Dosing Nitrogen > what counts, elementary or molecular

[kosmo83]

Hi,

i have now a maybe small problem in interpretating scientific papers/articles and the advises for dosing fertilizers.

There are numbers like "25ppm of nitrogen for every watering"
What kind of nitrogen ? The elementary or the molecular ?

And there are now the next issue, the type of "nitrogen"

1g of nitrate has only 0,226g of nitrogen
1g of ammonium = 0,777g nitrogen
1g urea = 0,467g of nitrogen

K-lite (normal variant) has 12,3% nitrate and 0,6% of ammonium
So 2,78% of nitrogen from nitrate and 0,47% from ammonium.

So only 3,25% N in total (a quater of the declared nitrogen)

So... if you give 25ppm calculated with the written nitrogen, than you give only arround 6,5 ppm elementary nitrogen!

All scientific papers and article say, the most important part of a fertilzer for growing orchids is nitrogen!

So, it can't be unimportant which type is important.

For me, it has to be the pure N, because that's what the plants use, the form is only like a chelat (EDTA etc.) and is just a source for nitrogen.

My observation : I mix a fertilizer for my cattleyas myself, the idea of k-lite as baseline.
But between early dec and early january, a waited for some ingriedients so I used normal Peters Grow-Mix and Hakaphos Azerka (20-7-10+3MgO).
Under my 280 watt HCI-Lights, my BLC. King of Taiwan becomes a bit purple, so I can see how fast she grows by green stripes of new leaf-tissue that wasn't exposed to light.

This green stripes became a lot smaller since I my fertilizer with 10-3-4,5-(+7,3 MgO), dosed to 50PPM Nitrogen, these stripes became a lot smaller, but the root-grow was more.

 

[Ray]

Hi,

i have now a maybe small problem in interpretating scientific papers/articles and the advises for dosing fertilizers.

There are numbers like "25ppm of nitrogen for every watering"
What kind of nitrogen ? The elementary or the molecular ?

Elemental. 25 ppm N means 25 mg of nitrogen per kilogram of solution.

And there are now the next issue, the type of "nitrogen"

1g of nitrate has only 0,226g of nitrogen
1g of ammonium = 0,777g nitrogen
1g urea = 0,467g of nitrogen

K-lite (normal variant) has 12,3% nitrate and 0,6% of ammonium
So 2,78% of nitrogen from nitrate and 0,47% from ammonium.

So only 3,25% N in total (a quater of the declared nitrogen)

Nope. Using the K-Lite example, the granular product is 12.9% nitrogen. 12.3% of that 12.9% (95% of the total) is from a nitrate source and 5% is from an ammoniacal source.

 

[kosmo83]

Elemental. 25 ppm N means 25 mg of nitrogen per kilogram of solution.

Nope. Using the K-Lite example, the granular product is 12.9% nitrogen. 12.3% of that 12.9% (95% of the total) is from a nitrate source and 5% is from an ammoniacal source.

What ppm means, is clear to me... the problem was 25ppm elementary nitrogen, or 25ppm nitrogen source (nitrate/ammonium).
So if your fertilizer contains 12,9% of a Nitrogen-source, 12,3% nitrate, 0,6% ammonium means to me, K-lite has only 3,25% elementar nitrogen.
This in mind, i have to put 0,77 g/l fertilizer-powder in my water ?

It's the same with MgO > Most fertilizers write 3% MgO, but this is only 1,8% Mg and so on.

For all other elements, it is maybe not so important, but, for nitrogen, from my point of view, it is important, which kind of nitrogen or nitrogen source counts for the fertilizer

 

[Ray]

Sorry, but you're wrong.

In the US at least, K is expressed as weight percent K2O, P as P2O5, and everything else, including nitrogen, is elemental weight percentages.

To create a ~100 ppm N solution with K-Lite, one must add 770 mg of powder to a liter of pure water. 770 x 12.9% = 99.33 mg.

If your earlier assessment was correct, the required addition would be over 3 grams/liter.

 

[kosmo83]

Verry interesting topic, I had some phone-calls, to a fertilizer-reseller, to a prof. of botanic and so on.
I think, my guess is correct, but the last answer will give ICL, the reseller will ask, bacouse he is curious too, BUT, for now, the consensus is:
Fertilizer-producer define 10% of Nitrate as 10% Nitrogen > in a 100kg of 20-20-20 are 13,1 kg urea, 2,4 kg ammonium and 4,5 kg of nitrate.
Nitrogen as a gas is not usable, so nitrogen-molecules like urea are treated like they are 100% nitrogen.

With these kind of fertilizer they give recommondations, how much to use for the fields...

And the official studies calculate the nitrogen to elementary nitrogen.

 

[Stone]

What ppm means, is clear to me... the problem was 25ppm elementary nitrogen, or 25ppm nitrogen source (nitrate/ammonium).
So if your fertilizer contains 12,9% of a Nitrogen-source, 12,3% nitrate, 0,6% ammonium means to me, K-lite has only 3,25% elementar nitrogen.
This in mind, i have to put 0,77 g/l fertilizer-powder in my water ?

It's the same with MgO > Most fertilizers write 3% MgO, but this is only 1,8% Mg and so on.

For all other elements, it is maybe not so important, but, for nitrogen, from my point of view, it is important, which kind of nitrogen or nitrogen source counts for the fertilizer

Ray is correct. If the fertilizer says 10%N then there is 10% elemental nitrogen in the fertilizer (presuming they are not cheating you) You can work out the ppm in your solution by multiplying the %N listed on the packet x 10 x the number of grams it says to use per litre. This will not tell you the form of N of course.

 

[kosmo83]

Ray is correct. If the fertilizer says 10%N then there is 10% elemental nitrogen in the fertilizer (presuming they are not cheating you) You can work out the ppm in your solution by multiplying the %N listed on the packet x 10 x the number of grams it says to use per litre. This will not tell you the form of N of course.

Hi,
I had today a conversation with a fertilizer-producer and he said, for them, nitrogen and ammonium, nitrat or urea are the same!
So they don't have 20% of elementary nitrogen, they have 20% of nitrate, ammonium and/or urea and call it nitrogen.
But from the chemical aspect, it is just 20% of nitrogen-sources.

And than, we have the next problem, 20% of ammonium deliveres more nitrogen, than 20% of nitrate!

For normal plants, it's not a problem, give them more than needed, everything is fine!

But we fertilize with a bit of nothing...

 

[gonewild]

Isn't elemental nitrogen a gas?

 

[Ray]

Isn't elemental nitrogen a gas?

Yes, but it is absorbed by plants as solutions of nitrates, ammoniums, or urea, then decomposed and recombined into whatever phytochemicals the plant "desires".

 

[Stone]

Hi,
I had today a conversation with a fertilizer-producer and he said, for them, nitrogen and ammonium, nitrat or urea are the same!
So they don't have 20% of elementary nitrogen, they have 20% of nitrate, ammonium and/or urea and call it nitrogen.
But from the chemical aspect, it is just 20% of nitrogen-sources.

And than, we have the next problem, 20% of ammonium deliveres more nitrogen, than 20% of nitrate!

For normal plants, it's not a problem, give them more than needed, everything is fine!

But we fertilize with a bit of nothing...

You cannot have just nitrate. Nitrate is an anion and always comes with a cation eg, Calcium nitrate. Same with ammonium. Ammonium is a cation and always comes with an anion eg, Ammonium sulphate. Plants take up nutrients as ions. If you add water to calcium nitrate the plant will take up nitrogen as the anion nitrate. The nitrate ion has one atom of nitrogen and three atoms of oxygen. This is what the plant takes up.
You are correct the sense that not pure nitrogen (N2) is listed the fertilizer but the anion nitrate. So, for example, calcium nitrate has 11.9% nitrate and 17% calcium. When you say ammonium delivers more N, it is true that most ammonium compounds have more available N than nitrates. It is up to you to determine how much N as nitrate or ammonium to give your plants and this is governed by the choice and concentration of the fertilizer. As I said, the amount of available nitrogen (as nitrate or ammonium) is listed on the packet and you can work out the ppm - N you require by the method I mentioned above.
To repeat, when someone says this particular plant needs 100ppm N, they mean 100ppm nitrate or ammonium or a combination.
Does that help?

 

[Ray]

calcium nitrate has 11.9% nitrate and 17% calcium.

I’m going to need some help understanding that.

What makes up the remaining 71.1%?