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[APD] Re: Nitrogen forms and soil

>I have 20 KGs of potting soil in my 90 Glls planted tank . Actually I struggle a lot to find one without additives or >fertilizers just to found out the one that I bought released quite a few phosphates in the water which is giving me >a hard time with algae. Unfortunately, It was to latte when I learn that actually Ms Walstad recommend Miracle >growth. potting soil . I will experiment in the near future with organic potting soil and will post my finding in this >forum. I would like to recommend one of her articles posted in the wet Thumb Community for those interested >in the other side of the fence of low tech / maintaines planted tanks 


Hola Mario,
It's the NH4 in the soil, not PO4 or K or anything else really.
You can boil the soil, or soak it for 2 weeks to remove the NH4/urea amd make it into NO3.

Aquatic plants do not "prefer" NH4 in all cases. This is a bit misleading to those using CO2. When you supply very low levels of NH4 and have non CO2 tanks, this slow growing plant can get a lion's share of NH4 from normal waste break down. This is good since the plant is not able to have a high growth rate, nor is able to spend much energy on N uptake since it's CO2 limited and needs more energy for that. 
But if a CO2 enriched tank........this issue changes.

There's an associated transport cost when a nutrient is at a very low concentration.
So when the NH4 is at very low concentrations, the plant has to put more active energy into trying to sequester the nutrients. 

This works both way for the algae as well.
But plants are better at it(we add far more plant biomass than algae) and have far more reserves. 

Still............NO3 can be dosed at much higher levels than NH4 can ever possibly be.
Then the NH4 can be removed effectively and we can top off with lots of NO3 as well.

The issues of concetration of your nitrogen source and how you are trying to use it horticulturally is VERY important.

We cannot have 10ppm of NH4. 
Try it and see. Don't plan on any fish or other critters. 

But 10-20ppm of NO3 can be added.

Uptake is about enzyme kinetics and __concentration__ certainly influences uptake.
Plants do not have to use as much energy at higher concentrations of NO3. 

An important note:
They also have dual transpot systems for NO3.
A low level NO3 trasporter that is always "on" and takes in small concentrations of NO3 very well. NH4 transports are always on as well.

The other is inducible, and you have to have the higher NO3 levels for the plant to "make"/induce this one that can take in large amounts of NO3 at higher concentrations only. This helps at high light levels more so. 

When a plant gets acclimated to higher NO3, it can take in the NO3 faster because of this inducible system. It has the enzymes to work with. If you drop the NO3 levels, this low affinity NO3 transporter will ground up and not be needed any longer. 

Some of the data I have shows that there is certainly an increase in plant health and growth at higher NO3 levels(20ppm). I've dosed NH4 in the past and I've never found any growth difference between that and NO3 in any CO2 enriched tank to date.

It might be true for some plants and in a non CO2 system since the plant is so CO2 limited. 
Algae certainly prefer NH4 and are use to limited CO2:-)

NH4 is the one nutrient you want to limit. Careful when you refer CO2 and non CO2 methods and systems, the growth rates, thus the uptake rates and processes are different.

Tom Barr





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