Hi Jim, I don't know anything about charcoal and soil, but I'd point out that tropical rain forest soils are usually clay with a thin layer of organic matter on top. It may be that the charcoal is used to lighten and aereate the clay.

For sandy soil, the best soil amendment is clay. Plain cat litter works great (10-15% by volume).

Tropical rain forest soils are usually very different in structure from soils in temperate regions. That quantity of rain and the endless warmth makes their chemistry and structure very different from the soils where there are four seasons. I also have no experience with charcoal, but I wouldn't assume that because charcoal works as a soil amendment in the Amazon that it also would work in the USA.

I read on the WWW that charcoal is highly alkaline and rich in potassium. So if that's what your particular soil needs then maybe. I know here in my part of California more alkaline material is not what I need.

Also, be aware that charcoal will soak up other chemicals and nutrients. That's why it is used for filtration.

Well, farmers in the past used to torch the old grass in the pastures, as it apparently improved the pasture for the next year (practice outlawed later by the way, as more things often got torched than just a grass, not to mention the wildlife). I also know, that wood ash diluted with water can work as mild fungicide and bug deterrent (I remember back in the village some leaf veggies got dusted with ash to prevent certain kind of bugs damaging them and it worked really fine).

I would be cautious of using it as soil amendment though, as usually nothing really wants to grow where the pile of ashes/charcoal was before. If anything, that means you can overdo it easily.

Our house was built partly in the winter months and every day the workers made fires from downed tree limbs in a section of the yard; they'd huddle around those fires in work breaks to warm up. Later I tried to grow many rhododendrons in this same area. It was supposed to be a temporary holding area for ultra happy growth! But everything died over many months' time, even though I had improved the area with hauled-in dirt, more humus, and peat moss. The finished soil was far too sweet and was too unbalanced in terms of nutrients. I think a little bit of wood ashes goes a long way, and I'd guess that the same would apply to charcoal.

The wood ashes didn't kill pathogens, by the way, but apparently furnished them with a friendly environment for multiplying and killing our rhododendrons. The plants mainly died of nematode damage.

Best wishes,
Mary

There are charcoal soil products on the market, but I don't have the time to find out their names. The areas in the Amazon where charcoal was used are still fertile today, where other land that is just slashed and burned are useless after a few crops. Apparently the charcoal does just what dimitrig says: soaks up minerals and things that are usually washed away. I might use it myself, but I'm on solid clay, so just add organic material in the form of leaves and compost.

Steve

Compost is good for every kind of soil.

Here are my experiments and things I've found out about charcoal in the garden.

Here is a link that might be useful: Charcoal in the Garden

Are you talking about ashes from charcoal or actual charcoal? We put the ashes in the soil, but not the charcoal.

I have heard of Terra Petra also. My experiments will consist of me adding finely ground charcoal to the next few plantings I do. Papaya and roses for sure.

The charcoal will come from our Brita filters which we use for our well water. I thought perhaps the charcoal might hold the nutrients and release them over a period of time.

Some of us have used horticultural charcoal for years as an ingredient in potting mix for orchids, gesneriads & other house plants. It's not as easy to find these days as it once was. You can use activated charcoal (for aquariums) as a substitute, but that's quite a bit more expensive than basic horticultural charcoal. It was once hyped as a soil "sweetener" or some such beneficial. I'm not convinced that it does much more than add a bit of texture and assist in drainage -- but there are other additives that can accomplish those things. I still use it (primarily, I think, because I'm a hopeless creature of habit), but only in my potting mix for indoor use.

Thanks for the link to the video, Butterflyman.

Steve

This fall, I created a new rose garden to be ready for spring and I mixed in some hardwood charcoal to see what happens. It won't be planted until spring. My biggest problem was getting the pieces small enough to mix into the soil. I tried running a batch through my 8 hp chipper but I watched with horror as a black cloud of soot drifted towards the neighbor's white house! I beat it with hammers and logs and even ran over the bag with my car. Soaking it in a compost tea or Miracle-Gro to improve it and make it more workable sounds like a good idea. Hopefully it will hold nutrients and change the cation ratio in my sandy soil to make it more fertile. I appreciate all the feedback I am getting and the links to the articles.

I could not link this directly (too long). If you put the following string "Charcoal addition to soils in NE England" into Google Scholar you will find a scientific article.