[APD] Re: Gw/NH4

[Thomas Barr <tcbiii at earthlink_net>]

> Thomas Barr wrote:
>> When a healthy well growing plant is supplied with a
>> fair amount of NH4 as a nitrogen source(fish/critter
>> wastes) and suddenly you stop adding things like
>> PO4/K/Traces, the plant growth stops/shuts down.
>> So does NH4 uptake.
 
> Sorry, I have to disagree on this theory Thomas. Aquatic plants can store
> reserves of nitrogen and will do so quite efficiently.

If you run the NO3 levels at zero ppm for more than 2 days at high light,
stem plants stunt. I've done this enough times the wrong way to know. Trying
to get plants to have a nice red color using N limiting methods really gave
me a lot of experience. Some plants are more tolerant, but if the fast
growers are maintained well, then it follows the slower growers will also do
well. A number of other folks on this list can attest to this.

I'm saying that a PO4(or trace/K+) limited tank/plant is going to have
slower uptake and growth than one that is non limited. Make this limitation
severe enough, and the ability to remove/assimilate NH4 from the water
column will be reduced.

That's all I said in the above statement.
Still disagree?

> Nutrient uptake is
> independent of growth (but not vice versa).

Okay, then where is the plant going to put the nutrient's it brings in? Just
keeping some is normal for maintenance storage but this is finite(a plant's
"gas tank" is only so big). At some point the plant has to do something with
the intake and has to grow and many of the plants we keep are weeds and grow
like fire. 

Small amounts/brief time periods may be independent, but there is certainly
interdependence with nutrient uptake and growth.
Some plants have a finite size but as the old tissue dies, it is replaced by
new tissue and these new tissues have to be supplied from nutrient building
blocks. Some recycling of nutrients is common in many plants, especially
when they are low on something/light nutrients etc. The leaves themselves
can be storage organs.
 
Many plants simply stop growing and idle if nutrients/CO2/water run out.
No correlation there? Perhaps on a very short time scale.

But if something runs out for awhile, the ability of NH4 uptake is reduced.

> In fact, in a well fertilized
> tank with automatic CO2 injection, the plants should keep growing fairly
> well until the available non-mobile nutrients in solution, such as calcium
> or magnesium, are used up.

Or any limiting nutrient within the system. Why Ca or Mg in particular?
"Well fertilized"? What does that mean? All the nutrients are supplied?
 
> I've seen green water appear spontaneously in a tank before but usually
> accompanied by feeding & harvesting of the majority of fast growing plants.

That's what I've been saying on this list for a few years. You reduce the
NH4 uptake(removing many plants) and adding more food. You likely also pull
up and good deal of that soil (I'd take it that you do use this?) and the
associated NH4. 

When the normal uptake of NH4 produced within the system is disturbed, the
NH4 builds up and the bacteria don't/cannot make up for the loss in plant
uptake in time and algae get a free meal of NH4.
Bacteria can convert the NH4=>NO3 but the present amount of bacteria are
only use to eating a low amount of NH4 that might be leftover from the
plants. Therefore the bacterial colony is reduced and small. It takes time
for the bacteria to grow and multiply and catch up to the extra "food"
suddenly added to the system.

NH4 is a good sign that conditions are ripe for algae to grow in.
If you do a water change right after the big hack/pruning, GW does not
appear.

You can use NH4 and try the same tank etc without NH4, say add NO3 and see.

Chronic GW cases often have small amounts of NH4 at some point, little/not
enough bio media to help suppress the NH4 spikes that occur. I can add
everything else except NH4 to a tank, NO3 etc to high levels and not ever
get any GW, I add urea and or NH4, I get GW.
I can do the same thing by adding more and more shrimp to a system till it
reaches the breaking point. More light makes it easier for GW to grow and
bloom.  

> With heavier feeding of rich foods such as blood worms, BG algae seems to be
> the result. Any filament algae present also grows well but it grows best
> when there is a surplus of N, it seems.

Why then does adding KNO3 to many tanks improve plant health/reduce BGA
growth?
At higher levels, NO3 or NH4 etc can destabilized a system.
At too low levels the same can happen as well.
Too low NO3 level is a classic case.

This is why I suggest a range of a parameters(high and low and also a
frequency of dosages). It is also why I suggest water changes + dosing.
Keeps the nutrients from running out, and from building up too high.
Bit easier for the routine of folks than testing everything each time.
   
> Steve P > Sorry, I have to disagree on this theory Thomas. Aquatic plants can
> store
> reserves of nitrogen and will do so quite efficiently.

Why add KNO3 then? Just once a week or a month?
 Sure plants store things like NO3 in the vacuole(s) and other goodies. But
that's a finite supply. It doesn't last that long(maybe 30-48 hrs in a high
light/CO2 tank). The plant's "gas tank" is only so big and holds only so
much. 

A plant stressed from very low levels of N/K/P is going take in the same
amount of NH4 that a healthy plant that's not stressed?Label the nutrients
and see for yourself which is able to remove the NH4 faster.

This statement above I made was about why the NH4 uptake is reduced and NH4
's relationship to GW causes. This something I've actually done a fair
amount of work on and talked and helped many folks over a number of years.
I can get into the biochem if you wish on how plant's regulate Nitrogen
metabolism. I've posted some info before not too long ago on N assimilation.
  
Tom Barr
    

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