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Adding magnesium sulphate or calcium nitrate to the soaking water makes all the difference. It replaces the sodium and potassium on the fibres. It's all to do with the high cation exchange capacity of CHC. The sites on the CHC fibres are very unlikely to be left empty by soaking, they need to have an ion attached, so replacing with one that you want is the best method. Eventually drenching with fertiliser solutions when watering will do it, but the roots may sulk a bit until the levels come down.

I use epsom salts in my fertilizer. Thanks.
 
I use epsom salts in my fertilizer. Thanks.

But do you add enough epsom salts to conteract the potassium in your fertilizer?

Chances are the CHC is sucking up the bulk of K from your fertilizer rather than the orchid. (Unless its a big plant in a small pot on a warm sunny day).

For instance MSU for RO water has 3-4 times the amount of K than Mg. If you don't have enough Mg (or Ca) to conteract the K then the K will end up replacing all the Mg you origionally used to get the K out of the CHC in the first place.

This is the reason why I'm looking at going to a low potassium fertilizer (like blood meal).
 
Rick, are there any low-potassium commercial formulations or brands you've identified in your research so far?
 
...If you don't have enough Mg (or Ca) to conteract the K then the K will end up replacing all the Mg you origionally used to get the K out of the CHC in the first place....

i don't understand much of the chemistry involved but i thought that if Ca and Mg (and possibly K) didn't appear at a certain ratio, they would be antagonistic and unavailable.
 
Rick, are there any low-potassium commercial formulations or brands you've identified in your research so far?


I just found out that plain old Miracle Grow is 30 10 10. So 1/2 strength would be 15 5 5

Blood meal (according to Wikipedia) is something like 15 <1 <1
 
i don't understand much of the chemistry involved but i thought that if Ca and Mg (and possibly K) didn't appear at a certain ratio, they would be antagonistic and unavailable.

Can't just say "yes". There are bio factors and chemical / ion exchange factors.

From the standpoint of ion exchange factors in potting mixes, there is a priority of selectivity. Generally the potting mixes want to take in the monovalents and give up the divalents. In order to drive it the other way you need to have more divalents available. If you present a 50/50 mix of divalents and monovalents, there will be a selection to take up the monovalents until the concentration of divalents is high enough to produce enough ionic or charge "pull" on the media to balance or reverse the selection process.

From the plant bio process there are two (at least two) basic systems, which are not mutually exclusive. One is ion uptake and the other is various metabolic processes. The requirements for correct ion ratios to avoid antagonism is probably more important from the standpoint of intracellular metabolic requirements. Ion uptake can be both passive and active, which means that environmental ratios of ions can be overcome for specific metabolic needs.

In the environment available K is relatively rare, especially for orchids living on limestone cliffs and up in trees. But if you analyze leaf content for minerals, there is more K than either Ca or Mg. If you look at marine kelp, it has more tissue K than Ca and Mg, but sea water has more Mg than Ca and K. K is actively selected and pumped into plant cells from inherently low concentrations (especially compared to the normal environmental amounts of Ca and Mg). My present hypothesis is that orchids, coming from nutrient impoverished environments, are very efficient at K uptake, but do not have the metabolic hardware to deal with excesses (i.e they can't turn off the pumps easily). And over the course of a year using balanced fertilizer mixes in bark or CHC substrates, you can quickly end up providing an environment with an excess of available K.

Most fertilizers were developed based on testing of common agriculture plants (which are very fast growing compared to orchids) and are harvested to varying extents. Looking at the agriculture litterature its interesting to note that the K consumption (not leaf concentration) of corn (temperate plant completely harvested to the ground every year) is many times greater than for coffee (a tropical plant with only the fruit harvested regularly), but if you analyze tissue, the concentration of K is about the same for the 2 plants.

Corn and wheat will reduce soil K to extremely low levels so during the growth season you need to add a ton of K, but coffee growers don't throw nearly as much K to their plants as corn growers do. And I think orchid growers should use even less.

Orchids in generally grow even slower than coffee and generally don't have a harvestable commodity (except for periodic big floral spikes). The big multis can put a lot of K into new tissue growth during the growing season, but smaller compact species probably can't handle nearly as much. There's not much growth in the winter, but how much do you cut back fertilizer in the winter, building up K in your potting mix?

This post is really starting to ramble, but my short answer is that no, the uptake of nutrients is not passive and even from a solution of ions at set ratios.
 
I just found out that plain old Miracle Grow is 30 10 10. So 1/2 strength would be 15 5 5

Blood meal (according to Wikipedia) is something like 15 <1 <1

Correct me if I'm wrong but the numbers are just ratios eg one third = 2 sixths. Dilution changes the concentration but the ratio is the same. In the numbers above it could be written 3.1.1 but that wouldn't look good from the advertising perspective even though its the same.
 
Correct me if I'm wrong but the numbers are just ratios eg one third = 2 sixths. Dilution changes the concentration but the ratio is the same. In the numbers above it could be written 3.1.1 but that wouldn't look good from the advertising perspective even though its the same.

I may need correction, but I thought that those numbers represent formula % by weight.

Yes those ratios would reduce down as you point out but I don't think the fert manufacturers scale up with the values just for marketing reasons. The vast bulk of fertilizer is designed and sold to agribusiness that purchases (without much emotion), and the concentration numbers are critical for calculating application rates to large areas.
 
I may need correction, but I thought that those numbers represent formula % by weight.

Yes those ratios would reduce down....


i think the ratios stay constant
a 100 ppm N solution of 20-10-20 is only different than a 200 ppm N of 20-10-20 solution in that it is half as strong, right?
 
i think the ratios stay constant
a 100 ppm N solution of 20-10-20 is only different than a 200 ppm N of 20-10-20 solution in that it is half as strong, right?

That is true but to come up with 100 ppm or 200 ppm you are calculating your dose (i.e tsp/gal) based on a dry formula that contains 20% by weight nitrogen.

So in the case of Miracle Grow 30 10 10 if recommended dose is 1tsp per gal to get 100 ppm of nitrogen, I was backhandedly indicating that if you use it at 1/2 rate of recommended dose you would be using it as if it was 15 5 5 . This was to compare to the MSU I use which is 12 6 13 with a suggested use rate of 1/2 tsp per gal (which I think targets around 200 ppm N).

The NPK fertilizer values should be usable to calculate the dose required to achieve final application target concentrations of NPK.

We've ran these calculations on other threads in the past, so may need to look up some of these for checking.
 
looking up the label on the Robert's pure water MSU fert (12 6 13), it is 12% by weight N, 6% by weight phosphate (not elemental P) 13% potash (not elemental K)

The NPK values are actual product concentrations and not simple ratios.

Recommended dose is 1/2 teaspon, which I'm pretty sure is shooting for about 200 mg/L nitrogen.
 
looking up the label on the Robert's pure water MSU fert (12 6 13), it is 12% by weight N, 6% by weight phosphate (not elemental P) 13% potash (not elemental K)

The NPK values are actual product concentrations and not simple ratios.

Recommended dose is 1/2 teaspon, which I'm pretty sure is shooting for about 200 mg/L nitrogen.

I think we are both right. They are both a ratio and by standardisation, become a concentration. See if this makes sense -
The addition of the percentage sign means its a ratio (percent = 'out of 100')- by weight in this case. It becomes a concentration when a specified amount of ingredient is included in a specific amount/volume/weight of product or when specified amount of product is added to a specified amount of water.(I assume there is a standardised weight for fertilizer quoted ratios (which means I can't divide down the ratio)).ie N = 12gram% or 12 grams per 100 grams of total product. In the Roberts the 12+6+13 = 31g of active ingredient in 100g product (if grams% is the standard)
So, in this example, if you add 1/2 teaspoon or 20 teaspoons to a gallon/litre the ratio of the elements is the same - 12 6 13, but the concentrations are different. By specifying the amount to use a concentration can be determined.
A bit like adding cordial to water. It depends on how concentrated the cordial is to determine the amount of water you need to add to taste. But an assumed standard (??? grams% weight) gives the ratio a concentration.

This link is interesting - www.kr5e.com/fertilizer.doc
 
I think we are both right. They are both a ratio and by standardisation, become a concentration. See if this makes sense -
The addition of the percentage sign means its a ratio (percent = 'out of 100')- by weight in this case. It becomes a concentration when a specified amount of ingredient is included in a specific amount/volume/weight of product or when specified amount of product is added to a specified amount of water.(I assume there is a standardised weight for fertilizer quoted ratios (which means I can't divide down the ratio)).ie N = 12gram% or 12 grams per 100 grams of total product. In the Roberts the 12+6+13 = 31g of active ingredient in 100g product (if grams% is the standard)
So, in this example, if you add 1/2 teaspoon or 20 teaspoons to a gallon/litre the ratio of the elements is the same - 12 6 13, but the concentrations are different. By specifying the amount to use a concentration can be determined.
A bit like adding cordial to water. It depends on how concentrated the cordial is to determine the amount of water you need to add to taste. But an assumed standard (??? grams% weight) gives the ratio a concentration.

This link is interesting - www.kr5e.com/fertilizer.doc

Getting closer. % is a unit-less ratio until you specify (in this case % product by weight). So 1% is 1 gram for every 100 grams or 10 grams per Kilogram. You could switch to oz and pounds if you like, and ultimately we convert to english volume measures (tsp/gal) since most of us don't keep a balance in our kitchen.

And yes you need a final concentration target (usually 200 mg/L or ppm N).

Typically all the conversions are done for us and end up on the bag at the prescribed usage rate (anything from 1/2 to 1 tsp/gal is common). Which is the general basis most orchid growers end up communicating to each other by.

So if most of us hobbyists are using a 200mg/L N target and using fertilizers at the recommended dose rate of 1/2 tsp per gallon, then the NPK ratios are meaningful to compare both ratio and total dose of those constituents.

Also the portion after the cumulative %NPK is not inert as you implied above.

The rest of the material (after NPK) will contain all the other ions (like the sodium, calcium, magnesium, sulfate, chloride...., and trace materials.
 
Also the portion after the cumulative %NPK is not inert as you implied above.

The rest of the material (after NPK) will contain all the other ions (like the sodium, calcium, magnesium, sulfate, chloride...., and trace materials.


This point is the crux of this thread.

Trying to get the right balance of K, Ca, and Mg with your irrigation water, and the ion exchange/adsorption characteristics of your potting mix (in this case CHC)
 
Getting closer. % is a unit-less ratio until you specify (in this case % product by weight). So 1% is 1 gram for every 100 grams or 10 grams per Kilogram. You could switch to oz and pounds if you like, and ultimately we convert to english volume measures (tsp/gal) since most of us don't keep a balance in our kitchen.

And yes you need a final concentration target (usually 200 mg/L or ppm N).

Typically all the conversions are done for us and end up on the bag at the prescribed usage rate (anything from 1/2 to 1 tsp/gal is common). Which is the general basis most orchid growers end up communicating to each other by.

So if most of us hobbyists are using a 200mg/L N target and using fertilizers at the recommended dose rate of 1/2 tsp per gallon, then the NPK ratios are meaningful to compare both ratio and total dose of those constituents.

Also the portion after the cumulative %NPK is not inert as you implied above.

The rest of the material (after NPK) will contain all the other ions (like the sodium, calcium, magnesium, sulfate, chloride...., and trace materials.

Yes, agree.
Inert's probably not what I meant. ?? not the active constituent?? not what we're paying for??not biologically relevant.....or my favourite "other stuff"!
The trace elements are important. Do you know if they are actively added (aside from Mg/Ca etc. Like Br, Cu etc) or 'contaminants'/by products of impure raw ingredients??

What did you think of that link suggesting 125ppm for N?
 
Yes, agree.
Inert's probably not what I meant. ?? not the active constituent?? not what we're paying for??not biologically relevant.....or my favourite "other stuff"!
The trace elements are important. Do you know if they are actively added (aside from Mg/Ca etc. Like Br, Cu etc) or 'contaminants'/by products of impure raw ingredients??

What did you think of that link suggesting 125ppm for N?

Several fertilizer brands do purposely add trace elements. The link you posted specifically mentions the MSU fertilizer formula that does include trace elements (on purpose). I know David Mellard. He's kind of in the same line of business as I'm in, and knows his orchids, water, and chemistry. I think 125 mg/L is just fine. I think the semi hydro system uses chronic low doses less than half of that. I also know a few growers that never use fertilizer at all, and grow great stuff just using their local drinking water.

I also think its dangerous for our orchids to focus on a single parameter (like nitrogen) without considering the interactions of light, temp, humidity, potting mix chemistry, and the rest of the nutritional factors.

Your best bet for good results is to find somebody that is getting the results you want with the plants that you like, and then replicate what they are doing for all the above parameters. With more experience, you can start to dissect your program and see what parts could stand improvement, and gather information to custom tailor your own program for optimization.
 
Your best bet for good results is to find somebody that is getting the results you want with the plants that you like, and then replicate what they are doing for all the above parameters. With more experience, you can start to dissect your program and see what parts could stand improvement, and gather information to custom tailor your own program for optimization.

Absolutely!
I've learnt more by visiting other growers orchid houses and taking in the 'environment' and asking questions, than from most books. Hands on learning is so helpful. The trick is tweaking things to suit your own conditions. Its so much harder than it looks.
 
Absolutely!
I've learnt more by visiting other growers orchid houses and taking in the 'environment' and asking questions, than from most books. Hands on learning is so helpful. The trick is tweaking things to suit your own conditions. Its so much harder than it looks.

Yup

That's why these threads get so long, convoluted, and contentious.
 

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