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Root Health - Rockwool vs Perlite

Posted by aegean (My Page) on
Sun, Jul 25, 10 at 17:24

I have different types of lettuce growing in my DIY NFT system. As a medium, I used rockwool cubes and cups filled with perlite.

The roots of those grown in rockwool cubes don't look healty. The part that remains above the solution is yellow. Down below, the part that is in contact with the solution is white.

The roots of those grown in perlite filled cups seem to be ok. They are all white. Note that the cups are suspended above the water level as well, so the upper part of the roots are not in contact with the solution.

Please see photos below.

What is the reason of this? Should I let the rockwool cubes sit on the bottom of the gully?

Follow-Up Postings:

RE: Root Health - Rockwool vs Perlite

Are the rockwool cubes dry? I'm sure that the yellowing is just because that part of the root system is always dry, and has nothing to do with the type of growing medium. You can try to set them directly in the stream of nutrients, but with the roots coming directly out the bottom like that, they will probably just tip over. Also If placed directly in the solution, the rockwool cubes will remain continuously saturated. That may not be much of a problem for lettuce though. I would probably just try to get the bottoms of the rockwool cubes closer to the water level. And/or get the water level to rise a couple of times a day to saturate the rockwool cubes, but still remain above the water level..

RE: Root Health - Rockwool vs Perlite

homehydro, thank you for the help.

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