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Crushed granite as aeration?
- Thread starter P-NUT
- Start date
AgentPothead
Just this guy, ya know?
I think he means decomposed granite, which is used as a base a lot for paths and driveways. It's basically like fine gravel so it drains very well. I don't have any knowledge of it being used in marijuana growing, but I think they use it in bonsai tree soils.
AgentPothead
Just this guy, ya know?
Uh, for it to drain it has to have air pockets. That's kind of how drainage works.
Switcher56
Comfortably numb!
That would be correct. Available in varying sizes know as "chicken grit" from you local feed store
AgentPothead
Just this guy, ya know?
You seem to have taken care of that.
Ive heard of people getting away with pea gravel and I was looking into granite dust for mineralizing and saw the rock yard has a 3/8 to dust grade and thought to myself maybe I could kill 2 birds with 1 stone. I just really wondered if anyone tried it before and the results. Please no internet fisticuffs guys.
St. Phatty
Active member
On my land the natural soil is de-composed granite.
It is a LOT like concrete. Has a similar effect on seedlings.
Best use I've found for it ... Kitty Litter.
It is a LOT like concrete. Has a similar effect on seedlings.
Best use I've found for it ... Kitty Litter.
the_niño
Well-known member
the reason to use those lighter materials for drainage is cut down on the weight of the soil. making transporting containers easier. rocks, sand, granite>> will all have the same drainage effect, but with a heavier weight.
i have been using sand for drainage in my mixes. are you trying to say that it does not work??
the idea is to use the cheapest, locally available amendments...
Excellent!
St. Phatty
Active member
Of course, granite is often found with quartz.
And quartz is often found with gold.
So there's nothing wrong with DG (de-composed granite).
I use the sand & gravel from sluicing sessions in the garden, mixing it with leaves & other biomass.
Cannabis I give special treatment. The closest the DG gets to the Cannabis soil mix is, I mix natural sand (with granite) in with storebought potting mix, steer manure, etc. to make the BASIC soil mix, then add in the special
things the plants like.Human urine, for example.
I know itll be heavy. Im gonna screen it at 1/8" and put the fines in my garden and use the 1/8"-3/8" pieces. Ive got super rich swamp soil and homemade castings. The swamp soil and castings are good on their own without extra drainage but Im thinking looooong term and I dont want it to eventually turn to clay muck. Ive used pumice and rice hulls before but wanted something I could get local here in fl and granite is easily available at landscape supply places. If its detrimental then I will use pea gravel instead as I know people have used it successfully in long term no till situations. I just thought granite would serve the same purpose and possibly leach some micronutrients into the soil over time.
T
Teddybrae
Mate ... do your own thing! I 'm in the same boat as you at this very moment. I cannot obtain Coconut Fibre (there's none in my state at the moment) and am either faced with the cost of purchasing 1000L Perlite at an exorbitant price per bag ... or visiting the local Concrete company and getting graded gravel/sand for a fraction of the price. the only downside to that is driving home a heavily loaded vehicle which I 'm sure I can transcend.
The bottom line is that my soil packs down and needs to be loosened with something or I don't get no crop this season.
And I seem to recall my very first crop grew in dried horse shit and fine sand. grew 8 footers out of 5 gal drums and I bought a car out of that one!
SO ...
hyposomniac
Active member
I had to do some digging outside recently because too much topsoil eroded into a place it shouldn't have-- on top of a gravel drainage bed, larger sized maybe 3/4-1".
It formed a mud that mixed into the gravel, and totally plugged up the drainage.
Water isn't going to flow through granite chunks, just around them. Water will filter through lava rock.
Think about adding marbles to mud.. an analogy I read somewhere.
Also, are you in a pot?
Pure speculation here, but I bet the weight of the gravel would cause it to form a layer over time, probably at the bottom (or maybe at the top due to its size, like macadamias in a shaken nut mix) So, even if the gravel retained it's draining ability, you would have a bottom of a pot that drains well, with a plug of soil above it that doesn't drain well. I believe that is the perched water table
It formed a mud that mixed into the gravel, and totally plugged up the drainage.
Water isn't going to flow through granite chunks, just around them. Water will filter through lava rock.
Think about adding marbles to mud.. an analogy I read somewhere.
Also, are you in a pot?
Pure speculation here, but I bet the weight of the gravel would cause it to form a layer over time, probably at the bottom (or maybe at the top due to its size, like macadamias in a shaken nut mix) So, even if the gravel retained it's draining ability, you would have a bottom of a pot that drains well, with a plug of soil above it that doesn't drain well. I believe that is the perched water table
T
Teddybrae
Oh come on! sands have always been used for potting mixes ... (anyone got an OLD Readers Digest Gardening Guide?)
Lost in a SOG
GrassSnakeGenetics
Grit doesn't directly aid aeration. Horticultural grit can speed infiltration through the medium but that doesn't really help us as we don't want the water to just run through the medium as fast as possible necessarily more we want the uniform quality of the soil to not over compact or become boggy, whether that grit will help I'm not sure.
Some grits can harm aeration by forming boundary layers with the soil greatly slowing water movement.
Some grits can harm aeration by forming boundary layers with the soil greatly slowing water movement.
T
Teddybrae
The way I see things ... air trapped in yr porous material is there because of the action of water.
That is: the water you pour on, or rain, will displace any air. As the water drains out new air is then 'sucked' into the spaces thus 'aerating' the soil.
For example: I understand this process is one of the advantages of ebb and flow hydro setups because 'flooding' and subsequent rapid drainage (often thru fine gravel) carries lots of helpful oxygen to the roots.
There is an optimum size of gravel for this but don't know it off hand.
St. Phatty
Active member
Last summer I was a lot better about keeping to a schedule for the watering. Watering in the afternoon because the plants were in black pots and the roots were too hot.
So lots of bubbling up top, followed by a half hour of dripping. In porous soil.
Definitely, as water flows out of a container, it pulls air into the soil from the top. There is no other way - you wouldn't end up with a vacuum there.
If I was more fanatic, I'd put up an O2 drip to suck more oxygen down into the cubby holes 2 feet down.
I heard the roots like oxygen. Did I get that right ?
I think of the root system & the dirt together are sort of like a lung.
I would love to know what happens with using the gravel for aeration. I think it could work like Perlite - Perlite works because it doesn't compress and keeps the mix from compacting. It creates spaces for air and the irregular surface has lots of pores for air. But perlite is closed-cell just like gravel - aiir, water and roots cannot get inside the chunks of perlite.
Gravel could work the same, with the one difference that it's much heavier. I'd be worried about the weight actually pressing down on the lighter elements in the mix like the fibrous peat or coir strands and crushing them. it probably depends on the exact rock too, if the gravel has a smoother surface than perlite it won't work. Rocks with a rough surface like lava rock are used in soil mix.
https://buildasoil.com/collections/aeration/products/small-black-lava-rock?variant=12367261728885
FWIW, I love perlite, cannabis loves it, I would pay whatever it costs to get it
Gravel could work the same, with the one difference that it's much heavier. I'd be worried about the weight actually pressing down on the lighter elements in the mix like the fibrous peat or coir strands and crushing them. it probably depends on the exact rock too, if the gravel has a smoother surface than perlite it won't work. Rocks with a rough surface like lava rock are used in soil mix.
https://buildasoil.com/collections/aeration/products/small-black-lava-rock?variant=12367261728885
FWIW, I love perlite, cannabis loves it, I would pay whatever it costs to get it
Lost in a SOG
GrassSnakeGenetics
The extra compaction would be your issue.. Perlite weighs nothing so cannot compact and ruin the quality of your soil..
