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ph run off question organic soil


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i've been having something odd occur of late.

my run off ph has consistently been 7.1 or 7.2 no matter the ph of water going in. it's usually 6.0 or very close to.

i've got dolomite in there doing it's thing but my understanding is lime doesn't buffer higher than 7 - am i wrong?

also i've heard from one source that an over abundance of microbes to fungi in the mix can throw the balance out in this direction (i use aerated tea with focus on bacteria) - is this true?


the girls are looking healthy enough but theres some twisting in the new leaves so something's out. i have added more dolomite than i usually would with this mix, should i just keep on with what im doing or will this high run off continue being problematic?


soil mix is:

sa composters potting mix as base soil



blood and bone 

dolomite lime



i use charlie carp, seasol and natures own guano as liquid additives as needed


any opinions?

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Heya Asterix =) , ya mix is too hot, because ya adding guano as well. also , how much Dolomite did you add? only need about a handful for 45lt of mix.

basically, I think ya set up a nice soil mix, but you only really need the seasol to keep em healthy once and a while.

The seasol will help you keep healthy bacteria and a good rhizosphere..... you already have blood and bone, worm castings, compost, potash, so no need to add more ferts/food.


Back off the carp, and guano for now, flush with PH 5 water, maybe 4 times the pots capacity, this should get rid of some of the Ph problem, but ya cant take out what you already added in dolomite, if it was too much.


Peace. Nibbler.

Edited by The Hash Nibbler
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gday nibbler


i ve just done a flush but not at those ratios so ill give that a shot a see where it puts me


its hard to say whats happening with the dolomite ive put in two or three times that amount but that mix is only used for a little over a third of the container


will let you know how it goes.


thanks :)

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okie dokie big flush complete! using nibblers recommended specs.^

... this soil is SOILIDLY around seven . i flushed with water as low as 4.8 and the runoff only ever came to was 6.9. when i watered at 6.8 last week the runoff was 7.1 so its not moving much either way


I cant find any info on the web about this phenomenon. and its hard to be objective here without you guys seeing everything i'm doing so my plan of attack is to repot into some fresh soil ( new leaves are clawing so i don't think riding it out will work)


its pretty safe to say its a case of too much dolomite - we live and learn

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Shit happens Gaul =) , Just remember for next time. The dolomite is hard to budge PH wise if ya use a bit much, thats it's job, to buffer mediums/soil to PH 7

It will slowly come down with flushing, but will keep plants too moist if ya have to do it for too long.

Re-pot if possible, and maybe keep the dolomite out, if ya need it later, can always sprinkle a teaspoon on top of the soil and water it in.

Best of luck. Nibbler

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My understanding is that dolomite is that dolomite raises ph so not the best to use in any amount if your looking to keep  your ph where it is  . There are other alternatives for cal/mag that are closer to the ph of 6. Calcium nitrate, magnesium nitrate and magnesium suphate are used to buffer coco and may be a better alternative. Ive currently got this calcium additive that ph's around 4 . Just dont have it handy to be able to tell you what it is. Using ph'd water wont do anything btw as it will swing straight to the ph of your medium.


Good topic Cheers



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Only in Australia will growers attempt to ph soil,...never in the history of western civilization, will you ever get a soil grower attempting to take a serious Ph reading of his soil, and expect it to be accurate, I draw comfort that in the old 

soviet empire one would be sent to the Gulag for such a trifle, but then again there are members here that may well question Asterisk's solution to soil..?  in the first place

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thanks riverrat - thats the conclusion ive come to though this little hiccup


ive mixed half a block of peat into the rest of this soil with the hope it'll bring the ph down (i still have 30 odd kilos)  - will be a while but ill post the results once i test it 


the soil in question has been used like supersoil - fertile stuff at the bottom of the container, toped up with regular potting mix.. i get the feeling this may be a catalyst in the problem here - in the sense they both hold a different ph. i'll be making a more consistent mix in the future.


this is fun!

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Hi asterisk, i use sulpher to lower ph in soil its available at bunnings for about $7 a bottle works well. Ive also got a plant in peat atm i find my peat to be very alkaline even when washed extensivly not sure what yours is like but u can get soil ph testers from bunnings to ... And PHed soil isnt as accurate as PHed water but still very important not sure why anyone wouldnt agree certain nutrients will only be absorbed at certain ph levels so of course you will benifet from a correct PH...



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