Conservation agriculture(CA) is a concept for resource-saving agricultural crop production that strives to achieve acceptable profits together with high and sustained production levels while concurrently conserving the environment .CA is based on enhancing natural biological processes above and below the ground.Intervations such as mechanical soil tillage are reduced to an absolute minimum ,and the use of external inputs such as agrochemicals and nutrients of mineral or organic origin are applied at an optimum level and in a way and quantity that does not interfere with, or disrupt, the biological processes.
Conservation agriculture (CA) aims to achieve sustainable and profitable agriculture.CA holds tremendous potential for all sizes of farms and agro-ecological systems, but its adoption is perhaps most urgently required by smallholder farmers, especially those facing acute labour shortages. It is a way to combine profitable agricultural production with environmental concerns and sustainability and it has been proven to work in a variety of agro-ecological zones and farming systems.
Main principles of conservation agriculture
Conservation agriculture systems utilize soils for the production of crops with the aim of reducing excessive mixing of the soil and maintaining crop residues on the soil surface in order to minimize damage to the environment. By doing this CA will
- Provide and maintain optimum environments of the root-zone to maximum possible depth.Roots are able to function effectively and without restrictions to capture high amounts of plant nutrients and water.
- Ensure that water enters the soil so that plant never, or for the shortest time possible, suffer water stress that will limit the expression of their potential growth.
- Favour beneficial biological activity in the soil in order to maintain and rebuild the soil structure, compete with potential in-soil pathogens, contribute to soil organic matter and various grades of humus.
- Avoid physical or chemical damage to roots that disrupts the effective functioning.
The three principles of conservation agriculture include
Direct seedling involves growing crops without mechanical seedbed preparation and with soil disturbance since the harvest of the previous crop. The term direct seeing is understood in CA as synonymous with no-till farming, zero tillage, no-tillage, direct drilling, etc.
Land preparation for seeding or planting under no-tillage involves slashing or rolling the weeds, previous crop residues or cover crops; or spraying herbicides for weed control, and seeding directly through the mulch. Crop residues are retained either completely or to a suitable amount to guarantee the complete soil cover, and fertilizer and amendments are either broadcast on the soil surface or applied during seeding.
A permanent soil cover is important to: protect the soil against the deleterious effects of exposure to rain and sun; to provide the micro and macro organisms in the soil with a constant supply of “food”; and alter the microclimate in the soil for optimal growth and development of soil organisms, including plant roots.
The effects of soil cover
- Improved infiltration and retention of soil moisture resulting in less severe, less prolonged crop water stress and increased availability of plant nutrients.
- Increased humus formation
- Reduction of impact of rain drops on soil surface resulting in reduced crusting and surface sealing
- Consequential reduction of runoff and erosion.
- Soil regeneration higher that soil degradation.
- Better conditions for the development of roots and seedling growth.
The rotation of crops is not only necessary to offer a diverse “diet” to the soil micro organisms, but as they root at different soil depths, they are capable of exploring different soil layers for nutrients. Nutrients that have been leached to deeper layers and that are no longer available for the commercial crop can be “recycled” by crops in rotation. This way the rotation crops function as biological pumps. Furthermore, a diversity of crops in rotation leads to a diverse soil flora and fauna, as the roots excrete different types of bacteria and fungi, which in turn, play an important role in transformation of these substances into plant available nutrients. Crop rotation also has an important phytosanitary function as it prevents the carry over of crop-specific pests and diseases from one crop to the next via crop residues.
Advantages of conservation agriculture
Economic benefits that Improve production efficiency
- Time saving and thus reduction in labour requirement
- Reduction of costs, e.g fuel, machinery operating costs and maintainance, as well as reduced labour cost.
- Higher efficiency in the sense of more output for a lower input.
Agronomic benefits that improve soil productivity
- Organic matter increase
- In-soil water conservation
- Improvement of soil structure, and thus rooting zone
The constant addition of crop residues leads to an increase in the organic matter content of the soil, but with time this will extend to deeper soil layers.
Environmental and social benefits that protect the soil and make agriculture more sustainable
- Reduction in erosion, and thus of road, dam and hydroelectric power plant maintenance costs
- Improvement of air quality
- Biodiversity increase
- Carbon sequestration
Residues on the soil surface reduce the splash-effect of the rain drops, and once the energy of the raindrops has dissipated the drops proceed to the soil without any harmful effect. This results in higher infiltration and reduced runoff, leading to less erosion. Soil erosion is reduced close to the regeneration rate of the soil or even adding to the system due to the accumulation of organic matter.
Limitations of conservation agriculture
The most important limitation in all areas where conservation agriculture is practised is the initial lack of knowledge. There is no blueprint available for conservation agriculture, as all agro-ecosystems are different.
The success or failure of conservation agriculture depends greatly on the flexibility and creativity of the practitioners and extension and research services of a region. Trial and error, by both official institutes and the farmers themselves, is often the only reliable source of information.
However, as conservation agriculture is gaining momentum rapidly in certain regions, there now exist networks of farmer organizations and groups of interested people who exchange information and experiences on cover crops, tools and equipment and other techniques used in conservation agriculture.
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