Re: N-P-K

["Ben B" <benrx at naxs_net>]

Well, you kinda overanalyzed the intent for which I was looking for the
information.  However, the discussion was interesting regardless.  Thanks.
Very cool.

The page on Walstad's book didn't have what I was looking for on it.  I'll
keep looking.

Thanks again,
Ben
www.aquatic-plants.org

> Date: Tue, 18 Jun 2002 09:04:33 -0700
> From: Thomas Barr <tcbiii at earthlink_net>
> Subject: Re:NPK ratio's
>
> > Subject: N-P-K
> > A few months ago there was a thread about someone that had come up with
> > research/theory supporting a fixed ratio of N-P-K that plants needed.
>
> Plants species have a wide range of needs. You can get a "middle range" by
> doing dry analysis and assuming what's in the dry weight, is what the
plant
> needs.
>
> But(!!!) the dry weight analysis plants need to be in the health that you
> desire.
>
> A healthy optimally grown plant will have different ratios of many major
> macro nutrients than say a weak plant. You need to know that your plants
are
> indeed healthy and what you want to test for first.
>
> Then there are issues such as what light intensities you are interested
in.
> The nutrient ratios for a plant grown at 1.5w/gal vs 4-5w/gal will also be
> quite different even if they are the same plant etc.
>
> Then there are issues of luxury consumption, (e.g. plants take up more PO4
> than they need for good growth).
>
> Then is the issue of types of N, such as NH4 and NO3 and the ratios
supplied
> to the plants etc.
>
> It can be done, but it's going to take a fair amount of work to get good
> results.
>
> I've just eye balled and guessed and have come fairly close. There will
> always be a few plants......in anyone's NPK ratio that won't do as well as
> the rest. With plants, there's always exceptions.
>
>   The
> > study is also mentioned in Walstad's book "The Ecology of the Planted
> > Aquarium."  I am trying to find the thread in the archives, and I have
> > looked all through Diana's book and cannot find it.  Does anyone
remember
> > what I am talking about?  Something about critical ratios maybe?
>
> Well you can find this on page 105.
> But, this is for only one single plant.
>
> Be very careful in using a book such as this of generalizing and scaling
up
> to ALL aquatic plants. Most of these studies are for _one_ particular
plant.
> Many plants will be different. Many plants have other mechanisms and ways
to
> accomplish submersed growth.
>
> This is why comparative studies and testing more than one single plant is
> important in ecology. You find other trends, often ones you never
expected:)
>
> Regards,
> Tom Barr
>
> > Ben in SW Virginia
> > (anyone else out here?)