Reading fertilizer contents

I was reading this morning about a fertilizer that's 4-6-8. I'm confused. Are the numbers just proportional, so 4-6-8 is the same as 2-3-4? Or do they refer to the N-P-K content of some specific unit of measure, so 4-6-8 is more powerful than 2-3-4?
Kathy
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4-6-8 has twice the nutrient concentration as 2-3-4. Twice as much nitrogen, twice as much phophorous, etc. Kinda like the current generation of concentrated laundry and dishwashing detergents. For an equal volume of each fertilizer, such as a handful, the answer to your question is: yes, the 4-6-8 is more powerful than a handful of 2-3-4.
If you applied twice the normal rate of 2-3-4, you/d get the same results as a regular application of 4-6-8.
What nutrient concentration you should use all depends on what your asking your plant to do.
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TQ wrote: .............

...also depends on what the plant is able to do. Adding more fertilizer than the plant can use soon makes it grow less well rather than better. TQ, I know that YOU know that. Just added it for others.
Steve
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Aha! So the numbers must refer to something. So in a 2-3-4, that's two somethings of nitrogen per some standard measure. Do you know what the units are?
If I have 2-3-4 liquid and 2-3-4 powder, are they the same per cup or the same per pound (assuming that weight and volume don't necessarly match)? Are they the same only after being mixed according to instructions ("1 cup per gallon of water" or some such) or ar they the same as-is from the purchased container?
Kathy
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Kathy wrote:

N is nitrogen, P is phosphorus, K is potassium. The numbers are percentages. So if you see 30-10-10 on a bag of fertilizer you know that it will deliver 30 percent nitrogen, etc., with the remaining 50 percent being filler/carrier and maybe trace elements. -aem
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aem wrote:

For those interested in a little advanced information (trivia?) there is a little more to what the numbers on the bag mean.
The first number is Nitrogen and it is expressed as the amount (percentage) of actual N in the container. Now, you can't have a bucket of pure N and just put an amount in the fertilizer bag. Nitrogen comes in different forms. Different fertilizers use Nitrate nitrogen, ammoniacal nitrogen, urea, or (often) a combination. No matter which form is used, the first number listed is just the N part of the molecule.
You might think it would make sense if the other 2 numbers used the same rule. It would make sense but that's not how they do it:
The 2nd number is P phosphorous. Not just the weight of the P but the weight of the entire P2O5 molecule. The weird part is, if the manufacturer uses something other than P2O5 to provide the P, the number on the bag refers to what the weight (percentage) would be if they HAD used P2O5 to provide the P.
The same for the 3rd number. K, potassium is weighed in as the entire K2O molecule, even if they actually use no K2O in the bag at all. The number is how much K2O it would take to provide that much K IF that is what they had used.
Weird, huh?
Steve
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Hey, that's great! That answers all my questions! Now I get it. Thanks!
Kathy
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