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.