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keithrs
Guest
I was wondering how important it is to add charcoal to potting mixes. I had read that plant can use it as a carbon building base since we don't grow them in leaf litter or there natural media per say.
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NYEric
Well-Known Member
I put it in mixes because it has filtering qualities, IMHO. 
In the 40+ years I've been growing, I have heard a lot of comments about charcoal "sweetening" the mix - helping purify it by trapping wastes. However, in order to be an efficient "trap" for such chemical species, the charcoal would have to be "activated", which greatly enhances the number of adsorption sites.
I suspect that the mere heat conversion from wood to charcoal does "activate" it to some degree - primarily at the surface I imagine - but its probably orders-of-magnitude less than that seen on truly activated carbon, drastically limiting its trapping capacity, and likely rendering it no more effective than other media components at absorbing stuff.
Having said that, I will add that all solid potting media components still absorb and trap minerals and wastes, which is why we need to repot regularly, even if the medium has not significantly decomposed, and I doubt that the charcoal does much to extend the time a mix stays viable.
I suspect that the mere heat conversion from wood to charcoal does "activate" it to some degree - primarily at the surface I imagine - but its probably orders-of-magnitude less than that seen on truly activated carbon, drastically limiting its trapping capacity, and likely rendering it no more effective than other media components at absorbing stuff.
Having said that, I will add that all solid potting media components still absorb and trap minerals and wastes, which is why we need to repot regularly, even if the medium has not significantly decomposed, and I doubt that the charcoal does much to extend the time a mix stays viable.
Trithor
Chico (..... the clown)
I used to use zeolite in my potting mix for the same reason that people use charcoal, but stopped when it was pointed out to me that it has a high adsorption of nitrogenous compounds. It is used extensively in the farming of fish to reduce nitrogen in the water, obviously not ideal if you are trying to feed your plants!
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keithrs
Guest
I'm talking more about Terra Preta. Not so much to "soak up" bad things in the mix.
I use it because it used to be a lot cheaper than bark and was a good inert filler which doesn't breakdown. And because it was 'tradition'.
We use it because roots seem to attach to it readily.....plus it keeps the mix from compacting. Plus we've used it in our mixes for at least 109 years:wink:
Paphman910
Well-Known Member
In my opionion, I think charcoal is a good additive as it keeps the medium from getting compacted and overly wet. To me it is just a substrate for the roots to attach to especially the epiphytic orchids.
Stone
Well-Known Member
Zeolite has a very high CEC. As an example, peat has a CEC of between 50 and 200 m.e./L where's zeolite 1000 to 1500 m.e./L. It is sometimes used in the bedding plant industry to completely eliminate ammonium toxicity. The fact that we use rather larger and course materials in our mixes with rather low CEC ( around 100 m.e./L on average ) compared with the natural substrates like clay, humus and leaf mold/moss where paphs grow, I think including a small amount of course zeolite in a mix could do nothing but good. Obvously its not essential to have a high CEC when you are feeding regularly but it helps to ''even out'' the highs and lows of periodic feeding. Yes it would capture NH04, Ca, Mg and K but the plants will have access to them when they need it. Without a high CEC you need a constant trickle of nutrients for best results.
I wish I could find a course zeolite but I can only get hold of 1-2mm particles.
I use charcoal for the same reasons as the others. It seems to be more a tradition than anything else but the mix just looks better with it.
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Eric Muehlbauer
Guest
Cec?
Cation Exchange Capacity
Stone
Well-Known Member
CEC = Cation exchange capacity. So cations like Ca, Mg, Al, K, Na, H+ being positively charged are attracted to negatively charged sufaces where they are held loosely. The CEC of a particular material is limited by the number of negative charges on the its surface. So if you apply Ca or NH04 it will exchange places with Mg or K or whatever. A plants roots can release H+ ions which can exchage places with ammonium for example and then be uptaken by the plant. I'm no chemist but I think thats how it works.
I have no idea of the CEC of charcoal.
I have no idea of the CEC of charcoal.
Charcoal is good
Charcoal is good.
Have no idea why charcoal is good.
But charcoal is good to add to your mix.
Just make sure you use genuine hardwood charcoal made from Tropical Rainforests. (It really is the best) :drool:
Using charcoal in your potting mix prevents the charcoal from being burned and thus you are saving the planet.
Seriously over the years I notice a difference in the long term health of potting media that has charcoal added. Probably because the charcoal does not decompose as fast as other organic media so it helps maintain the physical condition of the media. I doubt it has any real benefit as far as absorbing toxins that help the plants.
Charcoal is good.
Have no idea why charcoal is good.
But charcoal is good to add to your mix.
Just make sure you use genuine hardwood charcoal made from Tropical Rainforests. (It really is the best) :drool:
Using charcoal in your potting mix prevents the charcoal from being burned and thus you are saving the planet.
Seriously over the years I notice a difference in the long term health of potting media that has charcoal added. Probably because the charcoal does not decompose as fast as other organic media so it helps maintain the physical condition of the media. I doubt it has any real benefit as far as absorbing toxins that help the plants.
The Orchid Boy
Well-Known Member
I love using it from drainage and airation purposes instead of perlite. I hate how perlite sticks to my wet hands.
Stone
Well-Known Member
Migrant13
Mature growth?
I don't think the charcoal will absorb much in the way of nutrients. Basically it absorbs gases not so much dissolved solids.
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ALToronto
Guest
Lance, charcoal will not adhere to anything. Maybe that's another reason why it's used for orchids.
My only experience with activated charcoal was in Russia, as a hangover cure. It's very effective for that.
My only experience with activated charcoal was in Russia, as a hangover cure. It's very effective for that.
Trithor
Chico (..... the clown)
So judging by the comments, I should hunt down that bag of zeolite again. They were nice consistant 8-10mm pieces, a bit like a fine gravel. It did make the pots a bit heavier when I was using it. (5 parts bark, 1 part chopped shagnum, 1 part coarse perlite and 1 part zeolite) We also have ready access to hardwood charcoal coming out of Namibia, perhaps I should add that in as well, just dont know how to beak it up and grade it without making a hell of a mess.
