Osmocote plus disaster

[_Maq_]

the <"TAN, ammonia (NH3) / ammonium (NH4+)"> is a gas / monovalent ion and it won't be bound by <"any CEC in the substrate">

Clays do can bind ammonium. Think of cat litter. Beside that, ammonium adsorbs well on organic matter and iron (hydr)oxides.

I have also tried freezing ice cubes of EDDHA-Fe and adding them to the substrate. I've added equivalent of 0.2ppm to my substrate without any visible water staining (I've read that EDDHA-Fe stains water at concentrations as low as 0.1ppm).

That's misunderstanding. Chelates protect iron from oxidation in oxidized water. Oxidized iron settles in the substrate and gets dissolved again in suboxic or anoxic conditions. Pumping chelated iron into reduced environment is... misunderstanding. (And waste of expensive fertilizer.)

the root feeding ultimately ends up becoming a water Colum dosing

Not necessarily. It always depends whether given species adsorbs on soil complex (= basically sand + clays + iron oxides + organic matter).
These species do NOT adsorb: chloride, sulfate, molybdate, nitrate, sodium, potassium, magnesium, calcium.
These species DO adsorb: fluoride, phosphate, ammonium, iron, manganese, zinc, copper, nickel.
These species may participate in clays' CEC: protons, ammonium, sodium, potassium, magnesium, calcium, aluminum, iron a.o.

 

[dw1305]

Hi all,

Clays do can bind ammonium. Think of cat litter. Beside that, ammonium adsorbs well on organic matter and iron (hydr)oxides.

They do. You can actually <"buy zeolites"> (like <"clinoptilite">) specifically to remove ammonium (NH4+) from solution, via ion exchange.

If you want to measure the CEC of calcareous soils in the lab. you use a <"strong solution of ammonium acetate (C₂H₇NO₂)"> to replace the cations that are there, and then flush out those ammonium ions and measure their amount via titration.

Having said that I don't think it makes any practical difference to the potential issues with Osmocote (or any other <"TAN containing"> root capsules).

What I should have said is that ammonium (NH4+) is the most <"lightly bound monovalent cation"> via the <"Lyotropic"> (<"Hofmeister">) series.

...... Yes it could, the multivalent cations are more strongly bound. You can get the sequence from the <"lyotropic series">, with the proviso that it also depends upon the ratio of ions. Al+++ and Fe+++ are the most strongly bound ions, and Na+, K+ and NH4+ the least strongly. Copper, Zinc etc are divalent and will be bound less strongly than iron, but more strongly bound that K+ or Ca++ & Mg++.

This means that it will be exchanged for any other cation. As an example, if you had hard, alkaline (calcium (Ca++ & 2HCO3-) rich) water all the TAN would be as ammonia (NH3) and even if you reduced the pH, and the TAN became NH4+, those ammonium ions wouldn't replace the Ca++ ions because they would be at a low concentration and they would <"be less strongly bound">. <"Calcium adsorption on clays: Effects of mineralogy, pore fluid chemistry and temperature"> & <"https://www.css.cornell.edu/courses/260/Soil Colloids 3.pdf">

These species do NOT adsorb: chloride, sulfate, molybdate, nitrate, sodium, potassium, magnesium, calcium.
These species DO adsorb: fluoride, phosphate, ammonium, iron, manganese, zinc, copper, nickel.
These species may participate in clays' CEC: protons, ammonium, sodium, potassium, magnesium, calcium, aluminum, iron

Where did that come from? I'll be honest <"I'm not convinced">.

from <"Cation-exchange capacity - Wikipedia">.

cheers Darrel

 

[_Maq_]

Where did that come from?

Pavel Pitter: Hydrochemie.
This textbook also describes in detail the rules for adsorption (CEC), not only on clays, but also ferric species, and organic matter. Then, it describes sorption on soil sorption complex, which consists of most abundant components of soils. An important note is that this complex's sorption capacity is greater that the sorption capacity of individual parts.
Another good source is some agricultural literature which divides chemical species into more or less movable in soils. And agricultural practice is also telling. Par example, most American farmers ceased using nitrate fertilizers and use ammonium (injected under the soil surface) plus nitrification inhibitors. The advantage is obvious - ammonium, in contrast to nitrate, stays bound in the soil. Farmers save money spent for fertilizers and the runoff of nitrate into surface waters is diminished.

 

[dw1305]

Hi all,

Par example, most American farmers ceased using nitrate fertilizers and use ammonium (injected under the soil surface) plus nitrification inhibitors. The advantage is obvious - ammonium, in contrast to nitrate, stays bound in the soil

I know a bit about that, <"it isn't primarily a nitrate (NO3-) issue">, it is to stop ammonia (NH3) <"escaping into the atmosphere">.

...... The government has agreed to reduce ammonia emissions by 8% in 2020 and 16% in 2030, compared to 2005 levels. Around 88% of ammonia emissions in the UK come from agriculture. ........

Soil water can retain a lot of ammonia (NH3) gas (ammonia is very soluble), so injecting it into the soil is a win win situation.

I've had the good fortune to visit several older style sewage works and they <"produce enough atmospheric ammonia"> to really make your eyes water.

cheers Darrel

 

[dw1305]

Hi all,

plus nitrification inhibitors.

Should have done that bit as well, these are actually urease inhibitors <"Urease Inhibitors Effects on the Nitrogen Use Efficiency in a Maize–Wheat Rotation with or without Water Deficit">. When you are using urea (CO(NH2)2) as your nitrogen source microbes (and plants) with the <"urease enzyme convert urea to ammonia (NH3)"> and then that ammonia may escape to the atmosphere before being taken up by plants.

The conversion, via the <"urease enzyme">, possessed by plants and some microbes, is: (NH2)2CO + H2O urease→ CO2 + 2NH3. So two ammonia molecules for every urea molecule catalyzed.

By slowing the rate of ammonia production there is a greater probability that the <"fixed nitrogen"> (in all its forms) will be taken up by the crop plant.

cheers Darrel

 

[dw1305]

Hi all,

This textbook also describes in detail the rules for adsorption (CEC), not only on clays, but also ferric species, and organic matter. Then, it describes sorption on soil sorption complex, which consists of most abundant components of soils. An important note is that this complex's sorption capacity is greater that the sorption capacity of individual parts.

Probably the best I've got (and probably not as good as your Czech. reference) is:
<Nieder, R., Benbi, D.K. & Scherer, H.W. ((2011) Fixation and defixation of ammonium in soils: a review. Biol Fertil Soils 47, 1–14 . <"Fixation and defixation of ammonium in soils: a review - Biology and Fertility of Soils">.

Unfortunately it looks like we are back in to <"shades of grey">, with a lot of intersecting factors.

Method of fixation

.......... Ammonium fixation is greatest in 2:1 type clay minerals such as illite, vermiculite, and montmorillonite. Clay minerals possess negative charges balanced by cations, for example, NH+4 or K+. The physics of NH+4 is closely related to that of K+ because both ions have similar ionic radii and low hydration energy. ..... For both NH+4 and K+, the same mechanism is responsible for fixation and both fit exactly into the ditrigonal holes in the basal oxygen plane of 2:1 clay minerals. The penetration of both cations into the clay mineral interlayers causes the clay layers to collapse to 1 nm, and NH+4 and K+ ions are trapped between silicate sheets and largely withdrawn from exchange reactions (Nommik 1965). Therefore, both cations held in the interlayers of collapsed 2:1 clay minerals are said to be “fixed” and the term “fixed NH+4” was formerly used.....

Availability of fixed NH4+ to plants and microflora

........ With decreasing NH+4 concentration in soil solution, NH+4 ions diffuse from clay mineral interlayers. Therefore, factors such as fertilizer N application, plant cover, soil organic matter, microflora, clay content, and clay mineral composition that affect concentration of NH+4 in soil solution may promote either release or fixation of NH+4. Because of methodological limitations (such as proper separation of recently fixed NH+4 from native NH+4 f) and the involvement of several factors and processes influencing soil N dynamics, it is still difficult to describe the dynamics of fixed NH+4 especially under field conditions..........

I'll see what I can find for "Wet Paddy" Rice (Oryza sativa) as that is likely to be the closest analogy to aquarium substrates.

cheers Darrel

 

[dw1305]

Hi all,

I'll see what I can find for "Wet Paddy" Rice (Oryza sativa) as that is likely to be the closest analogy to aquarium substrates.

This one? <"https://acsess.onlinelibrary.wiley.com/doi/full/10.2136/sssaj2018.11.0436">.

....... The Nitrogen Soil Test for Rice (N-STaR, Oryza sativa L.) has been calibrated and is being used to predict rice nitrogen (N) fertilizer rates. ...........Seven soils representing five clayey and two loamy soil textures were collected from various rice-producing regions across Arkansas from the 0- to 15-cm and 15- to 30-cm soil depths. Total CF-NH4 and CF-NH4 recovered by N-STaR varied greatly across soils and soil depths with a range of 35 to 299 mg N kg soil–1 and 6 to 21 mg N kg soil–1, respectively. The N-STaR recovered as much as 15% of total CF-NH4 and recovery was greatest for silt loam soils. Alkaline hydrolyzable-N (AH-N) concentrations were strongly influenced by soil drying conditions and the alkali used with a higher level (22%) of AH-N recovered from oven-dry than field-moist soils and a higher (7%) recovery of AH-N with NaOH than KOH. These results indicate that the N-STaR method recovers a small, but significant percentage of total CF-NH4 and may capture the portion of CF-NH4 that may be plant available during the growing season......

cheers Darrel

 

[_Maq_]

cheers Darrel

Your ability to find out sources quickly is amazing. Me, I often keep some piece of info in my head, and when asked, I'm stuck with a desperate question where the hell have I read this?

 

[dw1305]

Hi all,

Your ability to find out sources quickly is amazing.

It isn't really me, it is just putting appropriate search terms into "Google Scholar".

In this case I know some bits via my "day job", and I know that there are some "rules" for CEC (and AEC). What I still don't know is how the bits fit together for aquarium substrates. I use 90% sand, but I don't tend to disturb it very much (although I have Malaysian Trumpet Snails (Melanoides tuberculata) so it is going to have some CEC, but I'm going to guess not very much etc.

The "problem" with Rice is that there is a huge amount of research, so you have to really refine your search term to winnow the grain from the chaff.

and when asked, I'm stuck with a desperate question where the hell have I read this?

I'm still like that, but now I've read / posted so much on UKAPS (since 2007 ish) that the chances are that its on the forum somewhere.

cheers Darrel