Industrial agriculture has made deserts of previously fertile fields. Yet they don’t have to stay that way for ever—barren terrain can soon regain its fruitfulness with the miracle of terra preta, the ‘black earth’.
There was great excitement when researchers began to examine what was possibly the most fertile soil in the world a few years ago—terra preta, the Portuguese term for ‘black earth’, in the Amazon region. It was man-made and had lost nothing of its excellent quality for thousands of years (the oldest such soil is approximately 8,000 years old). The core element is biochar (mostly charcoal), which is thought to remain stable in the ground virtually indefinitely and store and retain nutrients and water. Other components include compost, various-sized clay fragments, human and animal waste, organic waste including bones and fish bones, as well as presumably aquatic biomass such as algae. This mixture ensures a considerably higher concentration of calcium, magnesium, phosphor and potassium in this soil than the ground around it. Researchers also discovered that an above-average number of fungi appear in this black soil, which also encourages plant growth.Terra preta is beneficial in a number of ways: a) it is able to bind nitrogen and carbon from the air in the ground; b) the humus content remains stable over long periods; c) the biochar’s large inner surface and the increased humus content means that nutrients entering the ground remain available to plants and are not lost; d) water is absorbed and stored in high quantities; and e) the eventual yield is considerably higher than in the surrounding area. Furthermore, the soil can even regulate itself. When, after its discovery, farmers began to market it, whole areas were cleared within just a few decades. But after the Brazilian government passed an export ban for fear of losing this “Amazonian treasure”, the mined soil grew back within ten to twenty years. The phenomenon hasn’t yet been fully explained; it is assumed that it is linked to the optimally functioning microbiology of terra preta, amongst other things.
Also still largely unknown is how this soil came to be. Any information about it “was lost along with the eradication of the original inhabitants of the Amazon region,” writes Gerald Dunst, soil expert from the eco-region of Kaindorf in Styria (Austria), in his book Humusaufbau - Chance für Landwirtschaft und Klima (“Producing Humus—A Chance for Agriculture and Climate”). One hypothesis is that biochar was composted together with organic waste.
Man-made black soil with legendary properties—the discovery in the Amazon should be a clarion call to the whole world. Farmer Herbert Mietke from Lindendorf near Seelow in Brandenburg (Germany) was one of the first to try to improve his sandy earth this way. Its humus content was a mere 0.7 per cent (akin to desert conditions) with poor water absorption after rainfall, and its yield was accordingly small.
Three years ago, together with Bruno Glaser from the University of Bayreuth, he mixed 30 tons of compost and up to 20 tons of biochar (charcoal) into the upper layer of soil over one hectare. Through mineralisation, the compost provides nutrients which are retained by the porous biochar in much the same manner as water. The results already speak for themselves: the humus content has tripled to 2 per cent, the soil’s ability to store water has doubled and the yield has increased by 40 per cent.
“Plenty more is still possible,” says Glaser, who currently lectures at the University of Halle Wittenberg. He believes they can increase the humus content to between four and eight per cent with regular and moderate additions of humus and biochar. Overall he sees “plenty of potential for agriculture.” There are no panaceas, due to the varying soil types and existing materials: “We want to find out how the principles work and how to optimise material flows in such a way as to make it possible for people to generate their own fertile earth following the terra preta principle, and at no great cost.”
Fertile soil would also save on artificial fertilisers; a saving in the most common sense of the word since in the years to come fertiliser costs will rise along with energy prices and the price of phosphor, reserves of which are slowly diminishing. “There is a predominating atmosphere of change for farmers working with humus. It could therefore also counteract the problem of migration from rural areas,” says Glaser.
One pioneer in biochar research is the organic wine mail order company Delinat, or rather the Delinat Institute for Ecology and Climate Farming, based in Switzerland. In spring 2011 it began what is by its own account the largest biochar experiment in Europe to date. About a dozen organic vineyards throughout the continent are participating, each providing one hectare for researching biochar as a means of improving the soil, supplying nutrients, and putting a stop to greenhouse gas emissions. A 2007 trial organised by the Delinat Institute has already ended. The results indicated that “using biochar in particular improves water and nutrient availability, leading to improved soil quality and other benefits.”
These benefits are manifold: increased vine resistance and thus a reduced need for pesticides; stimulation of microbial activity in the earth; a reduced need for fertiliser; improvement in crop taste, nutrient content and durability as well as a drop in CO2 emissions and groundwater pollution.
Given the current situation, it is high time to take a thorough look at ways to improve the soil and understand the huge significance of humus even in our own garden. In a narrower sense, humus is the “dead” organic soil substance i.e. everything that once lived. It is produced by the organisms living in the ground, from bacteria to earthworms, by means of decomposition processes. Humus in turn is of central importance for the soil life; for the soil’s ability to store water and nutrients. Did you know that more organisms live in one handful of healthy soil than there are people in the world? Our well-being depends on the well-being of fungi, bacteria, mites, springtails, snails, earwigs, woodlice and earthworms: some organisms make the leaf epidermis soft, while others nibble holes in the dying leaves, which are eventually eaten by the earthworms together with the soil and which produce the best, most fertile humus earth through their waste.
No humus, no life. No healthy soil with sufficient humus equals no healthy plants; no healthy plants equals no healthy animals or humans. Around the world, industrial agriculture is harming the soil and thus the humus content—and for decades the organic substance of fields has been getting smaller and smaller. About 15 to 20 tons of soil is stripped per hectare per year from an ordinary cornfield with a ten per cent gradient—about ten times more than new soil formed by humus production. Over the last few years, however, the trend has been reversed for the first time but for some experts this is still not enough. August Raggam, a soil and biomass specialist who spent many years lecturing at the Technical University of Graz (Austria), for example, explains that, according to international classification, the low humus content actually makes fields deserts. Originally, local soil would have contained at least 60 kilograms of humus per square metre. Below 10 kilos of humus would be considered desert—and soils in German-speaking countries mostly contain no more than 8 kilos of humus per square metre. “All our European fields are deserts: we are therefore at the lowest limit. People try to cover it up,” he says. A little trick camouflages the true extent of the humus deficiency: earlier, the analysed soil was taken from a depth of half a metre, now it’s only 20 centimetres. “When you halve the depth, you double the percentage.”
Humus production only works when the soil’s ecosystem is intact. “The earth is the digestive organ—the stomach—of the plant. If we overburden the “stomach”, the soil gets diarrhoea, so to speak, and the plant develops problems,” explains Swiss compost consultant Urs Hildebrandt in the film Humus—The Forgotten Climate Chance. The use of untreated liquid manure, for example, is particularly bad, leading to problems in the groundwater and a widespread disappearance of the aerobic (oxygen-loving) microflora. This microflora is the “farm hand for plants”, and only it can produce humus. “These aerobic creatures have similar requirements to humans and animals: they need oxygen, food and water. They make the soil beautifully organic,” adds Hildebrandt’s wife Angelika, also an expert ecologist. Any possible toxic substances are quickly broken down so it is important to make sure that an aerobic process occurs during composting.
The Swiss German sister publication of Facts are Facts, ZeitenSchrift, issue 50, reports that it’s even possible to use humus to make the deserts bloom, as seen in the Sekem Project proposed by ‘Alternative Nobel Prize’ winner Ibrahim Abouleish. A layer of humus of approx. 30 cm was gradually added to desert ground by means of a sophisticated compost system. At the current time, more than 2,000 people are working according to biological-dynamic principles at Sekem’s main base. The project has consequently become a standard blueprint for Egypt and beyond.