CA is a set of soil management practices that minimize the disruption of the soil's structure, composition and natural biodiversity. Despite high variability in the types of crops grown and specific management regimes, all forms of conservation agriculture share three core principles. These include:
- maintenance of permanent or semi-permanent soil cover (using either a previous crop residue or specifically growing a cover crop for this purpose);
- minimum soil disturbance through tillage (just enough to get the seed into the ground) ;
- regular crop rotations to help combat the various biotic constraints;
CA also uses or promotes where possible or needed various management practices listed below:
- utilization of green manures/cover crops (GMCC's) to produce the residue cover;
- no burning of crop residues;
- integrated disease and pest management;
- controlled/limited human and mechanical traffic over agricultural soils.
When these CA practices are used by farmers one of the major environmental benefits is reduction in fossil fuel use and greenhouse gas (GHG) emissions. But they also reduce the power/energy needs of farmers who use manual or animal powered systems.
Conservation agriculture is largely the product of the collective efforts of a number of previous agricultural movements, including no-till agriculture, agroforestry, green manures/cover crops, direct planting/seeding, integrated pest management, and conservation tillage among many others. Yet CA is distinct from each of these so-called agricultural packages, even as it draws upon many of their core principles. This is because CA uses many of the available technologies in unison, resulting in something many believe to be much greater than the "sum of its parts."
The following terms are often confused with conservation agriculture:
- No-till (NT)/ Zero till (ZT)
NT and ZT are technical components used in conservation agriculture that simply involve the absence of tillage/plowing operations on the soil. Crops are planted directly into a seedbed not tilled after harvesting the previous crop. Not everyone utilizing no-till technologies adopts other important components of CA. One major difference is that NT or ZT do not necessarily leave residue mulch. Some recent research data suggests this is vital, since without the residue mulch many of the benefits of CA are lost or decreased in value.
- Conservation tillage/ Minimum tillage/ Reduced tillage
These are tillage operations that leave at least 30% of the soil surface covered by plant residues in order to increase water infiltration and cut down on soil erosion and runoff. Conservation tillage is an intermediate form of CA since it keeps some soil cover as residue from the previous crop. But some tillage is usually done. It developed as a management system after the “Dust Bowl” of the 1930’s in the Mid-West areas of the USA. It was found to reduce erosion by protecting the soil surface from wind and rain.
- Direct planting, direct drilling, plantio direto and siembra directa
These are terms used for ZT in other countries like Australia and South America. They use special equipment (e.g. NT drill) to plant seeds directly into crop residues left on the soil surface without preparing a seedbed beforehand.
- Direct seeding
This term is usually associated with growing a rice crop like any other cereal crop without producing seedlings that are then transplanted into the main field. However, it can also be called NT or ZT if the seed are drilled without tillage.
- Organic farming
Organic agriculture does not permit the use of synthetic chemicals to produce plant and animal products, relying instead on the management of soil organic matter (SOM) and biological processes. In some parts of the world, farms must be inspected and certified before their food products can be sold as organic, indicating that no synthetic chemicals were used in producing them. But organic farming uses the principles of CA to some extent and one objective similar to CA is to maintain and improve soil health. Unlike organic farming, CA does allow farmers to apply synthetic chemical fertilizers, fungicides, pesticides and herbicides. Many farmers rely on using these to control weed and pest problems, particularly during the early transition years. As soil physical, chemical and biological health improves over time; the use of agrichemicals can be significantly reduced or, in some cases, phased out entirely.
CA is often used synonymously with ZT that is also believed to require heavy implements and large tractors. However, CA can be used by farmers with large or small holdings as follows:
- Manual systems can include practices that build hills (eg. The traditional Iroquois Indian “Three Sisters” system) or basins (W.African Zai system) or use hand held planters (jabbar planters or matracas) or planting sticks to get seed into the ground without tilling the soil.
- Animal traction systems can be as simple as making a furrow for placement of seed and micro-placement of nutrients to planters that can place seed and fertilizer even when residues are present.
- Tractor power systems range from low horsepower, two wheel tractor systems to large, high horsepower 4-wheel or more models. They can be low cost no-till seeders manufactured by local artisans building on existing seed drills or expensive machinery developed by large tractor implement companies.
Farmers who do not own tractors can also avail of the tractor powered systems through use of hiring or service providers, a common system for plowing in many developing countries.