There are several diverse hydroponic systems available on the market and it can be challenging to know which one to employ. The core systems that are used are:
• Flood & Drain / Ebb & Flow
• NFT (Nutrient Film Technique)
• Deep Water Culture
• Drip System
This post will supply a summary of each system and describe how it operates and what are the best kinds of fruits and vegetables to grow in it.
We will begin with a popular method and the first on the list – Flood & Drain
Flood & Drain
This technique uses pumps to flood the crops and their roots with water at specific intervals and for a selected quantity of time. This system is totally programmed. Timers are employed to toggle the pumps on and off at assigned times, and the water used in the flood has diluted nutrients within it. This allows the seedlings to get all the food it needs direct at the roots. The frequency of the flood and drain will vary depending on what variety of crop you are producing and the type of substance you are growing in. For example, clay pebbles drain quickly and as a result will require more floods per day, but a different medium like rockwool will take longer to drain and hence require less flooding per day to keep the roots saturated. When the flooding has finished and the pump turns off, the water empties back into the main reservoir.
Crops can be produced using this technique on specific elevated tray platforms or in an individual pot system. Trays are ideal for growing crops that achieve about a metre in height. For crops growing taller then a flood and drain pot system is a good idea.
Tray Platform
Employing a tray platform enables gravity to be used throughout the drain. Right now we are cultivating strawberries in our display tent of flood and drain. The tray platform system is great for these plants as they will not grow too high and conflict with the light. A grow tent is recommended to put this system in because it holds all the clutter of wires and grow mediums and features a highly reflective layer on the interior.
The trays come in various sizes, but we are using a 1m square tray for the strawberries. The tray is positioned on a stand and the water cistern (containing nutrients) is underneath – this results in a neat, tidy kit. You will find two nozzles at the middle of the tray, one which is connected to a pump which sends water out of the reservoir below into the tray, and the second nozzle drains the water away using gravity.
Timers enable you to set the number of times the systems floods and drains on a daily basis – and that is pretty much it. Flood and Drain trays are straightforward pieces of kit to use and put together. As we are using a tent the grow lamp is fastened to one of the rails above the strawberries and currently we are simply waiting to harvest.
Pot System
The pot system is different to the tray as you may have many pots as you want as long as you ensure you have the right size of reservoir. In a pot system the water tank will generally be in the form of a water butt rather than a deep tray. The pots which are used are made up of an internal and external pot. The plant sits in the internal pot within a medium such as rockwool or clay pellets and this is placed in the outer pot. There will be a bit of space in between the inner and external pot to allow water to flood the roots effectively. There are a couple of differences from the tray method.
1. The addition of a brain pot.
2. The use of gravity and water pumps.
Brain Pot and Flood Cycle
This is an independent pot to the central reservoir and it maintains the flow and drain of water, thus the name "brain".
The timer is attached to the brain pot and the primary electricity source. The times you would like the flood to occur are set on timer and this automatically starts the flood and drain periods. Water is either pumped or passes by gravity into the brain pot from the reservoir when a flood period commences. The brain pot is connected to the individual pots by flexible pipe and as water circulates and floods the brain pot, it likewise fills the pots. As soon as the pots are completely flooded a stop flow switch in the brain pot switches the stream of water from the water tank off, hence the pots do not overspill. This enables the roots of the crops to bathe in the nutrient loaded water. Following a time lapse the timer will instruct the brain to start pumping the water from the brain pot back into the reservoir and consequently draining the water from the pots. On top of removing the water from the pots this course of action enables fresh oxygen to be forced into the pots supplying the roots.
These are ingenious systems and appear in a range of sizes ranging from a 4-pot system to a 48-pot system. The systems do not incorporate the lighting fixtures and if you check out my profile you can easily see the publications I have written on the different lighting used in hydroponics.
Helpful hints for using flood and drain
• Keep an eye on your system as pieces of medium can choke the pump device if they get in the water.
• Keep the reservoir filled and provided with a superior nutrient to keep your plants nourished.
• Typically flooding needs only to be performed when the lights are on.
• Be careful and look for root blockage in the flexible pipe connecting the pot to the brain pot. As roots establish this may be a concern.