing room for plant roots is the simple remedy for gas exchange, helping to eliminating root rot or other root diseases. It is also important that the channel has good longitudinal strength. If allowed to sag, damming will occur as seen in the round pipe. Poor strength will also add to the costs, as additional stands would be required to eliminate this problem. One of the most important features when choosing an NFT channel is whether or not it comes in one or two pieces. That is, does it come with a base and lid, or just a single one-piece pipe? The channel is generally supported every 3-4' depending on the plants, and the angle on which they are laid (approx. 40 : 1) ensures nutrient flows down the channel preventing stagnation or pooling. Two piece channels, ie, lid and base, is highly desirable to facilitate good access for cleaning and the removal of dead or dying plants that can cause blockages. More importantly, it is essential to be able to remove this organic waste before it breaks down and enters the nutrient. Easy access to cleaning your channel is essential. The two piece channel allows the channel to be cleaned quickly and most important effectively, but also rapid turn-around means less labor costs. When the lid is removed, the channel may hold a growing medium to use in a drip feed (eg Growool) system or scoria for a flood and drain system. The removable lid also gives the grower the option of using other growing systems. In each case the nutrient solution can be collected and not wasted. This fact should be a major consideration, as it is anticipated that future government legislation will prevent growers from draining to waste. One piece channel may cost less, but denies essential access for 'servicing' and cleaning.

Feeder tubes (5mm diameter), two to each channel, will provide sufficient nutrients to meet the 1-2.5 liter per minute requirement.

Plant roots have three main components:

1. Primary roots: These are the large diameter roots which first emerge from the propagation block into the nutrient solution and grow rapidly.

2. Secondary roots: These are smaller diameter laterals emerging from the primary roots. The large surface area of these roots makes them vital in taking-up nutrients and water from the nutrient solution.

Plants don't always take-up nutrients and water from the solution in the same ratio as added They have a mechanism known as "active" uptake which enables plants to determine what they want to take-up from all that is provided in the solution only if the nutrient solution is well balanced. This is why NFT is so successful for growing plants.

3. Root hairs: These are vital to the health of the plants. Root hairs take-up atmospheric oxygen which is essential to plants.

Root hairs are the lungs of the plant. Most plants cannot absorb sufficient oxygen from the solution for healthy growth so it follows that the roots of your plants should always have roots hairs present and above the solution level in the channel. It is essential to keep the solution from pooling so that roots are not submerged. This is achieved by having an adequate slope and appropriate inlet solution flow.

Grow material

For NFT or other similar grow system a grow material block with the following qualities should be used.

Have sufficient strength to support plants.

Minimal wicking and non capillarity technology, means no nutrient salt build up.

Be pH neutral, sterile and inert.

Substrates must be free of diseases, weed seeds and residues of disinfectants, pestersides, herbersides and other unwanted toxins. Appropriate distribution of air, since roots need oxygen and give off gasses approximately 20 percent of the total volume should be occupied by ambient gas when saturated.

Maximum water availability for the plant roots and should hold approximately 80 percent of its total volume when saturated. Using weak physical forces to retain the water.

Provide accessible nutrient solution with consistent chemical characteristics willing to release stale nutrients with every irrigation cycle, ensuring plants are bathed in a fresh, oxygen rich solution.

Have uniform dimensions to optimise the sowing process.

Centered holes for the seeds to rest in the plug enabling the seed to root easily which results in fewer twisted seedlings. The root tips can then easily penetrate the plug, resulting in uniform emergence and ensure that the seedlings are firmly anchored.

Control Equipment

Monitoring and control equipment maintain nutrient concentrations (including total amount of salts), pH, and water level. An electrical conductivity (EC) controller and a pH controller are commonly used to regulate the operation of dosing pumps or solenoid valves. These pumps, or valves, control the transfer of fertilizers and acid to the catchment tank. A mechanical floating valve or a variety of electronic controls can easily maintain a constant water level in the catchment tank. A great variety of safety devices and precautions are available to guard against failure of the pH and salinity controllers. Timers are routinely installed that can override either of the two controllers and prevent the continuous addition of fertilizer or acid to the solution for periods that exceed a normal, expected time span. Also, small tanks for the stock and acid solutions can be used, so that the crop would not be damaged, even if all their contents were added to the catchment tank; the disadvantage of this approach is that the stock solution tanks must be topped up regularly. Plants grown with the NFT technique can tolerate a wide range of nutrient concentrations. Of the system components that come in contact with the nutrient solution, have as many as possible made of plastic because metal can release potentially toxic levels of certain micronutrients, such as zinc and copper into the solution. Ensure that the main pump can handle corrosive solutions; therefore use stainless steel or plastic-bodied pumps. Self-priming pumps are preferable, but avoid the submersible types because they eventually corrode and can fail. By using several smaller pumps instead of a single large one, the solution continues to flow even when one pump fails. Also, a pressure-sensitive switch can activate a spare pump if the main one fails and the pressure in the system drops. Because of the widespread use of plastics, select only materials that are not phototoxic. As a general recommendation, FDA-approved, UV-stabilized, HDPE (high density polyethylene) and PVC are acceptable, but do not use plasticized PVC (used in the manufacture of flexible hose) or butyl rubber sheet lining (used for waterproofing reservoirs) in NFT because they may be phototoxic. Plastics are more likely to cause photo toxicity when new. A PVC product should be manufactured using a Calcium Zinc Stabilizer or better still, an Organic Stabilizer. Plastic surfaces quickly lose their potential photo toxicity when exposed to nutrient solution. Therefore, before planting a crop, flush out the new hydroponic installation entirely for 1 day with a dilute nutrient solution that is then discarded.

Various techniques have been developed to further increase oxygenation of the nutrient solution. Two separate return pipes can be arranged to enter the catchment tank at right angles to each other so that the returned nutrient solution converge well above the solution in the tank. Also instead of discharging the nutrient solution into the catchment tank through an open-ended pipe, a tee or other pipe modifications can be used to encourage dispersion, spraying the water through the air. A more deliberate attempt to increase mixing and aeration of the nutrient solution in the catchment tank involves the direct return, under pressure, of some of the nutrient solution pumped by the main circulation pump and can incorporate a low cost, easy to install ‘venturi systems which provides ample aeration to the nutrient solution. Oxygen is a very good disinfectant, and cleans the water sterilizing by killing harmful anaerobic (not oxygen compatible) bacteria and pathanogens that cause diseases. This includes bacterial wilt, pythium fungi, fusarium fungi, and others.

The mixing or agitating the nutrient solution is extremely important in that it aerates the solution replacing oxygen and removes the unwanted gasses that are present. In addition care must be taken in the amount of oxygen present in the nutrient solution as this must be a well balanced solution of the correct minerals needed for plant growth. The oxidizing properties of oxygen will reduce the concentration of iron, manganese and sulphur to form insoluble metal oxides or elemental sulphur destroying the mineral rich nutrient solution which plants cannot use