The poor through test .

[Masdyman]

I have been reading a article about feed(i think Atlantis orchid society ),ph etc it goes on about a pour through test to test the medium in which the orchid grows ,by which you feed your orchid ,leave it for 30 mins then pour 2 oz of distilled water through the pot .This water you then test the ph & EC , if the EC reading is less than 1 ms/cm which is 1000ms right ?then this is a sign the orchid isn't getting enough feed,Then you can feed at a higher strength for a while to get the EC higher in the medium .
If you feed at 125 ppm N then they recommend the EC should be between approx 1.5 -2.5ms/cm this seems high to me .The medium PH should also be between 5.8-6.2 for the majority of orchids.
I did this test and here are my results
My RO = PH 6.5 /12 microsiemens
feed strength =PH 6.2/620microsiemens
poured through water result = PH 6.5/120microsiemens

What do you think of this test ? going by the advise in this article , i can increase my feed strength but for my Masdevallias don't want to feed any higher than 75 ppm N(approx 620ms) @every watering which i have been doing .

[Masdyman]

Originally Posted by Masdyman

I have been reading a article about feed(i think Atlantis orchid society ),ph etc it goes on about a poor through test to test the medium in which the orchid grows ,by which you feed your orchid ,leave it for 30 mins then poor 2 oz of distilled water through the pot .This water you then test the ph & EC , if the EC reading is less than 1 ms/cm which is 1000ms right ?then this is a sign the orchid isn't getting enough feed,Then you can feed at a higher strength for a while to get the EC higher in the medium .
If you feed at 125 ppm N then they recommend the EC should be between approx 1.5 -2.5ms/cm this seems high to me .The medium PH should also be between 5.8-6.2 for the majority of orchids.
I did this test and here are my results
My RO = PH 6.5 /12 microsiemens
feed strength =PH 6.2/620microsiemens
poored through water result = PH 6.5/120microsiemens

What do you think of this test ? going by the advise in this article , i can increase my feed strength but for my Masdevallias don't want to feed any higher than 75 ppm N(approx 620ms) @every watering which i have been doing .

Is this one above your heads

[jrodpad]

It's "pour" through. Not "poor" through.

Unless of course, it is actually a poor test, in which case you wouldn't want to use it. I would imagine, though, that as long as you manage to pour in a manner that is not itself poor and you properly saturate each pore in the potting medium, the results should be pure.

Yes. Above my head.

[RosieC]

Sorry, over my head as well.

Ray might be your best bet to know/understand it.

[Masdyman]

Yes it is pour ,a obvious mistake i missed .
But reading my post you get what i mean.
With this being as American article thought it would be well known ,obviously not .

[Undergrounder]

Hi Masdy, i believe the article you're talking about is originally a Perdue university publication. At least the one i've read was.

First off, the idea that an EC of less than 1 is insufficient might only be true for fast growing herbaceous plants, and not orchids. I think the point was made in the article with other plants in mind. Orchids (and especially Masdies) are generally lighter feeders and suffer salt injuries more readily. If that orchid society quoted the article directly, they might have missed that point.

125ppm Nitrogen might equate to an EC of 1.5 - 2.5 once you add in the other nutrients - 125ppm of Potassium, Phosphorous, Magnesium, Calcium, etc. But it might not, that might be a question for Ray.

I can't remember how you're supposed to interpret the pour-through results as to whether they equate to the real levels in the root zone, or are just an indicator... if you're using nutrient feed with an EC of 0.62, it seems strange to me that the EC at the root zone is only 0.12.

I'd be interested to hear Ray or others' comments on this, because i'm having my own pH and EC battles at the moment and still trying to get me head around it. You're lucky you're using RO water, the tap water i get is very alkaline and reads at a pH of 8.0 straight out of the tap. It's then a battle to get the pH down while also keeping the TDS low.

[Ray]

You guys are giving me MUCH too much credit!

I won't claim to know much about the methodology, but the first thing that catches my eye is the EC. That value is going to vary with nutrient and water supply, isn't it? For example, with the MSU RO formula, the solution EC at 125 ppm N will be 1.0 mS/cm + whatever the water adds (presumably close to zero, as it's intended for pure water). For the Well Water formula, the fertilizer contribution will be 0.85.

Concerning the pour-through results - what does that tell us? I think the pH is significant, as it tells you about the complete root-zone environment, i.e., what impact your medium has on the conditions, and not just the fertilizer solution. (If you use inert media like LECA, your solution IS the primary factor.) What I'm less sure about is interpreting the EC of the poured-through solution.

It seems to me that it is really a measure of what is NOT trapped by the medium, which therefore would be what is available for the plant to absorb. If that interpretation is correct with no additional "Buts...", the Masdy's speculation about increasing the feeding strength seems reasonable. However, what I don't know is:

1. How do the plants react with the solution in the fully drenched medium immediately upon application of the solution? (Seems to me the solution itself is the primary environment at that point), and
2. Upon subsequent waterings, how much of the stashed-away chemistry can become redissolved and available for the plant to take up?

[Undergrounder]

Here's the article:

http://www.extension.purdue.edu/extm...O/HO-237-W.pdf

I didn't re-read it fully but i noticed they recommend using it to graph the trend of EC and pH over time, not so much as a one-off test.

And used in that way it seems more valid.

Make sure you're following the directions precisely, otherwise you could be diluting your final results..

[Masdyman]

My medium is CHC and i used plain RO @ PH 6.5 to do the pour through test ,the resulting water came out @ PH 6.5 also .I thought the two would have been different , and the EC would have been higher.Is the plain poured through water really going to grab enough from the medium to give you a accurate indication of EC ?
I don't know what to make out from this test and don't know how much orchids continue to grab from the medium after the initial application of solution .

[Masdyman]

These are the 3 articles i am referring to specific to orchids .

Resources