Culture document

[keithrs]

Ya I saw this article when I was looking at things in the past.

Actually if you look at table 3 it shows that as K goes up, Ca an Mg go down (and significantly) all those little ABC's off to the side denote which items in that column are statistically significant.

In table 3 they only show the lowest K at 100 ppm (for Phales) 50ppm for the other genera, so we are dealing pretty much with the old MSU data that looked at orchids already exposed to high K.

Note that the K is always higher than Ca/Mg This ain't like it is in the jungle, where K is lower than 5ppm and Ca higher than K

How about the fact that the Catt. had a dramatic reduction in growth as N went up and even more so on root production!

 

[keithrs]

The first several months of Low K I was still feeding N between 75 to 100ppm with K dropped down to around 20 ppm. And already seeing noticeable differences. Klite didn't come in til 9 or more months, and I started out at roughly 80 ppm N initially (at least for the spring summer months after it came out around December). I don't think I cut back to 30-50 ppm N until somewhere late summer (need to check when I started checking pot conductivity), and results were well under way by then.

Typically people cut back in winter by either cutting concentration, frequency, or both. Some don't feed at all for the entire winter season. During warmer months I'm pretty religious about weekly feeding. During winter if its snowy, cold and gray, it doesn't hurt my feelings to skip a week or two. This year I'm doing something a little different. I might make up a batch of Klite to feed at 50 or so ppm on Sunday. If the weather is crappy and cold, I might just water with maybe 5ppm N from the concentrate. I'm typically watering at least the mounted stuff daily, and give them daily shots at 5ppm(??) to use up the Sunday concentrate over the coarse of the week.

just to clarify... Thats weekly N fertilization?

 

[Rick]

just to clarify... Thats weekly N fertilization?

Yes, but as close as possible to weekly during winter/cold times. I really only have the weekends for feeding days, so if the sat/sunday is crappy, I skip the whole week typically. This winter a bit different with some very low rate feeding on the weekdays rather than skipping a whole week or two.

 

[Rick]

How about the fact that the Catt. had a dramatic reduction in growth as N went up and even more so on root production!

In some ways this paper is pretty crazy. If Ca was really 200ppm (as it eludes to in a couple vague statements besides the initial amount listed in methods) that's a hardness of almost 500!!!

This is very high TDS stuff they are playing with in general. Most of us wouldn't come close to subjecting our plants to high strength well water levels of Ca and Mg. So in general I'm not sure how relevant this paper is with regard for defining "proper levels" of feeding anything.

 

[Rick]

How about the fact that the Catt. had a dramatic reduction in growth as N went up and even more so on root production!

That only seemed to make a differnce for Catts. The sweet spot for the other two genera seemed to be 100 ppm N

But who grows orchids with 200 mg/L soluble Ca around?

 

[Stone]

What I see is the fact that (for Phals), persenatges of Ca went down a mere 0.37% in the leaf when the K was doubled and 0.73% when K was trebled.
Mg went down 0.05% and 0.13% respectively. K increased only just over 2% in the dry leaf from 5.77 to 7.92 when 3 times as much K was added.

With the Cym. K increased less than less than 1% (leaf content) from 2.48 to 3.31. Thats aprox. 30% increase at a K increase of 800%!
Ca decreased 0.88% of the dry leaf = 11% decrease at 800% K increase
Mg decreased 0.08% of the dry leaf = 20% decrease at 800% K increase. An no mention of deficiency symptoms and no effect on plant growth.

The point of this (the way I see it), is that slight variations of K up or down will have almost no antagonistic effect. For example if Klite had 4 times the K, you wouldn't notice. You need to add gigantic amounts of K before it starts making a nuisance of itself.

 

[Rick]

To put those numbers in parity with other studies multiply your percents by 10 to compare apples to apples. % by weight is 1/10th mg/g of material as a standard unit for most tissue sample designs.

Then everything doesn't seem quite so "mere". But the data also show that those "mere" percentages are statistically significant differences.

Then consider (again) that the amount of calcium in this system is 200 mg/L. When us folks using MSU in RO water at 100ppm N we have 100ppm K, but only 50 ppm Ca (inadequate to block excessive K uptake). This study (from 1978) buried the plants in calcium, which is something we've all been told is a no no.

I'm not surprised that an 8 month study didn't find significant growth issues with elevated K (with hybrids) with elevated Ca . (Actually leaf tip burn seems to be considered normal in this study, but included as another parameter to monitor). But on the flip side it also shows that elevating K doesn't get any benefits.

But this article definitely shows (and noted by its authors as significant) that orchids are capable of selectively picking up and sequestering K even when applied in conjunction of high concentrations of Ca.

 

[Rick]

Shifting numbers to compare to the Zotz work on wild Panamanian epiphytes (mg/g).

The Phaleanopsis from 100 to 300 ppm K additions (with 200 mg/L Ca)

went from potassium tissue values of 58 to 80mg/g (that's about a 25% increase in tissue K) while Ca dropped from ~32 to 24.3 mg/g (almost 30% drop)
The stats seem tight enough to pick off 15% drops in tissue Ca.

Also note that the highest tissue K in Zotz work is ~43mg/g (average of 16mg/g for orchids) in an environment where less than 1~4 ppm of K is readily available in the environment.

Also note that the average orchid in the wild contains more Ca than K, often twice the Ca than K (rather than 1/2 or less than K in high K grown plants).

Now what about jungle plants being bigger, no leaf tip burn, lasting for years, disease resistant........ All things panning out in many peoples collection since they dumped the K and ensured that Ca is higher than K (like in the Jungle where life is good).

 

[DavidCampen]

Also note that the average orchid in the wild contains more Ca than K, often twice the Ca than K (rather than 1/2 or less than K in high K grown plants).

Where did you get this data?

 

[Rick]

Where did you get this data?

Actually Stone supplied the Zotz 2004 article I referred to.

I have other articles on total nutrient flux in rainforrests, cumulative leaf litter concentrations, and leaf tissue composition for (non orchid) rain forrest plants. All pretty much the same basic trends.

I have an abstract (only) on tropical orchids in India which actually includes Paphs. I can't get hold of the whole paper, but the summary values are in the abstract which also show that K is less than Ca in wild Indian orchids.

 

[Stone]

I think what is really telling (unless its a typo) is that Ca was available at constantly 200ppm

That must be a typo! Why would you add Ca way above everything else??? 10 times more Ca than P? I don't think so. Must be 20ppm

 

[Rick]

That must be a typo! Why would you add Ca way above everything else??? 10 times more Ca than P? I don't think so. Must be 20ppm

Don't know I only saw the actual number documented once, but then there's a comment or two about using "high" Ca (and that would be more than 20ppm).

Some of the big primary orchid growers at the time were/are down in Florida. Especially places like Homestead and Plant City. Lots of old phosphate mines in those areas. Well water down there is super hard and may have up to 200ppm Ca. My well water in middle TN has Ca up to 170ppm the couple of times I've measured it. When the work was actually done (mid late 70's) I don't think a lot of people were concerned about RO or Rain water use. I doubt a giant commercial operation in Florida at the time could afford to use RO.


This copy was a reprint of the original 1978 publication. Maybe you could track it down?