Do not under-estimate the
need for post harvest clean-up. Failure to do this properly can result in
never ending disease problems, plumbing blockages, broken pumps, etc.
Two separate procedures are required to
ensure hardware is clean prior to replanting:
1.
Disease
preventative
2. Precipitate removal
1.
"Disease
preventative"
At the end of each crop, it is necessary to
sterilize the entire system to help prevent disease problems in the next
crop. The following guide will help remove organic buildup e.g. pathogen,
algae, slimes, dead/ decaying plant matter (Fig 11.4a):
Step 1.
Remove all plants and media then do as much
manual cleaning as possible. External cleanliness of system and growing
area is as important as internal.
Step 2.
Partly fill system with water. Lower the
water’s pH below 5 (Important!). Then, with subdued light
conditions, add household chlorine bleach** (50g/L chlorine) at ~5ml per
litre (4 tsp per Gal).
Step 3.
Mix well then, soak system for 24 – 72
hours. While system is soaking:
-
Re-circulating systems:
Run the pump for at least 15 minute cycles every hour^.
-
Run-to-waste systems:
Run the pump for a short burst once every hour^.
Step 4.
Discard this solution then flush whole system
several times with small volumes of fresh water to remove all traces of
chlorine, dislodged material, etc.
Note, several small volumes are more
effective than a single flush
Step 5.
Where fine drippers, sprayers (etc) are used,
it may be necessary to individually dismantle and clean each unit.
** Ensure to follow necessary safety
precautions and contact no metal parts.
|
^
Note that there must be adequate ‘contact’ time (e.g. minimum of 24
hours) between the chlorine and all surfaces e.g. system side walls,
pipes, etc. Pay particular attention to areas where there is
usually zero water flow e.g. dead-spaces in taps, etc. ‘Flooding’
may be necessary to contact ‘hidden surfaces’ e.g. underneath the
upper surface of channels.
Also, note that chlorine bleach will
not ‘dissolve’ algae or general solid material. Only wet brushing
will remove those contaminants. |
2. Precipitate removal
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