The Cal-Mag of my dreams?

Discuss repotting, soil, lighting, fertilizing, watering, etc. in this category.
User avatar
Steve Johnson
Posts: 4514
Joined: Thu Nov 03, 2011 4:44 am
Location: Los Angeles, CA (Zone 10b)

Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

I went back and looked at Mike's post -- see the line highlighed in red:
MikeInOz wrote: Mon Jan 23, 2023 6:23 am I would stick with the Dyna grow because it has more ammonium. But either one would probably be fine. My cacti get double the ammonium/urea N than Nitrate N. They are growing extremely well. Quite fast but still compact and with good spination. Mammillaria bertoltdii, leuthyi and hermosana have all flowered in their second year. Ariocarpus seedlings also growing fast (for arios). That's the kind of result I'm looking for! They obviously like the ammonium. I would be reluctant to change without a good reason. The osmocote also has much more Mo - 100ppm compared to your practically nothing. Mo is essential if plants are to convert nitrate in their tissues to usable ammonium. You might want give them a boost of Mo a couple of times a year. You should be able to get sodium or ammonium molybdate on ebay. When you use no soil or humus at all in your mix, you cannot leave out a single nutrient and you need to work out the best concentration. That is easy with fast growers like tomato but almost impossible with slow growing plants like cacti and that's another good reason to include some actual soil. Using some soil and/or compost (not sterile peat) in the mix will take the worry out of proper nutrition.
Unless he knows how much Mo is being released every time he waters his cacti, that's the unknown variable I mentioned earlier. We're at a disadvantage because Dyna-Gro ferts are general-purpose products, and based on a conversation I had with one of the Dyna-Gro people, they don't know if cacti need more Mo for efficient Nitrate-to-Ammonium conversion in the plant. With that said, here's a thought experiment, although it'll require making 3 assumptions:
  • "The osmocote also has much more Mo - 100ppm compared to your practically nothing." I'm assuming that Mike's Osmocote starts out with 100 ppm Mo before he puts it into his pots.
  • His cactus growing season lasts an even 6 months.
  • He waters his cacti twice a month.
100 ppm/12 = 8.3 ppm Mo being released by the Osmocote with each watering. We'll match it to 32 ppm Nitrate per watering with the Dyna-Gro 7-7-7, and that amount of Mo seems to make sense -- I don't see how the 7-7-7's 6 ppb does much of anything for Nitrate-to-Ammonium conversion in cacti. If my assumptions are at least close to the mark, we won't be talking apples-to-dump trucks anymore (maybe apples to kiwi fruit? :lol: ). If my first assumption is wrong, the other 2 go right out the window. Only Mike can tell us if assumption #1 is right or wrong.

While I do like his idea about giving my cacti a small Mo boost twice a year, hydroponic growing requires a steady supply of all nutrients with each watering. If I can get a more accurate ppm number for the Mo, I have absolutely no problem adding it to the fertilizer routine with the right stock solution and the right amount of it going into a watering solution.

By the way, and in case you were wondering...

From Promix (https://www.pthorticulture.com/en/train ... t-culture/):
  • "Molybdenum toxicity is very rare and, in some crops, the tissue can have several thousand ppm and still not show symptoms. In a few rare cases there has been report golden yellow appearance of the leaves."
I realize that refers to crops, but worth consideration as it may apply to cacti.

From Gardening Know How (https://www.gardeningknowhow.com/garden ... bdenum.htm):
  • "Plants can tolerate very high levels of molybdenum but do poorly with little to none of the element."
  • "Plants like cruciforms and legumes need higher amounts of the mineral."
Once again, the 2nd quote refers to crops, but it bolsters the argument in favor of the idea that cacti need a lot more Mo than the trace amount provided in the Dyna-Gro 7-7-7. If I've been getting away with it for 11 years, I'd rather correct the Mo deficiency before this becomes a significant problem. No rush trying to figure things out -- the start of the cactus growing season here in L.A. is at least 2 months away.
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
User avatar
Steve Johnson
Posts: 4514
Joined: Thu Nov 03, 2011 4:44 am
Location: Los Angeles, CA (Zone 10b)

Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

keith wrote: Tue Jan 24, 2023 8:28 pmI tested my desert soil its has a high PH 8 , low nitrogen and high Phosphorus and Medium high potassium. Trace elements I cant test for them but assume they are there. Its very sandy and volcanic in origin.
Sorry Keith, but I'll have to pass on getting the soil from Randsberg -- fine for cacti native to the Mojave desert, but I don't think it'll be a good fit for my Tephros or Eriosyce. Thanks for thinking of me anyway.
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
User avatar
MikeInOz
Posts: 479
Joined: Fri Feb 16, 2018 2:21 am
Location: Sth east Australia

Re: The Cal-Mag of my dreams?

Post by MikeInOz »

I don't have much time at the moment but this might help. All hydroponic solutions for various crops contain 0.05ppm Mo. It does not seem to vary among different crops so perhaps that is a standard optimum amount. Aim at that and you should be fine. Alternatively, give a watering with 0.5 grams/Lt Mo once or twice a season if your fertilizer has none and you don't use any soil in your mix. Too many calculations will make you go blind. :lol: One more thing, Mo is leached readily (just as nitrates phosphates and sulphates) and it's availability is lowered as pH falls.
Last edited by MikeInOz on Mon Jan 30, 2023 6:51 am, edited 1 time in total.
User avatar
Steve Johnson
Posts: 4514
Joined: Thu Nov 03, 2011 4:44 am
Location: Los Angeles, CA (Zone 10b)

Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

MikeInOz wrote: Wed Jan 25, 2023 2:36 amAll hydroponic solutions for various crops contain 0.5ppm Mo. It does not seem to vary among different crops so perhaps that is a standard optimum amount. Aim at that and you should be fine.
Oh, you're making this too easy! (Not that I'm complaining, mind you. :D ) I've been in the precision measuring business for over 35 years, and I have all kinds of nerdy wonky fun measuring things, so the calculations for a Sodium molybdate stock solution and the right amount going into a watering solution will be good mental exercise. Thanks for putting me on the right track!
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
User avatar
jerrytheplater
Posts: 1153
Joined: Mon Mar 22, 2021 7:38 pm
Location: Bloomingdale, NJ (USDA Zone 6b)
Contact:

Re: The Cal-Mag of my dreams?

Post by jerrytheplater »

Thanks for posting the information about Mo Steve. Good to know. It does seem like Mo can be used at a higher concentration without harm.

Mike's reporting of hydroponic solution concentrations of 0.5 ppm Mo and suggestion to use a 500 ppm solution of Mo to water once or twice a season for growers like Steve are very helpful.
The leaching information is good for those of us with peat in their mix.
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.
User avatar
Steve Johnson
Posts: 4514
Joined: Thu Nov 03, 2011 4:44 am
Location: Los Angeles, CA (Zone 10b)

Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

jerrytheplater wrote: Wed Jan 25, 2023 3:17 am Thanks for posting the information about Mo Steve.
You're welcome -- this is good stuff!

Another question for you, Mike...

Given the choice between Sodium molybdate and Ammonium molybdate, is there any advantage to choosing one over the other?
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
User avatar
MikeInOz
Posts: 479
Joined: Fri Feb 16, 2018 2:21 am
Location: Sth east Australia

Re: The Cal-Mag of my dreams?

Post by MikeInOz »

Steve Johnson wrote: Wed Jan 25, 2023 5:43 am
jerrytheplater wrote: Wed Jan 25, 2023 3:17 am Thanks for posting the information about Mo Steve.
You're welcome -- this is good stuff!

Another question for you, Mike...

Given the choice between Sodium molybdate and Ammonium molybdate, is there any advantage to choosing one over the other?
Either one. I think they both supply roughly the same amounts of the element.
keith
Posts: 1860
Joined: Wed Jun 12, 2013 3:50 am
Location: S. CA USA

Re: The Cal-Mag of my dreams?

Post by keith »

Hi Steve , if you don't use real desert soil it might be too different for you . Stick to what works that's the best advice. I got my first real cactus growing info from Steven Brack at Mesa 30 years ago and that's what I still use.
BTW I don't grow Mojave desert cactus they are difficult and there are not many species anyway. My cactus are mostly from the Chihuahuan desert and my succulents from South Africa.
User avatar
Steve Johnson
Posts: 4514
Joined: Thu Nov 03, 2011 4:44 am
Location: Los Angeles, CA (Zone 10b)

Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

keith wrote: Thu Jan 26, 2023 2:01 am Hi Steve , if you don't use real desert soil it might be too different for you . Stick to what works that's the best advice. I got my first real cactus growing info from Steven Brack at Mesa 30 years ago and that's what I still use.
BTW I don't grow Mojave desert cactus they are difficult and there are not many species anyway. My cactus are mostly from the Chihuahuan desert and my succulents from South Africa.
Hi Keith,

I'm on the same page with you on that -- stick to what works, and since I don't have any experience using desert soils in a cactus mix, I'll have to find a suitable replacement for the custom mix I got from the California Cactus Center in June 2011. Here's a sample of what it looks like:
CCC_soil_sample.JPG
CCC_soil_sample.JPG (123.25 KiB) Viewed 876 times
All I have to do is pick out the "boulders" (slight exaggeration) and bigger chunks of organic material (think that'll be tree bark). Add pumice for a 50/50 pumice-soil mix -- that's the mix my Tephros and 2 E. senilis enjoy growing in. I may have just enough of the CCC soil to repot them again, so I'm not too concerned about finding a replacement yet. If I remember correctly, the stuff from the CCC was basically SuperSoil -- unfortunately the SuperSoil of yesteryear was a lot better than the version we get today.
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
User avatar
Steve Johnson
Posts: 4514
Joined: Thu Nov 03, 2011 4:44 am
Location: Los Angeles, CA (Zone 10b)

Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

MikeInOz wrote: Wed Jan 25, 2023 8:54 am
Steve Johnson wrote: Wed Jan 25, 2023 5:43 am Given the choice between Sodium molybdate and Ammonium molybdate, is there any advantage to choosing one over the other?
Either one. I think they both supply roughly the same amounts of the element.
Thanks, Mike! 2 more questions for you:

1. Now that I'm aware of the Mo deficiency in the Dyna-Gro 7-7-7, I'm concerned about what 11 years of Nitrate buildup could be doing to the tissues in my cacti. If this has been showing up as abnormal stem growth, what should I look for? My powers of observation are pretty good, so your answer should tell me if anything is amiss in the way they've been growing.

2. I notice that there's urea in the Osmocote Cacti & Succulents formulation. How is urea converted to N available to the plant?

Question #2 is simply a matter of academic curiosity on my part.
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
User avatar
MikeInOz
Posts: 479
Joined: Fri Feb 16, 2018 2:21 am
Location: Sth east Australia

Re: The Cal-Mag of my dreams?

Post by MikeInOz »

Steve Johnson wrote: Thu Jan 26, 2023 10:58 pm

Thanks, Mike! 2 more questions for you:

1. Now that I'm aware of the Mo deficiency in the Dyna-Gro 7-7-7, I'm concerned about what 11 years of Nitrate buildup could be doing to the tissues in my cacti. If this has been showing up as abnormal stem growth, what should I look for? My powers of observation are pretty good, so your answer should tell me if anything is amiss in the way they've been growing.

2. I notice that there's urea in the Osmocote Cacti & Succulents formulation. How is urea converted to N available to the plant?

Question #2 is simply a matter of academic curiosity on my part.
Hi Steve

I'm not sure what the signs of Mo deficiency would look like in cacti but possibly paler than ''normal'' looking plants? Or yellowish blotching here and there? Or perhaps slower than normal growth in the nitrate is being stored and not converted in the plant tissues. The fact that cacti are so efficient in storing nutrients would probably make it difficult to detect without a side by side comparison over a couple of seasons or a lab test for nitrate/ammonium levels. Sometimes you just have to use the shotgun approach and give them everything in the hope that they will not run short of anything.
Urea is converted to ammonium in the medium after a couple of days but urea can also be taken up directly by at least some plants and probably all of them. Urea is used as a foliar spray to quickly overcome severe N deficiencies. The greening can often be seen in a matter of hours.
User avatar
Steve Johnson
Posts: 4514
Joined: Thu Nov 03, 2011 4:44 am
Location: Los Angeles, CA (Zone 10b)

Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

MikeInOz wrote: Thu Jan 26, 2023 11:48 pm Hi Steve

I'm not sure what the signs of Mo deficiency would look like in cacti but possibly paler than ''normal'' looking plants? Or yellowish blotching here and there? Or perhaps slower than normal growth in the nitrate is being stored and not converted in the plant tissues. The fact that cacti are so efficient in storing nutrients would probably make it difficult to detect without a side by side comparison over a couple of seasons or a lab test for nitrate/ammonium levels. Sometimes you just have to use the shotgun approach and give them everything in the hope that they will not run short of anything.
Hi Mike,

As always, many thanks -- I truly appreciate your willingness to share your expertise with us. :D

The best benchmarks I have are the cacti that have been with me the longest. Going back to the plants I purchased to start building the collection in 2011 and 2012, they're continuing to grow wonderfully, and if anything, the Potassium sulfate and CalMag supplements have made the situation even better. Same applies to the cacti I got after 2012. No yellowish blotching anywhere, although I do notice that some of the species I'm growing looker paler than they should. Regardless of whether or not this is due to an Mo deficiency, your advice on the details pertaining to an Mo supplement is coming just in time, so I'll add it to my fert regimen for the growing season about to begin.
MikeInOz wrote: Thu Jan 26, 2023 11:48 pmUrea is converted to ammonium in the medium after a couple of days but urea can also be taken up directly by at least some plants and probably all of them. Urea is used as a foliar spray to quickly overcome severe N deficiencies. The greening can often be seen in a matter of hours.
Based on my limited understanding, I thought that bacterial activity in soil is the only way to fix Nitrogen for uptake by the plants. If that's not the case (at least for cacti), it sounds like you may have effectively busted another myth. It also brings up one last question (at least for now)...

Most or all of the liquid fert concentrates we see have Ammonium N and Nitrate N, but no urea. IMO neither here nor there since cacti aren't picky about where they're getting the Nitrogen from. Do you have any thoughts about why Osmocote includes urea in the Cacti & Succulents formulation?
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
User avatar
MikeInOz
Posts: 479
Joined: Fri Feb 16, 2018 2:21 am
Location: Sth east Australia

Re: The Cal-Mag of my dreams?

Post by MikeInOz »

Steve Johnson wrote: Fri Jan 27, 2023 1:43 am
Last edited by MikeInOz on Fri Jan 27, 2023 2:16 am, edited 1 time in total.
User avatar
MikeInOz
Posts: 479
Joined: Fri Feb 16, 2018 2:21 am
Location: Sth east Australia

Re: The Cal-Mag of my dreams?

Post by MikeInOz »

Steve Johnson wrote: Fri Jan 27, 2023 1:43 am

Most or all of the liquid fert concentrates we see have Ammonium N and Nitrate N, but no urea. IMO neither here nor there since cacti aren't picky about where they're getting the Nitrogen from. Do you have any thoughts about why Osmocote includes urea in the Cacti & Succulents formulation?
Urea is converted to ammonium either in the soil by bacteria or in the plant using the enzyme urease. (they have recently discovered nickel is needed for that process but you can basically think of urea as ammonium because it is converted so quickly in the mix.)
N ''fixation'' from the air is done by blue-green alage and rhizobium bacteria ( eg if a cacti is growing near a legume of some kind it will have access to some of the nitrogen from rhizobium bacteria on the roots of the legume) and that too is made available to the plant but in much smaller quantities than fertilizers.
Urea is cheap. Secondly, if you include nitrate or ammonium, you also have to include an cation or an anion to go along with it (eg ammonium sulphate or ammonium nitrate etc. and calcium nitrate or potassium nitrate etc. So the balancing of the formulation may also play a part in deciding what form of N to use. The Osmocote is a blend of different prills containing different nutrient combinations unlike say nuricote which has everything in the one prill.
User avatar
Steve Johnson
Posts: 4514
Joined: Thu Nov 03, 2011 4:44 am
Location: Los Angeles, CA (Zone 10b)

Re: The Cal-Mag of my dreams?

Post by Steve Johnson »

Calculate This! Actually it's the name of a website with a handy-dandy ppm calculator. Going by Alpha Chemical's Sodium molybdate with a guaranteed analysis of 39.5% Mo, I calculated the correct ppm for 1 gram per half-gallon of stock solution. Then I went to an online unit converter, and my calculation showed that 2 teaspoons of stock solution add 544 ppb Mo to a gallon of watering solution. (Honestly, it wasn't that hard.) Given the importance of Mo in the Nitrate-to-Ammonium reduction process, I'll break my "Fertilizers explained" presentation out into 2 parts. Part 1 is already up, so I'll post Part 2 over the weekend. I already have the math worked out in US and metric measures, and to make sure we're on the up-and-up here, I'll do what math teachers tell their students --"show your work!" No need to do that here, so I'll show my work in Part 2. In the meantime -- for those of you with liquid fert concentrates containing a scant amount of Mo (or no Mo at all), a Sodium molybdate supplement will be just the ticket.
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
Post Reply