Adding BioChar to soil

Discussion in 'Planting, growing, nurturing Plants' started by SueUSA, Jun 30, 2010.

  1. SueUSA

    SueUSA Junior Member

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    I have seen several recommendations to add 5kg biochar to 1m2. That seems like an awfully dense combination.

    Does anyone know where this figure came from? Did it come from an 'official' source (someone who knows what they're talking about), or is it just some hot-air figure that some dolt threw out there, and everyone is taking for gospel? Or was it a simple typo error in the beginning?

    I see on the recent BioChar thread that Baz only adds a litre per M2, which sounds far more reasonable.
     
  2. Michaelangelica

    Michaelangelica Junior Member

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    Did you ever get an answer to this sue?
    I have read that Japanese Tea farmers add 100g of char per square M per year, with some results-reseach yet to be published.
    5K does sound a lot.
     
  3. SueUSA

    SueUSA Junior Member

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    Yes, I think so.

    The International Biochar Initiative https://www.biochar-international.org/biochar/faqs#q19 indicates that the 5 kg/m2 is the MAXIMUM that is usually used, but the RANGE is usually 0.5 to 5 kg per square meter.

    The same source also indicated that mixing biochar directly with compost is a good idea -- the biochar can help retain the nutrients in the compost. Our high rainfall washes soluble nutrients out of the soil, so anything that can help to prevent that is a good thing, and I think biochar and cover crops are the best (only) ways that I know how to do it.

    Since I make just a little biochar at a time, I have been layering or mixing it with my compost while storing it (call it 'hoarding') while I decide the most valuable places to add it.

    My usual practice is to make compost throughout the growing season for the following spring, which makes it available right away. Since I am usually half a year behind in using it, I thought adding the biochar as I put the compost in the containers would be a good place to store both of them through our wet winters, and the mingling of compost and biochar would be a good thing.

    If I had a lot of both, I would stir both together into the soil, then sow a green manure on top, figuring that the biochar and the green manure would both hold and store nutrients for plant use in the spring.

    I'm learning more every day, but the learning just stirs up more questions.

    Sue
     
  4. bazman

    bazman Junior Member

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    Depends on your Biochar? If you are using fire place coal always compost it or soak in a compost tea for a few months. By using composting, the intense action by all the bugs help break the strong hydroxyl bonds and nutrient to nutrient bonds, these can have a short term negative effect if applied direct to soils.

    If you are using a good quality Biochar like say mine :p I would add 5 generous hand fulls per m2 to start and then 1 per year around spring time. The pH of ours is 8.5 so check your soil before adding. a quick wash can help reduce pH levels, wash over a compost bin so you don't loose those extra nutrients.

    I have started soaking my BlackEarth Biochar in liquid sea kelp and worm juice for a few days before spreading to help charge it up with extra nutrients and moisture.
     
  5. SueUSA

    SueUSA Junior Member

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    Bazman, I only use wood, no coal, so I don't have to worry about that.

    No problem with alkalinity, my soil is 5.8. It's also short in calcium, magnesium, boron and sulfur, and very short in nitrogen, which is what you would expect with all the rain leaching it away.

    I like that idea of liquid kelp and worm juice!

    Since burning is prohibited through the summer here, I couldn't make the biochar I was planning on. Then an acquaintance said, "Why don't you just go to Cash & Carry and buy it?" C&C carries 40# (18kg) bags of natural hardwood charcoal for $13 (for BBQ).

    I just need to find the best way to grind it up. Do you think it would be easier to pulverize if I soaked it in a kelp/worm tea for a few weeks?

    Sue
     
  6. bazman

    bazman Junior Member

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    Charcoal from wood fire or natural hardwood charcoal are much lower quality that a purpose made Biochar product, batch pyrolysis or continuous flow pyrolysis is best due to the constant temperatures and environment used.

    Made sure the natural hardwood charcoal you buy does not contain any extra fire lighting chemicals.

    Pulverise first then soak, with my home made Biochar I spread it around the bottom of the wheel barrow and bash it with the end of my small sledge hammer, makes for a good work out, also do it where you have lots of fresh air as you don't want to breath in all that dust, I have also been told to use a concrete mixer with rocks added to it.

    Soak it until it sinks to the bottom, it should be charged by then.

    You can char beef bones and they contain lots of calcium, my dogs don't eat all the bone I give them and I find it does not break down in composts and takes a long time in soils, if it's turned into Biochar the calcium ends up lightly bonded to the carbon surface which plants can access.

    Baz
     
  7. digging

    digging Junior Member

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    Good point about the cement mixer and stones and the part about charing bones!

    Now I would think the amount of char used also depends on the depth of mixing? If I was double digging a new bed down a full two feet then I would think quite alot of char could be used, compaired with just surface spreading?

    Digging
     
  8. Michaelangelica

    Michaelangelica Junior Member

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    From an environmental viewpoint yes; and low temp hardwood char will hopefully have more bio-oils and therefore work better; but all char should have some effect on promoting soil microorganisms (and on Co2 sequestration).
    Char should always be used in conjuction with organic matter and, possibly also, trerracotta chips and/or a clay like zeolite.


    .
     
  9. digging

    digging Junior Member

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    So there is thinking that clay is good with char also or only baked clay bits?

    Digging
     
  10. SueUSA

    SueUSA Junior Member

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    Clay normally holds more nutrients than sand does, so I would think the combination of biochar and clay would be a good combination.

    Sue
     
  11. permasculptor

    permasculptor Junior Member

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    The clay thinking comes from the original Tera Preta in the form of terracotta pieces in the mix .I think Michelangelica was refering to the Zeolite which is like terracotta.
     
  12. SueUSA

    SueUSA Junior Member

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    Biochar and Terra preta aside, clay soil always holds more nutrients (and moisture) than sandy or sandy/loam soil. So I would think that if you have sandy soil (like mine), adding any form of clay would be an improvement, no matter if it were natural terra cotta dug from a river bank, bentonite in the form of clumping cat litter, or finely broken shards of clay pots.

    Sue
     
  13. bazman

    bazman Junior Member

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    I have quite a bit of clay stone from where I dug out my water tanks (20m3 left), I have been adding this to my food forest for years, and as the pile to quite large, I will be for years more. It's hard work moving by hand.

    I came across something awhile back by Stephen Joseph, I think it was him, talking about the benefits of adding clay with Biochar.

    I have also heard clay can contain quite a bit of salt, any idea if this could create a negative impact on food growing soils?? or does it just depends on your clay type and where you are?

    I think a little bit of everything and not to much of one thing is a good school of thought.

    I have found Biochar tends to move down into soil here, I also noted that in the Elmore field days Biochar trial plots, but that soil may have been turned but I didn't see any on the surface.
     
  14. SueUSA

    SueUSA Junior Member

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    Bazman, Digging asked an interesting question earlier in this thread, about incorporating the biochar in double digging.

    Have you heard if this would actually be very beneficial? You could certainly do it if you had tons of biochar available, but most microbial activity is in the top six inches (15cm) of soil, so wouldn't it be best to mix it at that level? Most people are going to have to work to create enough biochar for their own purposes, so it would seem that using it the most effective way possible would be best.

    Sue
     
  15. bazman

    bazman Junior Member

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    Hi Sue

    I can see much point in having Biochar in vegi garden soils below 15-20cm, plus it would take a large amount of Biochar to get it down that deep.

    I do add compost charged Biochar to my new fruit tree holes as 30cm below my top soil is clay so I like to dig some of this out and backfill with biochar compost.

    One of my raised garden beds has Biochar down to 40-50cm or so, but that soil is pretty bloody good to grow crops, but I have found Biochar tends to move down though the soil profile, where plastic tends to find it's way to the surface.

    Baz
     
  16. digging

    digging Junior Member

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    Is that "I can't see much point" or that it is a good idea to get it deeper into the soil for garden beds??

    Digging
     
  17. bazman

    bazman Junior Member

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    Sorry yeah it's a typo, fixed below.

    Hi Sue

    I can't see much point in having Biochar in vegi garden soils below 15-20cm, plus it would take a large amount of Biochar to get it down that deep.

    I do add compost charged Biochar to my new fruit tree holes as 30cm below my top soil is clay so I like to dig some of this out and backfill with biochar compost.

    One of my raised garden beds has Biochar down to 40-50cm or so, but that soil is pretty bloody good to grow crops, but I have found Biochar tends to move down though the soil profile, where plastic tends to find it's way to the surface.

    Baz
     

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