ph question

[Salvi]

I've got a few T. peruvianus that seem to have a light green/yellow coloring appearing on new growth and between the ribs as they expand..Would that most likely be nitrogen deficiency or a ph issue? I have read that too low of a ph will cause these cacti to do this.

If that's the case, what is the fastest way to raise the ph safely? I would rather not use hydrated lime.

Also, I have been spreading dolomitic lime on the soil surface.

Thanks guys.

[narayan]

I've got a similiar problem with one of my pachanois. I tried lowering the pH of the soil but that hasn't seemed to work so i'm just about to give it some fertiliser.

[teonanacatl]

 

quote:

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Also, I have been spreading dolomitic lime on the soil surface.

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then ur pH could be to high, get a pH test kit and mesure it. if its to high(to alkaline) use sulphur if its to low(acidic) use lime. a nutrient deficiency may not be the cause, at different pH's different nutrients(k,p,n, etc) become more or less available, see image

so check your pH if everything is ok with that then find out wat ur plant is deficent in and treat it.

[philistine]

Definatley do a pH test on the soil before trying to raise or lower it.

I can't remember exactly how it goes, something like

"pH is an inverse algorithm of the hydrogen ion concentration... blah blah something to the power of 10 blah..."

the short of it is, if your are trying to raise/lower soil pH by 1 (say pH 7 down to pH 6) your are actually making the soil ten times more acidic, or in reverse (pH 7 to pH 8) ten times more alkaline.

This means that once soil gets 2-3 points (on the pH scale) above/below neutral it becomes very difficult to correct the pH and some nutrients become locked up and unavailable, while others, such as aluminium & manganese in acidic soil can rise to toxic levels.

If the soil pH is sweet, try giving them some S.T.E.M. (trace elements)

I had a couple pachanoi's do this as well, but I already knew that the soil was at a good pH.

I gave them some "Manutec: Soluble Trace Element Mix" and within a couple of weeks they went back to a nice healthy dark green.

It also worked wonders on some sick Hydreanga's (how the f**k do you spell that?) I had which are now lush and green and flowering profusely.

[ 23. November 2004, 17:56: Message edited by: philistine ]

[Salvi]

thanks for the quick replies guys..I will do a ph test. Are those soil ph testers with probes accurate? I've seen those in stores at relatively low prices. Or do you need one that uses a solution etc. for an accurate reading?

philistine where is this S.T.E.M. available? I am in the U.S. so I might have to do some searching.

[philistine]

Ive only ever used pH probes in the lab at school, and they were always pretty wizz-bang and needed to be calibrated with chemical solutions anyway.

The garden pH probe/tester things Ive see on sale at bunnings (big hardware store chain in Australia) look a bit dodgy but Ive never used one. I reckon you'd be better off getting a soil testing kit from your local nursery or garden section in whatever big hardware stores you have around there.

They usually consist of a colour chart, some indicator soloution which your pour on your soil sample and this wierd white powder stuff (can't remebr what its called) that you sprinkle over your wetted soil. The powder changes colour depending on pH.

Ive always found this to be more than accurate enough for general gardening purposes.

Just make sure you test a few samples from a few different depths, especially the soil around the roots.

As for S.T.E.M, you shouldn't have to much trouble finding some in the gardening section of a hardware store or a nursery. Lots of fertilisers have trace elements in them, but just ask/look for a "trace elements" mix in a packet. You may have to go to a good nursery. It may not be labeled as S.T.E.M (mine's not but when you make an acronym from the title it is) but as long as it says to mix it with water in the directions you should be fine. Just make sure you follow the directions and then wait for a few weeks. The stuff Ive got says you should only need to use it once a year.

If you can't find any, try looking in a hydroponics store.

Good luck, let me know how it goes.

[ 22. November 2004, 11:29: Message edited by: philistine ]

[smogs]

infact isnt ph logarithmic... so the further away from 7 the larger the difference between the graduations??

not sure on that 1

[teonanacatl]

a pH of 6 is 10x more acidic then pH 7. pH of 5 is 100x more acid pH7

[Stonehenge]

A ph of 7 is neither acid nor base so you can't really say 6 is ten times as acid because 7 is not acid at all. 5 is ten times as acid as 6, thats true and 9 is ten times as basic as 8. 10 would be 100 times as basic as 8.

Stoney

[Darklight]

That's a lovely handy table there KMind, thanks! :D

[teonanacatl]

quote:

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A ph of 7 is neither acid nor base so you can't really say 6 is ten times as acid because 7 is not acid at all.

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7 may not be acidic but 6 is therefore 6 is 10x more acidic then 7, jus like 8 is 10x more basic then 7, wat gets really tricky is where u say 6 is 100 times more acid then 8 :D :D

[philistine]

Ive just edited my original post it should have said "..... to the power of 10" not "...by a factor of ten"

The inverse algorythm bit is referring to the fact that the scale is actually measuring acidity (hydrogen ions) but is displayed backwards ie: the lower the number, the higher the ion concentration.

[Salvi]

Well, I finally got around to doing a pH test. I used one where you take a soil sample, add distilled water, add testing powder, and then shake and let the color develop. It looks to be around 6.5. If I'm not mistaken these cacti like a much higher pH.

Like I said, I've been applying dolomite lime, but is there any faster method? Perhaps wood ashes?

[teonanacatl]

lime or dolomite will raise pH there should be instructions on your pH packet on how to do so. i dont think it is to do with the pH locking up nutrients i think it has jus ran out of one....my guess is iron which causes interveinal chlorosis on new growth, there are no other symptoms (i guess cacti would show the same conditions as leafy plants) give it some trace elements, u will notice improovement in a few weeks if uve fixed it..... wat soil are u using???

[Salvi]

Soil mix is composed of a standard potting mix (Miracle gro etc.) with added perlite, ironite, and bone meal. The potting mix is peat based, which I believe is the reason the soil is acidic.

"Soured pots will still grow, but the color and potency of the San Pedro cactus is second rate, and it will not grow as fast. The lowest the pH should get is 6.8, any lower and Pedro will start to grow out pale yellow. Hit sickly or yellowed plants with: lime, hardwood ashes, sunlight and fertilizer... They will improve."

http://www.bouncingbearbotanicals.com/cact...s_care_tips.htm

However I have seen other sources that recommend a lower pH. Anyone know what optimal trichocereus pH is?

[teonanacatl]

if u look at the pH graph thing "sausage diagram", u will see that most elements are most available to plants at 6.25 to 7 so any where in this range plants should grow fine, if a plant requires more calcium or magnesium then another plant it might like a higher pH. i grow mine in about 6.5 wil no probs so do many other people.

[philistine]

If thats the case, then I reckon it would be worth adding some chelated or soluble trace elements. I prefer to use a mix, but im pretty sure you can buy more specific nutrients, like teonanacatl said, it might be just an iron defficiency.

Have you managed to find any?

[Salvi]

Well, I haven't found any S.T.E.M. type nutrients, although I had some Ironite sitting around. It has 5% iron of which some is supposed to be soluble (doesn't say how much). Of course it has lots of other trace elements. Also, I picked up some "Flower Tone" organic fertilizer. Obviously this won't be fast acting, but it has all of the trace elements.

I went ahead and applied both of these, so we will see what happens.