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

Discuss repotting, soil, lighting, fertilizing, watering, etc. in this category.
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MikeInOz
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Re: Fertilizers explained (2-part presentation)

Post by MikeInOz »

"Steve Johnson" post_id=399524 time=1677652386 user_id=4655]
. If I add 10% zeolite to the mix, would you recommend that I alternate between water plus fert and water only at that dosage? The Ferty 3 I have in mind for Davide will give him a watering solution which contains 60 ppm N, 17.4 ppm P (P/N ratio = 0.29), and 91 ppm K. If he adds 10% zeolite to his mix too, how often should he be fertilizing whenever he waters?
Probably won't make much difference but with the added zeolite you will get protection against NH4 toxicity (if there is a potential for it) and you will have a mix that better holds the cations ammonium, calcium, magnesium and potassium. So missing a fertilization here and there will not see the plants starving. So I can't really recommend anything but you can safely flush out the mix every few waterings with plain water. But even if you don't,, once the zeolite is charged with the cations, any more of them will simply wash through and leave a ''bank'' of them for use by the plant if and when it needs them. Sorry if that's vague but I don't have any more detailed advice.
Question #2 -- that Ferty 3 dosage will break the 60 ppm N down to 42 ppm NH4 and 18 ppm NO3 per feeding. Would you still recommend 0.03 ppm Mo in a 10% zeolite/50% pumice/40% nonporous gravel mix? With the answers to both of those questions, I'll be ready to give Davide the recipes and instructions for the Ferty 3, Potassium sulfate stock solution, and how much of each should go into his watering solution.
Mo is an anion so will not be held by colloids (clay or humus) or zeolite. So I would say leave it unchanged as it would need to be replenished continuously.
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Re: Fertilizers explained (2-part presentation)

Post by Steve Johnson »

MikeInOz wrote: Wed Mar 01, 2023 7:22 am
"Steve Johnson" post_id=399524 time=1677652386 user_id=4655]
. If I add 10% zeolite to the mix, would you recommend that I alternate between water plus fert and water only at that dosage? The Ferty 3 I have in mind for Davide will give him a watering solution which contains 60 ppm N, 17.4 ppm P (P/N ratio = 0.29), and 91 ppm K. If he adds 10% zeolite to his mix too, how often should he be fertilizing whenever he waters?
Probably won't make much difference but with the added zeolite you will get protection against NH4 toxicity (if there is a potential for it) and you will have a mix that better holds the cations ammonium, calcium, magnesium and potassium. So missing a fertilization here and there will not see the plants starving. So I can't really recommend anything but you can safely flush out the mix every few waterings with plain water. But even if you don't,, once the zeolite is charged with the cations, any more of them will simply wash through and leave a ''bank'' of them for use by the plant if and when it needs them. Sorry if that's vague but I don't have any more detailed advice.
That's fine and you gave me a nugget of good information. NH4 toxicity has never been a problem since my fert regimen gives the cacti a 2-1 ratio of NO3 and NH4. Such being the case, zeolite is optional, and as I said in a previous post, they're doing just fine without it. However, since Davide's Ferty 3 flips the ratio around, I think it'll be more important that he includes 10% zeolite in his hydroponic mix. And he won't need to be quite as strict about fertilizing every time he waters. Concerning the Mo supplementing Ferty 3, 0.03 ppm it is, and I'll include the right amount of Sodium molybdate when I give him the fert and stock solution recipes.

As always, thanks for your help, Mike!
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
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Re: Fertilizers explained (2-part presentation)

Post by jerrytheplater »

MikeInOz wrote: Wed Mar 01, 2023 7:08 am
jerrytheplater wrote: Wed Mar 01, 2023 2:46 am
MikeInOz wrote: Wed Mar 01, 2023 1:03 am
Using raw coconut dust or partly decomposed and unheated (as in composting or solarizing) material is a good example of the wrong thing to do. The main drawback of using organic material in cacti mixes is the decomposition and reduction of AFP in mixes used for cacti which do not need to be repotted for extended periods. But that seems to be only a minor issue because the vast majority of cacti are not watered as much as other plants and most are repotted before any problems with AFP arise.
AFP? = Available Free Phosphate?
Air filled porosity. In other words, the space available that can hold air will reduce over time as organic particles become smaller and WHC (water holding capacity) will increase.
Thanks.
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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Re: Fertilizers explained (2-part presentation)

Post by keith »

I know there are many expert cactus growers in Italy what do they use ?

"Dear friends, my soil mix is composed by:"

20% zeolite
40% lapillus
20% dolomite
5% coal
10% coconut fiber soil
5% fine gravel
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Re: Fertilizers explained (2-part presentation)

Post by jerrytheplater »

MikeInOz wrote: Fri Feb 24, 2023 1:07 am
jerrytheplater wrote: Thu Feb 23, 2023 5:31 pm
MikeInOz wrote: Wed Feb 01, 2023 11:45 pm

''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.
Mike, I found the 2010 version of the book on the Internet Archive. I was able to join for free and look at it online to my hearts content. I read about the African Violet study and the text said the authors acknowledged that the amount of sun the plants get strongly outweighs any effect of increasing P content reducing flowers. So now, my violets flower almost non stop year round. But the plants are not filled with blooms, but it is more than a few. I've seen plants where the leaves are obscured by the flowers. I am using Dyna-Gro Bloom on them almost exclusively at 1/4 tsp per gallon. In US terms Bloom is 3-12-6, or elemental terms 3-5.2-5, which is a 1-1.73-1.67 ratio. I also have Jack's Classic African Violet food which is 12-36-14 or elemental 12-15.7-11.6, a 1-1.3-0.97 ratio. Both have very high P/N ratio.

It will be easy enough for me to switch to a lower P/N ratio fertilizer.
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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Re: Fertilizers explained (2-part presentation)

Post by MikeInOz »

jerrytheplater wrote: Wed Mar 01, 2023 6:28 pm
MikeInOz wrote: Fri Feb 24, 2023 1:07 am
jerrytheplater wrote: Thu Feb 23, 2023 5:31 pm
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.
Mike, I found the 2010 version of the book on the Internet Archive. I was able to join for free and look at it online to my hearts content. I read about the African Violet study and the text said the authors acknowledged that the amount of sun the plants get strongly outweighs any effect of increasing P content reducing flowers. So now, my violets flower almost non stop year round. But the plants are not filled with blooms, but it is more than a few. I've seen plants where the leaves are obscured by the flowers. I am using Dyna-Gro Bloom on them almost exclusively at 1/4 tsp per gallon. In US terms Bloom is 3-12-6, or elemental terms 3-5.2-5, which is a 1-1.73-1.67 ratio. I also have Jack's Classic African Violet food which is 12-36-14 or elemental 12-15.7-11.6, a 1-1.3-0.97 ratio. Both have very high P/N ratio.

It will be easy enough for me to switch to a lower P/N ratio fertilizer.
Sounds good Jerry. And Yes we should always keep in mind that light exposure trumps everything!
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Re: Fertilizers explained (2-part presentation)

Post by MikeInOz »

Steve Johnson wrote: Wed Mar 01, 2023 8:27 am
MikeInOz wrote: Wed Mar 01, 2023 7:22 am
"Steve Johnson" post_id=399524 time=1677652386 user_id=4655]
. If I add 10% zeolite to the mix, would you recommend that I alternate between water plus fert and water only at that dosage? The Ferty 3 I have in mind for Davide will give him a watering solution which contains 60 ppm N, 17.4 ppm P (P/N ratio = 0.29), and 91 ppm K. If he adds 10% zeolite to his mix too, how often should he be fertilizing whenever he waters?
Probably won't make much difference but with the added zeolite you will get protection against NH4 toxicity (if there is a potential for it) and you will have a mix that better holds the cations ammonium, calcium, magnesium and potassium. So missing a fertilization here and there will not see the plants starving. So I can't really recommend anything but you can safely flush out the mix every few waterings with plain water. But even if you don't,, once the zeolite is charged with the cations, any more of them will simply wash through and leave a ''bank'' of them for use by the plant if and when it needs them. Sorry if that's vague but I don't have any more detailed advice.
That's fine and you gave me a nugget of good information. NH4 toxicity has never been a problem since my fert regimen gives the cacti a 2-1 ratio of NO3 and NH4. Such being the case, zeolite is optional, and as I said in a previous post, they're doing just fine without it. However, since Davide's Ferty 3 flips the ratio around, I think it'll be more important that he includes 10% zeolite in his hydroponic mix. And he won't need to be quite as strict about fertilizing every time he waters. Concerning the Mo supplementing Ferty 3, 0.03 ppm it is, and I'll include the right amount of Sodium molybdate when I give him the fert and stock solution recipes.

As always, thanks for your help, Mike!
I did a bit more investigating into the nitrate/ammonium thing and read that the ''orange rot'' we often see in cacti is probably a form of Fusarium.
https://www.mdpi.com/2309-608X/8/4/364
According to the Handreck book, Fusarium favors 15 to 30 degrees C, Low to moderate moisture (good aeration), and high N - ''especially high nitrate'' It appears these pathogens use nitrate for food rather than ammonium so we don't want much un-converted nitrate sitting in the plants tissues.
Another good reason to make sure we give low N, not too much nitrate and always include Mo!
When I use liquid fertilizer occasionally, I use ''Part B'' of a hydroponic fertilizer (the part which contains everything but the Calcium nitrate) and add a small amount of ammonium sulphate and no nitrate at all. A combination of NHO4 and KNO3 is also possible to supply the N but then you would have to dissolve them separately again. Of course I then need to add Ca some other way because I am omitting the CaNO3, and top dressing gypsum seems to be the best way to do that.
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Re: Fertilizers explained (2-part presentation)

Post by jerrytheplater »

MikeInOz wrote: Wed Mar 01, 2023 11:20 pmWhen I use liquid fertilizer occasionally, I use ''Part B'' of a hydroponic fertilizer (the part which contains everything but the Calcium nitrate) and add a small amount of ammonium sulphate and no nitrate at all. A combination of NHO4 and KNO3 is also possible to supply the N but then you would have to dissolve them separately again. Of course I then need to add Ca some other way because I am omitting the CaNO3, and top dressing gypsum seems to be the best way to do that.
Mike, what is the typo, "A combination of NHO4 and KNO3"? NHO4 = ?
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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Re: Fertilizers explained (2-part presentation)

Post by MikeInOz »

jerrytheplater wrote: Wed Mar 01, 2023 11:57 pm
MikeInOz wrote: Wed Mar 01, 2023 11:20 pmWhen I use liquid fertilizer occasionally, I use ''Part B'' of a hydroponic fertilizer (the part which contains everything but the Calcium nitrate) and add a small amount of ammonium sulphate and no nitrate at all. A combination of NHO4 and KNO3 is also possible to supply the N but then you would have to dissolve them separately again. Of course I then need to add Ca some other way because I am omitting the CaNO3, and top dressing gypsum seems to be the best way to do that.
Mike, what is the typo, "A combination of NHO4 and KNO3"? NHO4 = ?
Sorry, should actually be (NH4) 2SO4 and KNO3
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Re: Fertilizers explained (2-part presentation)

Post by Steve Johnson »

MikeInOz wrote: Wed Mar 01, 2023 11:20 pmI did a bit more investigating into the nitrate/ammonium thing and read that the ''orange rot'' we often see in cacti is probably a form of Fusarium.
https://www.mdpi.com/2309-608X/8/4/364
According to the Handreck book, Fusarium favors 15 to 30 degrees C, Low to moderate moisture (good aeration), and high N - ''especially high nitrate'' It appears these pathogens use nitrate for food rather than ammonium so we don't want much un-converted nitrate sitting in the plants tissues.
Another good reason to make sure we give low N, not too much nitrate and always include Mo!
You might be interested in seeing this:

Turbinicarpus_polaskii10312011_01.jpg
Turbinicarpus_polaskii10312011_01.jpg (171.76 KiB) Viewed 2819 times
Yep, orange rot. That was on a Turbinicarpus polaskii I got from the California Cactus Center in June 2011 -- and the collection's first casualty. Mistake #1, growing the poor thing in this:

California Cactus Center "custom" mix
California Cactus Center "custom" mix
CCC_soil_sample.JPG (123.25 KiB) Viewed 2819 times
Mistake #2 -- watering it in mid-October when I should've stopped watering before the end of September. Although aeration in that mix wasn't good, the slow-release fert I got from the CCC should tell us a little something about the high N problem:

CCC_fertilizer.JPG
CCC_fertilizer.JPG (89 KiB) Viewed 2819 times
The sad experience led me to joining the forum in November 2011, and thanks to Darryl Craig of CoronaCactus Nursery being there in early 2012, he helped me learn from my mistakes. What you're witnessing here is the first and only time I saw orange rot on one of my cacti. Darryl was the one who recommended Dyna-Gro All-Pro 7-7-7 with a dilution rate of 1/2 tsp. per gallon, so there's the low N. Although I'll be recommending .03 ppm Mo for Davide's recipes, I'll go with .05 ppm when I start on the new fert regimen using the GH FloraMicro and FloraBloom supplemented by Ammonium sulfate, Potassium sulfate, and Sodium molybdate. With that in mind, I'll let the cat out of the proverbial bag:

FM-FB_plus_stock_solutions_01.jpg
FM-FB_plus_stock_solutions_01.jpg (88.95 KiB) Viewed 2819 times
FM-FB_plus_stock_solutions_02.jpg
FM-FB_plus_stock_solutions_02.jpg (66.75 KiB) Viewed 2819 times
FM-FB_plus_stock_solutions_03.jpg
FM-FB_plus_stock_solutions_03.jpg (65.62 KiB) Viewed 2819 times
I do have a couple of requests before I put this in action:
  • Everyone, please check my math -- if any of the calculations are in error, I'd appreciate it if you could give me the right calculations. I'll update my spreadsheet accordingly.
  • Mike -- you mentioned that S toxicity in cacti is quite rare. Please let me know if there might be a problem with 38 ppm S per feeding.
If everything looks good here, I'll post the Ferty 3 and stock solution recipes soon.
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
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Re: Fertilizers explained (2-part presentation)

Post by Steve Johnson »

Steve Johnson wrote: Wed Feb 22, 2023 8:08 am 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...
Hi Jerry,

I have a few more cacti I'll add to the list:
  • Astrophytum asterias from CoronaCactus received in July 2012. 1st flower in summer 2014, and a reliable bloomer until it stopped flowering last year. The species normally flowers in spring and summer, so I was thrilled to see this on 12/18/21:

    Astrophytum_asterias12182021.jpg
    Astrophytum_asterias12182021.jpg (106.03 KiB) Viewed 2807 times
    Maybe I shouldn't have been so thrilled. First of all, those flower colors appear "washed out" compared to what they normally look like -- example on 6/22/20:

    Astrophytum_asterias06222020_02.JPG
    Astrophytum_asterias06222020_02.JPG (122.37 KiB) Viewed 2807 times
    Second (kind of a red flag to me now), blooming well out of season. And the third red flag -- the plant aborted a couple of buds last spring, then no more buds after that. Unlike other Astrophytum species, A. asterias tends to be finicky about how it's grown. This leads me to wondering if mine got tired of being fed with 0.44 P after 10 years.
  • Mammillaria guelzowiana from Miles' To Go received in July 2013. Also a reliable bloomer until it stopped flowering last year.
  • Stenocactus lloydii also from Miles' To Go received in December 2013. Usually flowers late February-March, but no sign of buds that should've been setting by now.
It's possible that some species are more sensitive to a higher P/N ratio of 0.44 than others, and I think there may be a general sensitivity I won't know about unless and until I bring the P down to 0.3. If nothing else, the 2023 growing season should be an interesting test to see if the lower P leads to a noticeable improvement in all of my cacti by the end of summer. The test will begin once we get past this unusually cold SoCal winter.

Contrary to what I asserted here...
Steve Johnson wrote: Fri Feb 24, 2023 12:39 am
MikeInOz wrote: Sat Feb 18, 2023 12:42 amNo 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.
...I wonder if cacti really are just like all other plants in terms of their P requirements. Could it be that cacti do need lower P compared to nonxeric plants like orchids and African violets? This isn't just about flowering -- it's also about what excessive amounts of P could do to push cacti beyond their natural growth limits. From something I posted in "The Cal-Mag of My Dreams?", and I'll pull out the relevant quote:
Steve Johnson wrote: Wed Feb 15, 2023 11:08 pmHere'a an item of interest I found called Master gardeners: Desert soils and fertilizer by Lake Havasu City Master Gardener Steve Gissendanner (source https://apnews.com/article/5e06475955f8 ... 2d491782c6):
  • "Desert soils are often low in phosphorus as well. Phosphorus comes mainly from rocks, but most phosphorus is locked up in sediments and rocks, making it unavailable to plants." [My emphasis.]
This make a good argument in favor of the idea that a P/N ratio of 0.25-0.35 is optimal and anything above 0.4 is excessive for cacti being grown under cultivation.

When P is higher than N, that's a big excess, and even though we don't know what abnormal growth would look like, my guess is that you would see bloated weak-spined cacti that bear no resemblance to what they should look like according to type for the species. A P/N ratio of 0.44 is a much smaller excess, so I think it would take more than a few years before abnormal growth is apparent enough to be obvious. One thing we're not discussing here, but IMO should be -- the plant's longevity. Excessive P = shorter lifespan, and that could be the biggest problem when cacti are being fed with too much P in their diet. Of course that's merely conjecture on my part, and I don't know if this has been studied. But the excessive P-lower lifespan connection in cacti does seem logical.
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
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Re: Fertilizers explained (2-part presentation)

Post by MikeInOz »

Steve Johnson wrote: Thu Mar 02, 2023 4:48 am ..I wonder if cacti really are just like all other plants in terms of their P requirements. Could it be that cacti do need lower P compared to nonxeric plants like orchids and African violets?
The P/N ratio of desert soils averages around the 0.3 Mark. Sometimes higher sometimes lower. Stick to around that and perhaps not much lower than 0.2 and not much higher than 0.4 . I think you would be hard pressed to see a difference in plant performance. I use lime in my limestone species mixes so some of the P would probably get tided up into Calcium Phosphate so the ratio could very well be lower. I still have no problems with flowering. The requirements for P do not seem very high but that does not necessarily mean higher ratios would do serious harm in certain circumstances. One thing is for sure. High P to N ratios don't improve anything.
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Re: Fertilizers explained (2-part presentation)

Post by Steve Johnson »

MikeInOz wrote: Thu Mar 02, 2023 5:37 amOne thing is for sure. High P to N ratios don't improve anything.
You were the first one to point this out back in 2020, and that's when I started to learn a lot from you.

Going back to the General Hydroponics fert and stock solution recipes I posted this afternoon, I didn't get any negative feedback from you, so I think I may have nailed it on the calculations. If I have, I just wanted to ask you if 38 ppm S per feeding in the watering solution would be a problem. (You mentioned that S toxicity is quite rare in cacti, so I'd like to double-check and make sure.) Also, the watering solution will contain 33 ppm Ca and 10 ppm Mg. I can raise both with some TPS CalMag, but I don't know how high Ca can go before it becomes toxic. If I add enough to match it with 47 ppm N, would that be good or too much?
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
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Re: Fertilizers explained (2-part presentation)

Post by MikeInOz »

Steve Johnson wrote: Thu Mar 02, 2023 6:23 am
MikeInOz wrote: Thu Mar 02, 2023 5:37 amOne thing is for sure. High P to N ratios don't improve anything.
You were the first one to point this out back in 2020, and that's when I started to learn a lot from you.

Going back to the General Hydroponics fert and stock solution recipes I posted this afternoon, I didn't get any negative feedback from you, so I think I may have nailed it on the calculations. If I have, I just wanted to ask you if 38 ppm S per feeding in the watering solution would be a problem. (You mentioned that S toxicity is quite rare in cacti, so I'd like to double-check and make sure.) Also, the watering solution will contain 33 ppm Ca and 10 ppm Mg. I can raise both with some TPS CalMag, but I don't know how high Ca can go before it becomes toxic. If I add enough to match it with 47 ppm N, would that be good or too much?
38ppm S would be fine. Ca won't be toxic at any amount. Too much might interfere with K but I have not found that to be a problem yet and I use a lot of Ca.
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Re: Fertilizers explained (2-part presentation)

Post by jerrytheplater »

Steve Johnson wrote: Thu Mar 02, 2023 4:48 am
Steve Johnson wrote: Wed Feb 22, 2023 8:08 am 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...
Hi Jerry,

I have a few more cacti I'll add to the list:
  • Astrophytum asterias from CoronaCactus received in July 2012. 1st flower in summer 2014, and a reliable bloomer until it stopped flowering last year. The species normally flowers in spring and summer, so I was thrilled to see this on 12/18/21:


    Astrophytum_asterias12182021.jpg

    Maybe I shouldn't have been so thrilled. First of all, those flower colors appear "washed out" compared to what they normally look like -- example on 6/22/20:


    Astrophytum_asterias06222020_02.JPG

    Second (kind of a red flag to me now), blooming well out of season. And the third red flag -- the plant aborted a couple of buds last spring, then no more buds after that. Unlike other Astrophytum species, A. asterias tends to be finicky about how it's grown. This leads me to wondering if mine got tired of being fed with 0.44 P after 10 years.
  • Mammillaria guelzowiana from Miles' To Go received in July 2013. Also a reliable bloomer until it stopped flowering last year.
  • Stenocactus lloydii also from Miles' To Go received in December 2013. Usually flowers late February-March, but no sign of buds that should've been setting by now.
It's possible that some species are more sensitive to a higher P/N ratio of 0.44 than others, and I think there may be a general sensitivity I won't know about unless and until I bring the P down to 0.3. If nothing else, the 2023 growing season should be an interesting test to see if the lower P leads to a noticeable improvement in all of my cacti by the end of summer. The test will begin once we get past this unusually cold SoCal winter.

Contrary to what I asserted here...
Steve Johnson wrote: Fri Feb 24, 2023 12:39 am
MikeInOz wrote: Sat Feb 18, 2023 12:42 amNo 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.
...I wonder if cacti really are just like all other plants in terms of their P requirements. Could it be that cacti do need lower P compared to nonxeric plants like orchids and African violets? This isn't just about flowering -- it's also about what excessive amounts of P could do to push cacti beyond their natural growth limits. From something I posted in "The Cal-Mag of My Dreams?", and I'll pull out the relevant quote:
Steve Johnson wrote: Wed Feb 15, 2023 11:08 pmHere'a an item of interest I found called Master gardeners: Desert soils and fertilizer by Lake Havasu City Master Gardener Steve Gissendanner (source https://apnews.com/article/5e06475955f8 ... 2d491782c6):
  • "Desert soils are often low in phosphorus as well. Phosphorus comes mainly from rocks, but most phosphorus is locked up in sediments and rocks, making it unavailable to plants." [My emphasis.]
This make a good argument in favor of the idea that a P/N ratio of 0.25-0.35 is optimal and anything above 0.4 is excessive for cacti being grown under cultivation.

When P is higher than N, that's a big excess, and even though we don't know what abnormal growth would look like, my guess is that you would see bloated weak-spined cacti that bear no resemblance to what they should look like according to type for the species. A P/N ratio of 0.44 is a much smaller excess, so I think it would take more than a few years before abnormal growth is apparent enough to be obvious. One thing we're not discussing here, but IMO should be -- the plant's longevity. Excessive P = shorter lifespan, and that could be the biggest problem when cacti are being fed with too much P in their diet. Of course that's merely conjecture on my part, and I don't know if this has been studied. But the excessive P-lower lifespan connection in cacti does seem logical.
Steve
I've spent all day so far looking for the original article on the African Violet study. Just found it a few minutes ago. This is the conclusion at the end of the article: "These results show that light intensity is critical for bloom production of African violets, a high ratio of phosphorus and/or potassium to nitrogen is not necessary, and cultivar selection is important."

I also got a lot of other items too. I intend to check your numbers, but I wanted to do the violets first! I was looking for anything relating to Cacti, and did not find anything.

Comment on the Mo solution. Personally, I would not trust the scales you linked to previously to get an accurate 0.08 gram. In my opinion, you would be much better off to let the dilution give you the small weight needed. I intend to add 1.0 gram of Mo salt to a liter, and then take out the appropriate volume to add to the final 5 liter container.

One thing I learned from Ohugal or Oscar, is that in Belgium at least common consumer containers (Like our US gallon milk containers) are 5 liters in size. So, rather than use 1 liter for the amount of final fertilizer being mixed up, I use 5 liters. So, in my Mo dilution using Sodium Molybdate, I take 0.6 ml of the Mo stock solution to add to the final 5 liter of fertilizer. You could also put in 0.5 gram Sodium Molybdate in the first liter and take out 1.2 ml to put into the 5 liters. Gives the exact concentration of Mo as your calculations give. Final weight of Sodium Molybdate in the 5 liter container is 0.0006 grams. Or, 0.00012 gram per liter Sodium Molybdate.
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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