Why You Should Learn About PPM: A note on fertilizer strengths and seed starting

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Why You Should Learn About PPM

By ArtD
June 26, 2016

Many folks like to start their plants indoors from seed.

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Name: BetNC
Hendersonville, NC (Zone 7a)
Annuals Seed Starter Tomato Heads Hellebores Gardens in Buckets Plant and/or Seed Trader
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BetNC
Jun 26, 2016 8:47 AM CST
Regardless of the N-P-K analysis of a fertilizer, one usually adds 1 tablespoon to a gallon of water. BECAUSE: a gallon is the standard used for the analysis. . . .i.e. how much would one have to add to a gallon of water in order to get that analysis? The concentrated amount to add is almost always 1 tablespoon.

It's easier to make up a whole gallon, to get that N-P-K analysis and then use some portion. To make 1/2 gallon and get the same N-P-K, one would have to do some calculating and 1/2 gallon of half strength (whatever fertilizer) requires even MORE math (math! ptooey ptooey!!).

Seed starting relies heavily on propagation spreadsheets: what to do, when and how . . . .based on experience of many, many gardeners and many, many years And fertilizers require some common sense. Whatever fertilizer and strength one uses on the same variety of mature plant, is usually the one that should be used in seed starting process. Not all seedlings are to be fertilized beginning at the same stage or with the same fertilizer or with the same dilution. For instance, MG Tomato is used on mature tomatoes and the directions ON THE BOX says to use half strength for seedlings . . and a propagation spreadsheet reccomends beginning at 2 sets of true leaves. In contrast, MG Bloom Booster is often used for flowers and a propagation spreadsheet reccommends 1/2 strength beginning at the 2 sets of true leaves stage for zinnias. . . but for marigolds, it's 1/4 strength at the 3-4 sets of true leaves stage (I surmise this is because mature marigolds get 1/2 strength.)
Name: Art
Florissant, MO (Zone 6b)
Hummingbirder Annuals Bee Lover Butterflies Garden Photography Seed Starter
Garden Ideas: Level 1
ArtD
Jun 26, 2016 11:15 AM CST
Hi BetNC and thanks for taking the time to comment. You’re right in that adding one tablespoon of water soluble fertilizer to a gallon of water is pretty standard. That’s exactly why the advice to use some fraction of that (add only one half tablespoon for example) is not good advice for feeding your seedlings. One half tablespoon of 20-20-20, for example, is the same as one full tablespoon of 10-10-10 which will fry your new seedlings!
[Last edited by ArtD - Jun 26, 2016 4:06 PM (+)]
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Name: Baja
Baja California (Zone 11b)
Cactus and Succulents Seed Starter Foliage Fan Xeriscape Container Gardener Bromeliad
Hummingbirder Native Plants and Wildflowers Garden Photography Region: Mexico Plant Identifier
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Baja_Costero
Jul 5, 2016 9:26 AM CST
BetNC said:Regardless of the N-P-K analysis of a fertilizer, one usually adds 1 tablespoon to a gallon of water.


Not me. That may be what they put on the box but it is an obscene amount of fertilizer. For the good of the planet if nothing else, try a quarter or a tenth that much first (use the teaspoon instead of the tablespoon if you want an easy unit of measurement). If you aren't adding the minimum amount of fertilizer required to achieve the results you want, you are spending too much money and putting too much nutrients into the ground. My usual weekly dose in the container garden (50 ppm N) is 1/20 the suggested tablespoon dose recommended on the MG box.

You have to remember that fertilizer companies generally base their recommendations on what will sell the most product, not what you need in the garden.
[Last edited by Baja_Costero - Jul 5, 2016 9:42 AM (+)]
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Name: BetNC
Hendersonville, NC (Zone 7a)
Annuals Seed Starter Tomato Heads Hellebores Gardens in Buckets Plant and/or Seed Trader
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BetNC
Jul 5, 2016 8:15 PM CST
Baja_Costero said:

Not me. That may be what they put on the box but it is an obscene amount of fertilizer. For the good of the planet if nothing else, try a quarter or a tenth that much first (use the teaspoon instead of the tablespoon if you want an easy unit of measurement). If you aren't adding the minimum amount of fertilizer required to achieve the results you want, you are spending too much money and putting too much nutrients into the ground. My usual weekly dose in the container garden (50 ppm N) is 1/20 the suggested tablespoon dose recommended on the MG box.

You have to remember that fertilizer companies generally base their recommendations on what will sell the most product, not what you need in the garden.


I'm talking apples; you're talking oranges! To summarize again (hopefully this time will make this more clear): I'm merely pointing out that the printed analysis on the bag/box (N-P-K) is calculated on the industry standard of what is guaranteed to be in: (for water-soluble fertilizer) 1 gallon of solution when made according to the directions (which is usually 1 tablespoon of the concentrated product) OR (for granular fertilizer) 1 pound.

I think it's important to know how the companies come up with their guaranteed analysis. Of course, how one chooses to USE the product is totally the consumer's choice!
Name: Baja
Baja California (Zone 11b)
Cactus and Succulents Seed Starter Foliage Fan Xeriscape Container Gardener Bromeliad
Hummingbirder Native Plants and Wildflowers Garden Photography Region: Mexico Plant Identifier
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Baja_Costero
Jul 5, 2016 11:09 PM CST
If you like to add a tablespoon per gallon and dilute from there, fine. I'm all for everyone doing things their own way. But that number they recommend (1 tablespoon) does not have anything to do with the N-P-K content in a quantitative way. Art made that point very specifically in the article. It is a number pulled out of the air to sell product. It does not help you standardize or calibrate anything. 1 tablespoon of product in a gallon gives a different nitrogen concentration for each of the three MG products (an almost 2 fold difference).

One manufacturer will disagree wildly with another if you calculate the ppm N of their recommended dilutions. There is no industry standard for this. Even within one brand you may have big differences, like Art pointed out. For what it's worth, as I have mentioned, those dosage recommendations are close to useless in the real world, if you're interested in using the minimum amount of fertilizer to achieve the desired results. Which I am, and I think most people should be. To put it another way, all the MG recommendations tell you is how much is more than you will ever actually need for any given application. The only numbers that are standardized are in the N-P-K rating.

The easiest way to arrive at a consistent dose is to actually calculate the amount you need for a certain ppm N (no math required, you just plug two numbers into the form on the page in the link, and it spits out how many tablespoons). Start low and go up from there until you get what you want. Or you can take what works with brand A and figure out what works with brand B by the relative amount of nitrogen in the formula. If you are not doing these calculations then you are basically guessing at the final absolute strength of your fertilizer. Which, again, is totally fine. But it is not quantitative.

Spreadsheets strike me as a way overcomplicated substitute for common sense and fuzzy logic (ie. add more when more is needed, add less when less is needed). Rather than following complicated instructions or rigid formulas I prefer to observe and adjust. But again, to each her own. I tip my hat to you.
[Last edited by Baja_Costero - Jul 6, 2016 10:33 AM (+)]
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Name: Art
Florissant, MO (Zone 6b)
Hummingbirder Annuals Bee Lover Butterflies Garden Photography Seed Starter
Garden Ideas: Level 1
ArtD
Jul 6, 2016 10:29 AM CST
I never really understood why BetNC, in his/her original post, was pointing out the fact that adding 1 tablespoon per gallon was standard. There may have been some misunderstanding somewhere along the line; either on his/her part or maybe mine :-)
[Last edited by ArtD - Jul 27, 2016 7:36 PM (+)]
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Name: BetNC
Hendersonville, NC (Zone 7a)
Annuals Seed Starter Tomato Heads Hellebores Gardens in Buckets Plant and/or Seed Trader
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BetNC
Jul 6, 2016 5:22 PM CST
**shrug**

Oh, I totally understand the article, , ,why one should use PPM instead of a fraction of a given fertilizer (on seedlings).

There are quite a few of MG fertilizers, all with different N-P-K, and all recommending adding 1 tablespoon of that specific concentrated fertilizer to a gallon of water to achieve that quantitatively analyzed and guaranteed analysis; if one looks closely, MG All Purpose compared to MG for Vegetables compared to MG for Tomatoes all have different N-P-K. . . achieved by the company varying the composition of the concentrated product.

What I don't think either of you understand is that I did NOT promote ANY means of calculating and using fertilizers. What I DID was merely point out that the N-P-K analysis (printed on the product). . . rather than being as Baja_Costero says "It is a number pulled out of the air to sell product." is a guarantee
that the product/analysis has met the standards and is approved/backed by The Federal Standards Board (lab, method of analysis, technician certified and approved
etc. . I COULD go on).

Whatever, I am SOOOO over this. As a scientist and educator, occasionally I would encounter individuals who were not able to comprehend the difference between a statement of fact and what they believed.
Name: Baja
Baja California (Zone 11b)
Cactus and Succulents Seed Starter Foliage Fan Xeriscape Container Gardener Bromeliad
Hummingbirder Native Plants and Wildflowers Garden Photography Region: Mexico Plant Identifier
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Baja_Costero
Jul 6, 2016 5:49 PM CST
The number they pull out of the air is 1 tablespoon, not the N-P-K rating. I would appreciate a different tone and approach when I have tried very carefully to explain in reasonable terms where the boundaries are between numbers and guesswork. If you aren't going to read what I write then please do not debunk it. The personal attack does not serve anyone's best interest. Smiling Thank you very much.
Name: BetNC
Hendersonville, NC (Zone 7a)
Annuals Seed Starter Tomato Heads Hellebores Gardens in Buckets Plant and/or Seed Trader
Image
BetNC
Jul 6, 2016 6:08 PM CST
blah blah blah

You may DISLIKE a fact, but that does not make it any less true.

You may choose not to accept a fact, but (again) that does not make it any less true.

I have limited patience after explaining a THIRD time (each by using a different approach) to explain the FACTS; I'm not impressed or swayed by your "appreciating a different tone".

Get over it: the facts are the facts. . . . find someone else to argue nonsensically with.
Name: Baja
Baja California (Zone 11b)
Cactus and Succulents Seed Starter Foliage Fan Xeriscape Container Gardener Bromeliad
Hummingbirder Native Plants and Wildflowers Garden Photography Region: Mexico Plant Identifier
Image
Baja_Costero
Jul 7, 2016 12:18 AM CST
You are being incredibly rude and disrespectful. I would like to think we could disagree without the need for insults.
[Last edited by Baja_Costero - Jul 7, 2016 11:51 AM (+)]
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