Ca and Mg again

[gonewild]

It's cold and raining and I have too much time on my hands so here.....

http://www.falw.vu.nl/nl/Images/11 - heijden_tcm19-29530.pdf

One part.......

Perhaps the most important route by which free-living
microbes influence plant nutrient availability, and hence
plant productivity, is via processes of nutrient mineraliza-
tion, whereby soil microbes break down soluble and
insoluble organic matter and convert it into inorganic, plant
available forms. Most soil N (some 96–98%) is contained in
dead organic matter as complex insoluble polymers such as
proteins, nucleic acids and chitin, and these polymers are
broken down into dissolved organic N (DON) by extra-
cellular enzymes that are produced by soil microbes
(Schimel & Bennett 2004). This DON, which can constitute
a significant portion of the total soluble N pool, is either
absorbed by free-living soil microbes, or it is mineralized by
the microbial biomass (under conditions when microbial
growth is C limited), thereby liberating inorganic-N into the
soil environment. Alternatively, plants might take up DON
directly from soil, in the form of amino acids, thereby
by-passing the microbial mineralization step. This was
shown to be the case in many ecosystems, but especially in
those that are strongly N limited, such as in arctic This growing awareness of the ability
of plants to use organic N and compete with soil microbes
for N has led to a radical rethink of terrestrial N cycling and
especially the processes that control N availability to plants
(Schimel & Bennett 2004)

 

[gonewild]

and another....
http://omicsonline.org/nutritional-...n-into-plant-nutrients-2157-7471.1000e104.pdf

 

[Rick]

NH4 is strongly antagonistic to all cations and NO3. Urea is converted to NH4 within a couple of days so you can probably regard it as ammonium. Phal trial by Wang found best growth with 50/50 NO3/NH4 or higher NO3 up to about 75% I think.

Yes ammonium is antagonistic with all the cations, which MAY be why the Euro growers with high hardness water and high K fert where seeing as good
results with ammonia addition.

You are also correct about the conversion of urea to ammonia.

Ammonia also pushes the pH of the mix down way faster than with nitrate (mainly because of bacterial nitrification)

In general high N (especially with ammonia/urea as the base) just adds a lot of effort in pot management issues that could be avoided by just not fiddling with it.

 

[Stone]

Yes but as I have said several times each plant species have evolved in relationship with certain species of micro organisms.

Except for some (very few) which ascociate with a specific mycorrhiza and no other, most of the other organisms involved are universal so.....no!

Now finally you state that N fixing algae, bacteria and mycorrhiza are present in huge amounts in the pots. Why do you deny these organisms are absent in Nature?

Where did I say that

All three of these life forms provide N as living organisms not only on their death. They live and release N to plant roots constantly and this N does not show in soil or rainfall analysis reports.

Of course it does. With the possible exception from mycos which are mainly used for P anyway. (unless of course you can show me that these organisms live in symbiosis with the orchid and somehow transfer N DIRECTLY to plant without it becomming free first ....as in rhizobia or frankia species) Symbiotic organisms give and take.. give P, N etc....take sugar.
Free N fixing microbes use the N to grow then release it when they die, which could be a matter of hours, but it is released back into the environment.

 

[Stone]

It's cold and raining and I have too much time on my hands so here.....

http://www.falw.vu.nl/nl/Images/11 - heijden_tcm19-29530.pdf

One part.......

Perhaps the most important route by which free-living
microbes influence plant nutrient availability, and hence
plant productivity, is via processes of nutrient mineraliza-
tion, whereby soil microbes break down soluble and
insoluble organic matter and convert it into inorganic, plant
available forms. Most soil N (some 96–98%) is contained in
dead organic matter as complex insoluble polymers such as
proteins, nucleic acids and chitin, and these polymers are
broken down into dissolved organic N (DON) by extra-
cellular enzymes that are produced by soil microbes
(Schimel & Bennett 2004). This DON, which can constitute
a significant portion of the total soluble N pool, is either
absorbed by free-living soil microbes, or it is mineralized by
the microbial biomass (under conditions when microbial
growth is C limited), thereby liberating inorganic-N into the
soil environment. Alternatively, plants might take up DON
directly from soil, in the form of amino acids, thereby
by-passing the microbial mineralization step. This was
shown to be the case in many ecosystems, but especially in
those that are strongly N limited, such as in arctic This growing awareness of the ability
of plants to use organic N and compete with soil microbes
for N has led to a radical rethink of terrestrial N cycling and
especially the processes that control N availability to plants
(Schimel & Bennett 2004)

Yep thats all fine. And the point is?

 

[Stone]

Yes ammonium is antagonistic with all the cations, which MAY be why the Euro growers with high hardness water and high K fert where seeing as good
results with ammonia addition.

You are also correct about the conversion of urea to ammonia.

Ammonia also pushes the pH of the mix down way faster than with nitrate (mainly because of bacterial nitrification)

In general high N (especially with ammonia/urea as the base) just adds a lot of effort in pot management issues that could be avoided by just not fiddling with it.

You're not confusing NH3 with NH4 are you?

 

[gonewild]

Where did I say that

Go back and read what you wrote....

"There are huge amounts of a large variety of organisms in the pot, on the plant and in the roots including N fixing algae and bacteria and even mycorrhiza."

 

[Rick]

You're not confusing NH3 with NH4 are you?

The state of which is pH dependent. At the pH's ranges we work with in plants (<7.0) we work with 99% (at least) ionized NH4 (but measurement units in the lab are still NH3-N). From a math standpoint for calculation of application the difference is negligible.

Also of note is the high rate at which nitrifying bacteria convert ammonia to nitrate.

So like the case with urea (vs ammonia), only the fluid that immediately hits the roots (or leaves) gets the actual ammonia, while all the rest held in the potting mix gets converted to nitrate (most likely in less than a day in a nice dirty pot). So for the duration between feeding events the plant sees even more nitrate.

 

[Rick]

f those "groceries" a plant takes up:

This morning, I divided a vanda, and had 5 bare-root divisions. I measured their total root lengths, weighed them as-is, immersed them in 80°F water until the velamen was mostly transparent, and weight them again. On average, they weighed 101 g dry, 107 g "saturated", and had an average root length of 70".

So if I assume 10 waterings per month @ 3 ppm K, plus one at 25 (from the KelpMax), my plants are being exposed to something in the neighborhood of 5 ppm K on average. That 6 g of absorbed liquid, containing 5 ppm K, would carry 30 µg K. If it has absorbed that consistently over it's 10-year life, and has never lost any of it, then the plant should contain 10 years x 12 months x 10 waterings x 30 µg = 36 mg of K.

Ray
I think another component that should be accounted for in total mass balance uptake is direct foliar uptake. This looks to be a significant uptake mechanism in plants that may not need a lot of water to actually be transferred into the plant. This mechanism may also be biased to ammonia potassium and Mg(?)uptake. I also read that K attached to organics is sucked up through leaves more efficiently than as KNO3 (which still seemed pretty decent in a trial with turf grass).

I don't know about most folks, but I spray everything when I water/feed.

 

[Catt Mandu]

https://www.msu.edu/~warncke/E0486.pdf

Michigan State University seems to be pretty comfortable with the concept of K antagonism. Where's their proof or does MSU deal in pseudoscience?
(note this is a 1994 document, and K antagonism articles go back a lot farther than that)

They don't want to commit to any numbers except "do what you want as long as you don't go outside of the sufficiency standards"
(also note they use the term "toxicity" for exceeding the sufficiency standards at least once in this document)

The section on Mg is interesting in that they indicate that the soil equivalents of Mg must be equal or greater that of K and then Ca can be up to 10X greater than Mg.

The step I went beyond MSU was substituting the insitu (jungle) leaf tissue concentrations of NPK /Ca/ Mg for the agri-based sufficiency standards and extrapolating the eco-relevant concentrations of those nutrients into an application plan (that works).

Well, I read through the above article above on row crops, and while it does say K, Ca, and Mg should be in balance, and soil pH needs to be above 5 (there's the potential for numerous nutrient deficiencies at pH below 5), I am not seeing anything to support the ultra-low K idea.

So, where does this idea come from, that if you supply more than 10 ppm of K, adding Ca and Mg is a waste of time? Or that potassium will block the Ca and Mg uptake even if you add more Ca, for example?

Since we're talkin' row crops, let's see what the MSU folks recommend for fertilizers: http://fieldcrop.msu.edu/uploads/documents/E2904.pdf
It's a pretty common pattern; most crops, roughly equal N and K2O, much lower P2O5. The same article provides recommendations on Ca and Mg needs.

I have been hearing the low K story for a couple of years, and honestly, I don't see the logic in it. That said, do as you like! But, I do think it is reasonable that when a very specific claim is made (i.e., Ca and Mg supplementation is a waste of time if K supplementation is above 10 ppm), it is very reasonable to ask for some reputable proof (published science).

 

[Catt Mandu]

I agree that there's no need for the rudeness, Adam, but it can still be a fun mental exercise!

Lance - I have no doubt that ratios are important, but if I may extend your human analogy, a person in a grocery store isn't going to eat everything there.

Let's consider just how much of those "groceries" a plant takes up:

This morning, I divided a vanda, and had 5 bare-root divisions. I measured their total root lengths, weighed them as-is, immersed them in 80°F water until the velamen was mostly transparent, and weight them again. On average, they weighed 101 g dry, 107 g "saturated", and had an average root length of 70".

So if I assume 10 waterings per month @ 3 ppm K, plus one at 25 (from the KelpMax), my plants are being exposed to something in the neighborhood of 5 ppm K on average. That 6 g of absorbed liquid, containing 5 ppm K, would carry 30 µg K. If it has absorbed that consistently over it's 10-year life, and has never lost any of it, then the plant should contain 10 years x 12 months x 10 waterings x 30 µg = 36 mg of K.

If I take the dry mass of a plant to be 5% of its living mass, then the plant tissue analysis should show 36 x 20 = 720 mg/kg or 0.72 mg/g. With K being 0.0391 mg/mmol, then that would be 0.72/0.0391= 18.4 mmol/g dry weight.

How does that compare to the tissue analyses we've discussed? The only one I've grabbed (Marschner) shows sugar beets at 2.54.

Ray, a key problem with the above numerical exercise is assuming that the plant has never lost any of the K it has absorbed. This would be like me saying that over the course of 56 years, I have eaten an average of 2 eggs a week, 2 eggs x 52 weeks x 56 years = 5,824 eggs. At 2 ounces each, that's 11,648 ounces of eggs, or 728 pounds. You will just need to take it on faith that I don't weigh 728 pounds, and my mass does not consist entirely of egg. This is, of course, because I periodically "conduct a movement", getting rid of whatever nutrients I've processed, but no longer need.

Your Vanda does this too. Every time it drops a leaf, sheds an old root, jettisons some old plant stem or a spent bloom or flower spike, your Vanda is "debulking". It is well known that this is the manner by which plants get rid of wastes. As such, a calculation such as yours is missing an important "exit" for K to leave the system. There may also be other ways for K to leave the plant (for example, I have no idea if extrafloral nectar, produced by many orchids, contains any K, but it might).

 

[Rick]

So, where does this idea come from, that if you supply more than 10 ppm of K, adding Ca and Mg is a waste of time? Or that potassium will block the Ca and Mg uptake even if you add more Ca, for example?

The 10 ppm threshold is extrapolated from the work of Poole and Seeley (Cornell U. published back in 1978)

With a constant background of 200ppm Ca, applications of as low as 50 ppm K (in Cattleya and Cymbidium) and 100 ppm K (Phalaenopsis) were able to reduce Ca in leaf tissue. Progressive increase of K dose continued to decrease the Ca concentration in leaf tissue. As these were the lowest K doses tested, I had to extrapolate to get to a point where Ca was not antagonized as per insitu leaf tissue concentration values.

As far back as the Poole and Seeley paper was written, they recognized the phenomena as already well documented, and they reference work from 1954.

There's also documentation of this phenomenon by the Potash Institute.

 

[ALToronto]

The 10 ppm threshold is extrapolated from the work of Poole and Seeley (Cornell U. published back in 1978)

With a constant background of 200ppm Ca, applications of as low as 50 ppm K (in Cattleya and Cymbidium) and 100 ppm K (Phalaenopsis) were able to reduce Ca in leaf tissue. Progressive increase of K dose continued to decrease the Ca concentration in leaf tissue. As these were the lowest K doses tested, I had to extrapolate to get to a point where Ca was not antagonized as per insitu leaf tissue concentration values.

As far back as the Poole and Seeley paper was written, they recognized the phenomena as already well documented, and they reference work from 1954.

There's also documentation of this phenomenon by the Potash Institute.

So was this an extrapolation based on a mathematical model (usually some exponential relationship) or a simple straight line? Straight line would be most certainly wrong, and even a model well fitted to relatively high K experimental data would have a very large confidence interval at a point so far removed from the sample space.

Most often when scientists have to hold their noses and do statistics, they use the lognormal distribution to model data - the most overused statistical distribution, very easy to fit, and very inaccurate at either tail. I would not take an extrapolated value too seriously.

 

[DavidCampen]

The 10 ppm threshold is extrapolated from the work of Poole and Seeley (Cornell U. published back in 1978)

With a constant background of 200ppm Ca, applications of as low as 50 ppm K (in Cattleya and Cymbidium) and 100 ppm K (Phalaenopsis) were able to reduce Ca in leaf tissue. Progressive increase of K dose continued to decrease the Ca concentration in leaf tissue. As these were the lowest K doses tested, I had to extrapolate to get to a point where Ca was not antagonized as per insitu leaf tissue concentration values.

When you reference a paper it is generally considered to be proper to supply enough information so that another person can easily locate the paper.
Is this the Poole and Seeley paper you are referencing:
http://www.firetailorchids.com.au/_pdfs/poole_and_seeley.pdf

That paper does not support any of the claims you made above.

There's also documentation of this phenomenon by the Potash Institute.

Again, with no reference to the actual document this statement is worthless. Most likely is that it does not support your claims.

 

[Catt Mandu]

The 10 ppm threshold is extrapolated from the work of Poole and Seeley (Cornell U. published back in 1978)

With a constant background of 200ppm Ca, applications of as low as 50 ppm K (in Cattleya and Cymbidium) and 100 ppm K (Phalaenopsis) were able to reduce Ca in leaf tissue. Progressive increase of K dose continued to decrease the Ca concentration in leaf tissue. As these were the lowest K doses tested, I had to extrapolate to get to a point where Ca was not antagonized as per insitu leaf tissue concentration values.

[snip by Catt Mandu here]

I'm assuming the reference supplied by David is the Poole and Seeley paper that you were referring to (BTW, thanks David). If not, please provide the reference.

So, using the same kind of logic, and doing the same type of extrapolation, would you conclude from Poole and Seeley's Table 2 that nitrogen is antagonizing all of the other plant macronutrients in Cattleya and Phalaenopsis? Is the conclusion that we should stop providing N because it is causing deficiencies in the other macronutrients? IMO, clearly not. Nor is the data indicating that if you provide more of the other macronutrients, the plants will not respond to the nutrient increase.

Note also in Table 2 the leaf concentrations of K relative to N and P. K is consistently the higher of the three nutrients in the leaves (percentages in the order K > N > P).

What makes the most sense, IMO, is to provide nutrients in roughly balanced proportions to plant requirements. If you provide adequate supplies of N, P, K, Ca, Mg, and S, the plant will sort out what it needs. Add in the micronutrients if you are using a mineral-deficient water source. Also, adjust pH so that plants can utilize the nutrients you are providing.

 

[Rick]

So was this an extrapolation based on a mathematical model (usually some exponential relationship) or a simple straight line? Straight line would be most certainly wrong, and even a model well fitted to relatively high K experimental data would have a very large confidence interval at a point so far removed from the sample space.

No not completely based on math (and correct its not linear), but also considering insitu data. I have not found any literature indicating that solutes in the orchid environment are greater than ~10ppm. Generally less than 5 ppm.

Has anyone else located data indicating that orchids get applications of NPK at K concentrations >50ppm or even 25ppm?

 

[Rick]

I
Note also in Table 2 the leaf concentrations of K relative to N and P. K is consistently the higher of the three nutrients in the leaves (percentages in the order K > N > P).

Also note Table 3 when N was held constant and only K manipulated.

 

[gonewild]

Has anyone else located data indicating that orchids get applications of NPK at K concentrations >50ppm or even 25ppm?

I have some personally collected data I'll post later today or tonight that will help answer that question.

 

[Ray]

Catt Mandu - I agree 100% that there are losses (you should see my greenhouse floor every spring!). My point with the math was to show the very low amounts that we are applying.

We have done a lot of discussion of fertilizer concentrations and ratios, but very little in terms of mass actually absorbed by the plant. I was merely trying to bring that into the discussion, even with a great many "outrageous" assumptions.

 

[Rick]

What makes the most sense, IMO, is to provide nutrients in roughly balanced proportions to plant requirements. If you provide adequate supplies of N, P, K, Ca, Mg, and S, the plant will sort out what it needs. Add in the micronutrients if you are using a mineral-deficient water source. Also, adjust pH so that plants can utilize the nutrients you are providing.

That certainly is the mainstream hobby practice that I followed for years and got mainstream hobby results (which for me were merely adequate and limiting).

Dario is certainly free to stay within mainstream practices and should expect at least that level of satisfaction.