“
AN IMPORTANT STEP IN
RECOVERING MEDIA FOR
REUSE IS TO ELIMINATE
RESIDUAL NUTRIENT
WHERE NECESSARY.”
TIPS FOR TREATING ROCKWOOL
Viable rockwool cubes can be presoaked in water and
pasteurized in the microwave for 30 seconds to a minute.
Sleeves and other large sections can be scrubbed gently and
sterilized with a bleach or hydrogen peroxide solution and
rinsed thoroughly afterward.
TIPS FOR REUSING COCONUT COIR
There is some debate about reusing or reconditioning coconut
coir. One advantage of coco as a substrate is that it promotes
the growth of beneficial bacteria and fungi like trichoderma
and mycorrhizae that subsequent sterilization would destroy.
Coco enthusiasts advocate for the reuse of media without
sterilization, but only if there is no history of problems with
destructive microorganisms. There are other challenges, too. It
can be difficult to remove dead roots from coco, and used coco
will be less porous and have a higher water-holding capac-
ity as it ages. Since some root particulate will likely remain,
regardless of the cleaning strategy employed, it’s a good idea
to add an enzyme product to the end of a grow cycle that will
help speed organic deterioration so residual roots are less of a
problem. Loss of porosity can be dealt with by supplementing
reconditioned coco with new material or with another product
like perlite, especially if the coco is very fine or is reused more
than a few times. High residual salt concentrations may also
be present in recycled coconut coir, thus requiring EC testing
and distilled water flushing before reuse.
Not all types of growing media can be reused. Some like
starter plugs and small rockwool cubes weaken under the
onslaught of growing plant roots and are best discarded
after a single use. Check with the manufacturer for
recommendations. Even if reuse is not encouraged,
additional information may be available that
can help you evaluate the risks. A word of
caution here: Reused grow media is only
a money saver if you can cultivate
healthy plants with it. That’s an
important judgement call.
grow cycle
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