Fertilizers explained (2-part presentation) -- with 6/2023 update

[Steve Johnson]

As always, great discussion on this thread.

Mike and Steve, do either of you guys have any thoughts on whether this fertilizer regimen would be ok for agaves or ocotillo? If not, how should it be modified?

Aside from my presentation that started it all, this thread has turned out to be a gold mine of information -- go to page 1 and read through the exchanges between Mike and SDK1. You'll come to find out that all plants have basically the same nutrient requirements, and it really surprised me to know how much xeric and nonxeric plants have in common regarding their optimal N, P, and K ranges. Long story short, the new fert regimen I'm following will work well for cacti, succulents, and any other ornamental plants you're growing.

Even for roses? Yes -- you rose growers out there may find this rather enlightening:

https://www.rose.org/single-post/phosph ... good-thing

And finally, confirmation from Mike:

The same for everything. Just remember that many agaves grow on limestone so you might make allowances for that but even if you don't I suspect everything will be fine.

There's a lot of horticultural science out there, and many growers are simply unaware of it. We're getting a taste of it here -- for those of you who are interested (and a good dose of curiosity helps!), you'll find the whole thing to be fascinating.

[jerrytheplater]

Even for roses? Yes -- you rose growers out there may find this rather enlightening:

https://www.rose.org/single-post/phosph ... good-thing

Good article Steve. I copied a very interesting paragraph and added in two edits for my own use.

Another question to consider is the amount of phosphorus a rose plant can use. Analysis of plant tissues indicate that the amount of phosphorus in those tissues is around 1/6 of the amount of nitrogen and 1/4 that of potassium. (edit Jerry Smith 9-1-2023: 6-1-4 elemental, & 6-2.3-4.8 or 3-1.2-2.4 N-P2O5-K2O) In other words, of the three, phosphorus exists in the smallest amounts, leading one to wonder how much extra phosphorus the plant needs. Research linking increased phosphorus levels to increased blooming is scarce, while there is sound research that demonstrates that even small amounts of phosphorus are needed for bloom. Commercial growers of roses for cut-flower production typically use fertilizers with a 3-1-2 NPK (edit Jerry Smith 9-1-2023: N-P2O5-K2O) ratio. Roses are not the only crop where this has been explored. There is no plant that uses more phosphorus than nitrogen and potassium.

[Steve Johnson]

I found an article on hydrobuilder.com (https://hydrobuilder.com/learn/npk-rati ... t-balance/) which explains this rather well. There's only one limitation -- the article applies to hydroponic crop production, not growing ornamental plants like cacti and succulents. As we go through the following quotes, I'll comment on each one, pointing out things that are specific to cacti and succulents:

• "Nitrogen is responsible for producing robust, leafy growth. This is why you’ll see it in higher ratios during veg, and it will fall off during flower."

Not true for ornamentals -- N is used with the same ratio all the time. Also, N promotes stem growth in cacti and leaf growth in succulents.

• "Phosphorus does the opposite, helping your plants develop flowering sites and produce large buds. Traditionally, growers would ramp up the phosphorus during flower because of this."

Actually, not the best explanation because it applies only to crops, so here's a better one from The Spruce (https://www.thespruce.com/):

• "Phosphorus plays a key role in the growth of roots, blooming, and fruiting, which is why it is an essential nutrient for your plants in spring. Phosphorus contributes to many fundamental plant processes, such as rooting and seed formation."

Not just in spring -- P is essential for cacti and succulents throughout the entire growing season. Now back to Hydrobuilder:

• "Potassium, on the other hand, isn’t necessarily veg or bloom specific. Instead, it helps regulate a variety of plant functions, including strong root growth, increased resistance to disease and increased water intake, along with thick, sturdy growth."

Definitely true for all plants.

• "Magnesium and calcium go hand in hand, and are often an area where plants become deficient. Magnesium helps aid in the uptake and utilization of other nutrients, along with producing carbs and sugars to help during flower."

Once again, definitely true for all plants.

• "Calcium has a similar role in plants as in humans, helping produce strong cells and root walls. This leads to stronger plants. We've recently come to understand that calcium is actually the dominant nutrient in most plants." [My emphasis]

Quite a revelation, and it backs up a couple of things MikeInOz has said in previous posts -- "there's no such thing as too much Ca" and "there's no such thing as Ca toxicity". In fact, I offer the possibility that Ca higher than N could be a very good thing at least for cacti and succulents.

• "Sulfur helps produce chlorophyll, and plays an essential role in foliage and root development."

Applies to cacti and succulents too. Sulfur deficiency = chlorosis, and yellowing of the skin indicates a serious S deficiency. If you have a good amount of sulfate in your watering solution, chlorosis won't be a problem.

This brings us to...

Mulders_chart.jpg (87.83 KiB) Viewed 10051 times

• "This shows how nutrients interact with one another. Nutrients interact either antagonistically or synergistically.
  
  They can increase the uptake of one another. Or, they will fight among each other and can lock each other out if the balance/ratio is off."

Precisely why NPK ratios are key to knowing if your fertilizer is right or wrong for cacti and succulents. The ideal NPK ratio = 1:0.25-0.35:1.1-1.7. Simply put -- of the 3 primary major nutrients, ornamentals need the least amount of P. If your feeding regimen has the ideal ratio, all other nutrients are there in sufficient amounts, and you don't overdo it on the fertilizer (plus any supplements you may need), your plants will be happy, healthy and growing well over the years. (Many thanks to SDK1 for posting Mulder's Chart on 2/1/2023.)

[AirWreck]

I haven't finished reading this thread but wanted to throw this out there whilst I'm thinking about it. This is a trace mineral fertilizer that I've long used for all my cacti and gardening endeavors: Planters II
https://fertilizerbrokerage.com/wp-cont ... ations.pdf
"Derived from metamorphosed evaporite". Meaning its the evaporated remains of an ancient riverbed. As such, its rated for organic agricultural. its said to contain up to 30 trace minerals.

How good is it for cacti? I cannot say but its been in use for agriculture since the 1970s. This webpage says it can be used for xeric plants:
https://www.highcountrygardens.com/prod ... lizer-5-lb

its hard to find recommended application for potted plants but what I've found is 1tsp:6inch pot.
Something to consider.

[jerrytheplater]

I haven't finished reading this thread but wanted to throw this out there whilst I'm thinking about it. This is a trace mineral fertilizer that I've long used for all my cacti and gardening endeavors: Planters II
https://fertilizerbrokerage.com/wp-cont ... ations.pdf
"Derived from metamorphosed evaporite". Meaning its the evaporated remains of an ancient riverbed. As such, its rated for organic agricultural. its said to contain up to 30 trace minerals.

How good is it for cacti? I cannot say but its been in use for agriculture since the 1970s. This webpage says it can be used for xeric plants:
https://www.highcountrygardens.com/prod ... lizer-5-lb

its hard to find recommended application for potted plants but what I've found is 1tsp:6inch pot.
Something to consider.

I saw that 20% is soluble right away, so adding it to your pot should work out fine. When you water, a little will dissolve each time. Greensand is another trace mineral product naturally mined. It has a marine origin.

[hoopgod32]

• "Magnesium and calcium go hand in hand, and are often an area where plants become deficient. Magnesium helps aid in the uptake and utilization of other nutrients, along with producing carbs and sugars to help during flower."

Once again, definitely true for all plants.

• "Calcium has a similar role in plants as in humans, helping produce strong cells and root walls. This leads to stronger plants. We've recently come to understand that calcium is actually the dominant nutrient in most plants." [My emphasis]

Quite a revelation, and it backs up a couple of things MikeInOz has said in previous posts -- "there's no such thing as too much Ca" and "there's no such thing as Ca toxicity". In fact, I offer the possibility that Ca higher than N could be a very good thing at least for cacti and succulents.

Mulders_chart.jpg

Love this chart! Very helpful to see how everything works together and understand just how important proper balance is for plant health. Should be bookmarked for all hobbyist growers.

Per our last convo on a different thread about calcium binding, I did learn recently (thanks to a chemist friend) that calcium does indeed bind with phosphate. Calcium acetate (acidifying with vinegar) is the most effective at this due to its high solubility. The key to preventing this, as shown in the chart you shared, is to have the proper balance between cal:mag (synergistic nutrient) which is around 4:1 along with a roughly equal nitrogen:calcium. This explains why many fertilizers with high phosphorous content do not contain calcium -- they will precipitate at high levels in a single solution.

With that said, isn't excessive calcium that is out of balance with other nutrients actually detrimental for plant health? As shown in the chart, calcium can form antagonistic relationships with many other nutrients if it's in excess thereby preventing their uptake. This competes directly with the concept that "there's no such thing as too much Ca." It's possible Mike's statements are missing additional context, but I have to definitely push back on the notion that excess calcium has no negative impact.

Good excerpt from this article University of Michigan's Agriculture unit:

"If calcium is in excess it can simply out-compete other elements such as potassium and magnesium for uptake sites on the roots, or it can change soil chemistry by elevating pH to the point iron and boron become unavailable."

[Steve Johnson]

Man, this is complicated...

Per our last convo on a different thread about calcium binding, I did learn recently (thanks to a chemist friend) that calcium does indeed bind with phosphate. Calcium acetate (acidifying with vinegar) is the most effective at this due to its high solubility. The key to preventing this, as shown in the chart you shared, is to have the proper balance between cal:mag (synergistic nutrient) which is around 4:1 along with a roughly equal nitrogen:calcium.

We'll go through a few numbers. First -- when I dilute 1/2 tsp. of my General Hydroponics FloraMicro 5-0-1 per gallon of water, I get 33 ppm Ca and 10 ppm Mg. 1/4 tsp. nitrogen-free TPS CalMag adds another 15 ppm Ca and 4 ppm Mg for a total of 48 ppm Ca and 14 ppm Mg in the watering solution. Ca-Mg ratio is 3.4-1. I'm also adding an ammonium sulfate-potassium sulfate stock solution to the watering solution. Total N in the watering solution is -- 48 ppm. The only variable I can't account for are the amounts of Ca and Mg in my acidified water. All I can tell you is that my tap water is reading about 100 ppm carbonate per the MedLab Diagnostics test strips I'm using. Assuming that it's all CaCO3, we're talking about 40 ppm Ca. According to Vernier Science Education (https://www.vernier.com/experiment/wqv- ... -hardness/):

• "On average, magnesium hardness represents about 1/3 of total hardness and calcium hardness about 2/3."

This is a general statement, and I do realize that whether it applies or not will depend on local geology and water sources. Taking a water sample to my local test lab costs a few hundred bucks, and I can't justify the expense (I am just a hobbyist, after all), so we'll have to leave the amounts of Ca and Mg in my tap water as an unknown variable. The question for you is (and going by your best guess) -- am I fine with white vinegar or should I change to citric acid as my acidifier? Interesting side note by the way:

• TPS CalMag is derived from calcium carbonate and calcium magnesium carbonate. It includes -- citric acid.

With that said, isn't excessive calcium that is out of balance with other nutrients actually detrimental for plant health? As shown in the chart, calcium can form antagonistic relationships with many other nutrients if it's in excess thereby preventing their uptake. This competes directly with the concept that "there's no such thing as too much Ca." It's possible Mike's statements are missing additional context, but I have to definitely push back on the notion that excess calcium has no negative impact.

I brought the matter up with Mike via PM, so let's see if he responds here. In the meantime, I'll tell you that growing improvements in my cacti have been substantial ever since I started using a well-balanced fertilizer regimen with the TPS CalMag supplement plus the Ca (and Mg if it's there) in my acidified tap water last year. Yeah, I know -- anecdotal evidence, so take it for whatever it's worth.

Good excerpt from this article University of Michigan's Agriculture unit:

"If calcium is in excess it can simply out-compete other elements such as potassium and magnesium for uptake sites on the roots, or it can change soil chemistry by elevating pH to the point iron and boron become unavailable."

I'd be hesitant to extrapolate agricultural research and apply it to cacti being grown under pot cultivation. Also, the article you linked to assumes the presence of soil -- IMO doesn't apply to those of us growing cacti in a soilless mineral mix.

[AirWreck]

"If calcium is in excess it can simply out-compete other elements such as potassium and magnesium for uptake sites on the roots, or it can change soil chemistry by elevating pH to the point iron and boron become unavailable."

On a side note, the same is true for the human gut. Too much calcium interferes with absorption of other minerals such as iron. The chemistry of digestion is just as important as what you put on your plate to eat. By profession I'm a Nutritionist. All biological life needs a balanced intake. We should certainly assume the same to be true for our plants. The chemistry (chemical interactions) of the nutrients in our soil mixes needs to be considered. And yet, how well understood is that in the horticultural sciences? I see a lot of parents giving their children too much milk and I counsel them about it due to the effect of excessive calcium intake. They often look at me like I'm crazy like "are you telling me to starve my child?" or "but little Johnny likes milk." I'm sure many of y'all have gotten a similar response when telling people they don't need a calcium based soil mix to "mimic" that cactus's natural environment. What's the word for that, when calcium is a major component to the molecules and crystals in a geologic substrate?

[hoopgod32]

We'll go through a few numbers. First -- when I dilute 1/2 tsp. of my General Hydroponics FloraMicro 5-0-1 per gallon of water, I get 33 ppm Ca and 10 ppm Mg. 1/4 tsp. nitrogen-free TPS CalMag adds another 15 ppm Ca and 4 ppm Mg for a total of 48 ppm Ca and 14 ppm Mg in the watering solution. Ca-Mg ratio is 3.4-1. I'm also adding an ammonium sulfate-potassium sulfate stock solution to the watering solution. Total N in the watering solution is -- 48 ppm. The only variable I can't account for are the amounts of Ca and Mg in my acidified water. All I can tell you is that my tap water is reading about 100 ppm carbonate per the MedLab Diagnostics test strips I'm using. Assuming that it's all CaCO3, we're talking about 40 ppm Ca. According to Vernier Science Education (https://www.vernier.com/experiment/wqv- ... -hardness/):

Haha it sure can be! But it's fun we all get to learn together. I think your breakdown above is a perfect example of thoughtful nutrient delivery. Nothing is perfect, but you've clearly gone the extra mile to ensure a general balance without extreme excess. I think that's really the key to plant health in its entirety: limiting excess to preserve a general equilibrium.

Taking a water sample to my local test lab costs a few hundred bucks, and I can't justify the expense (I am just a hobbyist, after all), so we'll have to leave the amounts of Ca and Mg in my tap water as an unknown variable.

I noticed JR Peters (makers of popular Jack's Classic ferts) offers water analysis lab tests for $46 + one way shipping. I'm probably going to send mine in if just for the complete knowledge of macro/micro nutrients (and to think I'm fancy). I've also been meaning to test the soil of my in-ground citrus tree, so could be a two-in-one if you have something similar.

The question for you is (and going by your best guess) -- am I fine with white vinegar or should I change to citric acid as my acidifier? Interesting side note by the way:

• TPS CalMag is derived from calcium carbonate and calcium magnesium carbonate. It includes -- citric acid.

Very interesting side note Steve! I'll have to do some digging there. Can't say I'm preferential to either, will probably going with whatever is the most repeatable & cheapest without having to think much about it.

I brought the matter up with Mike via PM, so let's see if he responds here. In the meantime, I'll tell you that growing improvements in my cacti have been substantial ever since I started using a well-balanced fertilizer regimen with the TPS CalMag supplement plus the Ca (and Mg if it's there) in my acidified tap water last year. Yeah, I know -- anecdotal evidence, so take it for whatever it's worth.

Thanks for reaching out! Curious to hear Mike's thoughts. It's great you've seen such awesome results with both balanced fertilizer regimen and calcium inclusion. I'd like to think your thoughtful approach and optimization of balanced nutrients (calcium included) is a huge part of that! The wise adage "everything is fine in moderation" is quite applicable for plant nutrients in general -- it's typically excess that really tilts the table.

I'd be hesitant to extrapolate agricultural research and apply it to cacti being grown under pot cultivation. Also, the article you linked to assumes the presence of soil -- IMO doesn't apply to those of us growing cacti in a soilless mineral mix.

Absolutely! Very fair point. Pure mineral mixes may have unique delivery requirements, it's possible that informs some of Mike's viewpoint. I still think the underlying foundation of plant biology makes that link a good primer for a general approach to nutrient delivery -- cool, calm and as balanced as can be without losing too much sleep over it

[hoopgod32]

On a side note, the same is true for the human gut. Too much calcium interferes with absorption of other minerals such as iron. The chemistry of digestion is just as important as what you put on your plate to eat. By profession I'm a Nutritionist. All biological life needs a balanced intake. We should certainly assume the same to be true for our plants. The chemistry (chemical interactions) of the nutrients in our soil mixes needs to be considered. And yet, how well understood is that in the horticultural sciences? I see a lot of parents giving their children too much milk and I counsel them about it due to the effect of excessive calcium intake. They often look at me like I'm crazy like "are you telling me to starve my child?" or "but little Johnny likes milk." I'm sure many of y'all have gotten a similar response when telling people they don't need a calcium based soil mix to "mimic" that cactus's natural environment. What's the word for that, when calcium is a major component to the molecules and crystals in a geologic substrate?

That is a great comparison! The synergistic/antagonistic chart above surely spans across biology as a foundational part of nature. The gut is like soil -- it needs the right underlaying structure in order to process nutrients correctly. In reverse, it also needs to be fed the right balance of "food" (a whole food diet, limited junk) to thrive. Too much of one food, like carrots, will have adverse effects like turning you into an orange buffoon!

Regarding your question, are you referring to caliche soil? We have lots of that in Arizona. It is a layer of soil in which the particles have become compacted together with calcium carbonate to form a dense, concrete-like substance. Although, in-ground nutrient delivery is a whole different beast compared to siloed ecosystems in pots.

[Steve Johnson]

I noticed JR Peters (makers of popular Jack's Classic ferts) offers water analysis lab tests for $46 + one way shipping. I'm probably going to send mine in if just for the complete knowledge of macro/micro nutrients (and to think I'm fancy). I've also been meaning to test the soil of my in-ground citrus tree, so could be a two-in-one if you have something similar.

Ooh, thanks for reminding me about that! Sometime back, jerrytheplater mentioned getting my water tested by JR Peters, and I can certainly afford $46. I'm making a note of it as we speak -- not a huge priority at the moment, but I'll send out a tap water sample soon. When I get the results, the amounts of Ca and Mg in my water won't be a mystery!

Pure mineral mixes may have unique delivery requirements, it's possible that informs some of Mike's viewpoint.

Sorry to be blunt about it -- but as the lawyers would say, you're making an assumption of facts not in evidence. Mike's mix contains mineral gravel (I believe it's pumice and scoria), soil, his home-made compost and (believe it or not) cow manure. As far as I know, he has never used a pure mineral mix, and if that's the case, he doesn't have any direct hands-on experience with it.

I'll also mention that cacti aren't crops, neither are they African violets or ferns or other nonxeric plants -- or humans. Mike has a specialized knowledge of cacti most growers don't have, so I would defer to what he says about calcium as it pertains to cacti being grown under pot cultivation. Hopefully he'll chime in here soon.

[jerrytheplater]

I noticed JR Peters (makers of popular Jack's Classic ferts) offers water analysis lab tests for $46 + one way shipping. I'm probably going to send mine in if just for the complete knowledge of macro/micro nutrients (and to think I'm fancy). I've also been meaning to test the soil of my in-ground citrus tree, so could be a two-in-one if you have something similar.

Ooh, thanks for reminding me about that! Sometime back, jerrytheplater mentioned getting my water tested by JR Peters, and I can certainly afford $46. I'm making a note of it as we speak -- not a huge priority at the moment, but I'll send out a tap water sample soon. When I get the results, the amounts of Ca and Mg in my water won't be a mystery!

Well, you have a much better memory than I do. I don't remember that at all!

[Steve Johnson]

Per our last convo on a different thread about calcium binding, I did learn recently (thanks to a chemist friend) that calcium does indeed bind with phosphate. Calcium acetate (acidifying with vinegar) is the most effective at this due to its high solubility.

What are the implications of calcium acetate binding with phosphate? Let's investigate -- from Pub Med:

• "Calcium phosphate was unknown as a plant biomineral until recently reported in Neotropical Loasaceae. Here, we demonstrate its widespread occurrence in the trichomes of several plant families, including Brassicaceae. Calcium phosphate is the primary biomineral in, e.g., the bones and teeth of higher animals; in plants, it was only recently discovered in the stinging hairs and scabrid-glochidiate trichomes of South American Loasaceae (Ensikat et al. in Sci Rep UK 6:26073, 2016), where it appears to be deposited highly specifically, often replacing the common plant biomineral silica."

You can read the article's abstract in more detail here:

https://pubmed.ncbi.nlm.nih.gov/29234879/

Now, what does that have to do with cacti? You'll find the answer here:

https://shuncy.com/article/does-cactus-have-trichome

The take-away I get from this -- calcium acetate binding with phosphate = more abundant trichomes on cacti. Correct me if I'm wrong, but it's a pretty darn good implication.

[Steve Johnson]

This just in...

Here's what Mike has to say regarding calcium:

Ca is the most abundant element in soil next to silicon. As long as Ca is not in the form of Calcium carbonate and raise pH too high, it does nothing to interfere with other nutrients. Some cacti (and other plants) grow on pure limestone or pure gypsum. There is no need to balance Ca with other nutrients in most situations as long as they are ALL present in sufficient quantities. Ca will not cause toxicity. I know of no limit for Ca.

He clarified further by saying this:

But to add to the subject, EXTRACTABLE (plant available) Ca is often 10 times what K is in natural soils. So much for ''out-competing other elements''
The level of available Ca is not much lower than the N or K in a lot of hydroponic formulations where pH is adjusted. That should give a clue that Ca is only an issue for plants if it's in a carbonate form where plants from acidic soils might have trouble extracting Fe and Mn etc. In other words it is not the element Ca that is a problem but CaCO3 which can be for some plants. Just as this statement by hoopgod says...

"If calcium is in excess it can simply out-compete other elements such as potassium and magnesium for uptake sites on the roots, or it can change soil chemistry by elevating pH to the point iron and boron become unavailable."

The very fact that the concentration of Ca from the gypsum I use in pots would probably be greater than all the other nutrients from the Osmocote put together should be enough to convince folks that there in so such thing as ''excess'' Ca but there is definitely such a thing as excess CaCO3.

By the way, Mike is referring to the Osmocote slow-release cactus and succulent formulation available only in Australia and New Zealand. I should also mention that his part of Australia has the purest tap water I know of -- no Ca or Mg in the water. Here in the US, hard water is generally par for the course, but that depends on one's locality.

[hoopgod32]

Great find about trichomes Steve! Extremely fascinating article, had absolutely no knowledge about trichomes until now (thank you!). They sound absolutely beneficial for cacti including protection from external threats (disease, predators, environment, etc), absorption of moisture from the atmosphere and regulating temperature/water balance.

Here's what Mike has to say regarding calcium:

Ca is the most abundant element in soil next to silicon. As long as Ca is not in the form of Calcium carbonate and raise pH too high, it does nothing to interfere with other nutrients. Some cacti (and other plants) grow on pure limestone or pure gypsum. There is no need to balance Ca with other nutrients in most situations as long as they are ALL present in sufficient quantities. Ca will not cause toxicity. I know of no limit for Ca.

He clarified further by saying this:

But to add to the subject, EXTRACTABLE (plant available) Ca is often 10 times what K is in natural soils. So much for ''out-competing other elements''
The level of available Ca is not much lower than the N or K in a lot of hydroponic formulations where pH is adjusted. That should give a clue that Ca is only an issue for plants if it's in a carbonate form where plants from acidic soils might have trouble extracting Fe and Mn etc. In other words it is not the element Ca that is a problem but CaCO3 which can be for some plants. Just as this statement by hoopgod says...

"If calcium is in excess it can simply out-compete other elements such as potassium and magnesium for uptake sites on the roots, or it can change soil chemistry by elevating pH to the point iron and boron become unavailable."

The very fact that the concentration of Ca from the gypsum I use in pots would probably be greater than all the other nutrients from the Osmocote put together should be enough to convince folks that there in so such thing as ''excess'' Ca but there is definitely such a thing as excess CaCO3.

Thanks for clarifying with Mike! Good to know soluble calcium levels don't need to be perfect. Did you happen to ask him about phosphorous binding with calcium (in all forms)? It's hard for me to ignore the clear organic chemistry basis: calcium (acetate, carbonate, etc) have all been shown to bond with phosphorous making each into a more slow release form the soil needs to break down.

I have to think there's a gap in our knowledge somewhere. Does it have to do with ppm concentration? Pretty confusing - so tons of people are delivering limited phos/cal by adding a soluble fertilizer to their hard water? How is this not a known problem?