Charcoal added to soil significantly improves tropical soil fertility

[JohnyCanuck]

Charcoal, agriculture and climate change
by Richard T. Haard, Ph. D.

SNIP

Slash and Burn agriculture is practiced by 300 to 500 million people on one third of the 1500 million hectares of arable land on the planet. Yet pressures remain high for clearing of natural habitat in order to expand agriculture. This is because of the expanding population, countries need for export market income and American and EU demand for biomass fuels. In Brazil alone carbon emissions from annual forest clearing amounts to 20% of the total released in the country.

There is another type of tropical agriculture called slash and char which would promote soil fertility, allow for shorter rotation periods and also reduce dependence on chemical fertilizers. This farming technique was formerly practiced by the Amerindian people 500 to 2500 years ago and was discovered independently in Asia. It is quite a simple concept actually, as these native Amazon Rainforest farmers had only stone tools and felling the forest for fresh, fertile ground was very difficult. Instead, they conducted a smothered combustion of agricultural debris, and supplemented this with domestic manure and household debris. This charcoal built up in the soil over time and became a durable substitute for soil organic matter. This black carbon lasts for ten’s of thousands of years in the soil as opposed to a few seasons at best. The result is a soil with chemical and biological properties that convert unproductive tropical oxisols to fertile soils that are still farmed even 1000 years after the original people have disappeared.

SNIP

Readers of this column may recall my earlier writing about our studies at the nursery with charcoal as a soil additive.

Since 2003 we have been testing this material and a progress report on this research project is now posted at our website. We are encouraged by our early results from our block treatment study, a project that will continue for several more years. From our local fieldwork and also from reports of other hands on workers around the globe charcoal is an excellent material to use as a soil additive.

Burying charcoal improves the water holding capacity, soil pH, cation exchange capacity, base exchange and most important of all makes new habitat for beneficial microorganisms. The increase in surface area made available by charcoal is amazing. A single gram of charcoal powder can have a surface area of 1500 square meters. Far from being inert charcoal is a highly valuable component, providing active retention of nutrients as well as increased micro-life and stabilization of the chemical environment.

http://www.fourthcornernurseries.com/Article16.asp

[haele]

1. So long as it doesn't have petroleum or other accelerant chemicals in it, should be allright

The best growing soil we have always had at home is where we dump the ash from the fireplace or the grill (we don't use charcoal press briquettes if we can help it, we always try to get the naturally burned chunks). Charcoal and Ash have always been used to improve topsoil, especially for vine plants - not so much root plants, though.

Haele

[HamdenRice]

2. It's slightly different and is called terra preta (black soil)

Slash and burn relies on what you do -- adding ash and hence nutrients, to the soil.

Black soil has an as yet not fully understood mechanism that improves soil fertility over very long periods of time not based entirely on the nutrients in the wood.

There are even stranger, almost unbelievable characteristics of terra preita -- including an alleged capacity to regenerate itself. There are supposedly terra preta deposits that landowners "mine" and sell to farmers, and when they return after some months, there is more of the stuff.

http://en.wikipedia.org/wiki/Terra_preta

[jpak]

3. by Richard T. Haard, Ph. D.

:evilgrin:

[Botany]

4. Dick Hard

:rofl:

Although the article is neat

[Massacure]

5. But if you cut down an acre of forreest, turn the wood into charcoal and spread it...

Are you really doing anything beneficial for that acre of land? Those nutrients just don't pop out of thing air...

[kristopher]

6. Speculation is that the charcoal provides habitat for

Speculation is that the charcoal provides habitat for bacteria that are responsible for the productiveness of the soil. Someone posted a good article here a while back that discussed a study done in the soil of northern forests and the outcome was significantly different than in the tropics.

[Canuckistanian]

7. The benefit isn't the nutrients in the charcoal

It's the way charcoal HOLDS nutrients in the soil. Charcoal traps beneficial bacteria, complex molecules and water and keeps them around long enough for the plants to benefit from them.

And yes, the long term benefits far outweigh the initial expenditure of wood needed to create it.

Google "Terra Preta".

Here's the Wiki definition:
http://en.wikipedia.org/wiki/Terra_preta

[DCKit]

9. Most importantly, it provides habitat and storage of nutrients and water...

for mychorriza, a branch of beneficial soil fungi that provide water and nutrients to the roots of various plants in exchange for sugars and carbohydrates. The "threads" of the fungus increase the effective reach of the plant far beyond what the root system could ever attain.

Carbon in the soil provides millions (billions? trillions? brazillions?) of tiny pockets where excess water and various nutrients can be stored until needed.

I bought a 5 gallon bucket of activated charcoal on Ebay this spring and mixed it with my potting soil. While my tomatos aren't exactly going gangbusters (not enough direct sun), the S.O.'s balcony is a jungle.

I've read repeatedly that as much as 97% of the nutrients in the rain forest are locked up in living plants and animals. However, Terra Petra soils have been biologically active and fertile for, at least, 500 years. There's got to be something to it.

[Canuckistanian]

11. I've heard that Terra Preta takes a few years to take effect

Most plants don't see any benefits in the first year. Perhaps it takes that long for the fungus to start growing in the carbon.

Another interesting factoid. There's some speculation that charcoal contains a high percentage of C60 or "Buckyballs" and it is these molecules that trap nitrogen and CO2 that are beneficial to plants.

[XemaSab]

8. Some nutrients actually DO pop out of thin air

Nitrogen and carbon, for example.

[NickB79]

10. Too bad initial studies suggest terra preta doesn't do so much for temperate soils

http://www.sciencedaily.com/releases/2008/05/080501180247.htm

"They found that when charcoal was mixed into humus, there was a substantial increase in soil microorganisms (bacteria and fungi). These microbes carry out decomposition of organic matter (carbon) in the soil, and consistent with this, they found that charcoal caused greatly increased losses of native soil organic matter, and soil carbon, for each of the three forest stands. Much of this lost soil carbon would be released as carbon dioxide, a greenhouse gas."

I was pumped to try making my own terra preta for my garden this summer until I read that study :(