DWC is prone to Root Rot,
always due to low DO*
Altitude and
Salinity play an important role
in how much DO a solution can carry.
If you reduce your nute loads,
your solution can carry more DO.
If you live in Denver,
you may have a problem indoor growing
with any temps above 65ºf
If you check out
Roseypanties experiment, you will see he had much better result
using a reduced nute load.
There were two positive effects on the plants,
that were grown using the reduced nute load.
The first good thing that happened was,
his DO increased,
due to the reduced salinity,
of his nutrient solution.
Second, osmotic pressure was reduced in the rhyzome,
allowing the plant to take in more H2o
and thus grow faster.
What does this second statement really mean?
Take your hand,
and leave it in salt water for an hour.
What happens?
Your skin wrinkles,... why?
Because the salt
has caused the osmotic pressure
on the outdside of your skin
to be higher than the pressure inside your skin,
and as the water in your hand
is sucked out through your skin,
your hand actually shrinks
from the loss of fluid
and the skin becomes loose
and wrinkled.
It is harder for your plant
to uptake water and nutrients
when you use high nute loads,
because the salt creates negative osmotic pressure (hypertonicity)
against the semipermeable membrane
of the root cell walls.
Here is the Wiki "scientific answer".
Osmotic pressure is the hydrostatic pressure
produced by a solution
in a space divided by a semipermeable membrane (your roots)
due to a differential in the concentrations of solute.
Osmoregulation is the homeostasis mechanism of an organism
to reach balance in osmotic pressure.
Osmotic potential is the opposite of water potential
with the former meaning
the degree to which a solvent (usually water)
would want to stay in a liquid
and not pass through the membrane.
Hypertonicity is a solution that causes cells to shrink.
It may or may not have a
higher osmotic pressure than the cell interior
since the rate of water entry will depend upon the permeability of the cell membrane.
Hypotonicity is a solution that causes cells to
swell.
It may or may not have a
lower osmotic pressure than the cell interior,
since the rate of water entry will depend upon the permeability of the cell membrane.
Isotonic is a solution that produces no change in cell volume.
(this is what you want your nute solution to be)
When a biological cell is in a
hypotonic environment,
the cell interior accumulates water,
water flows across the cell membrane into the cell,
causing it to expand.
In plant cells,
the cell wall restricts the expansion,
resulting in pressure on the cell wall
from within called
turgor pressure.
(Swollen cells,
like swollen ankles or hands,
are not as productive.)
If you are good at math,
and want to get your nute solution perfect,
the osmotic pressure of a dilute solution
can be calculated using this formula
whereas
i = the
Van t Hoff factor M = the molarity
R = the gas constant, where R = 0.08206 L · atm · mol-1 · K-1
T = the thermodynamic temperature (formerly called absolute temperature)
Note: the similarity of the above formula to the ideal gas law
and also that osmotic pressure is not dependent on particle charge.
This equation was derived by van 't Hoff.
Now doing this calculation would be nice
if there are any college math majors out there,
but I use this chart,
and it has worked well for me.
_____________________
% of Nute Load________________
As you can see, 50-75% is very adequate,
and it has been my personal experience,
that I have improved yields
and better taste,
when I use the lower end of "Sufficient",
on that chart.
(*Dissolved Oxygen)
.
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