Reading and Interpreting Fertilizer Labels

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Re: Reading and Interpreting Fertilizer Labels

Post by bpgreen » January 4th, 2019, 1:58 am

andy10917 wrote:
January 3rd, 2019, 10:46 pm
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?
I'm not sure what you're looking for. The obvious answers are the percentages of N, P, and K in the bag. And the amount of slow release vs fast release N.

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Re: Reading and Interpreting Fertilizer Labels

Post by andy10917 » January 4th, 2019, 9:21 pm

Nope - I'm looking for what is the next thing that you should consider after you've done the preliminary inspections and calculations.

Hint: it involves the fertilizer's quality and the potential to cause bad results...

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Re: Reading and Interpreting Fertilizer Labels

Post by micvog » January 5th, 2019, 12:39 pm

My next steps would have been to determine whether the fertilizer is a good fit for my requirements including whether it matches up with my soil test/plan, good fit for the weather/season (i.e. not use fast release during the Summer, organics at the end of Fall, etc.), etc. But based on your hint, I would look at the salt index of the ingredients (i.e. prefer potassium sulfate to potassium chloride, etc.).

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Re: Reading and Interpreting Fertilizer Labels

Post by andy10917 » January 5th, 2019, 1:23 pm

OK, now we're making progress. What does the Salt Index tell us?

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Re: Reading and Interpreting Fertilizer Labels

Post by micvog » January 6th, 2019, 5:40 pm

Salt index tells how, on a relative scale, how much salt would be added to the soil from using a specific fertilizer. Higher levels of salt are bad for the micro-herd/soil biology.


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Re: Reading and Interpreting Fertilizer Labels

Post by Ruxie88 » January 6th, 2019, 5:57 pm

In addition, the higher the salt index, the higher the chances of "burning" the lawn.

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Re: Reading and Interpreting Fertilizer Labels

Post by andy10917 » January 6th, 2019, 8:15 pm

So now, what does "Salt" mean when used in the Salt Index?

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Re: Reading and Interpreting Fertilizer Labels

Post by Ruxie88 » January 6th, 2019, 8:46 pm

The amount of salt that will dissolve in the soil. To much salts makes it harder for seed/grass to absorb water from the soil.

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Re: Reading and Interpreting Fertilizer Labels

Post by andy10917 » January 6th, 2019, 9:50 pm

(The question wasn't just to you, but you're welcome to respond)

Let me be clearer - does "Salt" mean the stuff that you put on french fries, or does it mean something else?

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Re: Reading and Interpreting Fertilizer Labels

Post by bpgreen » January 7th, 2019, 1:14 am

andy10917 wrote:
January 6th, 2019, 9:50 pm
(The question wasn't just to you, but you're welcome to respond)

Let me be clearer - does "Salt" mean the stuff that you put on french fries, or does it mean something else?
Salt means a lot of different things in a lot of different contexts. The streams and rivers that flow into the ocean are considered fresh water. But the ocean is salty. Why? Well, the fresh water flowing in isn't all that fresh. For an exaggerated example, look at the great salt lake. Fresh water flows in, but the water that flows in evaporates ants leaves the small amount of salt behind. Over centuries, it builds up.

Now take it to the scale of a lawn. If you add fertilizers that increase salinity but you don't have precipitation to dilute it, you're going to have a lawn that is difficult to keep healthy. This is probably less of an issue in areas of high precipitation, but it can cause problems in a hurry in aid areas. It's part of why I don't fertilize and why I try to water as infrequently as possible.

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Re: Reading and Interpreting Fertilizer Labels

Post by Sensi » January 7th, 2019, 4:52 am

I use Sodium Chloride (NaCl) on my fries, but in addition to NaCl the term "salt" includes a number of other substances that result from an acid and base reaction. I apologize if I missed this, but where on the label will I find the salt index?

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Re: Reading and Interpreting Fertilizer Labels

Post by Ruxie88 » January 7th, 2019, 10:55 am

Sodium Nitrate (NaNO3) is/was commonly used in synthetic fertilizers.

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Re: Reading and Interpreting Fertilizer Labels

Post by Sensi » January 7th, 2019, 1:05 pm

Ruxie88 wrote:
January 7th, 2019, 10:55 am
Sodium Nitrate (NaNO3) is/was commonly used in synthetic fertilizers.
Good point. It's the baseline for the Salt Index, it's value is set at 100.

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Re: Reading and Interpreting Fertilizer Labels

Post by Green » January 10th, 2019, 11:14 pm

andy10917 wrote:
January 1st, 2019, 9:16 pm
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?
Assuming you already bought it:
-How much to apply to achieve your needs
-How that should be distributed with respect to soil grass's need for nutrients, seasonal timing, the fast/slow release N content in the bag, synthetic versus organic, etc.
-Whether you can water it in, or can time it with rain
-What you're going to apply it with and the calibration of that (type of spreader, etc.)

If you didn't buy it yet, you might want to shop around to see if prices vary, or if there's something else that achieve the same result at a better price, or similar.

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Re: Reading and Interpreting Fertilizer Labels

Post by Green » January 10th, 2019, 11:17 pm

andy10917 wrote:
January 6th, 2019, 8:15 pm
So now, what does "Salt" mean when used in the Salt Index?
Ionic compound; usually sodium as the cation (like in NaCl) is the one we try to avoid. I'm not sure if chloride content of a fertilizer (e.g. in MOP) directly implies that chloride is bound to sodium. I know you say MOP is harsher on the soil than SOP, but I'm not sure if that's due to the chloride itself. I mean, isn't sodium the real bad guy in high amounts? Does MOP contain NaCl?
Last edited by Green on January 10th, 2019, 11:20 pm, edited 1 time in total.

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Re: Reading and Interpreting Fertilizer Labels

Post by Green » January 10th, 2019, 11:20 pm

Sensi wrote:
January 7th, 2019, 1:05 pm
Ruxie88 wrote:
January 7th, 2019, 10:55 am
Sodium Nitrate (NaNO3) is/was commonly used in synthetic fertilizers.
Good point. It's the baseline for the Salt Index, it's value is set at 100.
And, what does that "100" mean?? Whoever created the salt index scale used NaNo3 as the reference frame for highest salt content (e.g. 100%)???

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Re: Reading and Interpreting Fertilizer Labels

Post by TimmyG » January 11th, 2019, 12:20 am

Green wrote:
January 10th, 2019, 11:17 pm
Does MOP contain NaCl?
MOP = Muriate of Potash = Potassium Chloride = KCl (which has a salt index of 116.2 vs. 42.6 for SOP)

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Re: Reading and Interpreting Fertilizer Labels

Post by Sensi » January 11th, 2019, 3:11 am

And, what does that "100" mean?? Whoever created the salt index scale used NaNo3 as the reference frame for highest salt content (e.g. 100%)???
100 is not the "highest", it's just a commonly used reference point value. You will find the 100 reference value used in lime evaluation also. 100 is the value given to the acid neutralizing ability of pure calcium carbonate, its CCE (calcium carbonate equivalency), but some lime products like Calcium Oxide and Calcium hydroxide have a higher CCE value than 100 while most lime products have a lower CCE value compared to calcium carbonate's 100 value. Ditto with the salt index. As TimmyG points out: If NaNo3 is 100 then SOP, comparatively, is 43 and MOP is 116.

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Re: Reading and Interpreting Fertilizer Labels

Post by Green » January 11th, 2019, 10:26 pm

TimmyG wrote:
January 11th, 2019, 12:20 am
Green wrote:
January 10th, 2019, 11:17 pm
Does MOP contain NaCl?
MOP = Muriate of Potash = Potassium Chloride = KCl (which has a salt index of 116.2 vs. 42.6 for SOP)
Now I understand the reason MOP isn't ideal. It's the KCl itself due to its salt index. Lebanon has an article called "Salt Index and Sodium" which I'm going to read.

Which is worse though, NaCl or KCl? Is it just the salt index that tells us this? And finding the salt index of NaCl would tell us the answer? Or, more to it than that?

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Re: Reading and Interpreting Fertilizer Labels

Post by andy10917 » January 11th, 2019, 11:06 pm

You're stuck on the idea of involving table salt (NaCl) whenever you see the word "salt". What about Potassium Sulfate ("Sulfate of Potash")? What about hundreds of other salts in inorganic fertilizers, and thousands that have no nutrient value in lawns or gardens?

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