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Fertilizers and acidification

Discuss repotting, soil, lighting, fertilizing, watering, etc. in this category.

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Re: Fertilizers and acidification

Postby Steve Johnson » Wed Nov 28, 2012 4:23 am

iann wrote:Any concentrated acid is dangerous. Concentrated (or glacial) acetic acid is highly corrosive and just the fumes will damage your lungs. Glacial acetic acid is fairly widely available although you won't run across it by accident. Mineral acids tend to be found more often in concentrated form and less often in dilute form because there is little use for the diluted forms. So people have developed the idea that they are "dangerous" while acids such as acetic and citric are "safe".

Citric acid is actually stronger than acetic acid, also triprotic, but it is less commonly available in concentrated form. Citric acid is useful for making buffers because of the dissociation constants of its second and third protons. In the diluted forms you're likely to find, both acetic acid and citric acid are safe, edible even :) There is some speculation that the acetates produced after neutralisation of hard water by acetic acid can be helpful in transport of nutrients into plants. Citric acid would presumably do the same, it is widely used as a chelating agent in cleaning, although I haven't seen anything written about it relating to plants. The two are closely linked chemically and both citrates and acetates occur in natural (animal) metabolic cycles that also involve lactic acid.

Should've qualified my comment on citric acid with the word "dilute". Since I haven't had the need for anything other than 5% vinegar, I'll stick with that as the safest recommendation for using it in acidifying hard water. I'll leave the subject of concentrated acids up to people who know how to handle them properly. By the way, thanks much for what you said about the speculation concerning byproducts of acetic and citric acids in nutrient transport for plants -- very interesting!
osac wrote:Have to find ammonium sulphate , but will go without it for now. I know that fish in aquarium secrete amonium and that plants love that but not sure that it is ammonium sulphate but it could be.
So when I get aquarium will use that water instead of distilled maybe.

Except that ... it's winter and not sure about using fertilizer now, maybe just once as I did not use it at all and than just watering without fert. during winter.

So... is it a good plan or I missed something. :-)

I believe your cacti are dormant now. That means no growth in the winter, so they shouldn't be getting watered or fertilized until they're ready to grow again in spring. I've heard that people use aquarium water for whatever nutrients are in it, but in my opinion that's not the best way because you'll have no way of knowing if your plants are getting enough or too much Nitrogen. As Ian and I said, Ammonium sulfate should be easily available at garden supply stores, although maybe not so easy to find in Croatia? (I'd be surprised if that's the case!) Not an urgent matter for you at the moment, and hopefully you'll be able to find it either locally or online.
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Re: Fertilizers and acidification

Postby iann » Wed Nov 28, 2012 2:22 pm

I consider the whole Ammonium sulphate thing to be a bit of a cult. If you can't find that exact chemical, just use any equivalent fertiliser. Use a commercial lawn fertiliser if you desperately want to provide high nitrogen. If you plan to go this route you really need to consider the implications of a high *proportion* of nitrogen in a very *dilute* fertiliser, the frequency of providing soluble fertiliser, and the capacity of your soil for storing nutrients in between the times that you supply them.

Just pouring on nitrogen will provide a wow factor as your plants turn green and grow (especially if they are nutrient-starved and in a depleted soil), at some point followed by a loud groan as they die. Hence the equally cultish old-fashioned advice to *never* apply nitrogen in any proportion larger than the other main nutrients. The only good thing that can be said about the older advice is that while it may stunt your plants it won't kill them.

The whole Ammonium sulphate cult appears doubly stupid if you plan on combining it with a more traditional cactus fertiliser. Combining a low nitrogen fertiliser with ammonium sulphate is effectively making your own Miracle Gro. Most commercial soluble fertilisers include ammonium sulphate as one of the ingredients. Despite what you might have read, there is little evidence that ammonium sulphate is any better for cacti than any other form of nitrogen, and certainly not that it is better than a combination of different nitrogen forms. Any plant that happens to prefer ammonium nitrogen will do find on a mixture such as a standard commercial fertiliser, while a plant that doesn't like it will not do well on just ammonium nitrogen. It is a fad diet for plants. There is an acidifying effect from some nitrogen forms, and ammonium sulphate is about the most acidifying form. This is a significant effect at the levels of nitrogen applied to a lawn or a field of corn, but pretty much irrelevant for a cactus in a pot.
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Re: Fertilizers and acidification

Postby osac » Thu Nov 29, 2012 9:27 am

Interesting post Iann,

I would like just to add as to my knowledge about underwater plants regarding ammonium is that plants prefer ammonium over other nitrogen molecules and will take that first.
Not sure about other plants and not sure about cacti but it takes less energy for the underwater plant to use ammonium over other form of nitrogen...

I do not want desperately Ammonium sulphate and I think I will not use it for now or for next growing season until I try just with acid water and normal cacti fert, maybe if that doesen't help will try with ammonium :-)

thank you all


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Re: Fertilizers and acidification

Postby CactusFanDan » Sat Dec 01, 2012 3:22 pm

iann wrote: There is some speculation that the acetates produced after neutralisation of hard water by acetic acid can be helpful in transport of nutrients into plants. Citric acid would presumably do the same, it is widely used as a chelating agent in cleaning, although I haven't seen anything written about it relating to plants. The two are closely linked chemically and both citrates and acetates occur in natural (animal) metabolic cycles that also involve lactic acid.

Interesting how you mentioned chelating agents as potentially beneficial to plant health. I've never really thought about it before, but it would make a good amount of sense for them to help the plant with nutrient uptake. I remember making up a stock nutrient solution for wheat once. I used Iron EDTA in the mix and EDTA is a very good chelating agent for metal ions. After a quick look on the ol' web it seems that adding chelating agents to your watering regime would be a good idea. It would increase the availability of metal ions to the plant. So you could acidify your water with citric acid or tartaric acid to add chelating agents to the water. Might be worth a try. Or if you can get a hold of it, maybe even try using EDTA? :-k

Another thing which popped into my head before, when considering what else you could add to your water, is to add Hydrogen peroxide to your water. This would help to mimic rainwater a little more, since rainwater naturally contains H2O2. It also spontaneously decomposes in the soil mix to water and oxygen. Used at a fairly low concentration, you're unlikely to cause any damage to the plant and there might be benefits to the plant's health. Or you could just water with rainwater in the first place! :P

Just some food for thought. :)
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Re: Fertilizers and acidification

Postby Steve Johnson » Sat Dec 01, 2012 8:18 pm

CactusFanDan wrote:
iann wrote: There is some speculation that the acetates produced after neutralisation of hard water by acetic acid can be helpful in transport of nutrients into plants. Citric acid would presumably do the same, it is widely used as a chelating agent in cleaning, although I haven't seen anything written about it relating to plants. The two are closely linked chemically and both citrates and acetates occur in natural (animal) metabolic cycles that also involve lactic acid.

Interesting how you mentioned chelating agents as potentially beneficial to plant health. I've never really thought about it before, but it would make a good amount of sense for them to help the plant with nutrient uptake. I remember making up a stock nutrient solution for wheat once. I used Iron EDTA in the mix and EDTA is a very good chelating agent for metal ions. After a quick look on the ol' web it seems that adding chelating agents to your watering regime would be a good idea. It would increase the availability of metal ions to the plant. So you could acidify your water with citric acid or tartaric acid to add chelating agents to the water. Might be worth a try. Or if you can get a hold of it, maybe even try using EDTA? :-k

Another thing which popped into my head before, when considering what else you could add to your water, is to add Hydrogen peroxide to your water. This would help to mimic rainwater a little more, since rainwater naturally contains H2O2. It also spontaneously decomposes in the soil mix to water and oxygen. Used at a fairly low concentration, you're unlikely to cause any damage to the plant and there might be benefits to the plant's health. Or you could just water with rainwater in the first place! :P

Just some food for thought. :)

Funny you should mention Hydrogen peroxide. I started using it to treat the roots of 3 cacti that needed repotting over the summer. First was an Epithelantha micromeris. One of our forum members recommended soaking the roots in 1% peroxide for 15 minutes, then letting them dry before repotting. This is an experiment which I dealt with in great detail on the forum about 4 months ago. If you wouldn't mind putting up with my "special" combination of OCD and DOTM (in other words, when my brain has the galloping trots! :lol:), you can read all about it here:

viewtopic.php?f=25&t=26807&p=237955&hilit=epithelantha#p237955

viewtopic.php?f=25&t=27345&p=241710&hilit=epithelantha#p241710

Next I had to repot a Melocactus matanzus that was in a bad way after I kept it way too long in a heavy soil-based mix. Basically the roots were being suffocated, so I transplanted it into the same pumice/DG mix I've been using with great success for the rest of my cacti. Same routine following what I did for the micromeris -- wash out the old soil from the roots in warm, soapy water, soak in 1% peroxide for 15 minutes, rinse the roots in running water, then let them dry out before repotting the plant in fresh, dry mineral mix. Okay, here's more DOTM as I describe the process and some promising results:

viewtopic.php?f=2&t=27502&p=243066&hilit=melocactus#p243066

And finally the third is a Gymnocalycium ochoterenae ssp. vatteri which I suspected might've had root mealies (it didn't). Same routine again, although since I repotted it at the end of September, I don't know if it would've given the plant's roots enough time to gain any benefit from the peroxide treatment. However, I do believe that the cases of my Epithelantha and Melocactus strongly suggest a connection between peroxide soaks and faster healing of the roots when cacti are transplanted. Of course this could all be just a coincidence, but if not, I'd be really interested to know what the implications could be for adding peroxide to my acidified water/fert regimen. My gut instinct is that it should be much more dilute if we're using it in the regular watering of cacti (and maybe succulents?). If anyone is already successfully using peroxide in their watering regimen, I'd certainly appreciate recommendations. By the way, watering with rainwater has been discussed elsewhere. If I could get it in ample amounts, I'd probably be able to dispense with the whole acidified water issue. Unfortunately I don't have that luxury, and I'd hate to think about what my cacti would look like if it weren't for the acidification I learned about from Elton Roberts. For those who can water their plants with rainwater all the time, blessings be upon you!

Regarding EDTA, I'm certainly willing to consider the possibility. However, I'm at a serious disadvantage since I don't have any background in chemistry or plant physiology as it pertains to the health of c&s, I'd be reluctant to try it on my cacti without some guidance from people who've been using EDTA with good results. Thoughts, anyone?
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Re: Fertilizers and acidification

Postby Astro » Sat Jan 05, 2013 1:25 am

Very interesting. I've been adding vinegar to my tap water, but I've been eyeballing it. Looks like I may need to get a pH meter to nail it down a bit.

One thing that is confusing though, is the use of 'ppm' in the sense of a weight ratio or even volume ratio. I'm used to it referring to a molecular ratio (which makes most sense to me as a physicist), so I was getting quite some different numbers until I looked up the convention :) Doesn't matter too much in the end, as long as we're all referring to the same thing.
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Re: Fertilizers and acidification

Postby DaveW » Sat Jan 05, 2013 9:59 am

I bought a cheap PH meter off EBAY and it was inaccurate Astro. Far cheaper to just get PH test strips for the few occasions you need them and they seem to be more accurate.

http://www.ebay.com/sch/i.html?_trksid= ... &_from=R40
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Re: Fertilizers and acidification

Postby Steve Johnson » Sat Jan 05, 2013 10:22 pm

DaveW wrote:I bought a cheap PH meter off EBAY and it was inaccurate Astro. Far cheaper to just get PH test strips for the few occasions you need them and they seem to be more accurate.

http://www.ebay.com/sch/i.html?_trksid= ... &_from=R40

I wouldn't dismiss your pH meter just yet, as it may have come with some instructions. Cheap doesn't mean bad -- my Milwaukee Instruments PH600 costs only US $21.95, and it's highly accurate. The key to using it properly is a pH test solution that keeps it calibrated at 7.0 (pH neutral) before I test the pH of the water that goes into my cacti. If your pH meter works the same way, chances are that you may not have looked at the instructions first.
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Re: Fertilizers and acidification

Postby hoteidoc » Sun Jan 06, 2013 1:28 am

:wink:
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Re: Fertilizers and acidification

Postby DaveW » Sun Jan 06, 2013 1:44 pm

Used the test solutions Steve and calibrated it. It worked OK on some things but gave readings way off for rainwater in my water butt. When I tested things using test strips they agreed with some of it's readings but gave the expected readings for rainwater in the butt. We have never been able to understand why it is OK with tap water but highly inaccurate with rainwater.

http://forums2.gardenweb.com/forums/loa ... 22258.html

The story of it here Steve:-

http://www.bcss.org.uk/foruma/viewtopic ... eter+DaveW
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Re: Fertilizers and acidification

Postby Steve Johnson » Sun Jan 06, 2013 8:43 pm

DaveW wrote:Used the test solutions Steve and calibrated it. It worked OK on some things but gave readings way off for rainwater in my water butt. When I tested things using test strips they agreed with some of it's readings but gave the expected readings for rainwater in the butt. We have never been able to understand why it is OK with tap water but highly inaccurate with rainwater.

http://forums2.gardenweb.com/forums/loa ... 22258.html

The story of it here Steve:-

http://www.bcss.org.uk/foruma/viewtopic ... eter+DaveW

Very active thread you have there on the BCSS forum, and I learned quite a bit about the workings of pH meters that I wasn't aware of before.

I stored up a few gallons of rainwater from a big storm we had several weeks ago, so I wanted to test it with my Milwaukee Instruments PH600 following your comments here. After calibrating the meter to 7.0 with my reference solution, the rainwater pH came out at 7.6. I live in a heavily urban area, so I wouldn't be surprised to see the water go slightly alkaline with all the crap floating around in the air. If your rainwater is testing that much more alkaline, I'd have to suspect your meter. Not sure if this is relevant to the discussion, but the instructions on my PH600 specifically state keeping it dry for storage -- no liquid immersion such as distilled water, buffering solution, etc.

So is my pH meter as accurate as I've been led to believe? I'm starting to wonder. I'll have to get a packet of pH test strips for comparison. If the strips tell a different story, then I'll have to suspect my meter as well. For my purposes it's simply a matter of confidence in the end results, so if other people who've been there before find that test strips are accurate enough, I'll have to rethink the wisdom of going as far as needing to use a pH meter. Besides, the strips are easier and certainly cheap.

Two more things spring to mind here:

1. Water hardness in southern California tends to go higher in Winter and Summer. Winter isn't an issue when the cacti aren't getting watered anyway. However, during the high heat of Summer I've found it useful to take note of this when I acidify. While we don't have to do it every time, I'd definitely recommend periodic tests of the water coming out of our taps in the Spring and Summer.

2. I try to keep the final pH of my watering/fertilizer solution to 5.5, but that's just me being "Mr. OCD". A range of 5.0-6.0 gives us plenty of latitude, so I suppose we don't need to be all that precise about it. With that said, I would be concerned about accuracy of the testing method, be it a pH meter, test strips, or a colorimetric indicator. If the test pH is off a few tenths, I doubt if the cacti would know the difference. However, if the test says 6, but the actual pH is more like 7, then we may have a problem.
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Re: Fertilizers and acidification

Postby DaveW » Mon Jan 07, 2013 11:34 am

Yes I suspect it is my cheap meter off EBAY Steve. As pointed out for the odd use though test strips are far cheaper.

My friend Roger Ferryman is in the US until later this month and emailed me this:-

"Drove 5000 miles round trip, and most of that was getting to and from the Saguaro park as we spent 10 days there and the Organ Pipe Cactus Park. Cold front hit the US as we left so most places were very cool. Little rains – did measure the rains at Tucson that lasted about 10 mins and read pH6.5.

The Grand Canyon was minus 14c and Flagstaff even colder. Did not do much in terms of cactus but all the sites we visited had sharp frosts by night."
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Re: Fertilizers and acidification

Postby hoteidoc » Mon Jan 07, 2013 8:19 pm

Steve, definitely surprised @ your 7.6 pH reading, although you're right anything out of urban area could be floating around! Years ago, when "acid rain" was just coming to awareness, most Northeastern rainwater was in the lower pH 6's, and "average" fallow fields pH was 5.5! And most of the acid was blamed on Midwestern (upper?) coal-fired power plants. I guess my reaction to pH meter -- having spent 10 yrs+ in research as tech, would be to probably be prepared to drop @ $100. But that's me - I have a $10 moisture meter that's fairly accurate -- once I figured out you need to angle under plant, 'cuz root ball can really hold H20, while periphery will read dry. Have enough date points & understanding with my current low organics/ hi NAPA/Turface soil to not use much.
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Re: Fertilizers and acidification

Postby DaveW » Mon Jan 07, 2013 8:45 pm

If you click on following pages some information on US rain PH here:-

http://www.classzone.com/books/earth_sc ... page01.cfm
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Re: Fertilizers and acidification

Postby hoteidoc » Mon Jan 07, 2013 10:42 pm

That's really scarey, 'cuz it's 10 yr old info & a full pH scale lower that stuff I'm guessing I knew/released in the 80's! :( :( :( Also puts in doubt the 7.6 pH rainwater reading!
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