[APD] RE: denifitication, Ca and PO4

["Thomas Barr" <tcbiii at earthlink_net>]

> Does the presence of calcium or phosphates in interstitial soil water have
> an effect upon nitrification of ammonia to nitrate?

Ca++ might buffer the the system since pH and Eh are related.
Ca and PO4 often co precipitate at higher Eh's/more O2.
 
> Is there a stoichiometric formula for nitrification?

Sure, 2NH4+ + 3O2 -> 2NO2- +2H2O +4H+ +energy(roughly -65kcal/mol)
and 2NO2- + O2 -> 2NO3- +energy(roughly -18kcal/mol)

While being aerobic, these processes can still occur down to 0.3ppm of O2.

> I found the following denitrification formula for Thiobacillus
 denitrificans:
>
> 55S + 20CO2 + 50NO3 + 38H2O + 4NH4(+) -> 4C5H7O2N + 25N2 + 55SO4(2-) +
> 64H(+)

> This illustrates that some bacterial denitrification does not require
> organic carbon sources.

Well no, the rate of _denitrification in aquatic systems_ is controlled
mainly by Carbon, Oxygen and Nitrate availability but is also influenced by
pH, soil texture, denitrifier population and temp. NO3 is typically reduced
all the way to N2 gas due to the high demand for electron acceptors. OM =>
carbon will influence that as will CO2 which is most often derived from OM
in an anaerobic layer. But if we add high CO2 for the plants, this might
help increase the rate of denitrification. But you's still need a large
pool of S in a pretty reductive region since the S inoputs would be from
SO4, so you need a source of reduced sulfur compounds.
Not something folks generally want in the tank.

For example: in highly reduced conditions, typically NO3-> NH4+ occurs
rather than denitrification due to the increase electron availability.
So while directly involved in the above equation, the amount of carbon will
play a huge role in whether the process is energetically favorable for the
microbes. 

But does require conditions that will have Sulfur, no O2, NH4 present and
NO3 present.
Also, it's possible to have NH4+ and NO3 present but...this layer will not
be particularly think in most cases. 

Plant __root__ density, NO3 flux in/out of the more reductive layers also
plays a role.

> I'm sure there are other formulae but I don't have time at the moment to
> spend hours surfing to find them all. Perhaps someone else with an
interest
> would like to assist doing Internet searching for this material.

Denitrification is controlled by positive feedback loops such as low N/P
ratios, redox/Eh, Photosynthesis, DOM(dissolved organic matter) and
negative feedbacks from O2 and DIN(dissolved inorganic N) concentrations.

>
> Background: I'm looking at materials that can be used within the
substrate,
> especially in clay balls, to provide nitrogen & possibly other nutrients
for
> aquatic plants.
>
> Steve P

I'm looking for some materials as we speak. I want a simple cheap easy to
make Jobes stick without the soft material and the NH4/Urea added in there
also.

Some clays such as illite(old term for fine grained micas), have 2:1
lattice structure. Both K+ and NH4+ can be bound to the Si-O laters like a
sandwich.
But then it's no long available to plants for uptake. Vermiculite has the
greatest capacity to bind NH4+ and K+.

But I want something that will dissolve in the substrate or/and release the
NO3 slowly and somewhat consistently over say 3 months to a year.
I think I'll give up on having the NH4 for the substrate.  

Just some hardered, porous, slowly dissolved material that I can add a fair
amount of KNO3, KH2PO4 to.
That's an easy to make DIY Jobes without the NH4/Urea.

Something heavy enough that will not pulled up and fluffed around, rock
like.

Most folks have KH2PO4/Fleet enemas/KNO3 so all we need is the material
that will hold and desposit the nutrients over time.
Clay works, but I want something better.

The goal to have some macro's in the soil is a good one, something I've
suggested and played with a dozen or so times over the years. 

But at least today we know the problems associated with the substrate and
fertilizer Nitrogen sources and associated algal blooms cause by the one
component, NH4. 
So we can move forward with a better substrate fert.
Some have been using Fertiplant, Dupla product or something made in
Belgium, but it's 50$ for a tub.
I think a cheaper DIY version can be made for 10$ or less and might be
better because we can make it to suit our own needs and also experiement
with various levels of macro's in the substrate easily. 
 
Regards, 
Tom Barr  





 



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