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

[jerrytheplater]

Mike,

Thanks for that, could you share the title and author of the book?

''Growing Media for ornamental plants and turf''
K.A. Handreck and N.D. Black
University of NSW press.

Mike

I think my first reply just got eaten!!! I'll skip what I said before.
So, I am trying to borrow this book. I found it at a college maybe about a 3 hour drive away. It is the 1984 edition.

Do you think it is worthwhile to look for the newer editions?

I will be trying Interlibrary loan again. My local library says they can't get it.

[Fohat85]

Thank you both for the suggestions and thoughts.
In Italy we have always adopted a different school of thought regarding fertilizers for cacti (which I would like to change).
In fact, we usually use a fertilizer which has an N-P-K ratio of 1-2-3. The low nitrogen value was chosen so as not to excessively stimulate tissue growth and to avoid an increase in perspiration and a decrease in protection against pathogens.
In this case Ferty 4 is often used.
Below is the composition table:

(N) (P) (K) + (Mg)
Ferty 1 : 20 7 10 + 2
Ferty 2 : 15 5 25 + 2
Ferty 3 : 15 10 15 + 2
Ferty 4 : 8 16 24 + 4

Hydrosolouble element stabilized by EDTA.
Boron (B) 0.02%; Copper (Cu) 0.03%; Iron (Fe): 0.075%; Manganese (Mn) : 0.05%; Molibdenum (Mo) : 0.001%; Zinc (Zn) : 0.01%

I have to decide which one to start with.

Ferty 4 is right out -- way too much P. Let's have a look at Ferty 1, 2, and 3:

• Ferty 1 20-7-10. 7% P2O5 x .436 = 3.052% P, 10% K2O x .83 = 8.3%. True NPK values 20-3.052-8.3, NPK ratio = 1-0.153-0.415. Not a good balance because P and K are too low.

• Ferty 2 15-5-25. 5% P2O5 x .436 = 2.18% P, 25% K2O x .83 = 20.75% K. True NPK values 15-2.18-20.75, NPK ratio = 1-0.145-1.383. Good balance between N and K, but P is too low. That can be supplemented with a Mono Potassium Phosphate stock solution -- good suggestion from Jerry, and I can help you out by calculating the right amount for the stock solution and amount of stock solution going into your watering solution.

• Ferty 3 15-10-15. 10% P2O5 x .436 = 4.36% P, 15% K2O x .83 = 12.45% K. True NPK values 15-4.36-12.45, NPK ratio = 1-0.291-0.83. Good balance between N and P, but K is too low. That can be supplemented with a Potassium sulfate stock solution.

Sulfur is an important minor nutrient for cacti, and I don't see S listed on any of the Ferty products. Unless your cacti are getting enough S from your well water, Ferty 3 with a Potassium sulfate supplement is your best option. Once again, I can help you out by calculating the right amount for the stock solution and amount of stock solution going into your watering solution.

Because Calcium is in fact a secondary major nutrient, your cacti may be able to get enough Ca from your well water, but I don't know enough about that to say for sure. Either Jerry or Mike should be able to guide you there. However, if the plants need another Ca source, the options are:

• A Nitrogen-free CalMag fertilizer supplement for your watering solution.

• Adding a small amount of limestone or gypsum to your potting medium. Whether it should be one or the other depends on species.

I prefer the TPS CalMag I've been using because it's easier and it works well for all species. Mike has a lot of experience with limestone and gypsum for cacti, so if that's the only option to you, let us know about the species of cacti you're growing, and he can guide you accordingly.

By the way, what do + 2 and + 4 mean? I've never seen that being listed on ferts before.

+2 and +4 refer to the magnesium ratio.
Thanks for the interpretation of each Ferty. I think I have fully understood the reasoning and have found the optimal product to try next season.
I tried to calculate with this fertilizer, please correct me if I'm wrong.

Labeled NPK is 15-15-30 so the real ratio is (1-0.44-1.66) and should be the optimal as you suggest.
The minor nutrient (hydrosoluble) are:
0,01%Boro (B) solubile in acqua
0,02% Iron
0,01%Manganese
0,001%Molibdenum
0,002%Copper (Cu)
0,002%Zinc (Zn)
This is the link here

I also have to analyze, as you suggested, the concentration of calcium and magnesium in my water.
I think I have very hard water, as I am already discussing in another topic

PS: i usually grow mexican plant

[Steve Johnson]

Labeled NPK is 15-15-30 so the real ratio is (1-0.44-1.66) and should be the optimal as you suggest.

I changed my thinking on that based on this recent post from Mike on 2/17:

No one knows what the affect of too much P on cacti looks like. The only way to know is to do a trial with blocks of identical seedlings and give each block ever increasing concentrations of P. But it would probably turn out to be rather pointless because we already know that we should not give too much P from the results of other trials for other plants. So why do it in the first place? The trial for African violets showed flowering decreasing by 50% when the P/N ratio was increased from 0.14 to 0.44. If we stick to somewhere around 0.25 to 0.35 more or less, there will be no problems. [My emphasis.]

What he's basically saying is that cacti are just like all other plants in terms of their P requirements for optimal growth. If they're not flowering normally (or not flowering at all) because the P is too high, this is a symptom of other problems we may not even know about until years have passed and we can't remember what our cacti looked like before those problems started. In my case, the problems I see in my cacti with 11 years of a 0.44 P/N ratio are remarkably minor, although lack of normal flowering in some of the species I'm growing point toward the need for lowering the P to a P/N ratio more like 0.3 in my fertilizer regimen. I really had to think this through, and the more I think about it, the more I realize that the general recommendation I get from Mike's comment is spot-on. Since the cacti in my collection have been doing well so far, they should do even better with lower P. My recommendation to you -- go with Ferty 3 and a Potassium sulfate stock solution you can add to your watering solution. I'll put a "recipe" together for you over the weekend.

I think I have very hard water, as I am already discussing in another topic

PS: i usually grow mexican plant

Jerry has a good response to that:

Pretty sure I remember Mike suggesting the use of coarse granule Limestone (CaCO3) or Dolomite (CaCO3-MgCO3) rocks, not the finely ground stuff like what is used on lawns. It dissolves a little at a time as you water. Finely ground can clogged your drainage in your pot. I have purchased coarse ground Dolomite as a gravel used in salt water aquariums.

I would not rely on your water for calcium. I like to water with low mineral water, like rain water. Add the minerals in your potting mix or fertilizer.

"I would not rely on your water for calcium" -- completely agree. Although it's theoretically possible to acidify well water, acidification only neutralizes bicarbonates, and it does nothing to neutralize the permanent hardness in your well water. Davide, since you have free access to distilled water, go with that. If you can store rainwater too, use it up first and you'll have distilled water as your backup. The idea here is to store an ample supply of pure water for the growing season -- IMO diluting it with well water may cause problems you won't want to deal with.

Jerry and I have similar recollections of what Mike uses as a Calcium source in his mix. However, I couldn't remember the specifics, so this may be more helpful:

@Mike: When adding additional lime, gypsum or both, is the process repeated each year? What are some common lime lovers and/or gypsum enthousiasts? As Steve I would also like to know if it's needed in the case of the GH/TA TriPart series.

A lot of the Texas and Northern Mexico plants grow in soils with both limestone and gypsum so I give them both. Things like arios, epithelanthas, many thelos, all astros, all coryphanthas and escobarias many mamms ( you have to check) pelecyphora, etc. No need to add limestone more than once. Gypsum is much more soluble so I add a bit at the start of each growing season. If you can use particles of gypsum which are say 2 - 3 mm in size they will probably last 2 years or more. Limestone will basically last forever.
All the other things like notos, rebutias, lobivia etc get a little gypsum but no limestone as they like more acid conditions. If you regularly add trace elements (especially if they are chelated ) there is not so much need to worry about the pH. (but I still try to keep it around 5.5 - 6). I have only seen severe chlorosis in 2 cacti. An echinposis and a Neobuxbaumia. If it gets too bad there is no saving the plant. So most things seem to tolerate a fairly wide range. Those products you mention seem to be for hydroponics and have nitrate as the major N source. I believe I read that cacti prefer ammonium to nitrate so I'm not sure if they are the best option?? The Ca would be from the CaNo3

The Nitrogen-free CalMag I get from TPS Nutrients is perfect, although available only in the US. Apparently our European friends can't find a CalMag fert without N, so I think Mike is pointing you in the right direction here.

[MikeInOz]

Mike,

Thanks for that, could you share the title and author of the book?

''Growing Media for ornamental plants and turf''
K.A. Handreck and N.D. Black
University of NSW press.

Mike, I made my first try to borrow this book from my local library and was told they could not get it. Today I went online myself and found it in the World Cat at a college about 50 miles from me in Long Island, NY. I called there and the librarian told me they have a 1984 edition that is loanable. She thinks that might be why my library didn't get it, since there are so many newer editions.

Question: Do you what is included in the newer editions compared to the 1984 edition? Should I expand my search to find the newest edition?

Jerry,
I have the 1999 edition. It says ''fully revised and expanded'' on the cover but I don't know more than that.

[Fohat85]

What he's basically saying is that cacti are just like all other plants in terms of their P requirements for optimal growth. If they're not flowering normally (or not flowering at all) because the P is too high, this is a symptom of other problems we may not even know about until years have passed and we can't remember what our cacti looked like before those problems started. In my case, the problems I see in my cacti with 11 years of a 0.44 P/N ratio are remarkably minor, although lack of normal flowering in some of the species I'm growing point toward the need for lowering the P to a P/N ratio more like 0.3 in my fertilizer regimen. I really had to think this through, and the more I think about it, the more I realize that the general recommendation I get from Mike's comment is spot-on. Since the cacti in my collection have been doing well so far, they should do even better with lower P. My recommendation to you -- go with Ferty 3 and a Potassium sulfate stock solution you can add to your watering solution. I'll put a "recipe" together for you over the weekend.

Ok, thank you!

[jerrytheplater]

Just a followup thought here...

There are a few species in my collection that are mature enough to flower but never have (or at least not as they should):

• Tephrocactus articulatus papyracanthus from the California Cactus Center purchased in June 2011 -- no flowers yet.

• Tephro inermis also from the CCC purchased in May 2012 -- no flowers yet.

• Coryphantha hesteri from Miles' To Go received in July 2013 -- came ready-made with a set of 5 buds that went into bloom. 2 flowers in August 2014, after that no buds at all.

• Copiapoa laui from CoronaCactus Nursery received in July 2013 -- 1 big beautiful flower in October 2014, and that's it.

• Ariocarpus fissuratus also from CoronaCactus -- blooms every other year, and November 2022 was the latest. Could be normal for the species, but if it flowers again after a growing season of lower P at 0.3 this November...

There may be other factors that explain the lack of flowering in these plants, but if they bloom with the lower P, I don't think it'll be a coincidence. Only one way to find out, and we have a lot waiting time between now and the end of the year.

I have read that Tephrocactus can be shy to bloom. It will be interesting to see if your planned reduce P does anything.

[jerrytheplater]

''Growing Media for ornamental plants and turf''
K.A. Handreck and N.D. Black
University of NSW press.

Mike, I made my first try to borrow this book from my local library and was told they could not get it. Today I went online myself and found it in the World Cat at a college about 50 miles from me in Long Island, NY. I called there and the librarian told me they have a 1984 edition that is loanable. She thinks that might be why my library didn't get it, since there are so many newer editions.

Question: Do you what is included in the newer editions compared to the 1984 edition? Should I expand my search to find the newest edition?

Jerry,
I have the 1999 edition. It says ''fully revised and expanded'' on the cover but I don't know more than that.

Thanks Mike. There is a 2010 edition. I'm not decided if I'm going to buy a copy or not. I'd really like to borrow one first.

[Steve Johnson]

Hi Davide,

Before I do the recipe calculations, I just wanted to make sure that we're talking about the Ferty 3 you'll want to use:

Ferty_3_guaranteed_analysis01.jpg (81.99 KiB) Viewed 3584 times

One thing I did notice is that the ratio of Ammonium N to Nitrate N is about 2-1, and the ratio of my FloraMicro-FloraBloom plus Ammonium sulfate-Potassium sulfate stock solution will give me the exact opposite with a 1-2 ratio in my watering solution. There's nothing at all wrong with Ferty 3's 2-1 ratio, so the only question I have is regarding its .001% Molybdenum. Is that enough, or will you need a Sodium molybdate stock solution too? I don't feel qualified to answer, and hopefully Mike will chime in here. Just remember -- Mo is required for Nitrate-Ammonium conversion in the plant's tissues. If the amount of Mo in Ferty 3 is good enough for efficient conversion, you'll be fine. What say you, Mike?

There's one other thing I'm kinda curious about -- guaranteed analysis states 10% P2O5 on the left. On the right, the description is neutral ammonium citrate and 12% P2O5 right below that. So which is it, 10% or 12%? 10 x .436 = 4.36% P and 12 x .436 = 5.232% P. The P/N ratios are 0.291 and 0.349 respectively -- both are quite acceptable, and I just wanted to point out the discrepancy.

We can wait and find out about what Mike says regarding my Mo question. In the meantime, please verify the Ferty 3 analysis I just showed you, then I'll go to work on the recipe.

Ok, thank you!

Always glad to help!

[Steve Johnson]

I have read that Tephrocactus can be shy to bloom. It will be interesting to see if your planned reduce P does anything.

Yes, Tephros do have a notorious reputation about that. They're also notorious about dropping segments for no apparent reason, which can be a problem since the plant needs to grow at least 8 segments before it'll bloom, and dropping segments before you get there means no blooming. My pine cone Tephro is still holding together (up to 10 segments now), but the paper-spine always drove me to distraction. Then last year it grew not 1, not 2, not 3, but 4 new segments (a personal record) for a total of 9, and it's holding together too (at least so far). Could be that the paper-spine was dropping segments due to a deficiency of K, Ca, and Mg, in which case the Potassium sulfate and CalMag supplements may have done the trick to strengthen the juncture between segments. Not the worst thing in the world if the Tephros don't flower with lower P, but I'll be thrilled if it happens.

[jerrytheplater]

I have read that Tephrocactus can be shy to bloom. It will be interesting to see if your planned reduce P does anything.

Yes, Tephros do have a notorious reputation about that. They're also notorious about dropping segments for no apparent reason, which can be a problem since the plant needs to grow at least 8 segments before it'll bloom, and dropping segments before you get there means no blooming. My pine cone Tephro is still holding together (up to 10 segments now), but the paper-spine always drove me to distraction. Then last year it grew not 1, not 2, not 3, but 4 new segments (a personal record) for a total of 9, and it's holding together too (at least so far). Could be that the paper-spine was dropping segments due to a deficiency of K, Ca, and Mg, in which case the Potassium sulfate and CalMag supplements may have done the trick to strengthen the juncture between segments. Not the worst thing in the world if the Tephros don't flower with lower P, but I'll be thrilled if it happens.

I have a Tephro too and it always drops off segments. I'm making a dish out of them. Maybe strength in numbers?

[Fohat85]

Hi Davide,

Before I do the recipe calculations, I just wanted to make sure that we're talking about the Ferty 3 you'll want to use:


Ferty_3_guaranteed_analysis01.jpg

One thing I did notice is that the ratio of Ammonium N to Nitrate N is about 2-1, and the ratio of my FloraMicro-FloraBloom plus Ammonium sulfate-Potassium sulfate stock solution will give me the exact opposite with a 1-2 ratio in my watering solution. There's nothing at all wrong with Ferty 3's 2-1 ratio, so the only question I have is regarding its .001% Molybdenum. Is that enough, or will you need a Sodium molybdate stock solution too? I don't feel qualified to answer, and hopefully Mike will chime in here. Just remember -- Mo is required for Nitrate-Ammonium conversion in the plant's tissues. If the amount of Mo in Ferty 3 is good enough for efficient conversion, you'll be fine. What say you, Mike?

There's one other thing I'm kinda curious about -- guaranteed analysis states 10% P2O5 on the left. On the right, the description is neutral ammonium citrate and 12% P2O5 right below that. So which is it, 10% or 12%? 10 x .436 = 4.36% P and 12 x .436 = 5.232% P. The P/N ratios are 0.291 and 0.349 respectively -- both are quite acceptable, and I just wanted to point out the discrepancy.

We can wait and find out about what Mike says regarding my Mo question. In the meantime, please verify the Ferty 3 analysis I just showed you, then I'll go to work on the recipe.

Ok, thank you!

Always glad to help!

Yes Steve is the same Ferty 3

[MikeInOz]

tissues. If the amount of Mo in Ferty 3 is good enough for efficient conversion, you'll be fine. What say you, Mike?

Probably just ok because there is not to much nitrate but I would add more. Wouldn't hurt to triple it to 0.03ppm. Of course that depends on the components of the mix.

[Steve Johnson]

tissues. If the amount of Mo in Ferty 3 is good enough for efficient conversion, you'll be fine. What say you, Mike?

Probably just ok because there is not to much nitrate but I would add more. Wouldn't hurt to triple it to 0.03ppm. Of course that depends on the components of the mix.

I came to a similar conclusion before you responded, although I shaded it down to 0.022 ppm. Davide, I'm 99% ready to post the Ferty 3 and Potassium sulfate supplement recipes, but I'd like to get it to 100% once we figure out the right amount of Mo. Please describe what's in your mix -- that means ingredients and proportions. When Mike sees it, he should be able to give us a more precise number. Hard to believe that such a tiny amount could make such a big difference to efficient vs. inefficient Nitrate-Ammonium conversion in the tissues of our cacti, and I can also understand why a tiny amount too high may lead to toxicity problems in xeric plants.

I mentioned a Promix article on Molybdenum here...

viewtopic.php?p=398919&hilit=promix#p398919

... so I just now went back and captured this screenshot:

Molybdenum.jpg (75.28 KiB) Viewed 3480 times

I'm fascinated by a couple of things -- first, the sentence underlined in red. I don't know what that means, but I'd like to find out. The sentence underlined in black is a bit fascinating because it provides more detail on the Mo/nitrate-ammonia conversion process.

[Fohat85]

Dear friends, my soil mix is composed by:

20% zeolite
40% lapillus
20% dolomite
5% coal
10% coconut fiber soil
5% fine gravel

For older plant (>30 years) i usually replace organic component with fine gravel.

[Steve Johnson]

Dear friends, my soil mix is composed by:

20% zeolite
40% lapillus
20% dolomite
5% coal
10% coconut fiber soil
5% fine gravel

For older plant (>30 years) i usually replace organic component with fine gravel.

Before Mike gives us an evaluation of your mix and what it means for determining the right amount of Mo, I just wanted to point out a few things...

Zeolite has good CEC (for members who don't know the term, "CEC" is cation-exchange capacity), so you won't need to fertilize with each watering as I do using my pumice-granite gravel mix. (Pumice has very low CEC and granite has none.) Once I show you the recipe, the nutrient dosages in parts-per-million for your watering solution will give us an idea on how often you should fertilize. Any recommendation I make will be nothing more than a guess, so I would defer to Mike if he has a better one. We don't have enough information for that yet, but we will soon.

5% coal -- do you mean charcoal? From Better Homes and Gardens Australia (https://www.bhg.com.au/charcoal-in-potted-plants):

• "Another great way to keep your plants healthy is by adding a layer of horticultural charcoal to the pot or planter.
  
  "This absorbs excess water from the roots of your plant and keeps the soil “sweet” by guarding against bacteria, fungus and rot. It also helps to eliminate odours, and is particularly effective in terrariums."

I can see that in nonxeric plants, but I don't know if it does anything given the fact that your mix is 90% mineral. Which brings me to the other 10%...

Coconut fiber = coir, and I believe you're using ground coir as your soil component. Not sure why you're using it in the mix for cacti that are less than 30 years old. It causes more problems than it solves, as Mike explains here...

viewtopic.php?p=398697&hilit=coir#p398697

...and here:

viewtopic.php?p=398705#p398705

If you need the 10% component for better water retention in the mix, try this instead:

viewtopic.php?p=398714&hilit=sphagnum#p398714

My recommendation at the moment:

• 20% zeolite and 40% lapillus have roughly the same water retention capability as the pumice in my 60% pumice-40% granite gravel mix, so you're fine there unless people who use both say otherwise.

• You and I share a similar Mediterranean climate -- get rid of the charcoal and dolomite (they're actually working against each other), and go with 25% coarse gravel. Mix it with 5% fine gravel -- remarkably close to the 40% granite gravel in my mix.

Because pumice retains a surprising amount of water, straight pumice in a humid climate takes too long to dry out. Unlike the high porosity of pumice, granite has a much lower porosity, so I use granite gravel as a "moderator" to let the mix dry out in a timely manner. Your gravel doesn't necessarily have to be granite as long as it's relatively nonporous. Cactus roots need something they can grab onto -- smooth aquarium pebbles won't do the job, so your gravel needs to have some roughness to it. I'm not convinced that you need a 10% component for additional water retention, although I don't know the climate in Rome well enough to say if you do or not. If you don't, the only reason for repotting is when cacti outgrow their pots and require bigger pots -- a nice problem to have!