calculating npk/nutrient profile

[*mistress*]

converting npk to ppm

converting npk to ppm

standards
1 tablespoon=14.78 ml (~15 ml)
1 ounce=29.57 ml (~30 ml)

to obtain the ppm of any nutrient in your plant food mix when the ounces of fertilizer per 100 gal of water and the fertilizer percentages are known, calculate:

nutrient in solution, ppm=.75*nutrient%*dilution rate, ounces/100 gallons

example:
gh flora nova bloom npk%: 4-8-7
@ .5 ounces/1 tbspn/15 ml per 1 gallon of water

nitrogen 4% [.75*4*50]= 150 ppm

phosphate 8% [.75*8*50]= 300 ppm

potash 7% [.75*7*50]= 262.5 ppm

calcium 4% [.75*4*50]= 150 ppm

magnesium 2% [.75*2*50]= 75 ppm

sulfur 2% [.75*2*50]= 75 ppm

chelated iron .1% [.75*.1*50]= 3.75 ppm

these should be the ppm#'s per 1 tablespoon of gh fnb, per gallon of water. please confirm using spreadsheets/other methods.

the above formula is easily scalable + convertable/reversible. just algebra...

hope this helps. enjoy your garden!

 

[dongle69]

15 ml/gal FloraNova Bloom from nutrient calculator spreadsheet:

n 231
p 201
k 336
mg 116
s 116
ca 231
iron 5.8

Between 2400 and 2500 ppm on .7 scale - about 3.5 EC!

 

[*mistress*]

15 ml/gal FloraNova Bloom from nutrient calculator spreadsheet:

n 231
p 201
k 336
mg 116
s 116
ca 231
iron 5.8

Between 2400 and 2500 ppm on .7 scale - about 3.5 EC!

is this per 100 gallons?

why the different #'s?

both approximations?

 

[dongle69]

is this per 100 gallons?
why the different #'s?

The ppm numbers I gave are from 15 ml of FNB per gallon of water, as you requested.
I'm guessing your method of ppm calculation is incorrect.
The nutrient calculator gives elemental ppm and also ppm based on true scales, once you complete the spreadsheet info.

gh flora nova bloom npk%: 4-8-7
@ .5 ounces/1 tbspn/15 ml per 1 gallon of water......
....these should be the ppm#'s per 1 tablespoon of gh fnb, per gallon of water. please confirm using spreadsheets/other methods.

 

[dongle69]

One thing I noticed in your calculation is there is no accounting for weight.
The nutrient spreadsheet requires grams per ml in calculating ppm for liquid nutrients.
Most nutrient bottles will have their weight listed, as well as their volume, so you can figure grams per ml.
But even accounting for weight, your calculations are too far off for the discrepancy to be just that.
Also, each individual nutrient element can have a different formula.
Where did you get your formula?

 

[*mistress*]

One thing I noticed in your calculation is there is no accounting for weight.
The nutrient spreadsheet requires grams per ml in calculating ppm for liquid nutrients.
Most nutrient bottles will have their weight listed, as well as their volume, so you can figure grams per ml.
But even accounting for weight, your calculations are too far off for the discrepancy to be just that.
Also, each individual nutrient element can have a different formula.
Where did you get your formula?

best of the growing edge, 2
greenhouse math, by samuel p. faulkner, phd:

what if you know how mucgh fertilizer you dissolved per 100 gal in a batch tank?... the problem is that you dont know the concentration of nutrients in the tank.

to obtain the ppm of any nutrient in your plant food mix when the ounces of fertilizer percentages are known, calculate:

nutrient in solution, ppm=0.75*%nutrient*dilution rate, ounces/gal

example given:
lets say you used a rate of 15 oz of a 20-20-20 water plant food for a 100-gal batch of fertilizer solution.

what are the concentrations of nitrogen, phosphorus, or potash in the batch?

it will be the same for all nutrients because they are all 20% by weight in the dry fertilizer.

the calculation is:
nutrient in solution, ppm=0.75*20*15oz/100gal=225 ppm each of n, p2o5, k20.

thus, substituting the #'s for flora nova bloom, @ 15 ml per gal, or 50 ounces per 100 gallons, using just the n, we have,

0.75*4*50 (since we are applying ~1/2 ounce per gallon, and a 1/2 ounce is ~1 tablespoon, for 100 gallons, we will have a total of 50 ounces).

formula a:

.75*4*50=150 ppm of n per gallon.

discovered another mathematical formula. lets see if it comes to similar #'s...

http://www.growfaq.net/index.php?sid=2170490&lang=en&action=artikel&cat=35&id=513&artlang=en

the formula for the ^ link is:
> one tablespoon (15ml) of fertilizer in a gallon of water:

(10xN)÷ 0.256 = ppm

therefore, we can insert the gh flora nova bloom, finding for only the n, we have,

formula b:
**(10*4)/.256=156.25 ppm of n per gallon.

this may also be helpful:
http://www.umass.edu/umext/floriculture/fact_sheets/greenhouse_management/fertcalc.html

the weights of the ferts are included in the calculations. the spreadsheet may be a little off. these formulas are from greenhouse engineering standards.

in both calculations ^, the n from ~15 ml/1 tbsp of fnb, is ~150 ppm. how did you get all the way to 200+?

hope this helps. enjoy your garden!

think it will be figured out though...

 

[dongle69]

Just download the spreadsheet.
It will help you out.
The growfaq link you posted is only good for dry nitrogen, not the other elements.
I did't run the samuel phd formula, but it is also only for a dry element, nitrogen.
Read that umass.edu link you posted and you will see they talk about diff formulas for diff elements, and give an example using p and k.
They show that 20-20-20 is actually 20-8.7-16.7
But still, only for dry ferts.

From the umass link:

We can use the simple rule, "Percent K and percent P equals 1.2 and 2.3," to convert from oxide to the elemental forms for phosphorus and potassium, that is, from %P2O5 to %P and from %K2O to %K.

Example 3. You have a fertilizer with an analysis of 20-20-20 (%N-%P2O5-%K2O). What is the percentage of phosphorus and potassium in the elemental form?

A. To solve the problem:

1. List all the variables to find out what is known and unknown:

a. Fertilizer analysis = 20-20-20 (20% P2O5 and 20% K2O).
b. Conversion rule: "%K and %P equals 1.2 and 2.3."
etc........
etc........
Answer: 20-20-20 contains 8.7% elemental phosphorus and 16.7% elemental potassium.

It doesn't need to be this involved, though.
Just download the spreadsheet!

 

[*mistress*]

thanks dongle69!

many questions gardeners may have dealing with npk & ppm may be answered in this thread.

enjoy your garden!

 

[*mistress*]

more data on this topic...

another nutrient profile calculator. claims converts liquid fertilizers npk to ppm:
http://www.firstrays.com/fertcalc.htm

and more discussion...:
http://forums.gardenweb.com/forums/load/hydro/msg0603442432330.html

seems as though there really is no standard relevant to npk, or ppm. especially npk. suppose this is why every state/country/territory seems to regulate labeling differently, and same content can be packaged differently.

actually did little further research and discovered that co's generally refuse to disclose the actual content of their formulations. proprietary in nature...

also, different mediums will have different ppms, given the exact same input of initial npk/ppms. this deals w/ cation exchange capacity, or the different porosities, moisture retention, and collidial charges held therein.

went even further and researched different co's, etc. etc. they dont want to disclose formulations, because of intense competition; i.e.g, drive for coins supremacy...

unless the nutrient is mixed by the gardener, themselves, from the actual greenhouse grade salts - they will probably never know the exact formulations, or exact ingredients used, or how they may react differently w/ others.

more interesting reading on this topic:

A criterion to determine whether an element is essential to plants is if the plant cannot complete its life cycle in the complete absence of the element (Salisbury and Ross 1978). In addition to the essential elements there are other elements, although not necessarily considered universally essential, which can affect the growth of plants. Sodium (Na), chloride (Cl) and silicon (Si) are in this category, all three of these nutrients either enhance the growth of plants, or are considered essential nutrients for some plant species (Wilson and Loomis 1967, Salisbury and Ross 1978, Styer and Koranski 1997).

The essential nutrients can be grouped into two categories reflecting the quantities of the nutrients required by plants. Macronutrients or major elements, are required by plants in larger quantities, when compared to the amounts of micronutrients, or trace elements required for growth (Salisbury and Ross 1978). Another useful grouping of the mineral nutrients is based on the relative ability of the plant to translocate the nutrients from older leaves to younger leaves (Salisbury and Ross 1978). Mobile nutrients are those which can readily be moved by the plant from older leaves to younger leaves, nitrogen is an example of a mobile nutrient (Salisbury and Ross 1978). Calcium is an example of an immobile nutrient, one which the plant is not able to move after it has initially been translocated to a specific location (Salisbury and Ross 1978).

The discussion of plant nutrients as elements does not allow for a more complete discussion of how plants access the elements from the root environment, and how hydroponic growers ensure that their crop plants are adequately supplied with nutrients. The term "element" can be defined as a substance that cannot be broken down into simpler substances by chemical means, the basic unit of an element is the atom (Boikess and Edelson 1981). With the simplest, or purest form of plant nutrients being the atom, nutrients are not often available to plants in their purest form. Pure nitrogen is an example of a nutrient element represented by its atom. When the atoms of different elements combine, they can form other substances which are based on a particular combination of atoms, substances based on molecules. Nitrate (NO3-), is a molecule based on nitrogen and oxygen atoms, nitrate is absorbed by plant roots as a source of nitrogen. Nitrate is an "available" form of nitrogen. The nitrate molecule has an overall negative charge, which causes the molecule to be fairly reactive chemically, and therefore more available.

The availability of nutrient elements to plants is generally based on the existence of the nutrient element as a charged particle, either a charged atom or charged molecule. An atom or molecule that carries an electric charge is called an ion, and positively charged ions are called cations, while negatively charged ions are called anions. The nitrate molecule (NO3-) is an anion, the iron atom can exist as the Fe+2 (ferrous) or Fe+3 (ferric) cations (Boikess and Edelson 1981). Plants are able to acquire the essential mineral elements via the root system utilizing the chemical properties of ions, particularly that to acquire negatively charged anions, the plant roots have sites that are positively charged. The plant is also able to attract positively charged cations to negatively charged sites on the root.

Water is a very important component in the acquisition of nutrient elements by the plants as the nutrient ions only exist when they are in solution, when they are dissolved in water. As solids, the ions generally exist as salts, a salt can be defined as any compound of anions and cations (Boikess and Edelson 1981). In the absence of water, the nutrient ions form compounds with ions of the opposite charge. Anions combine with cations to form a stable solid compound. For example, the nitrate anion (NO3-) commonly combines with the calcium (Ca+2) or potassium (K+) cations forming the larger calcium nitrate Ca(NO3)2 potassium nitrate (KNO3) salt molecules. As salts are added to water, they dissolve, or dissociate into their respective anion and cation components. Once in solution they become available to plants.

An important point to remember is that different salts have different solubilities, that is, some salts readily dissolve in water (highly soluble), and some salts do not. Calcium sulfate (CaSO4) is a relatively insoluble salt and would be a poor choice as a fertilizer because very little of the calcium would go into solution as the calcium cation (Ca++) and be available to plants. Fertilizer salts, by their very nature, are useful because they go into solution readily. In hydroponic culture, greenhouse growers formulate and make a water based nutrient solution by dissolving fertilizer salts.

In addition to existing as salts, some of the micronutrients; iron, zinc, manganese and copper, exist in chelates. A chelate is a soluble product formed when certain atoms combine with certain organic molecules. The sulphate salts of iron, zinc, manganese and copper are relatively insoluble and chelates function to make these mineral nutrients more readily available in quantity to the plants (Boikess and Edelson 1981).

&...

Moles and millimoles in the greenhouse; Just another couple of rodents? - Just when you thought you had all your rodent problems under control, some greenhouse vegetable growers have been concerned about millimoles and moles. Not to worry, these growers are not referring to four legged moles. Rather they are using another unit of measure to discuss fertilizer feed targets and root zone targets.

So, what exactly is a millimole? A millimole is one thousandth of a mole, and a mole is defined as the amount of a substance of a system which contains as many elementary entities as there are atoms in exactly 12 grams of 12 C (Carbon 12). Now, you were probably expecting that a definition would help clarify the situation, isn't that what definitions are supposed to do? The concept of the mole has come out of stoichiometry, that branch of chemistry which studies the quantities of reactants and products in chemical reactions.

Now a lot of chemists and physicists have argued for a long time over how to measure the masses of individual elements (some of those same elements that growers feed their crops in fertilizer feed solutions) and in 1961 they settled on using the mole. A good way to understand what a mole is and why to use it is to related it to the concept of a dozen. We understand that a dozen is twelve of something, be it cucumbers, eggs or whatever. A mole is 6.02 x 1023 of some entity, and chemists usually refer to actual molecules of a substance when they talk about moles, although you could have a mole of eggs or a mole of cucumbers. You would be quite the grower to grow a mole of cucumbers, tomatoes or peppers. The number 6.02 x 1023 , which in long hand is 602 000 000 000 000 000 000 000, is called Avogadro's number after the nineteenth century chemist who did some pioneering work on gases and was largely ignored for his trouble. The lesson here is that if you do something great and are not feeling appreciated for the greatness, someone, far into the future may name a big number after you.

Moles do relate to parts per million (ppm), they are both ways to measure how much of a given nutrient we are dealing with in a fertilizer feed sample, leachate or tissue sample. The difference is that ppm is a measure of mass (e.g. 1 ppm = 1 milligram/litre) and moles measure amounts. One mole of any substance contains Avogadro's number of entities or basic units. Those entities, as mentioned earlier, can be atoms or molecules or whatever you want. When we talk about one mole of nitrate nitrogen, NO3, we are referring to 6.02 x 1023 molecules of NO3, because the basic NO3 entity is made up of one atom of nitrogen (N) and three atoms of oxygen (O). If we are talking about a mole of iron, Fe, we are talking about atoms, because the basic entity of iron is the iron atom.

All atoms and molecules have different basic weights, some being heavier than other. If we talk about 1 ppm of NO3 versus 1 ppm of Fe, we are talking about the same mass of each, i.e., 1 milligram/litre. However, there will be a different number of basic entities or moles of NO3 and Fe in a solution which contains 1 ppm each of NO3 and Fe.

Now, we are getting close to being able to convert ppm to moles or millimoles, but we will first consider the concept of atomic and molecular weights. The atomic weights of all the elements can be found on the periodic table, that handy chart that we carried with us throughout all our chemistry classes. The atomic weights of the elements are given in grams per mole. The molecular weight of oxygen is 16 grams/mole, this means that 6.02 x 1023 atoms of oxygen weights 16 grams. One mole of nitrogen weighs 14 grams. By combining all the atoms which make up molecules we can arrive at the molecular weights. Therefore, the molecular weight of NO3 would equal 14 + 3(16) grams/mole or 62 grams/mole. One last thing to remember is that moles are related to millimoles the same way that grams are related to milligrams. So if moles are related in the range of grams, millimoles are in the range of milligrams.

We know that 1 ppm is equal to 1 milligram/litre, so to convert ppm to millimoles you divide ppm by the molecular weight of the element you are working with. For example:

* 1 ppm of NO3 = 1 mg/litre

1 mg/ litre of NO3 / 62 mg/mole = 0.016 millimoles of NO3 in one litre
* 1 ppm of Fe = 1 mg/litre

1 mg/litre of Fe / 56 mg/millimole = 0.018 millimoles of Fe in one litre.
* 1 ppm of magnesium (Mg) = 1 mg/litre

1 mg/litre of Mg / 24 mg/millimole = 0.041 millimoles of Mg in one litre.

As these examples show, a solution containing 1 ppm of various elements or molecules will contain different mole or millimole amounts of these same elements.

* To convert millimoles to ppm:

ppm = millimoles/litre x molecular weight (mg/millimole)
Example:
ppm NO3 = 0.016 millimoles of NO3 in one litre x 62 mg/millimole

= 1 ppm NO3


Once you can work back and forth between ppms and millimoles, you might be asking if there is any benefit to working in millimoles rather than ppm. If you are comfortable working with ppms and you are comfortable with designing and managing your fertilizer feed programs in ppms, stick to what you know. However, if you want to be working with actual amounts of atoms and molecules of the nutrients you are feeding then you may want to work with millimoles. Whatever the case, with a little practice you can work with either unit.

so, are the #'s for the molasses correct?

interesting that a number of new products are including molasses, carbohydrates (sugar), etc. in their mixes. ask them what is difference between theirs and the ordinary molasses, may get pause...

using the formulas provided, here is gh flora nova bloom, @ 15 ml per gal:
4% nitrogen
(10xN)÷ 0.256 = ppm
(10*4)/.256=156.25 ppm

8% phosphate
P2O5x 0.437=actual P
(10*8)/.256=312.5
312.5*.437=136.56 ppm

7% k
K2O x 0.83 = actual K
(10*7)/.256=273.43
273.43*.83=226.95 ppm

per dongle69, via spreadsheet, read above
n 231
p 201
k 336

per mistress, via greenhouse math, read above
n 156.25 ppm
p 136.56 ppm
k 226.95 ppm

the ^calculations are weighted for the change from one form to elemental in the p & k. still there is a difference in numbers... why? liquid form making the math funny?

also, is the potassium in molasses 'elemental'? different products have different labels, depending on region, state, etc...

all other nutrients are seemingly expressed in their elemental form, on the label. p & k being only exceptions. for whatever reasons, still listed as guaranteed analysis that is not actual elemental form. converting p & k to elemental amounts when doing calculations may be a good thing.

hope this helps.

 

[dongle69]

another nutrient profile calculator. only for npk, liquid fertilizers:
http://www.firstrays.com/fertcalc.htm

No accounting for liquid ferts on that calc.
There would need to be a place to enter weight.
You need grams per ml if liquid.
One gallon of FNB does not weigh the same as a gallon of Pure Blend Pro or Tiger Bloom, etc.
It does seem one step closer at least with proper elemental calculation of dry.
FNB is about 2.0EC at 8 ml/gal when tested with a meter.
Easy to see that almost twice that dosage (your 15 ml example) does not match your figures.
I can't say where the math is wrong.
Get the spreadsheet!

 

[dongle69]

Also, spreadsheet has author's email address to maybe answer your questions...

 

[*mistress*]

No accounting for liquid ferts on that calc.
There would need to be a place to enter weight.
You need grams per ml if liquid.
One gallon of FNB does not weigh the same as a gallon of Pure Blend Pro or Tiger Bloom, etc.
It does seem one step closer at least with proper elemental calculation of dry.
FNB is about 2.0EC at 8 ml/gal when tested with a meter.
Easy to see that almost twice that dosage (your 15 ml example) does not match your figures.
I can't say where the math is wrong.
Get the spreadsheet!

this may be helpful...

alright, bottles of flora nova bloom have weights provided on the front of the bottle.
there is the net weight, which is given in grams, or kilograms.

there is also the ml (milliliter) weight.

in the spreadsheet program (aka excel), the section Guaranteed Analysis, has a formatted row, titled Grams per ml if liquid.

after a little research, found that many bottles of flora nova have different net weights...

here is an example, using the standard ph spreadsheet, using slightly different weight ratios:

if the net weight of the bottle of fnb is 1.42 kg, or 1420 grams, and there are 946 ml, the grams per ml if lquid is,

1420 (grams)/946 (ml)=~1.50 grams per ml

the spreadsheet w/ this ratio, @ 15 ml per gal, gh fnb, is:

n 238
p 207
k 346
mg 119
s 119
ca 238
fe 5.948

so, we have 1380/(.95*946)=

1380/898.7=~1.53 grams per ml

inputting this # into the guaranteed analysis section of the spreadsheet gives us:

n 243
p 211
k 352
mg 121
s 121
ca 242
fe 6.063

seems as though each batch may have different weights, or different regions may require less actual weight to qualify for being labeled a "quart", or "gallon". so, they seem to use approximate weights; or send different weights to different locations. every ml costs, as the spreadsheet indicates.

in any event, w/out using strictly chemicals from scratch, may only get close approximations of actual content of npk. ea co uses different chemical compositions that react differently.

may be a good thing to change grams/ml ratio @ ea change of nute bottle, for more accurate readings. if that variable is off, may drastically change what #'s are. a .03 (1.50-1.53) differential altered the chem make-up of the solution. see above.

hope this helps. enjoy your garden!

 

[*mistress*]

here is a marketed blackstrap molasses product, recommending foliar spray, w/ ~npk 0-.5-3:

GreenSense Blackstrap Molasses
Phosphorus(p205) - Min. 0.5%, Potassium(k202) - Min. 2.0%
http://www.beorganic.com/products/images/PDFs/blackmolasses.pdf

 

[*mistress*]

...

 

[*mistress*]

seems as though dried molasses is simply molasses sprayed onto grain waste/particles, @~ 1:3 ratio.

 

[YosemiteSam]

ml is a volume measure...not a weight. Distilled water at a certain temp (that I cannot remember off the top of my head) weighs 1 gram...that is probably where the confusion comes from.

Nutrients, on the other hand, tend to weigh significantly more than water...the honest companies try to get that weight as high as possible without stuff settling out of suspension to give you more bang for your buck...water is expensive to ship.

An example would be a nute might have what is called a specific gravity (the weight of 1 ml of nute divided by the weight of 1 ml of distilled water) of 1.2...meaning it is 20% heavier than the equivalent volume of water.

That difference must be accounted for or the calculation will be meaningless. The calculator Dongle is referring to does this if you provide the weight/volume numbers...no thinking needed on our part.

The calculations you are referring to fail to compensate for the Specific Gravity of the liquid nutes. Therein lies the difference...and it looks like enough difference that one could end up burning their plants...least in my opinion.

 

[*mistress*]

goals of the thread...

goals of the thread...

the formula can be done by hand

the formulas retrieved from the net are different than the hard-wired/standardized/ph-calculator...

can that same formula be used to calculate the npk-ppm of molasses?
consolidate standardized long-form, hand-done formulas for converting npk values to total/individual ppm values, and vice versa.

also, formulas for converting standardized food 'nutrition facts' labels into npk, and ppm values. again, the actual formulas, and not necessarily the formatted cells of a calculator. perhaps, the actual formatted formula inserted into the program?...

to

highest goals
compile all relevant mathematical formulas relevant to converting npk values; approximate npk values; total ppm values; ec ; tds values; micromoles, etc, etc. formulas should be able to covert this/that element, and/or compound to smallest common denominator, etc.

eventually, goal is to find the total caloric need of a specific crop, for the life of the crop cycle. just as humans live on 2,000-3,000 daily calories, plants consume daily calories via sugar, elements, etc. a calorie being

calorie (cal) is the amount of energy required to raise the temperature of one gram of water by 1 °C. The gram calorie was once commonly used in chemistry and physics.

determine how different ph values may, or may not effect npk, and/or ppm values. and to the degree that ph affects ppms/npk ratios, how ph drift, or no drift affect ppm levels; or the inverse, cation exchange, or nute absorption.

if this thread survives that long...

objective
find the total amount of ppm/npk for healthy plant survival, growth and completion of flowering/fruiting, during 1 season.

from these subjective #'s, can minimize down to barest needs for entire season.

example, will applying only gh fnb only @ 1 tablespoon per gallon, every 2 weeks, or ~only 4 times per season, fulfill the plants needs? how many calories is this, total?

may find interesting #'s.
enjoy your garden!

 

[dongle69]

The author's email address is in the nutrient profile spreadsheet.
I would start there if you want the formula.

 

[*mistress*]

should be way to extract formula formatted into guaranteed analysis cell(s).

 

[Blue Dot]

havnt worked w/ excel in long moments... should be way to extract formula formatted into guaranteed analysis cell(s). any excel users familiar w/ acquiring formulas formatted into rows/cells?

That's funny, I was thinking the same thing. I figured the formula would just show up in the formula bar but no matter what I clicked I couldn't get it to show up.

There's gotta be a way though considering it's native excel.