rockwool affect my nutrient pH?
not alkaline! It is a common belief that Rockwool is alkaline
and that one has to continuously adjust the pH. This is not true.
When Grodan rockwool is new it contains some residual lime from
soak the rockwool in no lower than pH 5 water the day before use.
This is done to dissolve the lime. The lime will make the pH value
raise a full point. Immediately before use; you flush the rockwool
with your nutrient solution. When you flush, you also flush out
the dissolved lime.
From this point
onwards rockwool does not change the pH in any way. Exception:
If you condition your rockwool with a pH lower that 5, you may
also damage the fiber itself. As an example: If you use pH 4 water
for conditioning, the pH the day after will be 7. The lower pH
you use the higher it jumps. Once the fibers are damaged it might
take quite a while before the pH stabilizes. So never go below
pH 5 with rockwool.
Why does pH
change ? When the plant grows the pH goes up because of the root
activity. If the pH is not going up, your plant is not growing!
When the plant gets ready to set flowers or fruit, the pH will briefly
drop. So when you notice this drop, it is time to change to your
propagated plants have grown into the bigger DM blocks, you will
often go into a period of rapid growth. This means that your pH
will go up . Your EC (conductivity or TDS) will also tend to go
up. Be sure to water the blocks enough. You need to check EC and
pH in the blocks everyday. During this initial growing on, water
the blocks every 6-7 hours, but only while the light is on. If
the pH or the EC in the block is too high, the quickest way to
change it is to top water with balanced nutrient solution.
As the plants
get bigger 3-4 weeks after potting up the A0 cube, you will need
to water approx. every 5 hours. (1000 W light) Set your first watering
to start when your light switches on. Be sure to complete the last
watering no less than 2 hours before you switch your light off so
the blocks are not too wet during the night.