# NPK Equivalent for EI dosing



## original kuhli (Nov 28, 2006)

Given that there is a rough ratio associated with the EI method I'm left wondering if anyone has come up with the equivalent NPK rating? Apparently 10+ years after the KNO3 bombing we've decided to make KNO3 a controlled substance. 

Woopee, sounds like most vendors will still have access but the one I go to doesn't have it at this time.


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## plantbrain (Dec 15, 2003)

There's never been an associated ratio with EI, with good reason, it does not matter. I've heard more folks wind bag this issue that I could ever hope to count for all sorts of methods.

What matters is limiting values and what limits growth, see Liebig's law of the minimum.

Now for some crops, trying to tweak the levels of each NPK is wise, mostly from a fertilizer cost issue, but the rates of growth and the % in the plant's dry matter is measured also, 30,000 acres is a lot more than the 10 gal tank with plants when ferts cost you 10$ for a lifetime, so that's no trade off for us.

EI is more a concept for providing non limiting amounts of nutrients, and the ASSUMPTION THAT NON LIMITING NUTRIENTS DON'T CAUSE ALGAE. EI is still the only such method that states this and has demonstrated it time and time again.

It's based more on agriculture and liebig's law of the minimum, simple enzyme uptake ranges etc:










The D region as you can see is the largest easiest region to target and what most farmers do. They do not what to risk lower yields. We care less about that, mostly just not running out, or adding way too much, so it's the largest target to hit on the various choices given there.

So this is why there's no ratio really, just some "ranges", estimations that extend fairly wide, wider than most any other suggested. 

N ratios can go from 1:1, 5:1, 10:1, 20:1, 30:1 for example.

So ratios as some claim with the Redfield ratio(let's not discuss the errors in atomic vs mass ratios), clearly do not control algae in planted tanks either. 
Otherwise, such ratios would play havoc, but...........I've never been able to show they have. Further, Epstein and Bloom(3rd edition), two of the top folks in mineral nutrition, suggest the same thing as I have here(ratios do not matter much, stick with non limiting levels, do not get too far outside common sense). As far as Plant Science/Agriculture, this idea is well supported in theory and practice.

I suggested several ranges over the years, some suggested these as ratio ranges:


CO2 range 25-35ppm
NO3 range 5-30ppm
K+ range 10-30ppm
PO4 range 1.0-3.0 ppm
Fe 0.2-0.5ppm or higher (?)
GH range 3 degrees ~ 50ppm or higher

I know these ranges can be extended both up and down a fair amount.
They are just mid range targets. NO3 is a bit low actually here. 
I'd say 20ppm is the good range for non limiting based on Gerloff's research(1966) for a in critical concentration. 

Get what you can as far as KNO3. Might need to look more. Ca(NO3)2 is an option, good for soft water and then some K2SO4 etc.

Regards, 
Tom Barr


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## original kuhli (Nov 28, 2006)

Thanks Tom, maybe I should reframe my question. I use your EI method, basically I fertilize the hell out of things to chase the algae away. However, if I ask the question as follows:

I'm having difficulty getting pure dry ferts, there are lots of mixed ferts available and with some careful checking I can ensure that I'm deriving my nutrients from the KNO3 and KH2PO4. My question is, how do I calculate the NPK's on fert formula's into ppm equivalents in fluid?


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## plantbrain (Dec 15, 2003)

original kuhli said:


> I'm having difficulty getting pure dry ferts, there are lots of mixed ferts available and with some careful checking I can ensure that I'm deriving my nutrients from the KNO3 and KH2PO4. My question is, how do I calculate the NPK's on fert formula's into ppm equivalents in fluid?


Use moles/Liter.
Weight/volume.

I cannot see how KH2PO4 is illegal, seems more like as crack down on weed growing to me. They no longer sell stump remover anywhere? No one will ship to you from the USA? I spoike with Alan a few weeks ago, there was no issue unless that suddenly has changed in the last few weeks.

You can use most any dosing calculator that has Ca(NO3)2.
Also, try a Pharmacy, ask for Salt peter, 500grams etc.

There's 4 avenues.

1 teaspoon (5g) Ca(NO3)2 is similar to the 1.5 teaspoons of KNO3 recommended by EI. There's some play as both are salts and subjected to water uptake, but keep them as dry as you can. Then add K2SO4 to make up the extra K+. Some add KCL to the solution if they use an all in one macro.
It dissolves easier than K2SO4. I dose dry, so I do not have any such issues/dribbly mess due to large tanks.

I think that "ratio" for Ca(NO3)2 to KNO3 might be more useful for you.

Ca vs K accumulation is not going to be any issue, and you might need it more than say K+ anyway if the tap is low in GH. Then you'd add just the K2SO4 and MgSO4 instead of GH booster.

Regards, 
Tom Barr


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