proper ratio of n-p-k for cannabis etc

  • Thread starter mikegreenthumb
  • Start date
  • Tagged users None


GrowFAQ <GrowFAQ%20Basic%20Topics.html> :

*ChristianKungFu - Basic Elements and Nutrient Balance (long)*

Added by: snoofer Last edited by: snoofer Viewed: 256 times Rated
by 12 users: 9.55/10
*Basic Elements and Nutrient Balance*

Intro - N <#n> - P <#p> - K <#k> - Ca <#ca> - Mg <#mg> - S <#s> - Micros

I suppose a basic introduction to the nutrients would be in
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
by plants.
primary nutrients
secondary nutrients

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 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
judge results.
Seedling 5-3-4
Vegetative 5-2-3
Flowering 5-5-3

(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
more quickly.

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%
elemental P.
ITS 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
these micros.

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
HIGHLY acidic?

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 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.

Remember the formula<<<<<<<<< for PPM measurement? 10 grams in a liter
would result in 4800PPMs of P if fully dissolved. So if you mix 5mL (1
tsp) of this solution in one Liter of distilled water, you will have
diluted the solution to about 24PPMs....15mL (1 TB) would result in 72PPMs.

So lets try an example...Let's say you just entered the veg stage and
you need a gallon of water to feed your plants. You want about 100PPMs
of P in this solution. Let's work backwards.
1 Gallon=3.79 if you want 100PPMs in a gallon, you need
379 PPMs in a liter. We already see that per liter, 1TB=72 PPMs, so 5TB
would raise a Liter of water to 360PPMs....convert back and get 94PPM
per gallon (and 27PPMs Ca). Close enough!!!
That's 5 TB of that solution per gallon water. I know my math is hardly
conventional....sorry..........Yeah, I think we Americans screwed up the
metric here's a conversion table.

The only reason to use SP is because it seems easier to find in some
places. However, it dissolves a LOT slower with much more remaining
residue (remember the AVAILABLE phosphorous in year 1)...makes you
wonder how accurate the PPMs are. have SOOO much Ca and S
with mindful of other sources like Epsom, lime, etc
Remember, these PPMs are ESTIMATES! get a meter to be's an
investment. But one that will take you from quality to primo herb!

Side note--you can lessen the chance of overferting with P ferts by
making sure you have adequate potassium, which helps promote phosphorous
metabolism into plant compounds.

potassium is a bit weird. Its different from the other macronutrients
because it isn't a component of basic physical foundations like
proteins, fats, carbohydrates, etc. But it is crucial to photosynthesis,
enzyme synthesis and other biological functions on molecular level.

Because of its involvement in metabolism, K will influence dense buds,
better yields, and resistance to pests and diseases....I think it may
have some role in stem, root development, but cant remember for sure!

Anyway, like Phosphorous, most potassium sources are derived from
mineral the funky formula applies.

During the veg state you want a formula with nearly as much K as N,
while keeping P low...too often we focus too much on N. 5-1-3 or
5-2-3...something like that. Its pretty hard to OD on Potassium. For
those who actually care, the ppm limit is about 750...above this
wouldn't be an OD, but salt damage would be likely!

Remember, too much K will lock up Ca (and vice-versa).

...also provides 45% Cl, (I know those 2 figures don't add up but
remember that means 49% 'actual' K)so don?t use other ferts with high
Cl. You can let this sit for a while to let Cl dissolve just like TSP
solution. Its pretty highly soluble...much more so than the pain in the
butt SuperPhosphate! Watch the salt content of soil!

also supplies 11% Mg and 23% S....Good thing is that this wont change pH
much. But ya have to watch your other sources here so as not to get too
much S or Mg...DO NOT use with Epsom salts (magnesium sulphate)...also
be careful of limes with high Mg.

High salt index so be careful, but it does leech easy if make a booboo

also provides 18% not with SuperPhosphate or neutral!!

I use Muriate of Potash 0-0-60 (Potassium Chloride)....a bag will last
you decades...

I find that with this product, 1tsp=5grams.....Remember the formula
again....This time we are adding straight into solution first.
For veg stage again, we want about 150PPM. We see that 1 gram of potash
would be a fifth of a teaspoon...and would provide 600PPM per liter.
That same fifth of a tsp would therefore provide 159PPMs per gallon.
(600/3.79) Again, close enough!!

Its normally best to introduce potash alone into water first before
adding any other salts or solutions. The TSP solution and fish emulsion
are already chemically dissolved (liquefied) so I CAN add them in same
total fert mix with potash....but dissolve potash first!!...WORKS GREAT!

Calcium functions as a ?glue? in plant cell walls. It partially
regulates cell wall permeability and works as an enzymatic cofactor

Without Calcium, plant cells couldn't reproduce because it is vital in
meiosis and mitosis, cell-wall permeability and enzyme synthesis. In
addition to this role in cell division, on a larger scale, Ca is crucial
to the growth of the apical meristem (growing tip). Toppers pay attention.
Calcium is also important for seed germination...but that's not usually
an issue. It also helps to neutralize acids formed during metabolic

AND Ca helps promote P uptake as well as the uptake of Molybdenum
(Mo)...a neglected micro. But remember, too much Ca can lock up Mg or
K...high tolerance, but be careful, as always.

Despite the importance of Ca, most pre-mixed chemical ferts do not even
HAVE any Ca...your plant is missing out BIG time. You can tell too...the
plant will actually look retarded or deformed in some way!
Calcium primarily comes in salt form, so the percentages are straight
forward unlike P and K...most of the elements are from here on actually.

Now, the first few sources I list are limestones and aren't actually
chem ferts....this is an example of some things I use in conjunction
with salts. Limestones are great...most are aware of their great ability
to raise pH and mainly turn to lime for this reason, but they also
increases microbiological activity especially the nitrification process.
There are different types, just read ingredients. Some have high Mg,
some don't....look for high levels of Calcium Oxide/

This is what I use....has 52% total Ca...derived from Calcium Oxide and
Calcium Hydroxide and no other elements. 1 gram/L

20-30% Ca, 10-20% Mg....raises a bit more gently than Hydrated
Lime....seen a number of ranges.

usually around 30% Ca and 3% Mg...Good choice if you can find it.

This is the best for total control as it is about 70-75% Calcium with no
other elements to balance.

about 35% calcium but also a large amount of Cl...If you aren't getting
chlorine source anywhere else, go ahead...its easier to get than
CaO....Home Depot has it.

And don't forget our old friends SUPERPHOSPHATE AND
TRIPLESUPERPHOSPHATE....go back and look at those healthy Ca amounts!

*Magnesium (Mg)*
Magnesium is a central element of the chlorophyll molecule, so is
obviously crucial to photosynthesis. It is also an enzymatic cofactor
and has a role in uptake of many nutrients. It also helps seed formation
for you breeders!

Pretty Important which is why I like calling it a secondary rather than
lumping in with micros. Look at most of those chemical fertilizers and
you'll find a large number have NO Mg....that's why Epsom salts are so
popular with growers.

EPSOM SALTS (Magnesium sulphate)
11%Mg, 2%Ca, 14%S Very versatile...some work into soil, but I don?t
recommend this as they leech easily...might as well just add with water.
Can also use as foliar feeder too. Good point is the neutral pH, but the
main drawback with Epsom is high salt index. Don't use too much,
especially in soil that dries quickly.......Its other drawback is the
slightly higher S to Mg ratio. We actually want 3-4 times as much Mg as using Epsom, you are necessitating another Mg source to balance
this....gets complicated as you need to be mindful of your other sources
of S and Mg....don't overlap and OD!

just look at the previous post for refresher....but be aware these raise pH

60% Mg....nothin else...pure, great for specific deficiency treatment.

10% Mg and 11%N....don't really see the point here...N is so easy to
provide with other salts or ferts.

supplies 11% Mg, 22%K and 23% S....this is a good balance if you need
potassium...otherwise Epsom salts would be better...remember too much K
causes lockup.

*Sulfur (S)*
Sulfur is crucial in the formation of plant amino acids & proteins, as
well as respiration, cell metabolism. It also is an important part of
good root development and the metabolism of fatty has a
definite impact on the "bouquet" and taste of herb! Also keep in mind
that S helps to regulate N uptake, so a S deficiency also inhibits N as
(I've seen recommendations of N:S as high as 2:1 and 4:1. That seems
high to me...check the list I presented at the top of this post. That
would lead you to believe a 10:1 ratio is good for VEG doubt
the flower state is higher due to Sulfur's role in protein synthesis and
metabolism...I go for 5:1 or 6:1 tops, but again....start with
conservative amount and work the dosage up...keep notes for another day!)

Remember, plants can only uptake elements in ionic form, in this case,
SO4. There are pure elemental Sulfur compounds available that only need
to be oxidized for availability in plants. Obviously, water would serve
this purpose....but an S overdose severely lower pH... its hard to do
with most S compounds, but pure elemental Sulfur isn't real safe.

Whatever you use, it does leech easily, so don?t let soil get dry and be
sure to maintain a consistent S source THROUGHOUT the grow. If you use
some organics, you probably wont need to worry much as they release
ample S.

11%Mg, 2%Ca, 14%S First mention because so common and for good reason.
Provides two essential secondary nutes that often aren't found in
commercial chemical ferts, and it wont alter pH the
previous post... If you use it with restraint, you can supply a steady
source of S through the whole grow and increase the Mg and Ca ratios
with other salts.

I like this stuff!

provides 18% S....similar to sulfate of potash-magnesia, but TWICE the
potassium (50%)...careful of lockup if you have K supplied another way.

Good stuff, completely water soluble....20-25% S...WATCH the IS
an acid

Our good friends again....good product and I use this myself....only
drawback is that preparation (see post on Phosphorous) is a pain in the
ass for some who aren't used to their own fert. Remember gives healthy
dose of Ca out if using lime!

Stay away from AMMONIUM SULFATE...if you've followed the thread, you
know why!! If not, well, Im high and you're just gonna have to go back
and find out! CALCIUM SULFATE (GYPSUM) is very slow to
release...wouldn't recommend inside for short harvest.

I don't really bother to make a big fuss about micros because they are
used by the plant in such small amounts, that either you have them in
the soil or you don?t. If you go organic you'd have all the micros you
need. I use fish emulsion for N source because of its micros. You can
also use liquid iron, iron-sulphate or various 'citrus' ferts....they
both have essential micros.

I'm using a chelated "liquid iron" from ferti-lome. It has 0.05%
copper(Cu), 3.25% Iron (Fe), 0.15% Manganese(Mn), and 0.16% Zinc(Zn).

Some of the other liquid ferts can be used, but I find that the S
concentration ts TOO high in proportion to Mg.
Last modified: 15:53 - Nov 17, 2002

GrowFAQ © 2000-2004 Overgrow
faq:1347 "ChristianKungFu - Basic Elements and Nutrient Balance (long)"


not mine so dont ask me about or flame me over just found it wanted to share I FOUND very helpful and precious info

John Smith Esq.

tried to give you rep for this mike but site say i gotta whore out some more before i can give to you so ill say nice info in this post instead, so... nice info dude.


tried to give you rep for this mike but site say i gotta whore out some more before i can give to you so ill say nice info in this post instead, so... nice info dude.

thanks bro appreciate that yeah i came across it trying to figure out what issues were in my growroom and thought i would share



interesting that the author suggest 3-1-3 as the proper ratio. Everything I've been reading lately says the proper ratio is 3-1-2 or 3-1-4 - and that is all the way through from veg through bloom.

that's for pretty much all plants

I attached a file for folks to read. edit: I should probably mention, skip to the part about Tom Ericsson (sp) on page 3

scope this thread too:
View attachment 2006-11-Midland-TheGreenScene.pdf


My mistake, I read this quickly and thought it was the author's recommendation

To start, here are the approximate ratios of elements generally needed
by plants.
primary nutrients

the 3-1-2 and 3-1-4 ratios are based on plant tissue samples and fatman7574 claims to have tested cannabis.


interesting that the author suggest 3-1-3 as the proper ratio. Everything I've been reading lately says the proper ratio is 3-1-2 or 3-1-4 - and that is all the way through from veg through bloom.

that's for pretty much all plants

I attached a file for folks to read. edit: I should probably mention, skip to the part about Tom Ericsson (sp) on page 3

scope this thread too:

he suggest as base and for you to find what works "best for you" and it also said how to factor in what is actually obsorbable alot of shit in nutes isnt readily there for plants slow release so factor that in your formula as well


doesnt even mention calcium nitrate lol.

this was an interesting read, but the dude who wrote it is a weird o haha
Top Bottom