As well as problems from nutrient leaching and fertilizer run-off, conventional farms lose soil about 90 times faster than new soil is produced.
Drought and over-plowing in the 1930s resulted in dust storms that covered farm machinery.
Each year, 24 billion tons of the world’s soil blows or washes away, largely because of plowing.
Agricultural studies dating back to the early 1940s tabulating erosion from areas as far apart as the Himalayas and the U.S. show annual soil loss on plow-based farms average 1.5 mm of lost soil. Science Magazine reports,
As plows tear into the ground, they loosen the upper 6 to 8 inches (15 to 20 cm) of soil, exposing the dirt to rain and wind. Mechanized plows introduced in the 1930s have accelerated the loss.
Conservationists are exploring no-till agriculture. This method leaves fields unturned and allows crop stubble to remain on the surface to protect the soil; farmers plant new crops by making small holes in the layer of plant material.
Today’s plowless farms save our soil. No-till farms lose an average of 0.082 mm of soil each year, an erosion rate close to the natural geologic rate of 0.03 mm per year.
Indigenous soil management resists erosion
Natives of the Americas supplemented their soil with a remarkable method known as Black Earth or Terra Preta. [wiki]
Over a period of thousands of years, the way of life of the Koyapo tribe reveals that their soils, Terra Preta do Indio, were part of the everyday life of the people. [doc file].
Instead of today’s destructive slash and burn followed by plows, pouring carbon dioxide into the air even to produce green bio-fuels, natives covered up piles of logs and agri-waste with dirt and straw. Their footprint of carbon was returned to the soil as charcoal and nutrients using low-heat pyrolysis, heating their green waste and slash without oxygen
This indigenous method of making Dark Earth Soils – as deep as 1-2 meters [pics here] – are highly productive over prolonged periods and resistant to erosion. Philip Coppens wrote a readable article about dark earth here. Plants grow at least three times faster, without modern fertilizer. The natural soil builds a sustainable fertility with high levels of humus organic matter and nutrients such as nitrogen, phosphorus, potassium.
The properties of terra preta are amazing. Even thousands of years after creation, the soil remains fertile without need for any added fertilizer. Using terra preta also could reduce pollution from phosphates and nitrates entering groundwater and streams.
These highly productive soils would be beneficial to any farmer, anywhere in the world.
Google Video offers the BBC’s “The Secret of El Dorado” reporting that the people of 1491, the Americas before Columbus, possessed a secret with the power to transform our world and “their secret in the soil could be the solution to solving famine in the third world and other nations once and for all”….
How green is black dirt?
There is a huge potential for agricultural soils to reduce greenhouse gases and increase production at the same time. Before the industrial and green revolutions with the introduction of oil-based or mineral fertilizers, crop residues were a valued resource and returned to the soil as organic fertilizer. Research now shows there are critically needed benefits by directly returning carbon as well.
Biogeochemistry studies at Cornell are showing that carbon, black C, can reduce the greenhouse effect as well as help farmers. Charcoal can rebuild soil, replace nitrogen fertilizer and sequester carbon.
Amending soils around the globe can retain about 10 times more greenhouse gas than produced annually from the burning of fossil fuels.
The difference between terra preta and ordinary soils is immense. A hectare of meter-deep terra preta can contain 250 tonnes of carbon, as opposed to 100 tonnes in unimproved soils from similar parent material. WorldChanging declares that biochar’s capacity to capture carbon sound almost audacious.
Bio-Char is promoting carbon soil amendments and slash-and-char methods around the world showing that dark earth is more effective than fertilizer, compost or manure. Eprida has developed a sustainable closed loop charcoal technology noting that too little carbon in the soil contributes to topsoil loss, reduced soil fertility and lower agricultural yields.
The case for burying charcoal shows that pyrolysis is climate-friendly. Even if this approach would mean burning more coal as a large scale heat source for pyrolysis, it would yield a net reduction in worldwide carbon emissions.
Black-carbon and biofuel
Soil biology improved, added fertilizer reduced, water holding increased, erosion slowed to geologic rates, and alternative fuel? [link]
The Eprida technology uses agricultural waste to produce biofuel as well as high-carbon fertilizer. Converting wood or biomass to char produces far less greenhouse gas. The journal Biomass and Bioenergy reports that biomass in the oxygen-starved process of pyrolysis produces methane, hydrogen, and other products for combustion.
There are several challenges ahead, but it seems that carbon might be manageable after all. Even thousands of years after creation, the dark soil made by indigenous Americans remains fertile without need for any added fertilizer. Producing biofuel and capturing carbon fulfills modern demands as well.
We can look forward to healthy soil, cleaner streams, cleaner groundwater, replacing slash-and-burn with beneficial slash-and-char alternatives, and carbon sequestration.
and repairing our soils with charcoal amendments called biochar or agrichar offers a carbon sink to reduce greenhouse gases, new biomass fuels, and provides new models of sustainable higher-yield agriculture.