Salts from fertilisers

[Ray]

@Ray Do you prefer that users create new threads for the same related topic if the original thread is over "x" amount of years old? I would think it's better to keep the discussion in the same thread if it's about the same material or in direct reference to a previous post. In this way, the context is not lost and there aren't 24 new threads relating to the accumulation of salts (an exaggeration but you get my point); too many threads lead to difficulties in finding content relating to the same theme. I'm not saying this to be catty but I know you have your reasons and I genuinely don't know what they are.

I don't care one way or another and don't think that's a moderator's job, I was just pointing it out in case you hadn't noticed it and would be waiting for his response.

If a medium traps and holds mineral ions is it a good thing or a bad thing?
Assumption 1: If it traps and holds ions ( like a filter membrane ) then I would think the solution the plants receive isn't as mineral-heavy as it otherwise would be and becomes a benefit; I think this is what Dave @Paph Paradise would say about Charcoal. If this assumption is true then the salt would have to travel deep enough into the particle of media to minimize physical contact with a root.
Assumption 2: If the medium traps more and more ions and thereby releases more and more ions into the solution then one would assume something like Charcoal would be a detriment to the plant.

I don't think that's a constant. Fresh medium = rapid absorption and "sequestration", but as it ages, the accumulation is greater so can be detrimental.

What's worse too high of TDS or too low in fertilizer?
Not letting the media dry out seems to go well with the semi-hydro approach but that also means flushing I would think is critical if the roots are constantly soaking up a solution with a high TDS. The common sense response would be to fertilize less if you're using a mineral-high tap or well water but the potential consequence is the plant not getting enough of some critical nutrients like Nitrogen.

The plants have evolved with pretty low mineral concentrations, so I think that's preferred, but I also think every grower needs to find a balance and to consider his or her own situation.

When I had a greenhouse and fertilizer was metered into all my water, it was a constant 25 ppm N at every watering for all plants, no matter how they were grown, and that could be as often as daily in the heat of late summer. Bare-root vandas were watered more frequently than were potted plants.

Now that I have no greenhouse, I feed at 100 ppm N weekly, sometimes watering with plain water in between.

I think lower TDS is advisable, but I also don't think the typical grower has any idea what defines "low" or "high". For example, a 100 ppm N MSURO solution has a TDS of 740 ppm when mixed with pure water. Folks I've spoken to practically crap their plants when they hear that, thinking it's damagingly high.

 

[Russ1992]

I don't think that's a constant. Fresh medium = rapid absorption and "sequestration", but as it ages, the accumulation is greater so can be detrimental.

You mean you don't think those two assumptions regarding media are mutually exclusive?

Thank you for your other responses.

 

[Ray]

You mean you don't think those two assumptions regarding media are mutually exclusive?

On the assumption I am understanding your question correctly, no, they are not mutually exclusive.

A particle with a lot of absorption typically has a lot of very fine pores and cracks into which the liquid penetrate. As the solvent (water in this case) evaporates, it does so from the surface, effectively concentrating the remaining solution deeper and deeper into those crevices. Eventually, when it's dry, there will be a gradient from the concentrated "core" to the relatively solute-free surface. At that point, especially considering the truly low concentrations of the solutions we apply, the particles essentially keep the excess salts away from root access. Over time, however, the accumulated salts within the particles reach a higher concentration at the surface, where they can become damaging.

It seems to me that if you want to avoid all these problems, one should either go to ebb and flow tables or use a medium that does not absorb anything - my first thought was glass marbles, but I have recently been in contact with a German grower using styrofoam stips for his paphs. Then, you get to control exactly what the plant gets through the combination of concentration and frequency of application.

 

[Kinabalu]

What's worse too high of TDS or too low in fertilizer?
Not letting the media dry out seems to go well with the semi-hydro approach but that also means flushing I would think is critical if the roots are constantly soaking up a solution with a high TDS. The common sense response would be to fertilize less if you're using a mineral-high tap or well water but the potential consequence is the plant not getting enough of some critical nutrients like Nitrogen.

I believe generally around 100 ppm of N is recommended for Paphs, which is a good recommendation. Sometimes that is extrapolated to 100 ppm total per week however, which honestly doesn't make much sense because the plants have no idea what a week is...

If you keep diluting the fertilizer a lot then the plant can struggle to absorb certain nutrients, for instance the micronutrients which were already micro would then be "micro micro." That is important to remember with something like molybodenum which Paphs can struggle to absorb at regular concentrations. Also there is osmosis issues so the plant cannot just absorb all the nutrients from the soil without causing some stress, so it makes the plants life easier when there is more available nutrients to pick and choose. Ideally just fertilize at .5 EC heavily every watering with something like a jacks 10-30-20 (equal ammonium and nitrate) and that should keep the soil EC from fluctuating too much. Unless your media is very compacted or not watering frequently enough, then the concept is like pouring new coffee into a cup of old - the cup overflows but it is still the same coffee. The plants like the consistency.

The more important issue than EC is PH which changes very quickly and easily depending on the fertilizer and media. Inorganic medias are often less PH buffered, with the MSU types they often raise the PH to 7 in the soil after a day or two, this could be one reason why many growers dilute MSU or flush with pure water so often. I would strongly recommend investing in a middle range PH meter and always keeping an eye on the soil PH - you want around 5.5

 

[Russ1992]

On the assumption I am understanding your question correctly, no, they are not mutually exclusive.

A particle with a lot of absorption typically has a lot of very fine pores and cracks into which the liquid penetrate. As the solvent (water in this case) evaporates, it does so from the surface, effectively concentrating the remaining solution deeper and deeper into those crevices. Eventually, when it's dry, there will be a gradient from the concentrated "core" to the relatively solute-free surface. At that point, especially considering the truly low concentrations of the solutions we apply, the particles essentially keep the excess salts away from root access. Over time, however, the accumulated salts within the particles reach a higher concentration at the surface, where they can become damaging.

It seems to me that if you want to avoid all these problems, one should either go to ebb and flow tables or use a medium that does not absorb anything - my first thought was glass marbles, but I have recently been in contact with a German grower using styrofoam stips for his paphs. Then, you get to control exactly what the plant gets through the combination of concentration and frequency of application.

Oh wow Ray nobody has ever made this so clear. That makes total sense, thanks man!

Regarding glass marbles it would be a fun experiment for sure. I have had issues with semi hydro every time, but honestly I think I was just fertilizing too much and not flushing thoroughly or frequently enough. So giving it another go makes sense.

 

[Russ1992]

I believe generally around 100 ppm of N is recommended for Paphs, which is a good recommendation. Sometimes that is extrapolated to 100 ppm total per week however, which honestly doesn't make much sense because the plants have no idea what a week is...

If you keep diluting the fertilizer a lot then the plant can struggle to absorb certain nutrients, for instance the micronutrients which were already micro would then be "micro micro." That is important to remember with something like molybodenum which Paphs can struggle to absorb at regular concentrations. Also there is osmosis issues so the plant cannot just absorb all the nutrients from the soil without causing some stress, so it makes the plants life easier when there is more available nutrients to pick and choose. Ideally just fertilize at .5 EC heavily every watering with something like a jacks 10-30-20 (equal ammonium and nitrate) and that should keep the soil EC from fluctuating too much. Unless your media is very compacted or not watering frequently enough, then the concept is like pouring new coffee into a cup of old - the cup overflows but it is still the same coffee. The plants like the consistency.

The more important issue than EC is PH which changes very quickly and easily depending on the fertilizer and media. Inorganic medias are often less PH buffered, with the MSU types they often raise the PH to 7 in the soil after a day or two, this could be one reason why many growers dilute MSU or flush with pure water so often. I would strongly recommend investing in a middle range PH meter and always keeping an eye on the soil PH - you want around 5.5

Regarding MSU I thought most fertilizers acidify the potting mix over time just like how they lower the PH when you add them to water no? Maybe this depends on the specific ions involved in the ferts at different ratios/concentrations.

Regarding EC I'm uninformed on the topic so will need to research it.

There are plenty of good nuggets in here so thank you for that. What would you say is a good middle-range PH meter?

 

[Ray]

I believe generally around 100 ppm of N is recommended for Paphs, which is a good recommendation. Sometimes that is extrapolated to 100 ppm total per week however, which honestly doesn't make much sense because the plants have no idea what a week is...

Part of the issue is that we don't know the true rate and volume of uptake.

Taking my "bare-root vanda" example again, where the amount of fertilizer solution absorbed is limited to whatever the velamen holds after being saturated, then a single, 100 ppm N treatment should give the plant the same amount of nutrition as 4 treatments at 25 ppm N.

That gets more complicated when we add a liquid-holding component to the potting medium, as that increases the time the roots can be exposed to any applied nutrient solution - if they are in contact with it.

Then there's that "minor detail" factor, time. Once in contact with a nutrient solution, how long does it take for the plant to draw it into its vasculum and start distributing it to its tissues? If it was instantaneous, life would be far easier in this regard, but it's not. Is it hours? Days?

If you keep diluting the fertilizer a lot then the plant can struggle to absorb certain nutrients, for instance the micronutrients which were already micro would then be "micro micro." That is important to remember with something like molybodenum which Paphs can struggle to absorb at regular concentrations. Also there is osmosis issues so the plant cannot just absorb all the nutrients from the soil without causing some stress, so it makes the plants life easier when there is more available nutrients to pick and choose. Ideally just fertilize at .5 EC heavily every watering with something like a jacks 10-30-20 (equal ammonium and nitrate) and that should keep the soil EC from fluctuating too much. Unless your media is very compacted or not watering frequently enough, then the concept is like pouring new coffee into a cup of old - the cup overflows but it is still the same coffee. The plants like the consistency.

Unless taken to extreme, I don't see dilution as much of an issue. Most of those trace elements are routinely recycled within the plant, making the replenishment demand very low. There is an excellent grower I know who feeds calcium nitrate most of the time, an NPK blend quarterly, and only uses STEM (trace elements) once a year.

The more important issue than EC is PH which changes very quickly and easily depending on the fertilizer and media. Inorganic medias are often less PH buffered, with the MSU types they often raise the PH to 7 in the soil after a day or two, this could be one reason why many growers dilute MSU or flush with pure water so often. I would strongly recommend investing in a middle range PH meter and always keeping an eye on the soil PH - you want around 5.5

When I was first experimenting with S/H culture, using essentially inert LECA as a medium, I very carefully adjusted the solution pH to 5.5. I was stunned to see how widely and quickly the pH in the reservoir could change, going as low as 3.5 and as high as 7.5, depending upon time of day and time since application.

 

[Russ1992]

When I had a greenhouse and fertilizer was metered into all my water, it was a constant 25 ppm N at every watering for all plants, no matter how they were grown, and that could be as often as daily in the heat of late summer. Bare-root vandas were watered more frequently than were potted plants.

Now that I have no greenhouse, I feed at 100 ppm N weekly, sometimes watering with plain water in between.

Ray, are your plants just as happy getting 100 ppm N weekly as they were getting say 25 ppm N four times a week in the past? I would expect plants to do better getting fed lower amounts multiple times a week as that would mimic nature.

 

[Kinabalu]

Regarding MSU I thought most fertilizers acidify the potting mix over time just like how they lower the PH when you add them to water no? Maybe this depends on the specific ions involved in the ferts at different ratios/concentrations.

Traditional NPK fertilizers typically lower the PH since they contain ammonium/urea, when mixed with water they are typically around PH 5.5 and the plant's change the PH from there during absorption. MSU types are all or mostly nitrate which raises the PH when absorbed. The reason why MSU lowers the water's PH is because the fertilizer company adds an acid (I believe citric) to lower the PH to stop reactions between the calcium nitrate and other nutrients (phosphate, sulfate, micros...). But once in the pot the PH skyrockets to 7+ once the plant absorbs the nitrate.

Regarding EC I'm uninformed on the topic so will need to research it.

There are plenty of good nuggets in here so thank you for that. What would you say is a good middle-range PH meter?

EC is actually the standardized measurement for tds meters. Usually the meters can measure both but basically TDS meters measure EC then convert that measurement to give an estimate of PPM. Since conductivity of various ions varies the only way to know real ppm is by knowing how many mg/L or Kg. Thats also why different tds meter brands give different readings...

Just find a meter with good reviews and calibration solutions, otherwise they get out of whack after a while. Apera usually has good ones.

Part of the issue is that we don't know the true rate and volume of uptake.

Taking my "bare-root vanda" example again, where the amount of fertilizer solution absorbed is limited to whatever the velamen holds after being saturated, then a single, 100 ppm N treatment should give the plant the same amount of nutrition as 4 treatments at 25 ppm N.

That gets more complicated when we add a liquid-holding component to the potting medium, as that increases the time the roots can be exposed to any applied nutrient solution - if they are in contact with it.

Then there's that "minor detail" factor, time. Once in contact with a nutrient solution, how long does it take for the plant to draw it into its vasculum and start distributing it to its tissues? If it was instantaneous, life would be far easier in this regard, but it's not. Is it hours? Days?
.

Personally I have not grown Vandas and find the bare root growing style a bit strange. However, I will say the 1 dose of 100 ppm N supplies the same quantity as the 4 dilute doses way faster...

I have not performed soil tests on media from actively growing plants yet however I have done the next best thing which is using the PH meter religiously. Ray, as you noted with the PH changing rapidly throughout the day, that represents the state of absorption by the plants. If you prepare a fertilizer solution and let it sit over the same period of time, typically the PH does not drift much, usually just some nutrient fallout reactions or co2 absorbtion/dissipation via the air. So all those rapid PH changes in the pot are for sure from the plants and maybe some algae etc, releasing H+ and hydroxide ions depending on what they are absorbing at any one time. I do believe the absorption of some nutrients starts instantaneously while others like K are absorbed over a few days via diffusion.


https://www.aos.org/orchids/additional-resources/a-new-fertilizer-without-high-phosphorus.aspxIf you read this article on MSU's origin it is interesting to note that nowhere does it mention that MSU used the RO water fertilizer. They used the well water special with hard water, which buffered the PH while the fertilizer provided lots of K with some ammonium. The RO water MSU was simply advertised as the "equivalent" for pure water which it clearly is not since the nutrient ratios is very different, their thinking was the extra Ca nitrate replaces the hard water but in fact that raises the PH higher than hard water and provides no carbonate buffering so the PH varies much more. Because most orchid growers use pure water, the RO fert became the main type sold not the well water special that MSU used...

After reading Rick's paper on K lite, I am convinced he was experiencing PH issues with other fertilizers and I could not find any mention from him of what his soil PH tested as. Since K is a cation it can acidify the soil a bit which could be a serious issue if the plant is a bit starved of it and therefore acidifying the soil more than normal... when the PH goes out of range the orchids have a very hard time absorbing K, a well known issue in crops and hydroponics. Ironically, instead of buffering the soil PH with carbonates, I think reducing the K level drastically and increasing the nitrate level to increase PH can semi stabilize the PH and then the orchids can absorb enough K from the substrate, bark, sphag etc and hence why K lite is used. In inorganic media they get the required extra K from kelp extracts and even will substitute Na for K... the extra Mg helps too since a lot of orchids are a bit deficient.

The low rates of fertilization for MSU also suggests PH issues since it is easier for the plants to adjust the PH in more dilute solutions. The low N total ppm also prevents too fast growth that would starve the plant on a low K fertilizer if growing faster. As mentioned in Xavier's paper, a high nitrate and low P fert induces dark leaves and I think thats another reason why MSU is often used. I see Rick used bonemeal before K lite though which is high in phosphate and important for root growth and he noted improved growth.

For the record, all of Xavier's recommendations are dependable and often overlooked, so if you haven't read them:
https://www.yumpu.com/en/document/r...lture-and-propagation-concepts-and-guidelines
Hope that clarifies

 

[Ray]

The pH shifting from the use of the MSU fertilizers has little, if anything to do with the addition of citric acid, but is essentially entirely due to the form of nitrogen used The citric acid added to aid in solubility, is such a weak acid that pretty much any other addition to the solution completely overwhelms it, eliminating it as a "player" in the result.

Having spoken at length with the formulator, both "MSU" formulas were produced and greenhouse tested extensively prior to publication of the article. In fact, the "Well Water" version was actually created so that - when dissolved in the MSU greenhouses' water supply - the resultant nutrient package and acidity/basicity factors of the solutions were similar.

@Kinabalu is correct about TDS meters functioning, but I have yet to find one I would trust for absolute values because each and every solution needs its own conversion factor, and those meters don't allow for that. I have a HM Digital EC meter that has two TDS scales, and one is in the ballpark (but still not great) for K-Lite in RO, and well off in its other range, but both are off with other fertilizers.

Just using the three "flavors" of MSU - WW, RO & K-Lite (which was derived from the RO formula) - all made with the same raw materials in the same factory, the EC of the RO is 18% greater than the WW, while K-Lite is only 4% higher. Not too bad, right? Nope, because for a 100 ppm N solution of each, the TRUE TDS of the MSU RO and K-Lite solutions are 40% and 45% greater than that of the WW formula, respectively. Read this: Don't Trust Your TDS Meter.

 

[Paph Paradise]

On the assumption I am understanding your question correctly, no, they are not mutually exclusive.

A particle with a lot of absorption typically has a lot of very fine pores and cracks into which the liquid penetrate. As the solvent (water in this case) evaporates, it does so from the surface, effectively concentrating the remaining solution deeper and deeper into those crevices. Eventually, when it's dry, there will be a gradient from the concentrated "core" to the relatively solute-free surface. At that point, especially considering the truly low concentrations of the solutions we apply, the particles essentially keep the excess salts away from root access. Over time, however, the accumulated salts within the particles reach a higher concentration at the surface, where they can become damaging.

It seems to me that if you want to avoid all these problems, one should either go to ebb and flow tables or use a medium that does not absorb anything - my first thought was glass marbles, but I have recently been in contact with a German grower using styrofoam stips for his paphs. Then, you get to control exactly what the plant gets through the combination of concentration and frequency of application.

Going back to my Chemistry roots....technically with charcoal it is 'adsorption', not absorption. Paper towels absorb liquids, ions adhere to charcoal by adsorption.

We use charcoal in our mix since our water is relatively hard. The charcoal is likely effective for a short period before it becomes saturated, but we feel that it helps reduce salt stress on the new roots while the plants establish themselves in the new mix. Maybe we are kidding ourselves but the charcoal we have been getting lately is pretty good quality so it probably has some benefit.

Dave

 

[Roth]

The pH shifting from the use of the MSU fertilizers has little, if anything to do with the addition of citric acid, but is essentially entirely due to the form of nitrogen used The citric acid added to aid in solubility, is such a weak acid that pretty much any other addition to the solution completely overwhelms it, eliminating it as a "player" in the result.

Having spoken at length with the formulator, both "MSU" formulas were produced and greenhouse tested extensively prior to publication of the article. In fact, the "Well Water" version was actually created so that - when dissolved in the MSU greenhouses' water supply - the resultant nutrient package and acidity/basicity factors of the solutions were similar.

@Kinabalu is correct about TDS meters functioning, but I have yet to find one I would trust for absolute values because each and every solution needs its own conversion factor, and those meters don't allow for that. I have a HM Digital EC meter that has two TDS scales, and one is in the ballpark (but still not great) for K-Lite in RO, and well off in its other range, but both are off with other fertilizers.

Just using the three "flavors" of MSU - WW, RO & K-Lite (which was derived from the RO formula) - all made with the same raw materials in the same factory, the EC of the RO is 18% greater than the WW, while K-Lite is only 4% higher. Not too bad, right? Nope, because for a 100 ppm N solution of each, the TRUE TDS of the MSU RO and K-Lite solutions are 40% and 45% greater than that of the WW formula, respectively. Read this: Don't Trust Your TDS Meter.

In fact the MSU story is a 'bit different'. It is a copy of Coic Lesaint from the late 70s, both in the RO and well water. The basis of it was for simple plants ( tomatoes, etc...) that are able to live only on nitrate nitrogen, so they used ammonium to keep the pH in the proper range when using hard water, and only for that, and only for those specific food crops, and that's where the mistake began...

They did use the Well Water formulation in their greenhouses, and 'calculated' the Pure water out of it. It does not bring, of course, the same ingredients in the final solution, as the Well Water has a part of ammonium in the nitrogen source, that the pure water barely has, so both RO and Well ( even with the MSU Well water...) end results are completely different.

The Well water will give a bit over 30% of ammoniacal nitrogen with a total N of 19%, which is essential for good, strong growth of many orchids
The RO water will give below 10% of ammoniacal nitrogen with a total N of 13%, way not enough for many orchids grown at normal speed... And out of that, some orchids are fully unable to use nitrate as a nitrogen source. We detected several Phalaenopsis like that, no way they can process nitrates.

What happens sometimes is that nitrate would be converted into aminoacids in the substrate, by, we think. microorganisms, and then the plants could take them up directly, but the growth was really substandard, and the nitrogen available in the leaf analysis was below standard.

 

[Ray]

Going back to my Chemistry roots....technically with charcoal it is 'adsorption', not absorption. Paper towels absorb liquids, ions adhere to charcoal by adsorption.

We use charcoal in our mix since our water is relatively hard. The charcoal is likely effective for a short period before it becomes saturated, but we feel that it helps reduce salt stress on the new roots while the plants establish themselves in the new mix. Maybe we are kidding ourselves but the charcoal we have been getting lately is pretty good quality so it probably has some benefit.

Dave

I’m gonna hafta disagree, Dave.

Activated charcoal certainly adsorbs, but the horticultural charcoal we see for potting mixes doesn’t really have much area that’s activated at all (I’ve broken pieces that weren’t even burned to the center), and most of the accumulated residues are deposited and held through the same surface energy mechanisms as other type of media.

 

[Brabantia]

@Ray and Roth

We've been talking about MSU fertilizer and one question has always puzzled me....
When I compare the trace element content of fertilizers that have been used for decades to grow orchids, I find that MSU fertilizer has a higher content. If I compare the trace element content of Peters CalMag fertilizer with that of MSU fertilizer for a solution containing 50 ppm nitrogen for both fertilizers, I get the following results expressed in ppm: Peters Fe: 0.4 - Zn: 0.05 - Cu 0.05 - Mo: 0.033 and for MSU Fe: 0.67 - Zn: 0.17 - Cu: 0.17 - Mo: 0.068. So: 1.5x for Iron - 3x for Zn - 3x for Cu and 2x for Mo for MSU. I know that the price of chelated trace elements is high, so why did MSU University recommend such high trace element levels compared to other, more common fertilizers?

 

[Ray]

I guess my first question is “is Peters normal and MSU high, or is MSU normal and Peter’s low?”, or are both well in the range of usefulness and it doesn’t matter? I am only guessing that Peter’s uses the same raw materials, but in the MSU formulas, the only element that is chelated is iron.

 

[Brabantia]

I guess my first question is “is Peters normal and MSU high, or is MSU normal and Peter’s low?”, or are both well in the range of usefulness and it doesn’t matter? I am only guessing that Peter’s uses the same raw materials, but in the MSU formulas, the only element that is chelated is iron.

I have compared the oligo content of several fertilizers that can be used to grow orchids and I have never found another fertilizer as rich as MSU in the elements I mentioned in my first message.
Only iron is chelated... am I to understand that Cu, Zn and Mn are not?

 

[gego]

I have compared the oligo content of several fertilizers that can be used to grow orchids and I have never found another fertilizer as rich as MSU in the elements I mentioned in my first message.
Only iron is chelated... am I to understand that Cu, Zn and Mn are not?

Maybe sulfates of those elements. They are cheaper but need a lower pH solution for uptake.

 

[Ray]

I have compared the oligo content of several fertilizers that can be used to grow orchids and I have never found another fertilizer as rich as MSU in the elements I mentioned in my first message.
Only iron is chelated... am I to understand that Cu, Zn and Mn are not?

Correct. The ingredients are boric acid, calcium nitrate, copper sulfate, iron EDTA (the chelated one), magnesium nitrate, manganese sulfate, potassium nitrate, potassium phosphate, sodium molybdate, zinc sulfate.