Dosing Nitrogen > what counts, elementary or molecular

[Kosmo83]

Hi,

i have now a maybe small problem in interpretating scientific papers 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

@Ray what do you think ?

---------- Post added at 11:39 AM ---------- Previous post was at 10:17 AM ----------

My observation : I mix a fertilizer for my cattleyas myself, the idea of k-lite as baseline.
But between early dec and early january, I 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]

In fertilizer labels, it is the elemental N percentage that is given, and they just break down the nitrate/ammoniacal numbers for information.

So for K-Lite, 12.3/12.9=95% of the elemental N is nitrate and 5% is ammoniacal.

The form of the nitrogen indirectly affects the pH of the rhizosphere. Nitrate (a negative ion) uptake = secretion of a negative ion by the plant, driving the rhizosphere pH up over time. Ammonium is a positive ion, so the plants' secretions will be positive, pushing the pH down over time.

[Kosmo83]

Thanks,

but I don't think you are right with the labeling.

Maybe we take a different fertilizer.

Peters 20-20-20
In the desciption:
20% Nitrogen (4,5% NO3, 2,4% NH4, 13,1% Urea).

In this case, 20% of Nitrogen is just the sum of the different nitrogen-sources and not the elementary N.

Maybe the label on your fertilizer is different, but, I am from germany I have to go with common fertilizers (and mix them).

And I think, for a fertilizer like peters 20-20-20, 20 is not the elementary nitrogen, it is just the summ of nitrigen-sources in the mix.

[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.

[Kosmo83]

Now I sent 2 mails, one to ICL and one to Compo to help me with this question.

For me, it is logical, to count elementary nitrogen for PPM fertilizing, the plant won't use the OH, or H-atoms/ions.

If there was a label like this 20% N (40% nitrat, 60% ammonium) I have never asked.