Nino_G wrote: ↑Sun Jan 14, 2024 8:38 amI just find an article on sulfur deficiencies that says this:
"
A less obvious sulfur source for plants is from the atmosphere. Burning fuels releases sulfur dioxide, which plants take into their tissues during respiration. Plants vary widely in tolerance to sulfur dioxide because of the differences in the efficiency with which they absorb the gas and the plant’s ability to detoxify the pollutant and dispose of excess sulfur. Much sulfur absorbed by leaves is translocated to other plant parts, thus diluting it."
Since all of my plants are kept outside on the balcony, and I live in the urban area with plenty of traffic, could this be answer to my question?
Quite possibly. And what we're talking about isn't just vehicle traffic, it could also be industry (as in factories, power plants, etc.). Check out the air quality in Zagreb:
https://www.iqair.com/croatia/zagreb
If your cacti are taking up enough S from sulfur dioxide in the air, it would explain why you really don't need S in a fertilizer. This brings up another factor to consider -- from Wikipedia:
- "In atmospheric chemistry, NOx is shorthand for nitric oxide (NO) and nitrogen dioxide (NO2), the nitrogen oxides that are most relevant for air pollution."
Is it possible that your cacti are getting N from the polluted air? If so, it'll be nitrate and nitrite N in your rainwater.
Nino_G wrote: ↑Sun Jan 14, 2024 8:38 am
Steve Johnson wrote: ↑Sat Jan 13, 2024 10:05 pm
If you want more confusion, try this:
Most of all, I'm confused how did I manage growing cacti so far. Here are the facts:
- I've been growing cacti for more than 30 years (still have several Aztekiums, Strombocactus and Turbinicarpus in collection that are over 33 years old)
- For most of that time I've been using simple substrates that consisted of silica gravel/sand, crushed bricks and some peat and limestone or dolomite chips added for plants that are found on limestone in habitat.
- For the last 6 years I've been using 100% mineral substrates (pumice, scoria, zeolite, akadama)
- I've always been using commercial store-bought fertilizers for cacti without giving them much thought, except that they don't contain to much N
- Lately I've been using liquid fertilizer from German cacti nursery (Uhlig Kakteen) diluted to 1/5 of recommended dosage
. None of the above mentioned fertilizers (as far as I can remember) had sulphur (or calcium) specified as ingredient
- I never used tap water for watering, but rainwater, distilled water, and last several years demineralized water
- All of my plants are compact, healthy, overwinter without problem, flower in abundance and produce viable seed.
How to explain that?
Your approach to growing cacti is what we know as the "hard" style -- mimicking (or at least trying to mimic) what they would look like in the wild. Obviously you've done well with that approach for more than 30 years, so I'm not sure why you'd want to change your growing practice by experimenting with the Osmocote 11-11-18 slow release. Are your plants calcium-deficient? Obviously not, otherwise they wouldn't be looking so good (and you'd know it). Actually, there
is a reason why you might want to change...
I learned a lot about fertilizers and how various nutrients function in cacti from MikeInOz. If you haven't seen it before, go here...
https://www.cactiguide.com/forum/viewtopic.php?t=47603
...and while you're at it, read the follow-up posts from Mike and SDK1 for some of the science behind what I've been doing over the last couple of years. If you don't want to go through everything (and yes, it's complicated), I'll say this is simply as I can:
- With the right NPK balance and the right dosages of all nutrients (N, P, K, Ca, Mg, and S being the most significant), cacti under cultivation are able to achieve the kind of genetic growth potential that is impossible with their counterparts fending for themselves in the wild.
Using nitrogen as a benchmark, I've found that N in the range of 40-75 parts-per-million with each feeding is quite appropriate to 100% mineral substrates like the 60% pumice-40% granite gravel mix I use for almost all of my cacti. If N is more in the range of 20-25 ppm per feeding, this would be consistent with the "hard" growing style. Anything much above 90 ppm N per feeding, and growers end up with bloated-looking cacti being pushed beyond their genetic growth limits.
There's really no "right" way to grow cacti, so this is simply a matter of the grower's individual preference. I'm not sure if you'd want to change anything after 30-plus years of successfully growing so many cacti in the "hard" style. However, if you're up for some experimentation, I'll recommend that you A. avoid the Osmocote slow-release because it introduces too many variables you can't account for, and B. give me the guaranteed analysis of what's in the Uhlig Kakteen liquid fertilizer. From there I can determine if this would be worth pursuing on your end.