Tara McClure guides you through some of the most important decisions any hydroponics grower can make? Matching the growing system and growing media.
Does your choice of hydroponics growing system limit your choice of growing media? You may have more options than you think!
Which Growing Media Should I Use for a Top Feed Drip Hydroponics System?
Top feed dripper systems, as the name suggests, feeds plants by dripping nutrient solution slowly via a dripper stake or ring. Dripper stakes look a bit like tent pegs, only they're attached to a drip line which carries nutrient solution to it. The dripper stake then deliver nutrient solution into the growth media itself like a needle. Growers who use dripper stakes lose less nutrient solution due to surface evaporation. We recommend using two stakes per plant site so that they have a fallback if one of the drippers should clog. (One of the disadvantages of using dripper stakes is that it's more difficult to visually spot a problem before the plant starts to look thirsty! Check your dripper stakes often!)
Dripper rings tend to sit on the growth media surface, circling the base of the plant. They emit nutrient solution out of a series of tiny holes. Make sure the dripper ring is positioned so that the holes are facing downwards.
Gravity, the wicking ability of your growing media, and the capillary action of your plant's roots will distribute the nutrient solution throughout the root zone and growing media. Because the nutrient solution starts from the top (rather than the bottom as is the case with flood and drain) growers can benefit from automated irrigation right from the get go. New transplants with small root systems often need a bit of coaxing into flood and drain systems with manual top feeding until the roots are deep enough in the media.)
Rockwool products (slabs, blocks, loose fill) work great with top feed dripper systems. Try to keep the surface of the rockwool covered with protective, light-proof plastic to minimize algae growth.
Coco coir and soilless, peat-based potting mixes are also perfect for use with top feed dripper systems.
Remember, rockwool, coco coir, and soiless, peat-based potting mixes are all high absorbent growing media. Restrictive growing media such as these will become over-saturated if your run your drippers constantly. Careful monitoring is required to ensure that your plants are not over-irrigated. Keep irrigation cycles frequent as your plants grow. When in transition and flowering, some growers space their irrigation times out a little to allow the root zone to become a little drier. This technique is known to help steer plants more quickly towards generative development (flowering and fruiting) and prevent elongation—keeping plants squatter and easier to manage, especially indoors.
Clay balls (e.g. hydroton) are a favourite with dripper systems. They are non-restrictive, meaning that they absorb very little nutrient solution. This makes figuring out irrigation strategies a lot easier! It's damn-near impossible to over-saturate a plant when it's growing in clay balls because the spherical shape of the balls ensures that there are always air gaps available to the roots. Growers using clay balls in top feed dripper systems tend to adopt a constant drip cycle during daylight and vegetative growth, and a 15 mins on / 15 mins off cycle during daytime flowering and fruiting.
Liquid organic feeds should be used with the utmost care with dripper systems. It is not generally recommended. This is because organic feeds tend to clog dripper line and stakes more easily. Check with the manufacturer and, more importantly, check your plants!
Which Growing Media Should I Use for a Flood & Drain (Ebb & Flow) Hydroponics System?
There are many different flavors of Flood & Drain / Ebb & Flow. The basic principle, as you probably know, is to sit your plants in a tray and periodically flood nutrient solution into it.
Here are some of the common flood & drain options among hobbyist hydroponics growers:
-sit rockwool slabs or blocks directly in the tray
-fill plastic or fabric pots with expanded clay pebbles/rock/rockwool cubes, soilless mix or coco coir and sit the pots in the tray
-fill the tray directly with expanded clay pebbles and grow plants in net pots (filled with clay pebbles) bedded into the pebbles.
Which Growing Media Should I Use for a Gravity-Fed Wick System?
Coco coir is an excellent choice. Try mixing it 1/3 or 50 / 50 with perlite to increase aeration around the roots as this improves the drainage ability of coco coir. Organic potting mixes can also be used but, as with drippers, be very careful if using organic liquid feeds as they are generally more prone to blocking tubing.
Which Growing Media Should I Use for a DWC (Deep Water Culture) System?
The central idea behind DWC is that constantly-aerated water is the growing medium. However, most growers start their cuttings or seedlings off in net pots filled with expanded clay pebbles/Rock/Perlite—ideal for transplanting into a DWC system.
Which Growing Media Should I Use for a NFT (Nutrient Film Technique) System?
Similar to DWC, the idea with NFT is that little to no growing media (substrate) is used. Plants grow in a shallow stream of constantly flowing nutrient solution. Start cuttings and seedlings off in a net pot with a very small amount of media such as clay balls or sit plants in a neoprene collar using no media at all (great for growers taking aeroponic cuttings.) If you propagate your cuttings or seedlings in rockwool cubes for NFT, use air pruning techniques to insure that the roots have taken up as much of the block as possible (not just one or two roots poking out) for a seamless transition into NFT.
Which Growing Media Should I Use for a Aeroponics System?
Once again, aeroponics systems are all about not using any growing media at all! Plants are positioned so that their roots are suspended in a dark chamber with a fine nutrient mist. Net pots filled with just a little rockwool, clay balls, or coco chips are a great way to start seedlings or cuttings destined for an aeroponics system. The ideal method is to propagate cuttings in an aeroponic cloning machine and transfer directly into the aeroponics system—thus using no growing media at all!