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[APD] RE: Substrate fertility & growth rates

> > Adding more nutrients to the substrate will
> > not force plants to grow faster.
> Thomas, I think know why you said this because growth may be limited by
> or by lack of another nutrient. Also more than adequate growth rates can
> attained using only NO3 in the water and you desire a simple regime
> for newbies.

Well the plants could be at their max growth rate also, or they might be
stunted and need time to "fatten up" again.
This is certainly true with the plants we all love, Crypts.

The other reason is heck, these are traces, not macro's you simply are not
going to see immediate responses from the plants, they are more subtle and
problematic, often confounded in aqatic systems, unlike the more controlled
hydroponic set ups.

> We should be cautious about saying that hydroponic regimes (excepting Fe)
> are just as good as geoponic (substrate fertilization) at producing high
> growth.

Well, I think both is good for aquatics here.
I have enough experience with inert substrates and water column dosing to
say this.

Knowing there was nothing/not much in the substrate taught me a lot about
the water column.
I did this for a few years.

> Recall from our recent messages, the C blassii grown in the deep soil
> substrate was much larger (28") than the hydroponic ones (18") you
> mentioned. 

I did not say that.
I had a C.blassii get 18" easy, bloom etc at lower light, high CO2, rock
hard water, weekly 60% water changes, weekly NPK/Trace dsoings.
C. blassii does not get very big emergent. 

Of course final size is not the same as growth rate but still
> desirable. You didn't mention if 18" was the maximum size attained. Tank
> size & competition are confounds too.

55gal, a dozen other crypts or so.

> Little work has been done since the mid eighties since
> the dozen or so published studies were fairly clear in their results and
> there is not much money for this type of research (its also difficult and
> time consuming).

Well in some circles.
But over all we simply do not see what these researchers have found down
here in FL. 
Nor in our own tanks.

There's A LOT more light outside for one thing.
No CO2 enrichement to speak of.

Oh yea baby...........that changes things.

Hypereutrophic systems also have other destabilizing interactions that

We cannot get macrophytes to grow in Lake Apopka. They use to grow there,
but since about 50 years , none grow.
BGA's, you can see about 25cm down into the water.

Adding PO4 to many macrophyte dominanted lakes in Florida, increases plant
production.Florida lakes, subtropical/tripical lakes that are shallow,
warmer etc are much better suited in comparing research to aquarium

My tank does does freeze over every winter. 

>   "On the other side of the coin, there have been a plethora of studies
> which indicate clearly that rooted aquatic plants will not grow optimally
> a sand or other infertile substrate no matter how richly you fertilize the
> water column (perhaps the earliest is by Pond, 1905)"

I have some recent studies from Danish and the Dutch that suggested other
than Dave's research.
I think you can very often find inconclusive arguements going back and

My notion is that what are the observations and does the conclusion match
with what I know and have seen. 
I will entertain many ideas, but I try not to accept them. 

I'll give more on this later. 

> Thomas, you've also mentioned good CEC as a desirable quality of Fluorite.
> You must feel there is a benefit to having nutrients attached to those
> binding sites. Note that the highest CEC is from organic material: peat
> (100-150) or humus (200 cmol/Kg).


> BTW, I never try to FORCE my plants to do anything. They are completely
> indifferent to my begging, pleading or threats. I'm sure they do not
> appreciate anthropomorphic comparisons. How uncivilized of them! I prefer
> think that they do like gentle encouragement & praise.   ;-)

Yes, unlike certain folks, they don't fight back, then it's no fun:)
Tom Barr

> Teban (too many Steves around here lately)

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