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Training manuals and Guidelines
Introduction to Conservation Agriculture (CA)

 
What is CA?
 

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. Interventions 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. At field level, CA is characterized by three principles which are linked to each other, namely:

- Continuous minimum mechanical soil disturbance.

- Permanent organic soil cover.

- Diversification of crop species grown in sequences and/or associations.

(See also: http://www.fao.org/ag/ca)

Experience has shown that these techniques, summarized as conservation tillage 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. Those organisms macerate 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 macrospores leading from the soil surface straight to the subsoil and allowing fast water infiltration in case of heavy rain events. This process carried out by the edaphon, 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 as for example chisel ploughs. Most tillage operations are, however, targeted at a loosening of the soil which inevitably increases the oxygen content in the soil leading to mineralization and thus to a reduction of the soil organic matter which is, at the same time substrate for soil life. Thus agriculture with reduced 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.  As the main objective of agriculture is the production of crops changes in the pest and weed management become necessary. Burning of plant residues and ploughing of the soil is mainly considered necessary for python sanitary reasons controlling pests, diseases and weeds. In a system with reduced mechanical tillage basing 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. Synthetic chemical pesticides, particularly herbicides, are in the first years inevitable but have to be used with very much care to reduce the negative impacts on soil life. To the extent 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 the original "conventional" farming.  Therefore, although the entry point for the system is a reduction of mechanical soil tillage and thus a task for mechanization, it can only work if all agronomic factors are equally well managed. As a consequence the Latin American Network for Conservation Tillage, RELACO, which was founded with the assistance of FAO 10 years ago, changed in its last meeting its name into Latin American Network for Conservation Agriculture.  Conservation Agriculture, understood in this way, provides a number of advantages on global, regional, local and farm level: 

- It provides a truly sustainable production system, not only conserving but also enhancing the natural resources and increasing the variety of soil biota, fauna and flora (including wild life) in agricultural production systems without sacrificing yields on high production levels.

- 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 the global warming in special. Farmers applying this technique could eventually qualify for CO2 bonus points.

- 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 time, labour and, in mechanized agriculture, fossil fuels as compared to conventional cropping. This accounts respectively for the air polluting gases.

- Soils under conservation agriculture have very high water infiltration capacities reducing 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 spring that had disappeared long time ago started to flow again. The potential effect of a massive adoption of conservation farming on global water balances is not yet fully recognized.

- The system depends on biological processes to work and thus it enhances the biodiversity in an agricultural production system on a micro- as well as macro level including flora and fauna.

- 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 in peak times like planting and it reduces in mechanized systems the costs for investment and maintenance of machinery in the long term.

Disadvantages in the short term might be initially high costs of specialized planting equipment and the completely new dynamics of a conservation farming systems, requiring high management skills and a learning process by the farmer. Long term experience with conservation farming all over the world has shown that conservation farming does not present more or less but different problems to a farmer, none of them not to be resolvable. Particularly in Brazil the area under conservation farming is now growing exponentially and is in Brazil reaching the 10 Mill. ha mark. Also in North America the concept is widely adopted.  A programme on Conservation Agriculture was jointly carried out between AGSE and AGLS starting end of 1996 promoting the concept of a conservation agriculture based on reduced mechanical soil tillage, soil cover and crop rotations.

 

Related practices to CA

Many individual practices can be integrated into a conservation farming program. These include:

- No-tillage

- Minimum and reduced tillage

- Agro-forestry

- Trap cropping

- Cover and green manure cropping

- Alley cropping

- Contour farming & strip cropping

- Organic and biodynamic farming

- Stubble mulching

- Integrated pest (IPM) and weeds (IWM) management

- Crop and pasture rotation

Terminology

Conservation agriculture (CA)

This term, which has been promoted by FAO (Food and Agriculture Organization of the United Nations) since 2001, refers to cropping systems that comply with the three following basic principles: direct seeding, permanent cover (crop residue or cover plants) and crop rotation. This term is now becoming widely accepted, but its definition is not as specific as it was at the outset, when it closely mirrored DMC.

Biological or organic agriculture 

This refers to agriculture without reliance on commercial synthetic chemical inputs (fertilizers, pesticides, etc.). Ploughing and repeated tillage is acceptable (usually not implemented), but DMC can be practiced.

Agrobiology

This term was used by CIRAD in the 1990s in reference to DMC. It is no longer used to avoid confusion with biological agriculture.

Agroecology

Agroecology is a science that concerns all soil protection and fertility enhancement techniques, while also being productive without substantial chemical input application. This strategy improves the natural functions of ecosystems and thus intensifies biological activity in the soil, to the benefit of farmers and sustainable agricultural production. This term encompasses DMC, biological agriculture, etc.

Direct seeding

Direct seeding is a cropping system in which the seed is sown directly in untilled soil. Only a small seed hole or furrow is opened. There can be plant cover (permanent or temporary, dead or live) or the ground may be left bare, but generally there is a layer of crop residue.

Direct seeding mulch-based cropping systems (DMC)

This concept was launched by CIRAD in 1999 in reference to cropping systems that include no tillage and permanent plant cover on the soil. The expression ‘plant cover’ refers to dead mulch (crop residue, cover plants or dead weeds) or live mulch associated with the crop.

Simplified cropping techniques (SCT) 

This expression is used by the French farming community in reference to agriculture without tillage (or no-tillage techniques, NTT), but with scraping of the soil surface (shallow ploughing or scarification) to bury part of the crop residue, so the ground is generally left bare.

Conventional tillage

In USA, this term refers to all systems (with or without tillage) in which there are no more than 15% mulch cover (crop residue) after sowing. In France, these are traditional techniques with tillage.

Conservation tillage (CT)

This American term refers to systems in which at least 30% of the field is covered by crop residue when the crop is sown. In USA, this includes four tillage methods, with the first two being by far the most important:

- No-tillage (direct seeding): without tillage.

- Mulch tillage: whereby tillage is carried out with chisel ploughs and discs (typically American, not available in Europe), with less than 15% of the crop residue buried after a single pass, i.e. most of the residue is left on the surface. The crop is sown under the mulch layer with a special seeder. There is no equivalent in France.

-  Ridge tillage: permanent ridges are tilled, followed by direct seeding. Strip tillage (or strip-till or zone-till): only single, relatively narrow strips are tilled, often with a rotary hoe, to facilitate soil warming in the spring (used especially in the Corn Belt).

No-tillage, no-till, zero-tillage, direct seeding, dire...

All of these terms refer to systems without soil tillage, i.e. direct seeding, without specifying the soil cover conditions. In USA, at least 30% of the field is covered with crop residue (see below).

Reduced tillage

This American term refers to situations in which 15-30% of the ground is covered (crop residue) at the time of sowing. It is quite close to the current French SCT (TCS in French) concept and the former minimum tillage concept.

Minimum tillage

This term should be avoided because it is too vague. It has several meanings in USA, Canada and Australia, e.g. reduction in the number of equipment passes (during the 1960s), or exclusively surface scraping with or without crop residue (1970s). "

 

 

 

History of CA development

Soil degradation and erosion gave raise to direct seeding

The basic concept underlying direct seeding was developed and first implemented in nontropical areas, first in USA as of the 1960s, and then in southern Brazil (subtropical), Australia, Argentina and Canada as of the 1970s. Until then, agricultural practices were based on tillage, repeated spraying of soils and excessive monocropping, which led to very large-scale ecological catastrophies with heavy socioeconomic consequences. The most renowned example is the dust bowl (dust clouds covering infrastructures, fields, etc.) that occurred on the American semiarid Great Plains between the 1920s and 1940s as a result of soil degradation and severe wind erosion. Tillage was partially blamed as early as the 1930s in USA as a result of this national disaster. Comparable phenomena affected Australia in the 1950s and 1960s. In Latin America, direct seeding was first adopted by a few farmers as of the 1970s to curb severe water erosion phenomena in southern Brazil (Parana state) and Argentina, in the Central Pampas. Individual and collective awareness of soil erosion processes triggered the development of direct seeding in these different parts of the world.

DMC systems

DMC has short- to medium-term effects with respect to halting erosion, increasing soil fertility, stabilizing or even increasing yields, even on infertile wastelands, while also reducing fuel consumption. This innovation is based on three concepts that apply in the field, i.e. no tillage, permanent plant cover, and relevant crop sequences or rotations associated with cover plants.

In most of the situation a medium term process is required to integrate these three principles; smallholders need to adapt some of the new technologies to suit their specific conditions, as well as to improve their technical skills and to overcome others constraints (access to credit, to specific equipment...). DMC systems represents the main goal, however an iterative approach is often necessary in generating new systems and making adoption realistic.

First steps of no-till systems - without a permanent soil cover - cannot be compare to DMC systems. It is often a misunderstanding in talking about DMC but never experiencing the full benefits of these systems (integrated weeds and pests management, recycling nutrients leached deep into the soil, improving soil organic content and water use efficiency...). This concern for accuracy is crucial in order to avoid frequent mistakes and errors commonly committed by a lot of stakeholders in the field of research and development. Using the term DMC to systematically designate any system of zero cultivation is detrimental not only to scientific and technical quality rigorously developed but also detrimental to their strong reputation and their dissemination. Systems based on no-till have a low productivity and most of these systems does not express the powerful functions that characterize the DMC giving them their exceptional performance (Séguy and Bouzinac, 2008).

 

DMC is the cornerstone of the holistic approach due to the emergence of interesting ecosystem properties and the integration of scales (from soil aggregate to landscape unit management). This integration in a systemic approach is essential for a precise understanding of the dynamics of change. These scales combine the main objects of study impacted by climate and anthropogenic factors (Séguy and Bouzinac, 2008):

- The village, where the agricultural production is generated and the management of surrounding areas

- (forests, pastureland for animals), is the main location for the dissemination of innovative systems, structuring space and social organization (groups producers).

- Landscape units which integrate multiple flows (water, biomass transfer, labor, goods and services ...) and it is at that level that the environmental impacts of human intervention (indicators of sustainability, environmental economics) are considered.

- Field, with the characterization of the processes that underlie the sustainability of the systems generated.

Adoption of CA

 

Global Overview of CA adoption

No-tillage/Conservation Agriculture (CA) has developed to a technically viable, sustainable and economic alternative to current crop production practices. While current crop production systems have resulted in soil degradation and in extreme cases desertification, the adoption of the No-tillage technology has led to a reversion of this process. Soil erosion has come to a halt, organic matter content, soil biological processes and soil fertility have been enhanced, soil moisture has been better conserved and yields have increased with time. Data presented ten years ago at the 10th ISCO Conference in West Lafayette, Indiana, showed a worldwide adoption of the No-tillage technology of about 45 million ha (Derpsch, 2001). Since then the adoption of the system has continued to grow steadily especially in out America where some countries are using CA on about 70% of the total cultivated area. Opposite to countries like the USA where often fields under No-tillage are tilled every now and then, more than two thirds of No-tillage practiced in South America is permanently under this system, in other words once started, the soil is never tilled again. In the last years a big expansion of the area under No-tillage has been reported in Asia, especially in China and Kazakhstan where more than a million ha have been reported in each country. But also in Europe there is progress in the adoption. There are about 650.000 ha of No-tillage being practiced in Spain, about 200.000 ha in France and about 200.000 ha in Finland. No-tillage based conservation agriculture systems gain also increasing attention in Africa, especially in Southern and Eastern Africa. In many countries the area is still low due to the high percentage of small scale farmers, but the numbers are increasing steadily as well. Up to now No-tillage has expanded to more than 100 million ha worldwide, showing its adaptability to all kinds of climates, soils and cropping conditions. No-tillage is now being practiced from the Arctic Circle over the tropics to about 50º latitude South, from sea level to 3000 m altitude, from extremely rainy areas with 2500 mm a year to extremely dry conditions with 250 mm a year. The wide recognition as a truly sustainable farming system should ensure the growth of this technology to areas where adoption is still small as soon as the barriers for its adoption have been overcome. The widespread adoption also shows that No-tillage cannot any more be considered a temporary fashion, instead the system has established itself as a technology that can no longer be ignored by politicians, scientists, universities, extension workers, farmers as well as machine manufacturers and other agriculture related industries.

 

Household Level Financial Incentives to Adoption of Conservation Agricultural Technologies in Africa

Although several studies have been conducted to determine the viability of conservation agriculture in Sub-Saharan Africa, almost all such studies are fragmented – often country specific – and with undue emphasis on output effects. However, assessment of the attractiveness of these technologies in Sub-Saharan Africa requires a detailed case-by-case comparison of changes in output and input costs and benefits. This paper reviews a set of responses known collectively as “conservation” or “sustainable” agriculture. Though definitions vary, these technologies typically involve agricultural management practices that prevent degradation of soil and water resources and thereby permit sustainable farm productivity without environmental degradation

Farmers’ adoption of conservation agriculture: A review and synthesis of recent research

In light of growing concerns over the implications of many conventional agricultural practices, and especially the deep tilling of soils, the Food and Agriculture Organization of the United Nations (FAO), among others, has begun to promote a package of soil conserving practices under the banner of ‘conservation agriculture’. While the title might be novel, its associated practices have long been employed by farmers, and studied by social scientists seeking to understand the reasons for their adoption and non-adoption. This paper reviews and synthesizes this past research in order to identify those independent variables that regularly explain adoption, and thereby facilitate policy prescriptions to augment adoption around the world. While a disaggregated analysis of a subset of commonly used variables reveals some underlying patterns of influence, once various contextual factors (e.g. study locale or method) are controlled, the primary finding of the synthesis is that there are few if any universal variables that regularly explain the adoption of conservation agriculture across past analyses. Given the limited prospect of identifying such variables through further research, we conclude that efforts to promote conservation agriculture will have to be tailored to reflect the particular conditions of individual locales

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