Category Archives: Charcoal-Terra Preta

Terra Preta – Black Earth – Charcoal in the Garden

I’m using this site as a place to place links and websites about this topic.

How to make charcoal in a weber kettle.


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How to Cut Your Fertilizer Use by 50 Per Cent

One of the experiments I’m trying this year is to mix charcoal in with my fertilizer. I’m mixing it at a ratio of 1 to 1, so in essence I’m cutting my fertilizer use by 50%.While the new charcoal will capture some of the fertilizer nutrients over time, I don’t expect any big change since I’m putting this on fairly lightly.

I can always add more fertilizer later in the year if the plants look like they might need some help.

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Horticultural Charcoal

I am starting to find other sources of charcoal as I surf the web. Here are some sources of horticultural charcoal which comes in varying sizes.

  • Basques Charcoal ($108 for 70# – includes shipping via UPS)
  • Hummert (I bought 100# in St.Louis for $82 – March 2011) Charcoal in briquet form costs about 50% less.

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How Charcoal Briquettes Are Made

I found this video from the Discovery Channel. It doesn’t appear that there is anything “bad” in briquettes to preclude them from being used in the garden.

The recipe for briquettes is:

  • Wood
  • Anthracite coal
  • Lime
  • Corn starch

Note – a couple of other non-official sites also list a few other ingredients – borax, sodium nitrate, sawdust, mineral char. Site 1, site 2.

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Charcoal Fertilizer – Terra Preta

After doing previous charcoal experiments, (check out the Charcoal Category),  I’ve decided that this will be my first year to put charcoal over my entire garden. It will be interesting to see how long it takes to break down so I can incorporate it into my soil. There may be a PH, soil acidity, problem, but I will have to watch and see what happens with charcoal. I ended up using 100# of charcoal for all my gardens. Note – I have found at least one brand of briquettes, Wicked Good Charcoal, say that they only use corn starch as a binder. Other sources seem to have a few more ingredients, but nothing terrible.

Here are a few more sites I have found about Terra Preta


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Make Your Own Charcoal Soil Amendment

After a number of experiments, I’ve come up with an almost perfect way to breakdown charcoal – just add water. In my quest to make terra preta, I have tried to breakup charcoal to a usable size by using blenders and bricks, but my latest test proved the best. If you use charcoal briquettes and submerge them in water, the glue which hold them together breaks down and with a little gentle coaxing and kneading they break down into a black gruel. If you then let it dry out about 90% you can then easily break it up with your hands. You then have a great soil amendment.

At this point, spread it around your garden and try to work it into the soil.

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Filed under Butterfly Gardening, Charcoal-Terra Preta, Fertilizer, soil

Charcoal Experiment – August 11th.

Below is a picture of the charcoal experiment where I added unburned natural charcoal to the soil. The charcoal pot is the one on the right and seems to be doing the best. The plant without any fertilizer did die out and the one with just fertilizer, in the middle, is doing poorly. I’ll try this with different plants next year as this particular Verbena didn’t do well in other areas.

Charcoal in Soil Test

Charcoal in Soil Test

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