I don't do anything with Bull Nettle except avoid it.

I really don't know, but would think not. You mean the tea for plants? I looked it up and it looks nothing like European nettles and isn't ever the same the same Family of plants. The Bull nettle is Euphorbiaceae and the EU nettles are Urticaceae.

Yep, I've seen that nasty stuff, and our Florida nettles don't have anything on bull nettle....that stuff is horrible!

Spray N Grow has 2 products I've been spraying mine with, the spray n grow and Bill's perfect fertilizer; it's all natural. There is free shipping on orders $95 and more. Their web site is Spray-N-Grow. I grow in a shade house so I don't worry about the foliage staying wet, and you're supposed to mist it anyway.

Blakeeboo, Orchids magazine reported a test of Urea fertilizers some time back and the results of the actual scientific test was favorable. That is a contradiction of what I have always believed. Orchids take up Nitrogen in two forms ammoniacal and nitrate. This would mean that the Urea must be broken down by microbes to the ammoniacal condition before it can be used. The time for breakdown would depend a lot on temperature and moisture. The argument is that the Urea would be washed away before it is converted. I know of one nursery manager that does advocate the use of Ureal.
As you can see there are arguments for and against Urea and as far as I am concerned the jury is still out.

Another thing about urea is that producing it is not as environmentally friendly as organic fertilizers. I kick myself whenever I use it, but it's hard to find cheap organic fertilizers. I have compost, but didn't want to risk introducing diseases.

And oh yes, we definitely have stinging nettle in the US, especially in the Pacific Northwest, also of the family Urticaceae.

How is Urea nitrogen produced?

Yes you can! In some stores here, you can buy various sorts of dried herbs including dried nettle. The only thing you have to do is pour boiled water over it and guess what, it even doesn't tast bad :)
Some other herbs can be used fresh when you want to make thee from them, I don't know if this is the case too with nettles.

In spring, I collect the young sprouts and let them dry. My guinea pigs love this dried herb too.

That's cool i wonder if you could use it to make the fermented tea too?

Question about fertilizer for everyone, is Nitrogen/Phosphorus/Potassium percents by weight or mass?

I think the post you quoted [Do you know if you can make tea out of that kind of nettle?] was referring to the Bull nettle and NOT the stinging nettle. I would not make a tea for people out of the bull nettle, since it is a completely different plant.