Back to the soil
With higher energy prices, water pollution from chemical inputs, land degradation and other problems, agriculture has reached a crossroads – and all against a background of soaring world population growth. How can we feed the planet whilst preserving for future generations the resources needed for food production? The answer could lie in conservation agriculture.
There are billions of them just under our feet, although most of the time they live in obscurity. Buried under the tons of concrete and asphalt of our towns and cities and dowsed with chemicals in our countryside, the soil’s inhabitants suffer much aggression. This situation was exacerbated by the advent of intensive farming in the 20th century, which radically changed traditional farming methods. However, the soil is said to harbour nearly 80% of the Earth’s living biomass. Earthworms weigh the same as all the other animals on the Earth’s surface put together. Conserving and exploiting this unique biotope at the frontier of the organic and inorganic worlds is the raison d’être of conservation agriculture (CA), a new concept for working the land that aims to return the soil to its place as the linchpin of agriculture.
Millipedes, ants, bacteria, fungi… all these organisms have very specific roles to play. For instance, earthworms help to structure the soil. Worm burrows aerate the soil and assist water infiltration. The clusters of organic matter and soil particles that worms expel from their digestive tracts (known as worm casts or castings) are essential for the development of micro-organisms, which recycle them into nutrients and humus.
Such micro-organisms include fungi and bacteria. More than 80% of plants carry mycorrhizas, a symbiotic association between a plant and a fungus. Mycorrhizas colonise the roots of a host plant and increase its ability to absorb nutrients, protect it from disease, enhance its resistance to pollutants and facilitate its adaptation to unfavourable conditions, such as lack of water. Bacteria of the Rhizobiaceae family fix and reduce nitrogen in the atmosphere before converting it into nitrate. Some of these bacteria optimise the shape and number of root hairs, which also boosts a plant’s absorption capacity. The multiple relationships of interdependence that govern the lives of these plants, animals, bacteria and fungi turn the soil and its biocenosis (all the living beings in a biotope) into a complex and valuable ecosystem.
A lost world?
From the mid-20th century onwards, European agronomists believed that they could do without this valuable asset by using chemical inputs for an intensive farming system that is still in widespread use today. However, the drawbacks of intensive farming had already started to become evident in the 1930s, with the formation of dustbowls (dust storms that devastate crops) in the United States and Canada. To counter this catastrophic erosion arising directly from several decades of intensive monoculture combined with serious droughts, it became necessary to reduce or even abolish ploughing. The non-ploughing concept was taken up again by Brazilian peasant farmers’ associations in the 1970s in a bid to rescue their soil from the massive erosion that followed a national campaign to promote monoculture.
By treating the soil merely as an inert production medium, modern conventional agriculture has obliterated its crucial contribution to agriculture. It is an oversight that has cost dearly. “In Europe, the combined effects of agriculture, industry and urban development have meant that some 12% of the soil has been affected by water erosion. Organic matter, which is essential to maintaining soil fertility, is also in decline: 45% of Europe’s soil contains less than 2% organic carbon, a level considered to be low. This has hit the Mediterranean region very hard, as well as France, the United Kingdom and Germany,” explains Emilio González, General Secretary of the European Conservation Agriculture Federation (ECAF). The soil becomes compacted, impermeable, saline… It also becomes polluted, chiefly from an array of chemical inputs.
However, the idea of using soil biodiversity has come back into favour in a big way. While FAO (the Food and Agriculture Organization of the United Nations) is extolling the virtues of Rhizobium bacteria for pulse crops, scientists from the IRD, France’s Research Institute for Development, have used earthworms to revive production in tea plantations in Tamil Nadu, India.
The aim of conservation agriculture is to preserve soil in an integrated manner by exploiting its natural self-regulating ability. The CA technique drastically reduces erosion and could even guarantee long-term soil fertility. CA is applied in accordance with three basic principles.
The first basic principle is minimal soil disturbance. This means replacing mechanical ploughing with biological tillage by the billions of organisms living in the soil. “Not only does this save farmers time and fuel, ultimately it reduces the need for chemical inputs. In short, it costs farmers less to produce their crops,” says Theodor Friedrich, an FAO agricultural engineer who specialises in conservation agriculture. The second basic principle is permanent soil cover using crop residues or cover crops. This protects the soil from external aggressions and promotes the creation of mulch (a protective layer of organic matter that triggers the formation of humus and significantly reduces erosion).
The third basic principle of CA is crop rotation, which allows the soil to regenerate itself. In fact, every plant has a preference for absorbing a particular type of nutrient. By alternating crops from one harvest to another, it allows the soil to rebuild its store of the nutrients depleted by the previous crop. Crop rotation also cuts down on phytosanitary treatments, prevents chemical toxicity from monoculture, and lessens the chance of plants developing resistance to chemical treatments. Lastly, rotation helps to limit disease and invasion by parasites or adventive plants (weeds).
“Numerous research projects are under way in Asia and Africa to determine the optimal conditions for developing CA. The technique is of particular interest to countries in these regions where the effects of erosion tend to be more serious,” explains Francis Forest, head of the Direct Seeding and Cover Crops Research Unit (SVC) at the French Agricultural Research Centre for International Development (CIRAD).
CIRAD has also contributed to a European research project called KASSA (Knowledge Assessment and Sharing on Sustainable Agriculture), which came to an end in 2006. KASSA examined different experiences with CA throughout the world to identify which avenues of research would allow the technique to be developed in Europe. The project relied heavily on the experiences of Argentina and Brazil where, according to the FAO, around 60% of arable land is cultivated using the conservation agriculture technique, as well as on the experience of the United States. “Apart from the potential agronomic benefits of CA, it promotes the soil’s ability to fix atmospheric carbon dioxide (CO2), which is a considerable advantage in combating global warming,” emphasises Emilio Gonzàlez.
A delicate transition…
However, Rabah Lahmar, the CIRAD researcher heading up the KASSA project, warns: “Although CA is certainly an attractive proposition, its development is highly dependent on local conditions, i.e. natural, technical, sociocultural, economic, institutional and political conditions. It calls for a lot of expertise, especially during the transition phase from conventional agriculture to CA, the duration of which is hard to predict, as it varies from one place to another.”
It is not all roses during the transition phase either. “The transition to CA is accompanied by a variation in yield, which might be 10% to 15% higher, or, as in the case of Europe where high yields are the norm, 10% to 15% lower. Farmers also need to use more herbicides to control weeds effectively,” says Rabah Lahmar. “In fact, this is a controversial issue which would explain the lack of interest in CA in some quarters of the agricultural sector. Advocates believe that CA will restore the agro-ecosystem balance over time, although this has not been scientifically proven and it is impossible to say with certainty that pesticide and fertiliser use will fall.”
Theodor Friedrich has no doubts, however, saying: “Field experiments have shown a reduction in the use of chemical inputs five to ten years after introducing CA. As regarding yield, in 95% of cases no losses have been observed.”
…especially in Europe
“A possible avenue of research highly recommended by KASSA is to identify and accurately assess the risks during the transition phase and in the long term,” adds Rabah Lahmar. But it is not the only avenue of research. Understanding how soil functions under the CA system, determining suitable cover crops for each type of farming, soil and climate, developing an optimal crop rotation system and defining indicators to measure CA performance are all unknowns which the European scientific research sector could apply itself in elucidating. “To my knowledge there has still been no call for projects arising from KASSA results,” says Rabah Lahmar regretfully. “However, the European Parliament recently commissioned a study on the degradation of arable land and the methods that would help to mitigate the problem.” The project, Sustainable Agriculture and Soil Conservation (SoCo), jointly managed by the European Commission’s Directorate-General for Agriculture and Joint Research Centre (JRC) was launched in early 2007.
A Soil Framework Directive proposed in late 2007 might have drawn attention to CA’s potential for European agriculture, but following the opposition of France, Germany and the United Kingdom, the Council of Ministers rejected the proposal. Other European measures could well kindle more interest in CA, though. Theodor Friedrich predicts that, “the new Water Framework Directive has now imposed such heavy restrictions on agricultural waste containing nitrates and nitrogen that farmers will be unable to comply unless they adopt CA techniques. This will have the effect of reducing the quantity of chemical inputs spilled onto fields.” It remains to be seen if such a movement is established before Europe’s soil has degraded beyond the point of no return.
Julie Van Rossom