Principles of Conservation Agriculture

Conservation agriculture is a farming system that promotes minimal soil disturbance (i.e., no-tillage), maintaining permanent soil cover, and diversifying plant species. It also enhances biodiversity and natural biological processes above and below the soil surface, helping increase the efficiency of water and nutrient use and improving crop productivity and sustainability.

The three principles of conservation agriculture

1) Minimum mechanical soil disturbance (i.e., no-tillage) through direct placement of seed and/or fertilizer

Direct seeding or direct planting

Direct seeding involves growing crops without mechanical seedbed preparation, with minimal soil disturbance since the harvest of the previous crop. In conservation agriculture systems, “direct seeding” is understood as synonymous with no-till farming, direct drilling, and related practices.“Planting” refers to the precise placement of large seeds (e.g., maize and beans), while “seeding” usually refers to the continuous flow of seed, as in small grains (e.g., wheat and barley). The equipment penetrates the soil cover, opens a seeding slot, and places the seed into that slot. The size of the seeding slot and the associated soil movement should be kept to an absolute minimum. Ideally, the slot is fully re-covered with mulch after seeding, and no loose soil should remain visible on the surface.Land preparation for seeding or planting under no-till may include cutting or rolling weeds, residues from previous crops, or cover crops; or spraying herbicides for weed control, followed by direct seeding through the cover. Crop residues are retained either entirely or in sufficient quantity to ensure full soil cover. Fertilizers and amendments are applied either broadcast on the soil surface or banded during seeding.

2) Permanent organic soil cover (at least 30%) using crop residues and/or cover crops

Organic soil cover—keeping the soil covered—is a fundamental principle of conservation agriculture. Crop residues are left on the soil surface, but cover crops may be needed if the gap between harvesting one crop and establishing the next is too long. Cover crops strengthen conservation agriculture systems not only by improving soil properties, but also by enhancing biodiversity within the agro-ecosystem.While cash crops have market value, cover crops are primarily grown for their effects on soil fertility or as livestock feed. In areas where biomass production is limited—such as semi-arid regions or areas with eroded and degraded soils—cover crops are valuable because they:

Protect the soil during fallow periods
Mobilize and recycle nutrients
Improve soil structure and break up compacted layers and hardpans
Enable rotation within monoculture systems
Can be used to control weeds and pests

Cover crops are grown during fallow periods—between harvest and the planting of cash crops—using residual soil moisture. Their growth is terminated either before planting the next crop, or after the next crop has been sown but before competition between the two crops begins.Cover crops stimulate crop production, but they can also present certain challenges. They are beneficial for:

Protecting the soil when no crop is present
Providing an additional source of organic matter to improve soil structure
Recycling nutrients—especially P₂O₅ and K₂O—and mobilizing them within the soil profile to make them more readily available to subsequent crops
Providing “biological tillage” of the soil: the roots of certain crops—especially brassicas such as oilseed radish—are tap-rooted and can penetrate compacted or very dense layers, increasing the soil’s water infiltration capacity
Capturing nutrients that are easily leached, especially nitrogen (N)

Different plants, with diverse rooting systems, explore different depths of the soil profile. They may also absorb different amounts of nutrients and release distinct root exudates (organic acids), benefiting both soil and soil organisms. The presence of a mulch layer (dead plant material) in conservation agriculture reduces soil moisture evaporation while increasing water infiltration into the soil profile. The share of rainfall infiltrating into the soil depends on the extent of soil cover. Because different cover crops produce different amounts of biomass, residue density varies—and so does the capacity to increase infiltration.Vegetation cover is important in conservation agriculture to protect the soil from raindrop impact; to shade the soil and maintain the highest possible moisture content; and to recycle nutrients. It also has a physical—and potentially allelopathic—effect on weeds, reducing weed incidence and lowering the need for agrochemicals, and therefore production costs. Straw residues act as a cushion that reduces pressure on soil under wheels and hooves, playing an important role in reducing soil compaction.

3) Species diversification through diversified crop sequences and associations that include at least three different crops

Species diversification

Crop rotation is not only necessary to provide a diverse “diet” for soil microorganisms, but also because different crops root at different depths and can therefore explore different soil layers for nutrients. Nutrients leached into deeper layers that are no longer available to the cash crop can be “recycled” by rotational crops. In this way, rotational crops function as biological pumps.Moreover, crop diversity in rotation increases the diversity of soil plants and animals. Roots release different organic substances that attract different types of bacteria and fungi, which in turn play an important role in transforming these substances into nutrients available to plants. Crop rotation also has an important plant health function because it prevents crop-specific pests and diseases from carrying over from one crop to the next.Effects of crop rotation:

Greater diversity in plant production and, consequently, in human and animal nutrition
Reduced risk of pest and weed outbreaks
Greater distribution of biopores or channels created by diverse roots (different shapes, sizes, and depths)
Better distribution of water and nutrients within the soil profile
Improved exploration of nutrients and water across different soil layers through the roots of multiple plant species, leading to more efficient use of available nutrients and water
Increased nitrogen fixation through symbiosis between certain soil organisms and plants, and improved nitrogen/phosphorus/potassium balance from organic and mineral sources
Increased humus formation

Means and practices:

Designing and implementing crop rotations according to different objectives: food and feed production (grains, leaves, stems); residue production; pest and weed control; nutrient uptake and biological subsoil mixing/“tillage”; etc.
Using suitable/improved seed to achieve high crop yields as well as high residue production above and below ground, taking into account soil and climate conditions

Source (FAO):

https://www.fao.org/conservation-agriculture/ar/

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