Conservation tillage: the end of the plough?
Farmers around the world plough their land. The practise of turning the soil before planting is so universal that the plough has for centuries been a symbol of agriculture. But, over the last 25 years, more and more farmers have been abandoning their ploughs.
Annual average nutrient loss from sub-Saharan African soils is estimated at 24kg/hectare and rising. In South Asia, the cost of different forms of land degradation - such as loss of soil structure leading to erosion, compaction and formation of surface crusts, is estimated at US$10 billion a year.
Yet, in an impossible equation, as cultivable soils are gradually depleted, crop production levels must keep rising. FAO estimates that farmers will have to produce 40 percent more grain in 2020 to feed the world population.
Planting without ploughing
One of the most effective remedies for land degradation is "conservation tillage" - a revolutionary cultivation technique in which the fields are not ploughed. "This concept sprang directly from the recognition that mechanical ploughing is contributing to land degradation on a massive scale, particularly in tropical and sub-tropical countries," said FAO Senior Agricultural Engineer Theodor Friedrich.
In the early 1970s, farmers in North and South America started experimenting with conservation tillage and even "no-tillage". Using conservation tillage, farmers leave crop residues on their fields after harvest, instead of ploughing them in or burning them off. They plant new crops with specially designed planters. These guide the seeds down into a slot in the soil underneath the protective layer of mulch formed by rotting residues.
Often farmers using conservation tillage also plant "cover" crops - underneath the main crop or between two different crops - to cover and protect the soil. Cover crops have additional benefits according to the species planted. For instance, legumes enrich the soil with nutrients, while plants with strong, deep roots break up compacted soil.
Twenty-five years after the first experiments by farmers with no-tillage, this new method of crop cultivation is known as conservation agriculture - because it conserves the nutrients in the soil, conserves water by improving absorption and infiltration and conserves biodiversity by protecting the natural balance in the fields. (Conservation Agriculture Web site.)
Under conservation agriculture, traditional tillage is replaced by "biological tillage" - carried out by soil fauna - worms and bugs. To maintain healthy numbers of such animals, agro-chemicals must be used with special care and kept to a minimum.
The modern plough was invented and perfected for weed control. In the late eighteenth century, it saved European crops from quack grass (Agropyron repens), a devastating weed. When farmers first begin to practise conservation agriculture, herbicides are often necessary to control the weeds - but they must be used judiciously to protect the soil life. Experience has shown that after a few years, the quantities of agro-chemicals necessary tend to decline.
Integrated pest management (IPM) is essential to conservation agriculture because it helps build up soil biota and promote biological tillage. IPM techniques enable farmers to monitor and control pest levels in the fields without disturbing natural balances, and to resort to synthetic pesticides only when and where it is absolutely necessary. In conservation agriculture, pest levels are also kept under control by crop rotation.
No losers under conservation agriculture
Conservation agriculture is often referred to as a "win-win" situation, and it has benefits on many levels. For the farmer, there is
At the environmental and community level, the benefits include:
Conservation agriculture also has significant benefits at the global level, including:
Conservation agriculture around the world
At the turn of the millennium, conservation agriculture was being practised on about 45 million hectares, mostly in North and South America. In South America in particular, both smallholders and big farmers are rapidly adopting the new technology. In some states in Brazil, it is official policy. In Central America, Costa Rica has a Department for Conservation Agriculture in its Ministry of Agriculture.
Figures available show that no-tillage - the basic technology for conservation agriculture - is used to cultivate 52 percent of the arable land in Paraguay, 32 percent in Argentina and 21 percent in Brazil. Although in absolute terms the biggest area under no-tillage is in the United States of America, it is only slightly over 16 percent of the country's cultivated land.
South American conservation agriculturists are highly organized in regional, national and local farmers' organizations and are supported by institutions from North and South America. Such support is essential in enabling farmers to adopt a new technology that involves a radical change of approach to their life's work.
Outside of the Americas, uptake of the new technology has been slower. But, "There is great potential for the adoption of conservation agriculture in Africa," said Dr Friedrich. At present, some large farms in South Africa and Zimbabwe are using conservation agriculture, and no-till farmers' clubs similar to those in South America have been set up in South Africa. Initiatives to promote conservation agriculture for small farmers are under way in Cameroon, Ghana, Kenya, Malawi, Namibia, Tanzania, Uganda, Zambia and Zimbabwe, and other countries.
"These movements are the first steps in the right direction," says Dr Friedrich. The exceptionally high rate of soil erosion in sub-Saharan Africa could be reduced, yield levels could be stabilized and labour requirements for ploughing diminished if conservation agriculture were widely adopted.
"Another vast area where the adoption of conservation agriculture would be extremely beneficial is Central Asia," says Dr Friedrich. "In the countries of the former USSR, conventional agriculture is virtuallly impossible because of environmental problems such as erosion and because of a lack of farm machinery, which has to be replaced. Unless conservation agriculture is adopted, the investment in new machinery will have to be very high."
The benefits of conservation agriculture - as part of sustainable agricultural and rural development - are being discussed at the eighth session of the Commission on Sustainable Development, in New York from 24 April to 5 May.
3 May 2000