Biochar in potting mix, your experience

Has anyone put biochar in potting mix? If so, what was the recipe? How did things grow? I'm interested in making my own potting mix, but am not sure if biochar is a viable ingredient. I have lots of scrap hardwood and softwood and a TLUD biochar stove.

Personally, I think that biochar is grossly over rated in temperate climates.

Biochar began in the tropical rainforests of Brazil. In those soils, there is very little organic matter - it gets consumed while still on the soil's surface. Biochar was the unintentional result of their bonfires, latrines and junkyard (a waste product). In such an environment, having a long lasting organic material in the soil is beneficial. Not so much so in a more temperate region, where the organic material should be food for the soil microbes. Biochar is an inert substance that has little (if any) benefit for the soil life.

The carbon that it sequesters in the soil is mostly offset by the carbon that is released into the atmosphere in its manufacture. There is little, or no gain.

Biochar is well known for absorbing water, but I have yet to see any evidence that it will ever share that water once it has collected it. It will not water your plants or the soil. It is reluctant to give up the water that it has stored.

I think that perlite or vermiculite would be more beneficial in a potting mix. Save your fires for roasting meats.

I was of the habit of carefully leaving the char in the stove when I remove the ashes but my wife can't be bothered with that and she argued that it is supposed to be good for the soil any way. So I have been sifting it out and observing what it seems to do best. My conclusion is it does not hurt to mix it in but it is most beneficial to use it as a mulch on top. For starting plants it protects the emerging shoot from damping off. For large containers Larger chunks in a thick layer it suppresses weeds and deters pests. Surface watering pases through it without disterbance but water wicking up through the soil is not wicked to the surface. Worms come up to feed just under it further reducing undesirables.
So rather than make a potting mix I make a potting layers; compost, sifted garden sand with the seed, charcoal. Then I place the pots in a tray and water them from the top. After that I ad water to the tray and let the water wick up through the compost. This has been giving me good results without resorting to off farm inputs.

Gilbert, the prime purpose of biochar is that of increasing micro organisim viability, not water retention or soil loosening. When thought of in the way it works, it really has better uses than as a part of a potting mix.
That said, the one thing it will do for a potting mix is to act like an activated charcoal, it will "sweeten" soils that are sour and it will slow down the souring of a potting mix, probably the reason I have found charcoal in some blends I've purchased way in the past.

Gilbert Fritz wrote:Has anyone put biochar in potting mix?

5-10% by volume is a common target rate for soil mixes.
Use only 2-3% if you are making the well drained soil mix preferred by some horticultural growers.

Gilbert Fritz wrote:Has anyone put biochar in potting mix? If so, what was the recipe? How did things grow? I'm interested in making my own potting mix, but am not sure if biochar is a viable ingredient. I have lots of scrap hardwood and softwood and a TLUD biochar stove.

Last spring I added biochar to some of my home made potting mix and grew tomatoes, peppers and basil in both mixtures (all other factors being the same, as far as possible). There was no noticeable difference for any of the plants. The local biochar enthusiast for whom I did the experiment, suggested that potting mix was already so rich that the biochar didn't have a chance to show any improvement.

The risk in potting mix is it can take up available nitrogen.it should be inoculated before use in potting mix

I am also hoping to one day create a super potting mix that incorporates biochar grown from coppice birch, poplar, and willow from my property. Since I have a no till system, I feel that this is a good way to incorporate the biochar deeper into the soil (as opposed to spreading on the surface in compost and mulch layers).

I do not necessarily agree with all that John Polk wrote, though he may have made a few valid points.

From my own studies (not personal experience mind you-just academic) I find that my thoughts differ from his.

. Biochar was the unintentional result of their bonfires, latrines and junkyard (a waste product)

Those are some of the ingredients, and it appears that the general products which would end up in a midden (pre-Columbian waste heap) are much the same as what happens to be in these terra preta soils; however, whether this was an unintended system is contended. I think that it is equally or perhaps more to the effect of this volume of 'waste' being intentionally increased in order to facilitate soil building.

Speaking of the tropics vs temperate organic matter situations, and biochar in general, John writes:

In such an environment, having a long lasting organic material in the soil is beneficial. Not so much so in a more temperate region, where the organic material should be food for the soil microbes. Biochar is an inert substance that has little (if any) benefit for the soil life.

I'm going to try to sort out some of the material in these statements to clarify where I think that I differ from John. The char matrix is somewhat inert, in the same way that a greenhouse might be considered inert-it is a structure which creates an environment. To say that it has little benefit to soil life, is to ignore what that environment provides-In this case, habitat for microbial colonies and storage for small volumes of water (hardly non benefits). While it might be argued that the wood, in a temperate setting, would be better utilized being buried in hugulkultur or buried wood beds, to speak of biochar as if it's only benefit is long term nutrient storage, misses much of what I understand the biochar can offer the soil system in the (relatively speaking) short term.

Biochar is well known for absorbing water, but I have yet to see any evidence that it will ever share that water once it has collected it. It will not water your plants or the soil. It is reluctant to give up the water that it has stored.

Again I can't agree with John. I think the information is being provided to make a point that might not be accurate.

With charred material, a catacomb like structure is formed. It is true that there is a great deal of potential for the charred material to take water into it's many cavities. This is also the case with nutrients, when it is being charged. After nutrient inoculation (charging) some of this space is taken up by nutrients and microbial populations-both of which require water for their potential to be reached. The char does not steal water from the soil (at least not that I have come across), or withhold it from the soil community. As a porous aggregate, it holds some of the water which would normally flow around it and downward through the soil matrix-that is true-but because it is charged with microbial colonies, some of these colonial dwellers will overflow, all of them will be quenched of their thirst to a degree, and the populations will have a chance to grow. While biochar might not actively give water that it has passively captured and stored, plants and their partner fungal and bacterial populations can certainly seek nutrients and water from within the biochar particles. I have never read of biochar's reluctance to give water up; certainly it contains water, but it is not actively stealing it, or withholding it.

And on to other amendments which John suggests as alternatives.

I think that perlite or vermiculite would be more beneficial in a potting mix.

From the quick to find but possibly imperfect world of wikipedia: "Perlite is a non-renewable resource. The world reserves of perlite are estimated at 700 million tonnes." From what I understand, expanded perlite is the product that is most often sold and used in potting mixes. To top off it's unsustainable non-renewable nature, in order to create it's light expanded nature that we know, it has to be heated to between 850 and 900 degrees celcius. This heats the water within it thus creating steam and blowing out the structure (like popcorn), to create this expanded light nature. Pretty energy intensive from what I can gather.

While vermiculite might be a more common mineral ore then perlite, and while some of it available for garden supplementation is not expanded in that energy intensive manner, the mining and crushing, and hauling and marketing of this in plastic bags (the same as with perlite), all together hardly amount to a sustainable or green alternative.

Save your fires for roasting meats.

The same fire could be used to make your biochar.

I believe most people misunderstanding biochar and even know of biochar due to marketing.

generic views I have on biochar:
Biochar is a long term process.  Not really to be seen as big benefit initially perhaps.  I see it has soil conditioning and stability.
I see biochar main use as a home for microbes.  After bad weather soil life can come back faster.  Think of many seed points for this.
high quality biochar is more glass coal like than charcoal.  I would not trust bio char sources from reclaim nutrient company that makes reclaim compost and such.  Best is what you make as you know what the material is going in.

I scatter biochar in my pastures. Cattle and hogs eat it like popcorn, and when they poop it back out again, it is as inoculated as it could possibly be. This study, from Germany, indicates that this is a sound practice. I hope this is helpful.

http://www.ithaka-journal.net/pflanzenkohle-in-der-rinderhaltung?lang=en

The distinction that I'd like to bring to this thread is that by its very nature, potting mix is something that is used short-term, and then once the plant (usually an annual) has gone through it's life-cycle, it's disposed of.  Potting mix is a medium for short-term plant viability.  It's light (so you can carry the pot around), drains well, and encourages quick root growth.  It isn't intended to be a long-term home for a pecan tree.

Biochar is an amendment intended for long-term plant viability.  The biochar becomes a "reef" onto which a broad variety of microbial life attach.  The symbiotic relationship between microbes, fungi, plant roots and other biota (worms, anthropods, etc.) is what is of highest concern.  In a system like a food forest, where you have a variety of materials and actors working together in concert (from the mulch layer above the soil to the microorganisms and fungi that are deep within the soil profile working with the plant roots), biochar is part of a larger platform of soil life.

Is it worth it to spend the time and effort to create biochar for a very short-term plant-growing medium?  The benefits of even well-innoculated biochar may not be realized in such a short time frame.  I don't think it would hurt to add it to potting mix, but I don't think it would really help that much either.  

Hi Marco,

Good point. Though, of course, the potting mix would end up in the garden eventually. So if it could replace expensive perlite and give more long term benefits then perlite in the garden, I guess it would still be a good idea?

Ivan Weiss wrote:I scatter biochar in my pastures. Cattle and hogs eat it like popcorn, and when they poop it back out again, it is as inoculated as it could possibly be. This study, from Germany, indicates that this is a sound practice. I hope this is helpful.

http://www.ithaka-journal.net/pflanzenkohle-in-der-rinderhaltung?lang=en

I would inoculate the biochar with lab before feeding the pigs for even better.
http://theunconventionalfarmer.com/recipes/lactobacillus-serum/


Drake Video - Lab talk.

I never watched the pig one as I have no pigs so I am not sure if their is change for pigs or if it is different so I give both links.

I hope this helps some.

Happen to find this thread via a web search for "biochar in potting soil".

In my case, it isn't potting soil but seed starting soil mix. Ran across an attra pdf yesterday called; Potting Mixes for Certified Organic Production , which is mostly about seed starting mixes and includes recipes from Elliot Coleman and others. They also talk about many possible ingredients including biochar.
https://attra.ncat.org/wp-content/uploads/2019/05/pottingmixes.pdf

What caught my eye:

Research conducted at Iowa State University indicates that screened biochar can be used successfully to replace perlite in greenhouse potting media. The high pH of biochar can also neutralize the acidity of peat and eliminate the need for lime. A mix with 30% biochar and 70% peat moss had a pH and physical characteristics very similar to a commercial peat-perlite potting mix

They mention leaf mold being an old school ingredient which was used the way peat moss is today but leaf mold also has beneficial microbes. I've got some peat here and will probably use it along with some leaf mold/humus, biochar, old compost and homemade bone meal. When I up pot them, it will be more compost plus some aged goat manure.

When I run out of peat, I'll use all leaf mold. Hoping to come up with something that's made with 100% materials from the property. We have goats and any bucklings born this year will be banded and when 70-80lbs, processed and consumed. Food plus blood and bone meal/bone char.  

On days that warm up quick, I shut down the wood stove which halts the fire and leaves me with biochar. Not enough to bother with garden use, and where I am, it wouldn't be of any help and might actually hurt. Temperate with heavy soil.

Whatever I don't use to make seed starting or potting mix, I'll save for something. Maybe add it to some compost to be added to a raised bed for carrots that's mostly sand. I can get coarse sand locally at the concrete place.

John said, "In my case, it isn't potting soil but seed starting soil mix.

John, whether it is potting soil or seed starter mix, this is the advice that I would trust the most:

Bryant RedHawk wrote:Gilbert, the prime purpose of biochar is that of increasing micro organisim viability, not water retention or soil loosening. When thought of in the way it works, it really has better uses than as a part of a potting mix.
That said, the one thing it will do for a potting mix is to act like an activated charcoal, it will "sweeten" soils that are sour and it will slow down the souring of a potting mix, probably the reason I have found charcoal in some blends I've purchased way in the past.