• You are viewing the forum as a Guest, please login (you can use your Facebook, Twitter, Google or Microsoft account to login) or register using this link: Log in or Sign Up

KNO3 and Urea

fono555

Seedling
Joined
5 Jan 2019
Messages
13
Location
CA
I currently dosing macro with KNO3, K2SO4 and KH2PO4. I plan to replace a portion of kno3 by Urea.

Can I mix KNO3, K2SO4, KH2PO4 and Urea together?
What the proportion between kno3 and Urea I should use for the nitrate dosing? 1/5 Urea and 4/5 kno3?
 
I'd personally switch 4 parts of KNO3 for 1 part of Urea. It's a nitrogen bomb.
1 g of KNO3/100 l is appr 6mg of NO3 while 1g of CH4N2O/100l is appr 22ppm of NO3.
 
You mixed all KNO3, K2SO4, KH2PO4 and Urea together?
Did you decrease your total dosing of nitrate? As exemple you were dosing 10 ppm of kno3 but now you are dosing 7 ppm know + urea?
 
I don't dose nitrates at all. But I get appr 10 ppm of NO3 by water changes (appr every 10 days), so I use only KH2PO4 as a source of P and KCl/K2SO4/KHCO3 for K. And tiny amounts of urea while I see N deficiencies before water changes.
 
Oh ok. Thank you

Sent from my CLT-L04 using Tapatalk
 
Hi all,
I plan to replace a portion of kno3 by Urea.

Can I mix KNO3, K2SO4, KH2PO4 and Urea together?
What the proportion between kno3 and Urea I should use for the nitrate dosing? 1/5 Urea and 4/5 kno3?
You can do, there isn't any chemical reason not too.

You would need to do a bit of maths, urea (CO(NH2)2) is 46% nitrogen, but potassium nitrate (KNO3) is only 22.5%* nitrogen. That is near enough to say that half (should have been ~1/3)* of a gram of urea contains as much nitrogen as one gram of potassium nitrate.

*Edit March 2023: @palcente (very diplomatically) pointed out that I can't add up, and that <"that value should be 14%">.

If you want to convert the nitrogen to the nitrate (NO3-) equivalent you need to <"multiply by 4.43">.

Also it is like @Witcher says you have to be very careful with urea, because it is both nitrogen rich and converted to ammonia, (CO(NH2)2 + H2O + urease -> 2NH3 +CO2) via organisms with the <"urease enzyme">.

cheers Darrel
 
Last edited:
Thank you dw1305

Sent from my CLT-L04 using Tapatalk
 
Hi all, You can do, there isn't any chemical reason not too.

You would need to do a bit of maths, urea (CO(NH2)2) is 46% nitrogen, but potassium nitrate (KNO3) is only 22.5% nitrogen. That is near enough to say that half a gram of urea contains as much nitrogen as one gram of potassium nitrate.

If you want to convert the nitrogen to the nitrate (NO3-) equivalent you need to <"multiply by 4.43">.

Also it is like @Witcher says you have to be very careful with urea, because it is both nitrogen rich and converted to ammonia, (CO(NH2)2 + H2O + urease -> 2NH3 +CO2) via organisms with the <"urease enzyme">.

cheers Darrel
Hi Darrel, I am trying to teach myself how to dose Urea, and came across this post. You stated 22.5% N in KNO3, but when I did the math I got around 14%.

14/(39.1+14+(3*16))

I got 46% for urea, just like you. Could you tell me what I'm missing? Thanks. Matt
 
Hi all,
You stated 22.5% N in KNO3, but when I did the math I got around 14%.

14/(39.1+14+(3*16))

I got 46% for urea, just like you. Could you tell me what I'm missing? Thanks. Matt
I just can't add up, even more bizarrely the RMM of KNO3 is near enough 100, so it is always going to be ~14% N.

Cheers Darrel
 
Do it carefully would be my advice, kno3 is safer, and gives similar results. 🤔
I definitely think urea seems to result in stronger and larger growth (i.e bigger leaf size). I prefer this growth when using urea, but I do also think it comes with risks. It does seem to amplify the growth of already existing algae, I'm undecided on whether it can outright cause algae, but I don't think it does - so long as the plants are growing healthily.

I have noticed however that green dust algae on the glass increases when using urea.
 
Do it carefully would be my advice, kno3 is safer, and gives similar results. 🤔
Yes, I was using KNO3 and with my plant mass I had problems with high potassium build up.

I temporarily switched to Ca(NO3)2 and noticed positive response from my plants, but I foresee similar calcium build-up issues long run.

I am trying to find a way to dose NPK from independent sources.

Thanks,
Matt
 
@palcente If you really decide to use urea, here is my advise. Use it very sparingly and often rather than in higher doses, else you'll have nice algae surprises, specially GDA and hair algae. I've been there. Check my journal.
You could use the IFC calculator to have proper ratios and decrease your K proportion. IMO there is really no need to use urea, but as the say goes, to each its own.
IME the best way to mitigate accumulation is front loading and big water changes. I couple that with 90% WC every few months to make sure everything resets to the levels I need.
 
I definitely think urea seems to result in stronger and larger growth (i.e bigger leaf size). I prefer this growth when using urea, but I do also think it comes with risks. It does seem to amplify the growth of already existing algae, I'm undecided on whether it can outright cause algae, but I don't think it does - so long as the plants are growing healthily.

I have noticed however that green dust algae on the glass increases when using urea.
Ha! This leads to my eternal question: should my plants look and grow ideally (for example relatively common bacopa xyz growing and reaching full maturity leading to flowering etc. within 6-8 months as it does in nature) or should they look like and be overgrown (as you said bigger leaf size, most probably quicker maturity etc.) by using excessive amounts of specific ferts? Do we want our plants look like healthy cheetah quickly jumping through savannah or like Katie Price not being able to move quickly because of her overgrown boobs? I find urea and any other potent ferts as very useful tools but excessive amounts lead to rather undesired effects, not necessarily leading to healthy growth. In my opinion there is absolutely no chance for plant (which usually gets matured within let's say 8 months) to be healthy if it matures 2x or 3x times quicker - same like with human usually being matured within 25 years or so (including mental development) - what happens if for some reason human gets fully matured within 10 years including his or her brain? Not to mention chicken and other extremely quickly grown food we eat every day.
 
I am trying to find a way to dose NPK from independent sources.
I would suggest using MgNO3, KNO3 and Urea combined. You can also combine CaNO3 in the same mix if you like. for those who usually get algae with Urea, they are either adding way too much urea to begin with or there are other factors at play. Urea or NH4 alone usually doesn't cause algae unless present in excess amount along with other nutrients.
 
I definitely think urea seems to result in stronger and larger growth (i.e bigger leaf size).
I've made an experiment, comparing growth of multiple species with urea, ammonium, ammonium+nitrates, and nitrates exclusively. I can say that Mayaca fluviatilis and Tonina fluviatilis preferred ammonium (or urea, which is the same). Other plants seemed as if they didn't care.
Based on theory, I prefer ammonium and nitrates combined fertilizing. I believe some plants generally considered problematic (notably Tonina) may turn out easier if both forms of nitrogen are present and plants may choose at any moment as they wish.
I had problems with high potassium build up.
That's a topic I'm interested in. What were the visible effects of excess potassium?
90% WC every few months to make sure everything resets to the levels I need.
I'm afraid it works poorly as far as micronutrients - transition metals are concerned. They accumulate in the substrate. I consider it a potential danger, and I believe it happens, but it's extremely difficult to prove. Visible symptoms of micronutrient toxicity are difficult to distinguish from damage caused by other factors.
should my plants look and grow ideally (for example relatively common bacopa xyz growing and reaching full maturity leading to flowering etc. within 6-8 months as it does in nature) or should they look like and be overgrown (as you said bigger leaf size, most probably quicker maturity etc.) by using excessive amounts of specific ferts?
I wonder whether this analogy with animal 'obesity' truly exists. I've never stroke on anything resembling this problem in literature.
Urea or NH4 alone usually doesn't cause algae unless present in excess amount along with other nutrients.
That is what I've been believing as well, until now. My currently running experiment suggests that this assessment might be wrong, or perhaps valid only conditionally.
 
Back
Top