What is Conservation Agriculture?
What is Conservation Agriculture?
Conventional "arable" agriculture is normally based on soil tillage as the main operation. The most widely known tool for this operation is the plough, which has become a symbol of agriculture. Soil tillage has in the past been associated with increased fertility, which originated from the mineralization of soil nutrients as a consequence of soil tillage. This process leads in the long term to a reduction of soil organic matter. Soil organic matter not only provides nutrients for the crop, but it is also, above all else, a crucial element for the stabilization of soil structure. Therefore, most soils degrade under prolonged intensive arable agriculture. This structural degradation of the soils results in the formation of crusts and compaction and leads in the end to soil erosion. The process is dramatic under tropical climatic situations but can be noticed all over the world. Mechanization of soil tillage, allowing higher working depths and speeds and the use of certain implements like ploughs, disk harrows and rotary cultivators have particularly detrimental effects on soil structure.
Soil erosion resulting from soil tillage has forced people to look for alternatives and to reverse the process of soil degradation. The logical approach to this has been to reduce mechanical tillage. This led finally to movements promoting conservation tillage, and especially zero-tillage, particularly in southern Brazil, North America, New Zealand and Australia. Over the last two decades the technologies have been improved and adapted for nearly all farm sizes; soils; crop types; and climatic zones. Experience is still being gained with this new approach to agriculture and FAO has supported the process for many years.
Experience with Conservation Agriculture
Experience has shown that these techniques, summarized as Conservation Agriculture (CA) methods, are much more than just reducing the mechanical tillage. In a soil that is not tilled for many years, the crop residues remain on the soil surface and produce a layer of mulch. This layer protects the soil from the physical impact of rain and wind but it also stabilizes the soil moisture and temperature in the surface layers. Thus this zone becomes a habitat for a number of organisms, from larger insects down to soil borne fungi and bacteria (see section on soil biodiversity). These organisms grind the mulch, incorporate and mix it with the soil and decompose it so that it becomes humus and contributes to the physical stabilization of the soil structure. At the same time this soil organic matter provides a buffer function for water and nutrients. Larger components of the soil fauna, such as earthworms, provide a soil structuring effect producing very stable soil aggregates as well as uninterrupted macro pores leading from the soil surface straight to the subsoil and allowing fast water infiltration in case of heavy rainfall events.
This process carried out by the living component of a soil, can be called "biological tillage". However, biological tillage is not compatible with mechanical tillage; and with increased mechanical tillage the biological soil structuring processes will disappear. Certain operations such as mouldboard or disc ploughing have a stronger impact on soil life than others, such as chisel ploughs. Most tillage operations are, however, targeted at loosening the soil which inevitably increases its oxygen content leading in turn to the mineralization of the soil organic matter. This inevitably leads to a reduction of soil organic matter which is the substrate for soil life. Thus agriculture with reduced, or zero, mechanical tillage is only possible when soil organisms are taking over the task of tilling the soil. This, however, leads to other implications regarding the use of chemical farm inputs. Synthetic pesticides and mineral fertilizer have to be used in a way that does not harm soil life.
Burning plant residues and ploughing the soil are mainly considered necessary for phytosanitary reasons: to control pests, diseases and weeds. As the main objective of agriculture is the production of sufficient and healthy crops, changes in the management of pests and weeds becomes necessary with CA. In a system with reduced mechanical tillage based on mulch cover and biological tillage, alternatives have to be developed to control pests and weeds. Integrated Pest Management becomes mandatory. One important element to achieve this is crop rotation, interrupting the infection chain between subsequent crops and making full use of the physical and chemical interactions between different plant species. Chemical pesticides, particularly use of herbicides, are inevitable in the first years but have to be used with great care to reduce the negative impacts on soil life. After the point that a new balance between the organisms of the farm-ecosystem, pests and beneficial organisms, crops and weeds, becomes established, and the farmer learns to manage the cropping system, the use of synthetic pesticides and mineral fertilizer tends to decline to a level below that of the original "conventional" farming system (see section on Integrated Weed Management).
Advantages of Conservation Agriculture
Conservation Agriculture, understood in this way, provides a number of advantages on global, regional, local and farm level:
· CA not only conserves, but also enhances the natural resources and increases the variety of soil biota, fauna and flora (including wildlife) in agricultural production systems without sacrificing yields on high production levels. As CA depends on biological processes to work, it enhances the biodiversity in an agricultural production system on a micro- as well as macro level (see section on Agricultural Biodiversity).
· No till fields act as a sink for CO2 and conservation farming applied on a global scale could provide a major contribution to control air pollution in general and global warming in particular. Farmers applying this practice could eventually be rewarded with carbon credits.
· Soil tillage is among all farming operations the single most energy consuming and thus, in mechanized agriculture, air-polluting, operation. By not tilling the soil, farmers can save between 30 and 40% of labour time and fossil fuels (in mechanized agriculture) compared to conventional cropping.
· Soils under CA have a significantly higher water infiltration capacity which reduces surface runoff and thus soil erosion significantly. This improves the quality of surface water, reducing pollution from soil erosion, and enhances groundwater resources. In many areas it has been observed after some years of conservation farming that natural springs that had dried up many years ago, started to flow again. The potential effect of a massive adoption of conservation farming on global water balances is not yet fully recognized.
· Conservation agriculture is by no means a low output agriculture and allows yields comparable with modern intensive agriculture but in a sustainable way. Yields tend to increase over the years with yield variations decreasing.
· For the farmer, conservation farming is mostly attractive because it allows a reduction of the production costs, reduction of time and labour, particularly at times of peak demand such as land preparation and planting. In mechanized systems it further reduces the costs of investment in - and maintenance of machinery in the long term.
Requirements of conservation agriculture
Research and experience have shown that the following agronomic and economic aspects of conservation agriculture are important to farmers, and thus can provide the entry point for extension workers to discuss the advantages of CA:
- Seedbed should be of same quality as in conventional tillage.
- Alternatives for free-roaming livestock are needed, as they compact the soil through trampling.
- Increases in crop production and soil quality are required.
- Increase in organic matter of the soil.
- Capacity to control weeds.
- Capacity to reduce production costs.
- Same production level as conventional tillage.
- Accessible seeders - not too expensive
- Time saving
As tillage is often considered traditional, some cultural barriers that might aggravate the change process can exist in a region. For extension personnel it is always important to recognize these barriers. They include:
- Not understanding the technology.
- Being afraid of the economic risk.
- Not being able to buy equipment.
- Soils or crops are not adequate and need to be adjusted.
Change never appears "overnight" and will take time. Extension personnel therefore need to be patient and accept that agricultural technologies are adopted step-by-step, because farmers:
- Need to feel at ease with the new technology.
- Do not have the capital to invest.
- Cannot run a big risk, especially when the technology is unknown
- Need a learning-by-doing environment.
| || |