npk % vs npk ratio

maca9October 5, 2013

Hi all

I have potted citrus and use a liquid fert which is:

N - 10%
P - 4%
K - 6%

Plus trace elements Calcium, sodium, magnesium, sulphur, iron, manganese, copper, zinc, and boron.

I understand from a number of posts that the ideal NPK for citrus is 5-1-3.

Also from reading Taplas post on fertilizing container plants that the % for P and K needs to be adjusted to calculate the true ratio.

Specificially P % multiply by 0.43 and K% multiply by 0.83.

On this basis I guess my liquid fert is 10 - 1.72 - 4.98.

Or 10-1.8-5 when rounded.

I have 2 questions. Is my understanding/calulation correct?

And if so is this fert ok for citrus. It's obviously a little light on P and K in relation to the ideal 5-1-3 but pretty close.

Thanks for any help.

Cheers

Macca

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Ohiofem(6a Ohio)

I just reread the Fertilizing Containerized Plants post, and I will link to it for those who are interested. I believe your fertilizer has a ratio of 5-2-3. I don't think Al intended for us to adjust the numbers shown on the fertilizer container to show the true ratio. The Foliage Pro he favors is labelled 9-3-6, and he says the ratio is 3-1-2. I think that when he talked about adjusting the percents he was referring to the percents of each element found in the plant. Therefor, I think you fertilizer is slightly too high in P, not too light. But, it is close enough and sounds like a good formula since it also contains calcium, magnesium and trace elements. I hope someone else will comment on your question.

Here is a link that might be useful: Fertilizing Containerized Plants

    Bookmark   October 5, 2013 at 7:46PM
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fireduck(10a)

3-1-2 is the correct ratio...and plants take up nutrients in this ratio. Infrequently there may be a KNOWN deficiency that needs a bit more of that specific nutrient.

    Bookmark   October 5, 2013 at 10:41PM
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maca9

Thanks for the comments. It's great to try and clarify this.

Does anyone have a definitive answer?

Tapla in his post states:

"I use a liquid fertilizer with a full compliment of nutrients and micronutrients in a 3:1:2 ratio. Note that 'RATIO' is different than NPK %s. Also note how closely the 3:1:2 ratio fits the average ratio of NPK content in plant tissues, noted above (10:1.5:7). If the P looks a little high at 4, consider that in container soils, P begins to be more tightly held as pH goes from 6.5 to below 6.0, which is on the high side of most container soil's pH, so the manufacturer probably gave this some careful consideration. Also, P and K percentages shown on fertilizer packages are not the actual amount of P or K in the blend. The percentage of P on the package is the percentage of P2O5 (phosphorous pentoxide) and you need to multiply the percentage shown by .43 to get the actual amount of P in the fertilizer. Similarly, the K level percentage shown is actually the level of K2O ( potassium oxide) and must be multiplied by .83 to arrive at the actual amount of K supplied."

It is the application of the above to my 10% 4% 6% liquid fert I am trying to do.

Thanks all.

Macca

    Bookmark   October 6, 2013 at 12:05AM
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saoodhashim

As I understand from the extract that you posted, your application of 0.43 and 0.83 seems correct.

This multiplication by 0.43 and 0.83 was news for me.

Thanks for the post. I too would be eagerly waiting for replies.

    Bookmark   October 6, 2013 at 2:28AM
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greenman28 NorCal 7b/8a

Hey!
Ohio and I fertilize nearly identically, although she's better at consistent fertilization than I am ;-)
I, too, have heard/read that Citrus are heavier feeders on average, but I haven't purchased a specialty fertilizer - I've just stuck with Foliage Pro 9-3-6 weekly, with a supplement of Pro-TeKt 0-0-3 every few weeks. With my Meyer Lemon - a seemingly *very* hungry Citrus - I fertilize at 1.5 strength to keep it green and healthy.

Josh

    Bookmark   October 7, 2013 at 7:01PM
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maca9

Hi All

Al (Tapla) cleared up my question and he confirmed that my fertilizer labeled

N - 10%
P - 4%
K - 6%

Is in fact NPK of 10 - 1.72 - 4.98 as per his suggested calculation.

Cheers

Macca

This post was edited by maca9 on Wed, Oct 9, 13 at 15:38

    Bookmark   October 9, 2013 at 6:53AM
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Ohiofem(6a Ohio)

So I guess that means Foliage Pro is closer to 9-1.3-5 than it is to the "ideal" 3-1-2.

    Bookmark   October 9, 2013 at 9:28AM
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Oxboy555(Las Vegas)

Macca, in your last post, I think you mean:

N - 10%
P - 4%
K - 6%

Can you edit so as not to confuse people?

    Bookmark   October 9, 2013 at 1:06PM
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maca9

Oxboy - correct well spotted. I have amended.

Ohio - I think foliage pro is still 9-3-6 as it is not expressed as a percentage. That is the key part from Al's pos.

He states:

"I use a liquid fertilizer with a full compliment of nutrients and micronutrients in a 3:1:2 ratio. Note that 'RATIO' is different than NPK %s."

So from my understanding some ferts are already stated as a ratio. Where as some liquid fert (mine included) are actually labeled as NPK %. These need adjustment.

Al can no doubt clarify this as it is beyond my knowledge to be honest.

Cheers

Macca

    Bookmark   October 9, 2013 at 3:50PM
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Oxboy555(Las Vegas)

I think Ohio is correct about her 9-1.3-5 take. Probably close enough to the ideal ratio to worry much about.

But...why do the fert manufacturers make us bother with worrying about the .43 and .83 crap? What not state upfront the actual amt of the nutrient?

Here is a link that might be useful: Foliage Pro %

    Bookmark   October 9, 2013 at 4:31PM
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Ohiofem(6a Ohio)

I don't want to be difficult here, but I think we have some miscommunication somewhere. According to Dyna Gro, Foliage Pro is both 9-3-6 percent and 3-1-2 ratio.

    Bookmark   October 9, 2013 at 4:38PM
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maca9

Ok now I'm confused again..... haha.

I thought that what Al was getting at in his post on fertilizing container plants was that some liquid fert s are labeled with a ratio and some with a NPK%. In the case of NPK % there was a need to apply the calculation method to get the true ratio.

But seeing the Foliage Pro label it is a % and ratio of the same. 9-3-6.

Wheras my original question was around my liquid fert which only states

N - 10% P- 4% K-6%

So who knows...........

I guess what we do know is that Foliage Pro has been proven by many to be a great liquid fert.......

And with Foliage Pro not available in my country a 10 - 4 - 6 is not massively different.

Thanks everyone for the ineterest and comments and sorry if trying to understand something I've actually created more confusion.

Cheers

Macca

    Bookmark   October 10, 2013 at 12:45AM
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Ohiofem(6a Ohio)

In the United States, fertilizer manufacturers are required by law to report the percent of nitrogen (elemental nitrogen), phosphate (P2O5) and potash (K2O). By convention, that is what is also what the ratio is derived from. The law may be different in New Zealand.

From Wikipedia: In the U.K., fertilizer labeling regulations allow for reporting the elemental mass fractions of phosphorus and potassium. The regulations stipulate that this should be done in parentheses after the standard N-P-K values.

Here is a link that might be useful: NPK Rating from Wikipedia

    Bookmark   October 10, 2013 at 10:42AM
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TheMasterGardener1(5B)

Posted by Ohiofem 6a Ohio (My Page) on Wed, Oct 9, 13 at 16:38
"I don't want to be difficult here, but I think we have some miscommunication somewhere. According to Dyna Gro, Foliage Pro is both 9-3-6 percent and 3-1-2 ratio."

Maybe I can help clear it up.

A 9-3-6 IS a 3-1-2. They are the SAME "ratio"....

Having- 9%, with-3%,followed by-6% is in fact a 3-1-2 ratios.

Just like Miracle gro's 24-8-16 IS in fact a 3-1-2 ratio. 24%N-8%P-16%K=3;1;2

These percentages determine the ratios.

Example:

24%N-8%P-16%K is a 3;1;2

12%N-4%P-8%K is a 3;1;2

No matter how high or low the percentages are,if they line up in a specific manner that will determine the 'ratio'

    Bookmark   October 10, 2013 at 11:12AM
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tapla (mid-MI z5b-6a)

Fertilizers have reported NPK %s that are listed on the container, and identify the % Nitrogen, Phosphorous pentoxide (P2O5) , and Potassium oxide (K2O) in the product. When discussing fertilizer %s, separate the numbers representing the NPK %s with a dash (24-8-16, 12-12-12, etc).

To determine the ACTUAL % of P and K in fertilizers, you multiply the amount of P2O5 reported by .43, and the amount of K2) reported by .83.

Fertilizer RATIOS are the best reference point for determining what fertilizer is appropriate. If we consider only the NPK RATIO, 9-3-6, 12-4-8, 18-6-12, 24-8-16 would be equally appropriate (or inappropriate, if you prefer) because they are all 3:1:2 RATIOS (based on the amount of NPK REPORTED). Essentially they will yield approximately the same strength solution if mixed to the manufacturers specifications. Specifically, 24-8-16 diluted in twice the amount of water as the same measure of 12-4-8 yields the same concentration of elements and the same amount of each element per any given volume of solution. Note that when discussing fertilizer RATIOS and to avoid confusion, we should use a colon (3:1:2, 1:1:1) between the numbers to indicate you're discussing the fertilizers nutritional RATIO, rather than its NPK %s

Usually, when we suggest or discuss ratios, we use them as a function of the REPORTED NPK %s, rather than the ACTUAL NPK %s - it's just much easier than having to do the .43 and .83 factoring and plugging the results into whatever it is you're factoring.

Maca - I didn't realize I might have answered your questions here on 'Containers'. I looked all over the 'Citrus' forum yesterday or day before, and only stumbled on this thread today. I hope that between all the good folks that offered help, you got all the answers you needed.

Best luck.

Al

    Bookmark   October 10, 2013 at 4:51PM
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