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 by plants.
primary nutrients
O-45%
C-45%
H-6%
N-1.5%
P-0.5%
K-1.5%
secondary nutrients
Ca-0.5%
Mg-0.2%
S-0.1%
micronutrients
Fe-0.01%
Zn-0.002%
Cu-0.006%
Mn-0.005%

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 mixes!

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 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 recommended.

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.

NITROGEN
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!

FISH EMULSION
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 (P)
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 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 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 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.

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 Liters......so 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 system....so here's a conversion table. http://www.sciencemadesimple.net/EASYvolume.html

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. Besides...you have SOOO much Ca and S with this...be mindful of other sources like Epsom, lime, etc
Remember, these PPMs are ESTIMATES! get a meter to be sure...it'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 (K)
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 deposits...so 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).

POTASSIUM CHLORIDE (MURIATE OF POTASH) 0-0-60
...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!

SULPHATE OF POTASH-MAGNESIA 0-0-22
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.

POTASSIUM NITRATE (SALTPETER) 13-0-44
High salt index so be careful, but it does leech easy if make a booboo

POTASSIUM SULPHATE 0-0-50
also provides 18% S...so not with SuperPhosphate or Epsom....ph 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 water....no 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 (Ca)
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 activity.

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/

HYDRATED LIME
This is what I use....has 52% total Ca...derived from Calcium Oxide and Calcium Hydroxide and no other elements. 1 gram/L =520PPM/Liter=137PPM/gallon

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

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

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

CALCIUM CHLORIDE
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 S....by 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!

DOLOMITIC OR CALCITIC LIME
just look at the previous post for refresher....but be aware these raise pH

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

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

SULPHATE OF POTASH-MAGNESIA
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 acids...it 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 well.
(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 state....no 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.

EPSOM SALTS
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 much....read 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.

SULPHATE OF POTASH-MAGNESIA
I like this stuff!

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

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

SUPERPHOSPHATE AND TRIPLESUPERPHOSPHATE
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 too....watch 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.

Micronutes
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.