Reading fertilizer contents

[Kathy]

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

[TQ]

Post by Kathy
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?

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.

[Steve]

TQ wrote:
.............

....................
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.

...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

[Kathy]

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

[aem]

Post by Kathy
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?

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

[Steve]

Post by aem

Post by Kathy
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?

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

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

[Kathy]

Hey, that's great! That answers all my questions! Now I get it. Thanks!

Kathy