How Drip Irrigation Works
The Dutch who grow everything using this system, have mastered this technique. Nor do they just grow everything, they grow on an unprecedented scale compared to any other nation. The plants are propagated in a rockwool cube then grown on in a rockwool slab. The plants are individually fed using drippers. These drip emitters are designed to deliver at a set rate at a pre-set volume of water per hour.
Each dripper is wired to an infrastructure of tubes and delivery pipes, which are fed by one master pump. Most commercial systems are what are known as high-pressure drip systems and most domestic systems are known as a low-pressure drip system. These commercial high pressure drip systems are typically run to waste systems. This is when the nutrient is bled off and after dripping through the rockwool slab then simply allowed to run down the drain i.e. to waste. This ensures these plants get the exact maximum nutritional value from the nutrient solution and also cuts back on the possibility of bacteria or fungal problems like pythium. Most low-pressure drip systems are recycling or re-circulating systems where the nutrient returns to the tank then gets pumped back to the plants, then to the tank, so on and so forth.
These systems are relatively cheap compared to others and easily built once you get your head round the spaghetti of pipes, tubes and fittings. Drip systems are also very versatile and can be made in many shapes and formats allowing you a more modular design for your grow rooms.
The running costs of these systems are not cheap as after each crop you basically dispose of the rockwool slab and replace it with a new one. A 1 metre slab normally holds approximately 3 plants which can run up quite a bill if you have many plants. Also if you are running to waste then the cost of nutrient is very expensive indeed.
The main draw back with these systems is that the dripper can clog. Similar to the NFT system, if a dripper stops your plants will suffer. If you fail to notice that a dripper has stopped, the plants run the risk of dying or at least losing their potential to give good yields. These systems need constant maintenance and upkeep and are not recommended for the beginner. All drip irrigation systems are a little tricky to maintain, as you need to take constant pH and CF readings from your tank, from you run off and from your rockwool medium. This process is achieved by using a syringe to suck up a sample from inside the rockwool where the plants are growing. As the medium itself will hold a different pH and CF value to the tank and indeed even the run off. Then armed with this info you need to re adjust the system again and do all those tests once more until you are happy that you have the right levels that you require. This process can easily need doing once a day. It is also advisable when growing in rockwool slab culture to flush the salt out every 2 weeks with pH adjusted plain water. This needs to be done as rockwool tends to absorb unused salts which can build up, therefore need flushing every 2 weeks or so. It is also advisable to do this flushing out process to flush out any salt build-up that can concentrate in the drippers. Regular flushing can alleviate some of the maintenance problems of these systems. However, getting blocked drippers is part and parcel of this system so it is always advisable to clean them regularly and also to have ample spare drippers to swap when old drippers need cleaning. The above to one side, this is a very productive hydroponics technique and has served the Dutch very well. The rockwool slab does offer a lot more support that you would achieve if you were using NFT systems. It is also less prone to pump failure and as the slabs absorb a lot of water you do have some breathing space if the pump or drippers fail. It is very detachable and modular allowing easy expansion or removal of the system. Low pressure drip systems are more prone to dripper failure compared to high pressure drip systems, however, for Percy Throwers, the high pressure option is too expensive and industrial for a small indoor garden. Overall high levels of maintenance are required for both types of drip systems. The pipe work and drip lines also need regular replacement to combat clogging and salt build-up.
Ventura Action Drip System
Another entirely different drip irrigation system is that which uses Ventura Action to deliver the dripping effect. These are individual grow tubs or pots specially designed for the smaller gardener. The system consists of a large outer pot which acts as a smaller water tank. Inside this large pot is a shorter inner pot which holds the grow medium which is typically clay pebbles. This smaller pot sits inside the bigger pot but does not actually hit the water level of the bigger pot, which is the holder of the nutrient solution. In English, it is a pot within a pot; the smaller inner pot is where the plants grow, the bigger outer pot acts as the tank. A Ventura pipe is then placed through the upper grow pot and submerged under the water level of the outer pot. Air is pumped down the Ventura pipe which causes the water to be pushed up above the level of the top of the grow pot. This is then piped into a delivery tube with large holes punched into it. The tube runs completely round completing a circle joining back up to the Ventura pipe. Water pressurised via the air pump is then delivered through this drip ring which slowly but perpetually drips onto the clay pebble medium. The nutrient solutions then drips entirely through the clay pebbles back to the outer tank, which in turn is then pumped back via the Ventura pipe to the top and delivered to the clay pebbles. If you like, it is a cross between a NFT system and a drip irrigation system but uses clay pebbles as the medium for the plants to grow into. Due to the fact that an air pump is used to deliver the water through the Ventura pipe, the nutrient solution delivered is highly aerated. Also, the constant dripping effect pulls air down through the clay pebbles medium.
This system is typically only used for 1 to 3 plants or mothers. The reason for this is that to grow more would require more pots. Each has its own individual tank. This tank due to the small nature in size needs regular upkeep. To maintain lots of plants, you would need to maintain lots of tanks. This would be a too big a time consuming enterprise to undertake. Also, to adjust the inner tank you have to lift out the smaller inner pot which the plants are growing in. This again can be a costly exercise and it is very easy to damage the plants when lifting out and placing back this smaller inner pot. In recent years, a controller has been invented so you can link multiple individual systems together. But as the individual pots still have individual tanks passively connected to the controller, the controller fails to do its job in terms of pH and CF management, i.e. you get different pH and CF levels in the different individual pots, but also in the controller as well, making it very hard to maintain precise control of your lovely crops. Also, due to the small size of the outer tank, the system will need daily maintenance to keep the tank topped up and the pH and CF at the right level.
Algae is also very prone to develop in this system as the medium is fed from the top down ensuring that the top of the medium is continually wet. The constantly wet medium being exposed to long periods of light will always result in algae breakouts. As each system is packaged with its own individual air pump, the pumps after prolonged use can stop having the same problems but not as frequently as the NFT system resulting in a failed crop. On this note, the drip ring can also become blocked up with salt build-up and calcium deposits so this too needs regular cleaning.
All of the above to one side, this is an ideal first system and is an inexpensive valuable teaching aid to the hydroponicist. The system provides good aeration to the rootball and excellent support to your bigger yielding plants. It is good for mothers but it is necessary to be very careful when removing the inner pots to top up and adjust the CF and pH of the outer tank.
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| Nutrient Film Technique aka NFT |
Flood and Drain Pod Systems™ | AeroponicPod™ | The Aero Pod™ aka The Bubbler |
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