If the ferts were in the water column the plants would have no need to produce a nice healthy root system.
Make sense?
John Van Rees" ============================= A "victim" steps forth to take the bait:)
Thanks John, few do these days.
How do we over water aquatic plants?
How do terrestrial plants take nutrients in from the air?
If we check the fertilizing routines in terrestrial systems, foliar apllications are quite useful.
Does it help roots? Well, it does take a nutrient stress off the leaves thereby adding more for the roots.
In terrestiral systems, especially grasses and many others, water is a huge role for weeds. Plants will conserve water through their leaves and get as much as they can in the soil.
If we look at some research on a number of aquatic plant species, even when the roots where cut off, the relative growth rates remained the same in the control and the treatments(removed the roots) if the water column was non limiting(thereby not a confounding factor).
So the plants will take the nutrients in from the leaves first, then the substrate secondarily.
There are a few more complicating issues here but this is the generalized model.
I think this is still the best arguement for not fertilizing, so after a good pruning should we not fertilize for that week? But even still, the plant needs to take in more to grow better etc and adding ferts to both places will only enhance the growth of the roots regardless if the plants produce more growth with the strong roots or not.
The roots may simply be nothing more than a storage depot/storage organ(like a tuber) rather than a nutrient source in the substrate as far as a role.
Predicting the direction a plant will go when given a nutrient stress is not so simple. Some plants may grow more roots, some might not.
Many aquatic plants simply shut down and stop growing when the nutrients run out.
So the plant might be simply getting ready for "lean times ahead", rather than growing better/healthier.
The roots will grow better if the plant is given non limiting conditions, it has little choice if we force all the plant's resources into root production by removing all water column dosing.
Those resources have to come from somewhere and places a stress on the plant when it's weakest(after replanting/pruning).
So adding nutrients to the water column will allow more roots, not less I'd argue.
More roots will = more bacteria and a stable reductive region in the substrate=> better plant growth in some species(not all, some don't care even if they have roots).
Why not stop dosing after pruning when the cuttings have no roots?
Would we force the plants to grow stronger roots?
Do we want strong roots/more root biomass?
Do more roots look good in my tank?
We do not see any differences in the planted tanks then, so if the root issue is really an issue it seems, it would show a similar pattern even in an established tank after pruning.
The issue of a new tank is really something that makes me wonder about the roots role here. Are the roots, really that important in establishment? Yes. How do we grow better roots?
Seems to be by adding plenty of water column ferts since that where the plant will first take them in at.
But the plant would then have to translocate the nutrients from the water column, to the roots/hairs, so a little fert in the substrate will also help.
Still, why not add the nutrients to the water column?
Will aquatic plants, not terrestials, grow more root biomass(not total) when the water column is non limiting as well as the substrate?
I thin the plant will grow more, not less roots when you give the plant what it wants in both places, not force it to translocate.
If the water column is non limiting, roots play a much smaller role, our substrates have a rather high rate of flux of nutrients in/out. So the water column can supply most of the roots with what they need as well.
Bottom line is that I do not think we can say that a good/better % of root to shoot ratio is better for a new tank and that limiting the water column helps to that end in a significant manner.
It does not help in terms of algae nor plant health growth over all.
But I do think many plants will put more resources into their roots if they are slightly nutrient stressed.
If the plant does not find what it needs via the extra root growth, then what?
Will that help after spending the extra energy and resources?
Seems to me to let the roots do their thing and focus on having some nutrients available for the roots and lots for the leaves. I don't think this is going to make a difference in a _new_ tank though.
Regards, Tom Barr
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