Corking? Or Trouble?

[From0to10in2weeks]

First, thanks so much again for the continued coaching. Much appreciated!

I have a Mammillaria crucigera that needed a bigger pot in April 2015, so here's what came out of its potful of soil-less mix:

Well, I guess there is root bound. And there is really root bound.

No worries. And no disrespect to Kakteen, but you might want to ask them about why they don't have any Ca, Mg, or S in their fertilizer.

If they are so important I am indeed wondering why they are not included. But also, are they really that important given that specialist cactus nursery don't include them? (To be fair though to Kakteen Matk here in Berlin: they are actually not producing this product but are reselling it. I just named it that way since I bought it there.)

If this isn't possible for you, I wouldn't give up on the Kakteen Matk and Neudorf Schachtelhalmloesung ferts (must be in combination for better NPK balance -- I believe Jerry's calculated dilutions apply to the combo).

I made my own calculator. And found two mixture which get even closer to your suggested ideal ratio.

Screenshot 2021-08-16 at 19.51.02.png (54.48 KiB) Viewed 1702 times

You can address the lack of Calcium and Magnesium with a Cal-Mag fertilizer supplement.

I actually have a hydroponics/"growth" shop in my neighbourhood. They offer a Ca/Mg supplement but it doesn't state the ratio online. I'll check it out.

I'll recommend that you alternate between the NPK and Cal-Mag -- fertilize with the NPK ferts, fertilize with the Cal-Mag fert in the next watering, go back to the NPK ferts with the watering after that, and so on. (Am I making any sense?)

Yes, makes sense.

By the way, if your mix leaves any moisture at the bottom of the pot whenever you water, I'd also recommend that you water a little less frequently.

As mentioned, after giving the pots a bottom soak I place them on paper towels to drain the excess water at the bottom of the pot. And the bottom of the root ball yesterday was very dry after watering it one week earlier. In reasonable warm temperatures und with sunny days (indoor SE window sill with fan) these small pots dry out in 3-4 days with this soil mixture. To monitor this, I weigh the pots before and after watering and then weekly. The larger pots I water every 2 - 3 weeks.

by a nugget of wisdom about how to approach watering -- when in doubt, don't.

Understood.

Best.

[From0to10in2weeks]

Well, I'll be jiggered -- completely forgot about Epsom salt, which is Magnesium sulfate, highly soluble and easily available. From0to10in2weeks, that solves the sulfur problem, although you'll want to add a little bit of it to your watering solution with the NPK ferts, not the Cal-Mag fert. I believe that 15 ppm. S should be sufficient, but unfortunately I don't know the dilution for the right amount you'll need.

Thanks. Now, I do wonder if these adjustments and fine tunings are really necessary. I don't doubt your experience and success. But is anyone successfully growing cacti with off-the-shelf fertilisers? Or are most people doing some adjustments but never talk about it?

Thanks. Best.

[MikeInOz]

That's not root bound by any means. Espostoas don't like big pots anyway. It's good for another year at least. IMO, all it needs is more even moisture and perhaps more feeding.

[Steve Johnson]

Now, I do wonder if these adjustments and fine tunings are really necessary. I don't doubt your experience and success. But is anyone successfully growing cacti with off-the-shelf fertilisers? Or are most people doing some adjustments but never talk about it?

As far as I know, there's only one off-the-shelf fertilizer ideally suited to cacti and succulents, and Mike uses it -- check out the link:

http://www.cactiguide.com/forum/viewtop ... te#p382937

Not available in the US, but you may be able to buy it in Germany. I'm too much of a control freak to trust in time-release ferts, so I'll stick with my Dyna Gro 7-7-7 and the Potassium sulfate supplement which is the only adjustment I need to make. If you can't get the Osmocote (or you prefer liquid ferts), the adjustments I recommended for you in my posts should be helpful. With that said, Mike may want to do some fact-checking in case I'm off on anything.

Unfortunately I can't answer your questions because ferts don't seem to be discussed all that much. Kind of a shame that we don't have more information-sharing on such an important subject, but at least you're getting a little bit of it here. All I can tell you is that if the adjustments and fine tunings are right, the results make a positive difference -- it's the difference between growing cacti and growing them well.

That's not root bound by any means. Espostoas don't like big pots anyway. It's good for another year at least.

Thanks for correcting me on what I said about the pot, Mike!

[From0to10in2weeks]

Osmocote fertiliser is being sold in DE but unfortunately not the one for cacti and succulents. At least I haven't found it yet.

Best.

[From0to10in2weeks]

Hi all,

I was made aware of that the screen shot of my calculator is not really legible. Sorry about that. I had assumed you could read it when double clicking it.

So, here are screenshots of the individual sections.

1) Product Overview (I added the composition of a succulent fertiliser also sold by Uhlig Kakteen)

Screenshot 2021-08-18 at 18.54.14.png (94.59 KiB) Viewed 1637 times

2) Custom A
This is the mixture Jerry Plater suggested. I arrived at a slightly higher K/N ratio.

Screenshot 2021-08-18 at 19.00.31.png (104.82 KiB) Viewed 1637 times

3) Custom B
This gets me very close to the "ideal" NPK ratio.

Screenshot 2021-08-18 at 19.11.46.png (108.27 KiB) Viewed 1637 times

4) Custom C
And another one very close to the "ideal" ratio.

Screenshot 2021-08-18 at 19.12.18.png (106.18 KiB) Viewed 1637 times

Notes:

• I didn't check if the conversion ratios mentioned in the link provided by Steve (thanks!) are actually correct.

• Basic assumption: 1 ml = 1 g.

Then, the fact that the recommended frequency of fertilising is so different but don't correlate with the relative concentration of NPK in ppm suggests to me that there must be some additional factors determining the availability of these elements to the plants. That's of course assuming that the recommendation to fertilise the most frequent with the fertiliser with the highest NPK concentration is not simply driven by commercial interests...

Best.

[jerrytheplater]

Over here in the US in the Aquatic Gardening hobby we buy KNO3, KH2PO4, and K2SO4 to fertilize our aquariums. You could add them to your fertilizers and make the corrections needed. I posted this up in May. Maybe it will give you some ideas. viewtopic.php?f=25&t=46296&p=386242#p386242

Oh, be careful assuming liquid fertilizers have the same density as water. They usually don't. Dyna-Gro is a close to saturated solution and if my memory is correct the specific gravity is somewhere near 1.3.

[Steve Johnson]

There's a little something I'd like to share with you. Kinda detailed (isn't it always? ), and unfortunately more pressing matters keep me from getting into it until the weekend. To set things up, what I'd like to discuss involves a little something called cation-exchange capacity (CEC). I don't want to make assumptions about what people do or don't know -- if you already know about CEC, the following Wikipedia article is for anyone who'd like to learn more about it:

https://en.wikipedia.org/wiki/Cation-exchange_capacity

After all the years I've been growing cacti, I'm just now starting to learn about it too. For anyone who can answer this question -- what are the CEC numbers for granite, pumice, and Seramis? (My guess is that granite's CEC is pretty much zero.)

In the meantime, please don't underestimate the importance of Ca, Mg, and S to the long-term health of your cacti. If you're not getting any in your NPK ferts, you'll need to supplement them with Cal-Mag and Epsom salt.

[From0to10in2weeks]

Oh, be careful assuming liquid fertilizers have the same density as water. They usually don't. Dyna-Gro is a close to saturated solution and if my memory is correct the specific gravity is somewhere near 1.3.

Yes, I was suspecting as much. Which is why I pointed out my underlying assumption. And for that and many other reasons I think it is important to do analysis on the mixtures you make if you decide to go through all this effort. Water analysis in this concentration range shouldn't be expensive.

Best.

[From0to10in2weeks]

To set things up, what I'd like to discuss involves a little something called cation-exchange capacity (CEC).

Yes, I know what that is.

For anyone who can answer this question -- what are the CEC numbers for granite, pumice, and Seramis? (My guess is that granite's CEC is pretty much zero.)

There will be no single answer, especially for materials derived from nature. Why? Because it will depend on a gazillion factors. I am sure if you search the scientific literature for info on these questions you'll receive gazillion cubed answers. Very little of which will be relevant to your situation. If you want to know the CEC of the soil components you're using... you'll need to measure it yourself. Or better have it analysed by a reputable analytical lab.

In the meantime, please don't underestimate the importance of Ca, Mg, and S to the long-term health of your cacti. If you're not getting any in your NPK ferts, you'll need to supplement them with Cal-Mag and Epsom salt.

Please realise, just because an ingredient isn't listed on the label, doesn't mean it's not present. Most likely it may just have not been measured.

Thanks guys. That was entertaining. Best of luck.

[MikeInOz]

After all the years I've been growing cacti, I'm just now starting to learn about it too. For anyone who can answer this question -- what are the CEC numbers for granite, pumice, and Seramis? (My guess is that granite's CEC is pretty much zero.)

Steve, I would guess that seramis being made of clay may very well have a moderate CEC. I have never seen it here but I would use it if I could.
Granite would have zero CEC and I would assume pumice would also be close to zero. (like scoria or lava) If you want to boost your CEC a (and not use organic) use some zeolite.

[MikeInOz]

Please realise, just because an ingredient isn't listed on the label, doesn't mean it's not present. Most likely it may just have not been measured.


[/quote]

That's ok if you use soil or humus but if you don't you absolutely need to supply all nutrients. So hoping that something not listed and guaranteed to be in the solution, to be there is not the best way to go.

[Steve Johnson]

If you want to boost your CEC a (and not use organic) use some zeolite.

I'm not averse to the idea of tinkering -- since I've been doing so well with a soil-less mix, the possibility of adding zeolite to the mix is intriguing. I don't want to hijack From0to10in2weeks's thread, so I'll PM you with a few questions this weekend.

Thanks, Mike!

[jerrytheplater]

Please realise, just because an ingredient isn't listed on the label, doesn't mean it's not present. Most likely it may just have not been measured.

That's ok if you use soil or humus but if you don't you absolutely need to supply all nutrients. So hoping that something not listed and guaranteed to be in the solution, to be there is not the best way to go.
[/quote]

To repeat Mike in another way: Fertilizer labels are guarantees of the amounts of nutrients in that fertilizer. Yes they are rounded such that 10.8% would usually be listed as 11%, or 11.2% would be listed 11%, but the manufacturer is not going to add something in a significant amount and not state it. Just does not make economic sense. So don't assume you have a nutrient in your fertilizer unless it says so. I am not talking about trace amounts of a macro nutrient, like even 10 ppm Calcium. I suppose something like that could happen, but it wouldn't be significant for fertilizing our plants. Now if it were 10 ppm of Rubidium or other micro nutrient, that is a huge amount relatively speaking and would be listed on the label.

[MikeInOz]

So don't assume you have a nutrient in your fertilizer unless it says so.

There are plenty of fertilizers that give total NPK ''plus trace elements'' I would have no idea whether that contained Ca or not, Mg or not, B or not.