[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: NO3 vs NH4

Tom Barr wrote, in part:
>Folks parrot "a plant perfers NH4+ over NO3-" but as far as
>growth is concerned, a balanced ratio grows plants the best(A
>anion/cation balance provides the best uptake/growth), so say
>for corn, it's about 1:4.

Tom, do you think there's any difference between NH3 and NH4+? My
understanding is that ammonia, unlike ammonium, doesn't go through ion
uptake channels. Rather, its symmetric structure and neutral charge allow it
to permeate the plant directly, such that the plant doesn't have to expend
any energy on uptake.

I'm curious whether your experiments dosing with NH4+ salts were in tanks
with a pH high enough to convert a significant amount of NH4+ to NH3. I
would think this would make a difference.

My tank has a pH of about 8.0, so I'd expect roughly a 17:1 ratio of NH4+ to
NH3, meaning 5.5% would be NH3. This may not sound like much, but if it gets
consumed quickly then more NH4+ would turn into NH3 to maintain the

>A non CO2/carbon enriched tank can have all of it's N supplied
>via NH4 very likely from fish waste since the N needs remain low
>since the plant is limited by the amount of CO2 or light

I hope this proves to be true. My ammonia, nitrite, and nitrates are all
stubbornly stuck at undetectable levels, despite the moderate lighting (120W
on 125 gallons) and lack of CO2. I'm somewhat nervous that this is going to
lead to problems down the road.

- Jim