Ancient farming practice improves today’s soil

In a world with 6.7 billion human inhabitants, global food supply tops the agenda of many scientists. Now it seems a piece of prehistoric farming wisdom – combined with modern science – might help. It’s in the form of an ancient process called “biochar fertilization,” practiced by the pre-Amazon people 1,500 years ago.

We spoke with Mingxin Guo, professor of soil science at Delaware State University. Guo told EarthSky that heating organic waste creates biochar, a charcoal-like substance that can improve soil quality for hundreds to thousands of years.

Mingxin Guo: It improves the ability of the soil to allow water to pass through and encourages plant root development.

Biochar loosens up the soil, said Guo, and gives a plant’s root more freedom to grow. What’s more, biochar can also help stabilize climate change. That’s because when raw plant material enters the soil, it quickly decomposes and converts to carbon dioxide gas. The CO2 then rises to the atmosphere and acts as a greenhouse gas. But burned plant material – biochar – is more stable in soil. Through his research, Guo hopes to ignite interest in this simple but valuable technology.

EarthSky also spoke about biochar with John Reilly, associate director for research on the Joint Program of the Science and Policy of Global Change at M.I.T.

Reilly – who is an expert on impacts of climate change on agriculture – said that tropical soils are notably thin and not very suitable for agriculture. Through some soil amendment process not completely understood today, Reilly said, the early Amazonians overcame those limits to create areas in the Amazon that remained productive and where the effects on the soil are still visible today. He said biochar was a part of this process.

John Reilly: Biochar also is a byproduct of biofuels production, especially pyrolysis or other gasification techniques although the goal in those processes is usually to maximize the amount of biofuel – i.e. leave as little of the biomass as biochar as possible. So there would be some trade-off between using biomass resources to produce a lot of biochar, some of which would remain sequestered for a very long time or to maximize fuel production and save carbon emissions by displacing fossil fuels.

Our thanks to:
Mingxin Guo
Delaware State University

John Reilly
Associate Director for Research
Joint Program of the Science and Policy of Global Change
M.I.T.