What is the best way to plant a sprouting seed in aquaponics?

Q:

What would be the best way to plant a sprouting seed in aquaponics? Mesh pot with stonewool or just clay pebbles surround the seedling?

A:

The best way to sow a seed into an aquaponic system would depend largely on the type of seed you want to germinate. Smaller seeds such as tomatoes, capsicum, and many other vegetables would be best supported in the mesh post with stonewool or a similar moisture retentive medium, which will ensure there is enough water and oxygen around the seed and young plant for early development. These types of growing mediums also provide the support required for smaller seeds as they can easily become dislodged when substrates with a larger particle size are used, particularly if this is an ebb and flow type of aquaponic system. Larger seeds (especially those which are pre soaked before sowing) can be started in smaller grade clay pebbles, however, since clay pebbles don’t retain a lot of moisture and are very free draining, particular attention needs to be paid to the frequency of irrigation in the aquaponic system to ensure the seed or young plant never dries out during the critical establishment stage. Clay pebbles do have the advantage of being very highly aerated, so oxygen should not be limiting to the seed or seedling, however, moisture levels can be restrictive in the upper levels of the root zone where seeds are usually placed for germination. In these types of systems, salt can also accumulate on the surface of clay pebbles, which may restrict germination of some species. As a compromise it is possible to use one of the small propagation cubes of stonewool (one inch across) to hold the seed and place this cube directly down into the surface of the clay pebbles — the young plant will rapidly grow roots through the cube into the clay pebbles without the requirement for a mesh pot and a large amount of stonewool.

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Written by Lynette Morgan
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Dr. Lynette Morgan holds a B. Hort. Tech. degree and a PhD in hydroponic greenhouse production from Massey University, New Zealand. Lynette is a partner with Suntec International Hydroponic Consultants and has authored several hydroponic technical books. Visit suntec.co.nz for more information.  Full Bio

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