Aquatic Plant Science

The science of submerged aquatic plants in the aquarium hobby

    Interactive effects of phosphorus, zinc and copper


    Lawrence So

    Posts : 21
    Join date : 2016-07-20
    Location : San Francisco, CA

    Interactive effects of phosphorus, zinc and copper

    Post by Lawrence So on Sat Jul 23, 2016 1:46 am

    The effect of phosphorus (P), copper (Cu), and zinc (Zn) addition on the P‐Cu and P‐Zn interaction in lettuce (Lactuca sativa L.) was analyzed following a factorial design. The experiment was conducted in a greenhouse. Two levels of P (62 and 224 ppm), three levels of Zn (0, 0.17, and 0.34 ppm), and three levels of Cu (0, 0.03, and 0.06 ppm) were applied in all combinations to lettuce grown in perlite. The influence of the different treatments on the leaf P concentration suggests that the P‐Cu interaction was positive, whereas P‐Zn was negative. An increase in root absorption and retention and a decrease in translocation to leaves were observed for Zn and Cu when the nutrient solution was supplied at a luxurious consumption level of P.
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    TL; DR
    Excess phosphorus resulted in reduced translocation of both zinc and copper to leaf tissue, even though their concentrations were high in roots.  Increasing zinc reduced P in leaves but increasing Cu increased P in leaves.

    How does this apply to aquatic plant fertilization?  For one thing, it suggests that the suggested fertilization concentrations of trace elements are beyond ridiculous when comparing P:Trace element concentrations.  We should not be dosing in the ppm range but in the ppb range.

    Another is that excess P reduces availability of Zn and Cu, at least when it is absorbed through the roots. So we should avoid dosing excess amounts of P, especially considering how little is actually absorbed per week, <1mg/L.


    Posts : 3
    Join date : 2016-07-21

    Re: Interactive effects of phosphorus, zinc and copper

    Post by Positron on Mon Jul 25, 2016 10:39 am

    I've always wanted to try a low P 4 week session in my heavily planted 75g. If this is true, then it might partially explain why low P ADA style benefits from low micro dosing as well.

    There is definitely some kind of ratio we are missing. I've discounted macro nutrients too long as I thought they would be too complex to experiment with when coupled with micro testing.

    Personally I still dose 0.6 ppm PO4 3x a week. Testing reveals about 5 ppm by week's end.

    When I was remixing a new macro batch last week I seriously considered using only 0.1 ppm of phosphate.

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