Reading and Interpreting Fertilizer Labels

[andy10917]

This is a winter detailed discussion topic, to help members learn to read and select the appropriate fertilizers for their lawns and gardens. It many ways it will be a self-learning topic where guided questions will lead to an ability to do your research and make your own decisions.

So, let's start!! Below is a label for a fertilizer - answer the following questions, and post you answers for discussion:

(1) What are the source ingredients for Nitrogen (N) in the fertilizer?
(2) What are the source ingredients for Phosphorus (P) in the fertilizer?
(3) What are the source ingredients for Potassium (K) in the fertilizer?
(4) If you wanted to apply no more than 1 lb/K of any N, P (as P2O5) or K (as K2O) in a single application, how much of the fertilizer should you apply?
(5) How much Nitrogen would be applied by the application in Question #4?
(6) How much Nitrogen is in the 50 lb bag?

Make sure to explain your reasoning and logic!

[bpgreen]

I'll try.

This is a winter detailed discussion topic, to help members learn to read and select the appropriate fertilizers for their lawns and gardens. It many ways it will be a self-learning topic where guided questions will lead to an ability to do your research and make your own decisions.

So, let's start!! Below is a label for a fertilizer - answer the following questions, and post you answers for discussion:

(1) What are the source ingredients for Nitrogen (N) in the fertilizer?

I think that most nitrogen in fertilzers is derived from petroleum byproducts now, Some of the nitrogen in this is urea, some is ammonium, and some is slow release. Often, slow release nitrogen is coated, and sometimes it's in a form that needs to be digested by soil bacteria (which only works if it's warm enough for bacterial activity. If I'm reading this label correctly, the nitrogen here is released via chemical activity.

(2) What are the source ingredients for Phosphorus (P) in the fertilizer?

N/A. There's no P in this.

(3) What are the source ingredients for Potassium (K) in the fertilizer?

Sulfate of Potash (listed lower in the label)

(4) If you wanted to apply no more than 1 lb/K of any N, P (as P2O5) or K (as K2O) in a single application, how much of the fertilizer should you apply?

No more than 4.166 lbs per 1000 yards (1/.24 to get the amount for 1 lb of K)

(5) How much Nitrogen would be applied by the application in Question #4?

.5 lbs/k (there's half as much N as K)

(6) How much Nitrogen is in the 50 lb bag?

6 lbs (.12*50)

I don't understand the line at the end that it also contains non-plant ingredients, since I don't see where it contains plant based ingredients.

[andy10917]

Not bad. Let's get a few more people to offer their opinions before I post the answers to the first questions...

[Sensi]

(1) What are the source ingredients for Nitrogen (N) in the fertilizer?
Ammonium sulfate and urea (including WIN and WSN stabilized urea polymers) per guaranteed analysis

(2) What are the source ingredients for Phosphorus (P) in the fertilizer?
There is no P in this product per label: (12-0-24)

(3) What are the source ingredients for Potassium (K) in the fertilizer?
Sulfate of Potash/Potassium Sulfate per guaranteed analysis

(4) If you wanted to apply no more than 1 lb/K of any N, P (as P2O5) or K (as K2O) in a single application, how much of the fertilizer should you apply?
Unclear on the question. 8.33 lbs of product based on Elemental K (1 / .24 / .44 where .44 is the percent of Elemental K in Potassium Sulfate), 4.16 lbs of product if based on K2O (1 / .24). per 12-0-24 label 12% N and 24% K2O

(5) How much Nitrogen would be applied by the application in Question #4?
If Elemental K, 1 lb. of N (8.33 X .12), If K2O, .5 lb of N (4.16 X .12)

(6) How much Nitrogen is in the 50 lb bag?
6 lbs of N (50 X .12) per 12-0-24 label 12% N

[Dargin]

I already love this.

1. Source ingredients for nitrogen: 8.7% is water soluble nitrogen derived from ureaformaldehyde, dimethylentriurea, and methylenediurea. 2.3% is in the form of urea nitrogen, and 1% is ammoniacal nitrogen. This results in 12% total nitrogen.

2. There is no phosphorous present, as indicated by the 12-0-24.

3. SoP is the only listed ingredient containing any potassium (K).

4. With K being the highest percentage of all ingredients, K will read the 1lb/k limit first. It would take an approximate 4lb application of this fertilizer to reach ~1lb K/k.
4lbs of fertilizer x 0.24 (24% K) = 0.96lbs of K.

5. With the above application, ~1/2lb of N would be applied.
4lbs of fertilizer x 0.12 (12% N) = 0.48lbs of N.

6. Total nitrogen per bag equals 6lbs. 50lb total bag weight x 0.12 (12% nitrogen) = 6lbs nitrogen.

Probably too soon, but throwing this out there: is the 1% ammoniacal nitrogen derived from the ammonium sulfate (contains nitrogen and sulfur)?

Thanks.

[Sensi]

I would like to change my answers to questions 4 and 5 as to Elemental K, if the goal is the application of Elemental K. I believe the correct factor would be the percentage of K in K2O which is .83, rather than .44 (the factor for for SOP). Corrected question 4 answer for Elemental K is 1 / .24 / .83 = 5.02 lbs of product to apply 1 lbs of elemental K/k. Corrected answer for question 5 based on that Elemental K application rate would result in the application of .602 (5.02 X .12) lbs of N/k. I now think the original question was designed to determine 1 lb of K2O/k, not Elemental K. Overthinking, I guess.

[micvog]

1) Ureaformaldehyde, urea, ammonium sulfate, methylene urea (Reading the derived from section...)
2) None (P is 0 in the NPK)
3) Sulfate of potash (Reading the derived from section...)
4) 4.16# per K (1/.24 = 4.166)
5) 0.5# per K (4.166 x 12%)
6) 6# (50# x 12%)

[andy10917]

Taken all together, the answers are getting very close to correct, but I'm going to go another couple of days to see if anyone else wants to get their calculation/estimates considered.

[Wors]

(1) What are the source ingredients for Nitrogen (N) in the fertilizer? uf, urea, ammoninum sulfate, methylene urea

(2) What are the source ingredients for Phosphorus (P) in the fertilizer? No guaranteed P in this fertilizer with the middle analysis number being 0.

(3) What are the source ingredients for Potassium (K) in the fertilizer? Sulfate of Potash

(4) If you wanted to apply no more than 1 lb/K of any N, P (as P2O5) or K (as K2O) in a single application, how much of the fertilizer should you apply? The bag contains the most K at 24%. Divide the desired 1lb/k by decimal form of the 24% (0.24), so (1 / 0.24 = 4.17). So try to apply 4lb/k of fertilizer.

(5) How much Nitrogen would be applied by the application in Question #4? If we are applying 4lbs/k of K then to figure out N we take 4lbs multiplied by the decimal form of N(0.12), this works out to be (4 / 0.12) = 0.48 lbs of N. Just under half lb/k of N.

(6) How much Nitrogen is in the 50 lb bag? Multiply the weight of the bag by the decimal form of N(0.12), (50lb * 0.12) = 6lbs of N

[HoosierLawnGnome]

(1) What are the source ingredients for Nitrogen (N) in the fertilizer?
Dear Lord, everything but the kitchen sink!!!
ureaformaldahyde,urea,ammonium sulfate, methalyne urea,
for slow release ureaformaldahyde, metheylenedurea,dimethelyneturea

Pretty sure I butchered the spelling on the last 3
(2) What are the source ingredients for Phosphorus (P) in the fertilizer?
NNNNNNNNGGGGGGGG
(3) What are the source ingredients for Potassium (K) in the fertilizer?
Sulfate of Potash (SOP)
(4) If you wanted to apply no more than 1 lb/K of any N, P (as P2O5) or K (as K2O) in a single application, how much of the fertilizer should you apply?
4.166667 lbs
(5) How much Nitrogen would be applied by the application in Question #4?
1/2 lb
(6) How much Nitrogen is in the 50 lb bag?
6 lbs

[Green]

1. N sources: Regular urea (the 46-0-0 type), Ammonium Sulfate (is all ammoniacal N from AMS, or are there other types as well?), slow-release Methylene ureas (specifically Methylenediurea and Dimethylenetriurea. It may be splitting hairs, but how do these two behave differently, though?), and Ureaform (I guess this one is pretty rare...never seen a product with it before...?)

2. P sources: None.

3. K source: SOP

4. I work in percents. For 1 lb of the highest percent nutrient per thousand square feet: Potassium has the higher percentage, so we go by it. Eyeballing it, you'd need around 4 lbs per thousand because it's close to 25%, which is 1/4 of 100%. More accurately: 100/24=4.1667 lbs of fertilizer needed (rounded to the nearest ten-thousandth).

5. Easy mental math. The N:K ratio is 1:2 in lowest terms (12:24 originally), so half the amount of N is applied compared to Potassium. If you apply 1 lb of K, you're applying 0.5 lb N as well.

6. Total N in the 50-lb bag: Every time you apply ~4.17 lbs of material, you're applying ~0.5 lb N. There are 50 lbs of material in the bag though, so for every 4.17 lbs up to the total 50 lbs supply available, we have 0.5 lb N. This requires multiplying (1/4.17)*(50/1), or dividing 50 by 4.17. 50/4.17=11.99. But that's half lbs of N, or full lbs of K. 12/2=6 lbs of N in the bag.

[northeastlawn]

(1) What are the source ingredients for Nitrogen (N) in the fertilizer?
1% Ammonical Nitrogen, 2.3% Urea Nitrogen, 5.2% Water Insoluable, 3.5% slowly available water soluble Nitrogen

(2) What are the source ingredients for Phosphorus (P) in the fertilizer?

zero

(3) What are the source ingredients for Potassium (K) in the fertilizer?

24% Soluable Potash

(4) If you wanted to apply no more than 1 lb/K of any N, P (as P2O5) or K (as K2O) in a single application, how much of the fertilizer should you apply?

N=12%, P=0%, and K=24%
Therefore keep K(24%) < 1#
1# / (24%/100) = 4.167
Say Total Fertilizer Not to Exceed 4#

(5) How much Nitrogen would be applied by the application in Question #4?

4# x (12/100) = 0.48# of Nitrogen
Say Total N = 0.5#N

(6) How much Nitrogen is in the 50lb bag?

(12/100)*50#=6# in a 50# Bag

[BobL]

(1) What are the source ingredients for Nitrogen (N) in the fertilizer?
Urea - straight CO(NH2)2 - the fast release N in this mix - urease/AOB quickly breaks this into NH3 or NH4+ and HCO3-

Ureaformaldehyde - produced from urea and formaldehyde - decomposes into CO2 and NH3 slowly through microbial action, which is temperature/pH/moisture dependent.

Methylenediurea/Dimethylenestriurea - methylene ureas of different chain lengths, which affect release rate - also slow release, dependent on microbial action to break down to usable form.

(No moisture-activated coated products or temperature-independent IBDU in this, so maybe not ideal for cool season application.)

(2) What are the source ingredients for Phosphorus (P) in the fertilizer?
No P in this fertilizer (0 in 12-0-24).

(3) What are the source ingredients for Potassium (K) in the fertilizer?
Sulfate of Potash (SoP) - K2SO4 and a pain to find in straight 0-0-50 form to blend your own. Provides the Soluble Potash and Sulfur components in the analysis.

(4) If you wanted to apply no more than 1 lb/K of any N, P (as P2O5) or K (as K2O) in a single application, how much of the fertilizer should you apply?
Limited by K, which is most prevalent by mass percentage. 1lb/.24 = 4.166 lbs of product for 1 lb K.

(5) How much Nitrogen would be applied by the application in Question #4?
4.166 lbs of product at 12% N = 4.166*.12 = 0.5lbs. N.

(6) How much Nitrogen is in the 50 lb bag?
50lbs of product at 12%N by weight = 50*.12 = 6lbs. N in the bag.

[andy10917]

Last call for responses to the first post - I'll be writing up the answer and moving forward later today.

[andy10917]

So, here are my answers:

(1) What are the source ingredients for Nitrogen (N) in the fertilizer?

The Nitrogen sources are the various forms of Urea, and some Ammonium Sulfate. The differences in Urea forms are to either stabilize it, or to slow its release over a longer timeframe.

(2) What are the source ingredients for Phosphorus (P) in the fertilizer?

There is no Phosphorus in the fertilizer. The zero in the second NPK number tells us that.

(3) What are the source ingredients for Potassium (K) in the fertilizer?

The Potassium (K) is coming from Sulfate of Potash ("SOP"), also known as Potassium Sulfate. Just saying "Potash" isn't good enough - Sulfate of Potash is 0-0-50, and its cousin Muriate of Potash ("MOP") is 0-0-61, and much harsher on the soil and microherd -- due to a high Chlorine component. While SOP is significantly more expensive than MOP, it is worth the investment. We will allow some MOP is the early stages of a remediation regimen, but always switch to SOP as the regimen reaches the later stages. This gives the microherd time to recover and participate in handling leaves, compost, and natural/organic sources of nutrients.

(4) If you wanted to apply no more than 1 lb/K of any N, P (as P2O5) or K (as K2O) in a single application, how much of the fertilizer should you apply?

You should apply no more than 4.166 lbs per 1000 sq ft of the fertilizer, as the 24% of Potassium (as K2O) will reach 1 lb/K first.

(5) How much Nitrogen would be applied by the application in Question #4?

You will apply 0.5 lbs/K of Nitrogen with that application.

(6) How much Nitrogen is in the 50 lb bag?

6 lbs (calculated by multiplying 50 lbs by the 12% that is the Nitrogen components.


Any questions before we move on?

[micvog]

Will you be reviewing the pros/cons of the different forms of nitrogen as we go on? Besides the different forms being used to either "stabilize" or "slow its release", I am curious if there are other factors to consider as a consumer.

Thanks Andy!

[andy10917]

That depends on your expectations. Groups/types? Yes. But there are far too many specific names/formulas to go over them one by one - that is up to you to google if you're buying a certain fertilizer.

[andy10917]

Let's move on - now that you can read the very basics of a fertilizer label and you can find the source ingredients, what would be the next thing that you should concentrate on be, once you know the sources?

[bpgreen]

Let's move on - now that you can read the very basics of a fertilizer label and you can find the source ingredients, what would be the next thing that you should concentrate on be, once you know the sources?

If there's slow release nitrogen, is it slow release because it's coated or because it requires biologic activity to make the nitrogen available (although that's somewhat covered by the source if the nitrogen)?

[andy10917]

C'mon! This isn't a lecture from your college days - this is a guided learning exercise. After you know what the ingredients are, what are the next steps to go through in comparing fertilizers?