Conservation agriculture (CA) is aimed at reducing the effort and cost of farming in a way that protects and improves agricultural soils. It is based on three key elements:
- Minimizing disturbance of the soil
- Maintaining soil cover
- Crop rotation
The first, key step in CA is to minimize the disturbance of the soil—no plowing or harrowing is necessary. Using specialized zero-tillage seeders, seed is planted directly into undisturbed soil, along with the fertilizer it needs. This improves the soil fertility and eliminates the costs associated with plowing, mainly fuel and labor. Less fuel also means reduced emissions of greenhouse gases.
Leaving stubble and other crop residues from the past harvest on the soil surface and leaving the soil undisturbed protects farmland from wind and water erosion and from extremes of heat. The occurrence of dust storms is reduced significantly. It also increases infiltration of rainfall, reduces runoff, and reduces evaporation of moisture from the soil surface.
The stubble and crop residues accumulate in the soil, increasing soil organic matter, improving the soil’s structure and potentially sequestering carbon. This boosts the soil’s ability to hold water and make it available to plants. Removal or grazing crop residues in the field is discouraged as this often leaves the soil bare and unprotected. Likewise, burning crop residues makes the soil prone to erosion and valuable nutrients are lost from the system.
Conventional thinking says that plowing and burning crop residues help control weeds, pests, and diseases. But the same or better results can be achieved using crop rotation and judicial use of pesticides. Switching crops each season interrupts the cycle of pests and diseases that build up when the same crop is grown repeatedly, providing the foundation for integrated pest management.
When farmers initially switch to conservation farming, they may need some chemical help, especially with weed control, but this tends to decrease as they learn to manage weeds, pests, and diseases in an integrated way. Growing cereals continuously can lead to high populations of grass weeds, but these can easily be controlled in broad-leafed crops such as legumes and canola by using selective herbicides. Likewise, broad-leafed weeds can be controlled in cereals. Rotation can also boost soil fertility: legumes fix atmospheric nitrogen and make it available to subsequent crops, while “green manure” crops boost soil organic matter content.
But the benefits are not just to the environment. Yields from CA are commonly as high as those from conventional agriculture — and often higher in dry areas and marginal lands — thanks to the increased availability of soil water and nutrients and improved soil structure. And CA saves farmers time and money. Less cultivation means less fuel used in preparing the land, and more time available for other farm or family activities. Precision planting and better placement of fertilizer reduces seed and fertilizer inputs, further reducing production costs and improving efficiency.
Most farmers in Australia, Brazil, and Canada and many in the Unites States and other developed countries use conservation agriculture in a range of rainfall zones, soil-types, and farming systems. Many fields have not been ploughed for 30 or more years. They are getting similar or higher yields with fewer inputs, saving themselves time and money, and boosting their incomes.
ICARDA’s research shows that CA could have an even greater impact on food production and on farmers’ livelihoods in dry areas in developing countries. In dry seasons, some farmers practicing CA obtained a harvestable yield, while other nearby conventional farmers faced crop failure. The challenge is to adapt CA to meet the local needs and resources of smallholder farmers in developing countries.