KNO3 and Urea

fono555

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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?
 

Witcher

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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.
 

fono555

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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?
 

Witcher

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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.
 

dw1305

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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 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
 
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