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Plants Prefer NO3 to NH4??

Discussion in 'Advanced Strategies and Fertilization' started by ceg4048, Mar 25, 2005.

  1. ceg4048

    ceg4048 Lifetime Charter Member
    Lifetime Member

    Mar 21, 2005
    Likes Received:
    Local Time:
    5:19 PM
    Mr. Barr,
    Just recently tuned to your station here and read something astonishing. I don't quite remember which page. It may have been in a discussion regarding your enzyme article, however I believe you offered that plant NH4 uptake is poor at non-toxic levels and that at these levels typical of a healthy tank with normal or high fish loads the NO3 uptake is much higher.

    I'll have to admit to being a bit skeptical based on what I've read in the past, however, if your theory/data is valid then the implications would seem to challenge many popular beliefs. For example, that plants compete with the nitrifying bacteria for ammonia thus reducing their population. Another is that efficiency of wet/dry filters "steal" the NH4 which would otherwise be used by the plants, making them poor choices for planted tanks (among other reasons) or that cycling a new tank using many plants is somehow safer and quicker than cycling without plants since the plants would consume the NH4 and thereby reduce NO2/NO3 generation.

    I know that there are may terrestial NPK fertilizers that derive much of their Nitrogen via Urea and NH4 and that these are applied using very diluted concentrations.

    Could you therefore clarify the NH4/NO3 uptake mechanisms, or, if it requires another article to explain could you simply tell me if the implications I listed above hold to speak?

  2. Tom Barr

    Tom Barr Founder
    Staff Member Administrator

    Jan 23, 2005
    Likes Received:
    Local Time:
    5:19 PM
    Re: Plants Prefer NO3 to NH4??

    Sorry:) I've likely said more incriminating things.

    Based on a graph Diana Walstad suggested was a reason quite to contrary, yes, I did say in our tanks, that the graph shows that NO3 uptake is much higher while NH4+ is flat lining at our normal plant tank levels.

    Depends on what you are looking for in the graph and how it's applied to your situation and question.


    I've never found wet/drys to be an issue.

    Not dilute relative to the levels of uptake for NO3/NH4.
    They are toxic to fish and other life and a great way to induce algae.
    You can add 20-75ppm of NO3 and not get algae nor fish death.

    There will be a detailed article on N coming up.
    One appeared in the AGA's TAG and Aqua Palnta and Reef Art(Italian).
    Failry indepth but did not cover the graph issue with uptake that Diana suggested showed the opposite of what I see in the graph.

    Tom Barr

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