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

[SDK1]

SDK1. Thanks for these article links. I went to the first link by Park S. Nobel which you posted and found the download pdf link at the bottom and went to it. I was still behind a paywall and would need to pay $42.00 to download it. Viewing online for 48 hours was ONLY $10.00. I hate this. Seems to me like this knowledge is being kept hidden from the ignorant masses (like me). Only the high priests of scientific knowledge are allowed to look via their institutional position. Bugs me to no end.

It's unethical and I hate it too; I have a real bone to pick with academic journals and publishers.

I updated the link with a non-paywalled version. Posting it in this reply as well.

- https://www.eeb.ucla.edu/Faculty/Nobel/ ... 20Ecol.pdf

If you go to this page you can browse the various articles too.

- https://scholar.google.com/scholar?hl=e ... acti&btnG=

[jerrytheplater]

SDK1. Thanks for these article links. I went to the first link by Park S. Nobel which you posted and found the download pdf link at the bottom and went to it. I was still behind a paywall and would need to pay $42.00 to download it. Viewing online for 48 hours was ONLY $10.00. I hate this. Seems to me like this knowledge is being kept hidden from the ignorant masses (like me). Only the high priests of scientific knowledge are allowed to look via their institutional position. Bugs me to no end.

It's unethical and I hate it too; I have a real bone to pick with academic journals and publishers.

I updated the link with a non-paywalled version. Posting it in this reply as well.

- https://www.eeb.ucla.edu/Faculty/Nobel/ ... 20Ecol.pdf

If you go to this page you can browse the various articles too.

- https://scholar.google.com/scholar?hl=e ... acti&btnG=

Yeah, it is not the authors. I've gotten articles usually related to algae or aquatic plants by going to the author directly in their academic or commercial location. They often have their articles available for download there. I also use JSTOR because they have free reading privilege's of journals they manage. I didn't go there for this article. Thanks for doing it.

I was able to download the Nobel article. I just skimmed it, and noticed he did cover some cacti genera we'd be interested in. Now I'll go back and try your other links.

[jerrytheplater]

SDK1. Just started looking at the other links. As I see it now, the first two links are to the same article. The second goes to JSTOR and you need to log in to read it. The third link is also to a paywall. I have not signed in to JSTOR yet to look for it. That service is at least free. You can read online. Pretty sure you can't print-but my memory might be off.

I have not looked at the last links yet.

Edit: I just looked at the last three links. The first two work. The third does not. I have not seen Academia.edu yet. I'll try signing up.

[7george]

I managed to download that article for free from two websites. The resume says that the role of molybdenum is not very clear for plant growth...

You can try Researchgate.net as well.

[Fohat85]

Really thanks Steve Johnson for the explanation.
What do you think about Ferty 2 (NPK 15-5-25 + micro)

[jerrytheplater]

Davide

I looked at your fertilizer and see it is labeled like here in the US. On an elemental basis it has a ratio between N-P-K of 1-0.15-1.4. I would consider it low in P based on MikeinOz's original recommendations a few years ago of 1.0-0.4-1.5. If you are comfortable tinkering you could boost the P with Mono Potassium Phosphate KH2PO4.

I don't think I'd go out and buy a 25 kg bag unless I owned a greenhouse and had a huge collection! Hopefully it is packaged in smaller quantities.

[Steve Johnson]

Really thanks Steve Johnson for the explanation.
What do you think about Ferty 2 (NPK 15-5-25 + micro)

You're welcome, Davide! I agree with Jerry that the P in Ferty 2 is lower than we would like, so his recommendation for supplementing it with Mono Potassium Phosphate is good. Other than that, the only recommendation I would make (following Jerry's lead) is to get it in a smaller quantity unless you have a really big collection.

Here is Ferty 2's chemical analysis:

Total nitrogen (N): 15% of which, nitric nitrogen 8.5%, ammonia nitrogen 6.5%;
Phosphorus pentoxide (P 2 O 5 ) soluble in neutral ammonium citrate and in water: 5% of which, water soluble phosphorus pentoxide 5%;
Water-soluble potassium oxide (K 2 O): 25%;
Magnesium oxide (MgO) soluble in water: 2%;
Boron (B) soluble in water: 0.02%;
Copper (Cu) soluble in water chelated with EDTA: 0.03%;
Water-soluble iron (Fe) chelated with EDTA: 0.075%;
Manganese (Mn) soluble in water chelated with EDTA: 0.05%;
Molybdenum (Mo) soluble in water: 0.001%;
Zinc (Zn) soluble in water chelated with EDTA: 0.01%.

We can't remove excess nutrients from a fertilizer, but we can certainly add them -- not directly into the fert, but with stock solutions we'll add to a watering solution. With that in mind, Ferty 2 is short on Mo, so aside from a Mono Potassium Phosphate stock solution to bring the P up, I would highly recommend a Sodium molybdate stock solution as well. The other nutrient missing -- Calcium, and a Nitrogen-free CalMag supplement will be required.

Davide -- I don't have time to go through the technical details now, but if you can get Ferty 2 in a quantity that's usable for you, I'll run calculations over the weekend and give you the "recipe" for the fertilizer plus stock solutions. The other thing you'll need to find -- a Nitrogen-free CalMag fert.

I would consider it low in P based on MikeinOz's original recommendations a few years ago of 1.0-0.4-1.5.

Jerry, see this and note Mike's comment at the top of my post:

viewtopic.php?p=399308#p399308

Going by what he said here...

So, now to see what "too much P" is. Maybe its in the book Mike supplied. When is iron uptake impaired?

I would have to look it up but I think it says a P/N ratio of something like 0.3 is perfectly ok for most flowering plants. That ratio would quickly kill a lot of Australian plants sensitive to P! But I would say 0.4 would be more than enough for anything.

...I'd go by a P/N ratio of 0.3, not 0.4. I suppose anything in that range should be fine, although IMO it's best if we aim for the lower end of it.

[Steve Johnson]

Davide, try this -- Ferty 2 in a 1 kg bucket:

https://www.geosism.com/en/fertilizers/ ... ers-detail

1 kg = 2.2 lbs., and that should last you for a good while. Also, go to the Amazon.it website and find out if you can find a Nitrogen-free CalMag fertilizer there. The reason why it needs to be Nitrogen-free -- your cacti will get the right amount of N in the Ferty 2, and adding a CalMag with N to your watering solution will give them too much.

[jerrytheplater]

I would consider it low in P based on MikeinOz's original recommendations a few years ago of 1.0-0.4-1.5.

Jerry, see this and note Mike's comment at the top of my post:

viewtopic.php?p=399308#p399308

Going by what he said here...

So, now to see what "too much P" is. Maybe its in the book Mike supplied. When is iron uptake impaired?

I would have to look it up but I think it says a P/N ratio of something like 0.3 is perfectly ok for most flowering plants. That ratio would quickly kill a lot of Australian plants sensitive to P! But I would say 0.4 would be more than enough for anything.

...I'd go by a P/N ratio of 0.3, not 0.4. I suppose anything in that range should be fine, although IMO it's best if we aim for the lower end of it.

Steve

Mike was quoting a table in his book on plant media when he was mentioning the African Violet study-at least that is what I understand from his response to me asking where that table was located.

I searched N:P ratio to be sure I understood what it meant and found a bunch of articles, this being an open source one: https://besjournals.onlinelibrary.wiley ... 03.00820.x In it the author says, "We calculated N:P ratios by dividing N concentration by P concentration (both as percentage nutrient in the sample) within each plant tissue sample." So they analyzed the plant tissue for N and P concentrations.

Is the African Violet study looking at the N and P contained in the plants, or in the fertilizers? I don't know. But, if you plug in a typical fertilizer Nitrogen % of 9, you will get a P % of 64: N%/P% = 0.14. 9%/P% = 0.14 P%=64. That can't be correct. So it must be speaking of the nutrient concentrations in the plants themselves.

The post directly above the first link is Mike saying my 9.0-3.6-13.5 adjustment of Dyna-Gro Foliage-Pro (a 1.0-0.4-1.5 ratio) is "close to perfect IMO". That is the ratio you've been using here for almost two years now. Why all of a sudden is the P content being lowered? Haven't your plants been growing well these past two years?

The next quote you have has Mike giving a "P/N" ratio. Opposite what was given above. So, plugging in some numbers. P/N=0.3. If N is 1% then P is 0.3%. If N is 9%, then P is 2.7%. These numbers are more in line with the fertilizers we are using. I searched for "P/N ratio" and didn't find a single one in the botanical field.

If you remember the figure I quoted where Corn and Soybeans were being grown and available soil solution P was found to be in the 20 ppm range for "sufficient" P. The yield at that point was 90-100%. When soil P was up to 70 ppm, yield was still 90-100 %. The Dyna-Gro Foliage-Pro I use at 50 ppm N level has a 20 ppm P level. You'll find that in the chart I attached in the Cal-Mag thread.

So, I am still not convinced that we know exactly what ratio we should be using in fertilizers. I do know we have a member here that uses 20-20-20 fertilizer with trace nutrients to grow his plants. (20-20-20 N-P2O5-K2O works out to a 1.0-0.44-0.83 elemental N-P-K ratio) His plants are primo. I also saw a few years ago that the company Planet Desert used 1 lb of 20-20-20 per 1000 gallons (a 25 ppm N solution) to water their plants. It is not on the website now, but it was then. I don't use 20-20-20, and am not suggesting anyone should. But others are and it tells me we still don't know how much P is too much. That fertilizer is right near what Mike has been suggesting, at least in the N-P.

[Steve Johnson]

Hi Jerry,

Going back to the Dyna-Gro 7-7-7 I've been using for years, the P/N ratio of 0.44 has been fine in terms of plant growth and flowering. If anything, the Potassium sulfate and CalMag supplements have led to significant improvements in my cacti over the last couple of years. And that includes more flowering. With that said, you make a fair point -- do we really know the "ideal" ratio of P? Pegging it to a precise number doesn't make any sense to me, so IMO the 0.3-0.4 range I mentioned gives us some "wiggle room" to work with.

Going by trials with orchids and African violets, then applying the P numbers to cacti may be like comparing apples to oranges, so it would be helpful if we had an apples-to-apples comparison with cacti of the same species being grown under cultivation with various P/N ratios. We're talking about a trial that would take years to complete, and I don't know of anyone who has done it. I certainly can't, but I'm willing to run my own little test when I start growing my cacti with a P/N ratio of 0.3 instead of 0.44 this year. Of course the results I get by the end of summer will be nothing more than anecdotal evidence, although the before-and-after photos I take should tell me if they're good, bad, or indifferent. In the absence of large-scale trials on cacti under cultivation, I believe that anecdotal evidence coming from growers is all we have.

[Steve Johnson]

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.

[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.

[Steve Johnson]

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.

[jerrytheplater]

+2 is the Magnesium content, at least that is what it looks like from Davide's/Fohat's post: (N) (P) (K) + (Mg)

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.

[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 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?