proper ratio of n-p-k for cannabis etc
*ChristianKungFu – Basic Elements and Nutrient Balance (long)*
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*Basic Elements and Nutrient Balance*
Intro – N – P – K – Ca – Mg – S – Micros
I suppose a basic introduction to the nutrients would be in order. it
may be common knowledge for many, so just skip on ahead, but like I once
was, many are just getting familiar and knowing the basics makes each
additional step that much easier to grasp. So hang in there!
To start, here are the approximate ratios of elements generally needed
O, C, and H are provided through air and water mainly. We are
responsible for the rest.
Remember. this is a GENERAL approximation for all plant life, and
cannabis, like any other plant, has certain and specific biological
needs which call for some alterations to these percentages. There is no
scientific standard on the proper ratios of these elements for cannabis,
however it IS some agreement on the specifications for N,P,K during
different stages of growth.
This is also a generalization based on VEGETATIVE growth. seedling,
flowering, and flush stages require different ratios..phosphorus being
the obvious! But this is a good barometer for balancing your own fert
As far as specific cannabis ratios for N-P-K. here is a quick
reference. (these are just ratios. not recommended fert formulas) You
may find a number of different ratios presented by different ‘experts’.
Feel free to experiment, but keep a record of fertilizing, so you can
(Side note, many growers refer to N-P-K as macronutrients while
referring to the others as micronutrients. This gives the impression
that they aren’t as important. While its true that most organics and
some commercial soils have ample micronutrients. Ca, Mg in particular
usually need to be added, hence the distinction as SECONDARY nutes.
Sulfur often comes through various salts, so don?t worry as much. The
micronute ratios are so small that variances aren’t very significant in
terms of maximizing yield or quality. As long as you have some in there
you’re good. and its pretty hard to OD on most micronutes as long as
you aren’t pouring it on!)
Notice that the N and K requirements are very close. One mistake often
made by us growers is to use a high N fert while neglecting K. If you
use a 12-0-0, 5-1-1 or something similar, you NEED to supplement with K.
Of course, then during flowering we boost the P and lower the other macros.
Another reason the P,K figures are higher than maybe expected is due to
a bit of trickery on the fertilizer labels of commercial products.
The N figure is straight forward because N comes from organics or
salts. almost NEVER in mineral forms, but because P and K come in some
degree of rock/mineral form, much of it isn’t immediately available for
uptake by root system because the nutrients aren’t in ionic form.
Therefore, the label figures actually represent the amount of P2O5 and
K2O (NOT the amount of P,K) available in the FIRST year.
You can figure the ACTUAL amount of P by multiplying the label# by 0.44
and the K amount by 0.83.
For example, let’s say you’re using a superphosphate at 0-20-0. You’d
think that meant 20% Phosphorous. But it really means that, by weight,
20% of this fertilizer is phosphorous in MINERAL form of p2o5 available
in the first year. The actual amount of ELEMENTAL phosphorous would be
20 x 0.44 = 9% available phosphorous.
This labeling gimmick is why growers are FAR more likely to overfert
with N than with P,K and why we need a bit more P,K than usually
After all that, for the sake of confusion, I’ll just standard N-P-K
format when posting formulas, and let you do the math if you really want
to see exactly how much P is available.
As a result of a phenomenon involving growers’ increasing predisposition
for urinating on their plants, I’ll take a minute to touch on this.
Basically, urea nitrogen CAN be a good source of Nitrogen, but I don?t
advise this indoors in small containers. There are too many variables to
consider and monitor.
The problem with ureas is that they FIRST must be broken down into
ammonium nitrogen THEN further broken down into nitrate nitrogen.
Obviously this is a lengthy process so the grower must have a much
better sense of timing and be much more accurate in the dosage because
while nitrate nitrogen leeches out of soil, urea and ammonium N do not.
Many growers do not see immediate gains from urea and mistakenly fert
again leading to toxicity and pH nightmares.
If you use piss and are happy with results, you’re likely an expert or
just damn lucky. Knock yourself out. but wouldn’t advise it. If you
insist on the golden shower, I understand that pine bark helps to
facilitate the nitrification process making ammonium nitrogen available
That said, I would still STAY AWAY from ureas and ammonium. find a
nitrate source. In addition to the above problems, I forgot to mention
that if you use ammonium nitrogen ferts in the same medium as lime,
ammonia gas will be produced, much of the N will leave the soil medium
into the air.
Nitrate sources DO raise pH, which can lockup nutrients, so using them
alone may require some pH modifier like iron sulphate, but chances are,
you will be adding other ferts which lower pH. I’ll touch on balancing
these later on.
SODIUM NITRATE (Nitrate of Soda)
is GREAT! Its about 15% nitrate nitrogen with no ammonium or ureas. Good
pure source of readily available N. (Unfortunately, it is much harder to
locate nowadays because of the Oklahoma City incident) It will raise pH
by itself at about 1/3 the rate of limestone, so supplementing with iron
sulphate would be a good idea unless you have an acidic soil. Only
drawback is very high salt index. Be sure you have a medium that allows
leeching and do NOT overdo this.
Keep in mind, as you become more familiar with salt fertilizers, you
will find a myriad of products and combinations. For example, POTASSIUM
NITRATE is highly soluble and provides TWO key elements! K-45%, N-12%.
The only reason I’d avoid it is because you’d have to supplement with
more N during veg state anyway. and its high salt which leeches easy.
There are other salt sources, but they almost all contain too much
ammoniacal nitrogen. I use fish emulsion which is NOT a salt fertilizer!
is my favorite. bit stinky but not as bad as advertised! I actually use
it myself. Doesn’t alter pH, low salt index, water soluble– I love it.
I know, its an organic source really, but its one that I can easily work
in with salt fertilizers. The N-P-K ratio is usually around 5-1-1 and
supplies a number of micronutrients unavailable in chemical ferts. The
Nitrogen breakdown is about .5% ammonium-nitrogen and 4.5% water soluble
nitrogen. You could use this stuff alone during veg, although I would
supplement a bit with potassium. Then during flowering, you could still
use sparingly if needed while focusing more on salt fert mixtures.
Phosphorous helps to enhance growth and vivid colors, especially during
flowering. It will strengthen stems early in growth and will increase
blooms during flowering. pretty obvious why high P is so crucial
during flowering cycle!
Many sources of phosphate, especially those made to mix INTO the soil
before planting, come from mined phosphate rock which has very little
available P. remember, plants only uptake in ionic form.
A whole thread could be written on the processes which make P
available. I’m not an expert, so I’ll stay away from the details.
Basically, mineral phosphate deposits, taken from rock, are treated with
acid or extreme heat, producing a salt fertilizer much more readily
available to plants. Varying degrees of treatment result in various
amounts of available P which is water soluble. Rock phosphorous is the
beginning of it all. superphosphate and triple super phosphate are more
refined. phosphoric acid. oh yeah.
PHOSPHATE ROCK 0-3-0 has about 30% TOTAL available P, but only 3%
available, in p2o5 form, in the FIRST YEAR. and that means about 1.3%
ITS ROCK. it takes FOREVER to provide nutes.
Most SUPERPHOSPHATE is 0-18-0 and is about 85-95% water soluble. It also
consists of about 20% Calcium and 12% Sulfur. be careful you dont OD on
TRIPLESUPERPHOSPHATE 0-48-0 at 85-95% solubility. Also provides 14% Ca
and 1% S. My fave. much more soluble and not so high a concentration of
S and Ca. easier to control.
PHOSPHORIC ACID is about 0-45-0 and 100% soluble.
SuperPhosphoric Acid is 0-70-0 and 100% soluble. need I say these are
AMMONIUM PHOSPHATE. 11-48-0 . also high pH. besides, remember
ammonium N. yuck.
Obviously, the ACID forms are the most potent and are convenient because
they are completely soluble in water. However, you WILL DEFINITELY need
to balance the pH. DON?T think you can avoid doing so or you will screw
your efforts. Hydrated Lime is a cheap, easy way to do this. Don’t use
the lime with SP and TSP though. they already have high concentration
of Ca and too much Ca will lock up K.
I go with TSP over SP any day simply because it is much more
concentrated due to better solubility and therefore more accurate PPM
‘guesstimate’. My current source of P is TripleSuperPhosphate
0-48-0. you can even increase the solubility a bit by grinding further
in a mortar/pestle or coffee grinder. but I don’t bother. Let it sit in
a plastic bottle at the recommended dosage (if given) for a few days,
even a week maybe and periodically shake it up. You can even siphon off
the solution later and toss away the undissolved solids. Sounds like a
pain in the butt, but just mix a large bottle ahead of time and save it
away from light and air. It will last a few grows!
Dissolve @10 grams/Liter in distilled water. Let it work, open to air,
for about a week or so before using. swirl or shake it up a couple
times a day. This allows the Chlorine in the solution to interact and
dissolve into the air. That way, you retain the P ratio, but you reduce
the potential for Cl overdose.
GrowFAQ : *ChristianKungFu – Basic Elements and Nutrient Balance (long)* Added by: snoofer Last edited by: snoofer Viewed: 256 times Rated…