Ph fertilizing solution and calculation N

[Rick]

You have to understand that the water washing through does not tell you what the plant is consuming. It is probably the exact same, mineral/pH, etc., when you introduce the fertilizer as what is running out.

Leaf content analysis is the best way to tell you what the plant is consuming. And this may have much different values than what you are putting into the pot. But getting leaves analyzed is slow, relatively expensive, and you may run out of plant to analyze if its small.

However nutrient uptake is based a lot on environmental pH. So soil pH may be used as kind of a surrogate for understanding nutrient uptake. This is fast and cheap to do.

 

[Ray]

Leaf content analysis is the best way to tell you what the plant is consuming..

What the plant is consuming, yes. What the plant needs, no.

Plants have "pumps" that take in and store certain nutrients in the vacuoles, in case of a "rainy day", even if there is no deficit in the plant or its growing environment. If I remember correctly, phosphorus and boron, among others, fall in that category. So...a leaf tissue analysis will show you a greater level of those than the plant truly needs.

 

[Rick]

What the plant is consuming, yes. What the plant needs, no.

Plants have "pumps" that take in and store certain nutrients in the vacuoles, in case of a "rainy day", even if there is no deficit in the plant or its growing environment. If I remember correctly, phosphorus and boron, among others, fall in that category. So...a leaf tissue analysis will show you a greater level of those than the plant truly needs.

Potassium falls into this same category, but that is the point I've been advocating in several threads. In the case of K there generally is a scarcity in the environment so plants are super efficient at pumping K. If you supply lots of K, with reduced amounts of Ca and Mg, plants will have no control over the amount of K they uptake and end up with problems. With a normal low K high Ca/Mg environment plants have to "fight" for their K and much less prone to over dose. Same for bark/CHC substrates. When K is supplied without excess Ca, the "ion exchange" capacity of the bark is to expel divalent cations in favor of uptake of monovalent ions. I believe this is the basis of what people call "salt burn" or "old stale mix" that requires frequent replacement.

 

[Rick]

What the plant is consuming, yes. What the plant needs, no.

This is also perfectly true in that you compare what is in the leaves compared to a reference of good health (which includes the ability to withstand disease and add growths for multiple years). Also the point I have been making in several threads is that the nutrient priority of perennial rainforest plants from leaf analysis data is very different from what they can end up with in artificial culture.

The analogy is like looking at an obese individual, declaring that the optimal health norm, and saying that all human beings require high levels of sugar and fat in their diets.

 

[Ozpaph]

The method that Lance is recommending (collecting pot drippage) is pretty much what I've read from instructions from County extension agriculture services. So the method is standardized for many years in the general agricultural community. The more you deviate from it, the less you have directly comparable results to the wider community.

Do you have a link to the methodology and the results, please? I'd like to do it correctly.

 

[chrismende]

This thread is great, you guys! I'm just at the moment of realizing I want to really study this plant science! Go to school! Yee hah!

 

[Rick]

Do you have a link to the methodology and the results, please? I'd like to do it correctly.

It will take some digging since its awhile that I saw it. Locational memory tapering off since 50

May also have been a printed handout from a lecture with an Ag agent that's in our O society.

Also an AOS judge from the Atlanta center (David Mellard) (who works in waste water science like me) pieced together a similar methodology and published it in the general orchid press too (or maybe in the newsletter of one of the two Atlanta orchid societies:sob

I'll dig at this end. Try some google searches at your end too. I would expect lots of independent Australian agriculture activity going on too.

http://www.google.com/url?sa=t&sour...sg=AFQjCNFLqcd5wE-P6ih3GSlFIQiKiMZkug&cad=rja


Also try this link http://www.caes.uga.edu/publications/pubDetail.cfm?pk_id=7351#Testing


There's also a bunch of info from Bill Argo, and several of the links to Bill Argo documents refer back to Ray

 

[gonewild]

Leaf tissue analysis is way to complicated and expensive for hobby growers.

Leaf analysis is great if you know how to interpret the results. If not it can cause more confusion. You can't just have a test done and compare the results with a chart. There are no charts that would apply to the plants in your collection.

The chemical content of a healthy leaf growing under one set of conditions will greatly differ from the same plant growing under different conditions.
So to be able to utilize leaf analysis correctly you would need to make regular tests over an extended period of time, perhaps once a month for a year? That series of tests might establish a baseline level for the correct levels in leaf tissue. Then you could do further tests and compare the results to your baseline. Unless you do this relying on tissue analysis will give you a false perception of what fertilizer to use and when.

Even if you are able to determine by leaf analysis that your plants have an imbalance of nutrients in the tissues how many home growers have the equipment or knowledge to make the corrections without messing up the balance of another nutrient?

If a grower wants to rely on leaf tissue analysis to evaluate the plants health then they should also consider root and stem tissue analysis. Orchid growers don't need to go there unless you want to turn the orchid collection into a science project.

 

[Rick]

The chemical content of a healthy leaf growing under one set of conditions will greatly differ from the same plant growing under different conditions.

If a grower wants to rely on leaf tissue analysis to evaluate the plants health then they should also consider root and stem tissue analysis. Orchid growers don't need to go there unless you want to turn the orchid collection into a science project.

From going to both the commercial ag literature and rainforest research literature this is not true.

Whether you are looking at wheat/corn/mahogany/pecans/coffee/rice/sphagnum moss/kelp...the relative proportions of primary nutrients (and even many micronutrients is very similar in healthy plants, and not that variable under different growing conditions. What appears to be most variable is the definition of "healthy".

What has happened when plants go commercial is that the definition of "healthy" as become synonymous with "obese". And as it turns out with plants, being obese has as many inherent health issues as we see in humans. But with 50% of the US (human) population being overweight, society has redefined healthy as overweight, and high rates of conditions like diabetes and heart disease as normal.

Compared to commercial orchid production, large luxuriant glossy plants that last only 3 years are considered healthy, and conditions like Erwinia rots and rots after evening watering are considered normal.

Many of our jungle adventurers (included you Lance) have shown us many pictures of jungle plants that put our GH plants to shame. Most of these awesome specimen plants are probably older than the average length of time it takes most of us to kill plants in our GH's. Talking to experienced orchid judges it would seem that the bulk of plants that receive quality awards are dead after just a few years of getting awarded, and in review of awards records, the size of awarded flowers hasn't really got drastically better than for flowers of wild plants.

So I'm just not buying it that using commercial wheat production methods is the way to grow orchids.

 

[gonewild]

From going to both the commercial ag literature and rainforest research literature this is not true.

So I'm just not buying it that using commercial wheat production methods is the way to grow orchids.

In your first line you disagree with my point and in your last line you agree?

Without going to commercial ag literature I can tell you from my past experiences as an ag consultant (long ago) doing fertility tests and monitoring plant growth on a daily basis that there is a difference in the tissue content depending on growing conditions. I can't prove it with published literature but I know it. The difference may seem insignificant when looking at charts but if you live with and look closely at the plants you can see the difference as well. Just my opinion.

But putting that small difference aside I still don't think many home orchid growers can utilize the data from leaf tissue analysis to improve their plants health. It is just to difficult to interpret and react to.

Based on your last statement I think we agree completely?

 

[Rick]

I can understand the confusion.

"Wheat production" is my shorthand version of culture based on 6-8 month, seed to harvest growing strategy.

Pecan production is much more like orchid culture. Same plant year after year. Feeding for fruit/flower production and limited growth. Compared to wheat almost no fertilization is necessary.

What I'm finding surprising while digging through ag literature is that the basic leaf tissue nutrient levels are the same for healthy wheat as well as healthy pecans. The growing conditions are very different, but plants is plants, and the same chart for healthy wheat is really no different that the chart for healthy pecan trees for what to expect for healthy plants.

Tweaking for soil chemistries and adding nutrients is a site specific exercise, and generally a second set of analysis. This is where things really seem to get crazy and almost impossible to get "right" by use of a cohesive science.

It seems we go through endless exercises going from the bottom up for every growing condition possible, one nutrient at a time, while plants all seem to end up universally the same on a physiological basis. So in some ways leaf analysis is a "check" to see if you got your math right or measured the correct variables for the soil chemistry exercise. If the plant numbers aren't good then go back to the drawing board.

 

[Rick]

Maybe an example would help.

One of my first paphs was a blooming size lowii and got it in 2001/2002.

The plant put on 2-5 growths a year for the first four or so years and put out 2-3 spikes a year, often with 5 flowers per spike. I thought this plant was indestructible. How much healthier could it get?

After 5 years, it started loosing older leaves and growths to rot each time it tried to add a new growth. It also experienced some other non Erwinia type rots. It kept blooming, but on smaller and smaller growths. Couldn't keep descent roots on it no matter how frequently or the type of media it went into, or how much Pro tekt I poured on it.

It went from a peak of about 10 growths to 2 in 2-3 years. The last growth crapped out about a year or so ago.

Convention would say the plant succumbed to a variety of bacterial or fungal diseases. Looking back with newer knowledge I'm pretty sure went down in flames from potassium overdose.

I have plenty of other examples like it, and several plants in recovery mode as an alternative view from going down in flames.

I personally haven't got the leaf analysis thing going yet, but now would be a good time to get some baselines.

 

[Ray]

{This sort of discussion is precisely why I love this forum!}

A lot of this jives nicely with stuff Bill Argo shared with me. Specifically, he stated that tissue analysis aren't of THAT much value because they don't vary much, except in the cases of extreme deficiencies, making the results obvious.

I think the obesity-in-humans analogy may be headed in the right direction. I have no idea if it's a potassium issue specifically, but time and time again in animals, it has been found that while a "rich" diet certainly puts on the mass, it's a moderate one that leads to long-term health. So why not plants, too?

I grew my entire collection for years with Dyna-Gro "Grow" (7-9-5) at about 50 ppm N, and they grew well and flowered nicely. When I switched to the Greencare RO Orchid Special fertilizer (13-3-15) at 125 ppm N, I noticed much better growth and flowering - probably more overall mass of nutrients, coupled the the added Ca and Mg. After about 5 years though, I started to see a decrease in flowering. Don't forget I water fairly frequently, and have a lot of my plants in s/h pots with a reservoir, so am giving my plants a lot more "meals" than some.

About 9 months ago, I cut my feeding concentration to about 75-85 ppm N (same fertilizer) and I have had plants bloom that had not done so for a couple of years - lots of growths, few blossoms.

 

[Rick]

I think I'm getting frustrated looking at the system one variable at a time in a linear fashion while the true system is really a bunch of interconnected parts working in many directions. One week we look at N, then NPK, then Ca/Mg (as if they were independent of K), then pH, then TDS (as if this was separate from NPKCaMg), and then Silicates, and going back to N.:sob::sob:

Looking at the pH - bioavailability charts, the "optimal" pH for one nutrient is not the same as the for all the others. Nitrogen optimal pH also depends on the form of nitrogen (nitrates vs urea) you are using. K and Na doesn't care what pH it is!! and so it goes on.

I guess I'm thinking that leaf content has the potential to give you a holistic, big picture, of what the plant is experiencing. True it doesn't tell you how to fix it if it doesn't match a baseline data set, but tells you if the selected individual variables you are dinking with is getting in the right direction.

pH is also a holistic black box, but as noted above doesn't cover some key nutrients and antagonists.

The world is always looking for a simple, single unifying principle, but we ain't there yet for hobbiest orchid growing.

 

[gonewild]

Rick, I really like your ideas about potassium. Based simply on that one concept that varies from the normal thoughts, leaf analysis would not tell you much of value. True the leaf analysis will tell you if you have all the parts or not but it is not going to answer the question of whether there is too much or not enough for the particular plant you are growing. Like you said (I think you said it) any charts are going to have been done for commercial rapid growth (fat) and that is not likely the healthy growth rate desired for an orchid collection that should live for generations.

Most young living things require a huge diet of high protein content to grow fast enough to survive. But as the individuals mature their diet requirements change and normally become less in bulk and protein. Plants are not unlike animals in that requirement for long term survival.

Leaf analysis is far more useful for growing wheat than your pecans.
I think we are saying different things but we actually agree.

 

[Rick]

Leaf analysis is far more useful for growing wheat than your pecans.
I think we are saying different things but we actually agree.

Yes pretty close, but I looked up a Ag extension website for Georgia Pecan growers, and they really advocate the leaf analysis.

They have a whole protocol for selecting the right leaflet and comparison to baseline optimal concentrations.

Generally there is no fertilization for pecan groves, but management seems to revolve around what they called the "forage" plants growing under the trees.

This seemed to be more analagous to fertilizing by leaf litter composition levels of nutrients.