Key concepts and definitions
All agricultural, pastoral and forest outputs depend on production of biomass, which in turn depends on the combined and interacting physical, biological and chemical conditions of the soil as a medium for plant growth. All land-based animal and plant production systems use one or more of three main plant types: annuals, woody perennial crops and non-woody perennial crops. Soil-disturbing tillage may be used with any of them, though it is primarily associated with the first. The more diverse and complex is an agricultural system, the more stable and sustainable it will be in the face of unpredictable vagaries of climate and the market. Thus, annuals and perennials may be combined in various ways with livestock and trees in what are now commonly called agrosilvipastoral systems.
In humid and subhumid forest ecosystems, the living and non-living components are in equilibrium with each other: there is little erosion and runoff, resulting usually in clean water in the streams emerging from the area, and relatively smooth changes in streamflow during the year; there is litter on the soil surface beneath different canopy layers and plentiful biomass production, all resulting in high biological activity in the soil and on the soil surface. This usually creates almost perfect physical and hydric conditions for plant growth: a cool microclimate and high evapo-transpiration, good rooting conditions with good porosity and sufficient soil moisture.
However, the "best" quality of land should not be considered to reside only in its inherent native characteristics, as use does not necessarily imply degradation to poorer quality. Conversely, this does not preclude the active beneficial improvement of soils that are naturally poorly suited to preferred types of crop, pasture or forest production. For example, in acid savanna ecosystems (e.g. Brazilian cerrado) soil "building", recuperation or restoration may be needed to improve land quality for crop production since the chemical conditions in newly-cleared areas are very poor unless and until the soils are effectively built with the addition particularly of organic materials and phosphates.
In semi-arid and arid conditions, where lack of water is the main constraint for plant growth, the same concepts may apply, but in practice the instability and severity of the harsh climates make these ecosystems more easily disturbed and damaged by extreme climatic conditions and poor husbandry. The situation in more temperate climates is less extreme but soil erosion has proven to be quite severe where land management neither provides a good vegetative cover nor allows adequate regeneration to replace harvested biomass. Evidently the situation varies from place to place according to land use pressures, constraints and opportunities in regard to wise land husbandry or management.
Success in improving land husbandry in the most widespread farming systems depends largely on the degrees to which the farmers can include in their agricultural practices the following five mechanisms, which are most commonly found in natural humid and subhumid forest ecosystems without human disturbance (Mollison and Slay, 1991):
The concept of husbandry is widely understood when applied to crops and animals. As a concept signifying active understanding, management, and improvement, it is equally applicable to land (Shaxson et al. 1989, Shaxson 1997, Shaxson et al. 1999). Crop husbandry, animal husbandry and land husbandry all imply the following:
Poor land husbandry affects the potential of the land. Good land husbandry provides it with resilience, and sustains and may improve its productivity and other useful services. Better land husbandry indicates the process of improvement from poor to good land husbandry. All farmers exercise husbandry of their land. Some do it well, some badly.
Good land husbandry can be defined as the process of implementing and managing preferred systems of land use in such ways that there will be an increase - or, at the worst no loss - of productivity, stability, and usefulness for the chosen purpose (Shaxson, 1993). It involves the active management, by farmers and other land users, primarily of rainwater, vegetation, terrain, plant nutrients and soils, including their inherent biota. It is exercised at a variety of scales, from the field to the landscape, and embraces land under planted crops, pastures and plantations, and under native vegetation of every sort.
The encouragement of better land husbandry and the underlying philosophy suggest that conservation of water and soil is best achieved by promoting local land management strategies that benefit both the land user and the soil. Better land husbandry strategies (which may include planning of more-appropriate land uses and their management) enhance the soil's regenerative capacities to improve the vitality and resilience of the total soil ecosystem. Better land husbandry manages soil organic matter and creates and maintains favourable soil structure, rather than merely preventing physical loss of water and soil. It also embraces a better matching of uses with management, at several scales, of broader landscape characteristics which help maintain other essential ecosystem services in particular the hydrological and nutrient cycles.
Agriculture is based on changing a natural ecosystem to create a new habitat in which the plants and animals, which produce food and other requirements for humans, can thrive. The underpinning resources such as soil and water are managed on a basis that aims to maintain the long-term productive capacity of the new environment. The history of humankind lists our attempts and failures in maintaining sustainable systems. As long ago as 6 000 BC, villages in central Jordan were being abandoned after approximately 1 000 years in response to soil erosion associated with deforestation and poorly managed land, declining crop yields, and the inability to continue to feed the community.
Modern agriculture continues to affect the environment and humankind. Agricultural production systems in use today form a major part of environmental management in various ways. The major production systems can be classified as: intensive cropping, rainfed cropping, shifting agriculture, agroforestry, agropastoral, plantation and forest extraction.
Intensive cropping systems are based on high productivity, including monoculture, mechanisation, chemical inputs, biotechnology and irrigation. These systems may lead to degradation of natural resources if not managed appropriately, particularly through declining biodiversity.
Rainfed cropping systems are based on annual plant species, and are commonly integrated with livestock production. Crop rotation is employed to manage soil fertility yet these areas are commonly fragile and their intensification can easily lead to degradation of the natural resource base.
Shifting agriculture is based on the clearing of land to prepare a cultivation plot and subsequently abandoning this to re-growth and eventual natural reforestation. It is a stable form of agriculture under low population density regimes, but rising population density decreases the re-growth time available for forests and leads to this system becoming unsustainable. Some shifting agriculture has evolved into sophisticated agroforestry management systems while in others it continues to be practised in response to poor land tenure policies.
Agroforestry involves cultivation of perennial and annual crops together in a sustainable manner and is increasingly practised on degraded areas. The practice brings environmental benefits through soil protection and efficiency of utilisation of water and soil nutrients. It also creates a wider diversity of environments for wildlife and other fauna. Local knowledge concerning the utility of native species could be mixed with scientific information to develop future farming systems.
Agropastoral systems represent a variety of systems suited to resource poor or degraded areas and can impact severely on the natural resource base through overgrazing. More sustainable systems have to be developed, such as the integration of grazing livestock on small farms or the introduction of new pasture species with associated management inputs, and There is a clear need for more knowledge of traditional animal breeds.
Plantation systems are associated with such products as coffee, tea, palm oil, timber and rubber. These systems are based on clearing of native forests and are commonly monocultures. However, in some cases, perennial tree crops are also suitable for rehabilitation of degraded soils.
Forest extraction continues as farmers seek new lands and timber prices encourage exploitation of remaining native forests. The trend of large-scale forest destruction appears to have been reversed in more developed countries with a reliance on plantation forestry, although extraction continues in less developed countries.
Sustainability is a term that has come into widespread use, particularly during the past decade. Its use has been so extensive and it has been applied to so many distinct circumstances that it has come to be interpreted in many different ways. Some people have applied it to an unchanging system of production or to a lifestyle that can be perpetuated indefinitely. Such a static interpretation is inappropriate for farming systems.
The basic challenge for sustainable agriculture is to make better use of available biophysical and human resources, by minimizing the use of external inputs, by optimizing the use of internal resources, or by combinations of both (Pretty and Shaxson, 1998). Sustainable agriculture seeks the integrated use of a wide range of technologies in soil and water, nutrient and pest management, and agroforestry. A more sustainable agriculture, therefore, pursues:
The practical implementation of the principles and objectives of sustainable agriculture requires a technical tool that would change effectively from a conventional agricultural technology that exploits the soil and as a result may destroy its natural ecosystem functions, to a conservationist approach that conserves, and even regenerates the soil properties and the ecological processes and functions of the soil and its biota. This technical tool is called "conservation agriculture".
Conservation agriculture, as described in this report, derives from experiences with reduced - and zero-tillage - but is set out as an umbrella term that connotes systems of plant production - whether from crops, pastures, trees alone or in combination - which aim to satisfy the above criteria on a continuing basis, achieving both stable production as well as effective conservation and optimum use of water and soil components. It anticipates synergistic benefits that arise from combining the dynamics of improved soil productivity processes with the latent skills and enthusiasms of farmers and their rural families, the joint keys to sustainability.
Conservation agriculture is in fact widening the concept of better land husbandry including besides the husbandry of land and water resources also husbandry of crops, animals and other natural resources allowing the sustainable system to be commercially productive. The techniques that are involved minimise or avoid soil-damaging effects often associated with conventional tillage-based crop production methods, particularly in tropical zones.
Conservation agriculture in this way is able to control the problems of land degradation even under critical climatic conditions. Infiltration of rainwater is increased (Roth 1985). With this the soil erosion is reduced to a level below the regeneration rate of the soil and the groundwater resources are maintained or enhanced (Derpsch 1997).
Leaching of soil nutrients or farm chemicals into the aquifer is also reduced (Becker 1997) compared to conventional arable agriculture. The system depends on biological processes to work and thus it enhances the biodiversity in an agricultural production system at a micro- as well as macro scale including flora and fauna. It increases soil organic matter contents in agricultural soils in the absence of soil tillage, turning agricultural land into a sink for carbon, thus contributing to carbon sequestration (Schlesinger 1999).
The benefits arising from conservation agriculture have caught the attention of individual farmers, groups within rural communities, and local authorities. They have noted greater stability of agricultural production and security of livelihoods in the face of strong variations in climate and markets; improved availability - in quantity and duration - of groundwater and streamflow. At the same time this has reduced amounts of government funds - from local and national authorities - to be allocated for maintenance and repairs of roads and bridges, for recuperation of flood damage and for drought relief. A consequence has been that greater proportions of their limited funds can be applied to making positive improvements in other social services and infrastructure such as facilities for health, education and public transport.
The "conservation agriculture approach" already has been put into practice on a large scale, and it has become clear that the increased resilience of the land and soil systems has several other positive effects:
The term conservation tillage is properly used for all types of tillage that are designed to minimise erosion, for example contour ploughing. The term is not a synonym for conservation agriculture, therefore, since this is based on not disturbing the soil by tillage at all, or the minimum feasible extent.
However, on several occasions the term conservation tillage has been used to denote conservation agriculture. In this report, the term has been avoided whenever possible. When it does occur, the context should clarify the meaning of the term.
A technology whereby at the time of crop emergence at least 30 percent of the soil surface is covered by residues of the previous crop (Erenstein, 1999).
This is only a technique that refers to seeding/planting without ploughing or cultivation to prepare a seedbed. The same equipment is used in Conservation Agriculture. However, the term direct seeding can also be used for implements that combine primary and secondary tillage and seeding in one machine-tractor operation.
Organic agriculture is not a synonym of Conservation Agriculture (CA), as CA does not prohibit the use of farm chemical inputs but allows an adapted use of them. However, in some cases organic farming can be practised within the CA framework.
In residue farming, the residue or stubble from the previous crop is not ploughed under. Instead, it is left undisturbed (in place) to protect the soil surface and conserve soil moisture. The seeds are chiselled in between the stubble and the seedlings are allowed to sprout through the decomposing vegetative residue. Weeds are controlled by biodegradable herbicides.
Zero tillage is adapted to small, medium and large farmers, using hand planting methods, animal traction or mechanised planting/sowing. A characterisation of zero tillage follows (Landers, 2000):
Becker, H. 1997. Research gives Clues to Reduce Herbicide Leaching; US Agricultural Research Service Press Release, 1997.
Derpsch, R. 1997. Importancia de la Siembra Directa para obtener la Sustentabilitdad de la Producción Agrícola; V Congreso Nacional de Siembra Directa de AAPRESID, Mar del Plata, Argentina.
Erenstein, O.C.A. 1999. The economics of soil conservation in developing countries: the case of crop residue mulching. Thesis. Wageningen University. 301p.
Landers, J. N. 2000. Case study for Wageningen University: Zero tillage development in tropical Brazil. The story of a successful NGO activity. 37 pp. Unpublished document.
Mollison, B. and Slay, R.M. 1991. Introduction of Permaculture. The Tutorial Press, Harare, Zimbabwe. 198p.
Pretty, J. and Shaxson, F. 1998. The potential of sustainable agriculture. Paper prepared for the DfID Natural Resources Advisors Conference, 8 July, 1997. ENABLE. Newsletter of the Association for better Land Husbandry, No. 8.
Roth, C.H. 1985. Infiltrabilität von Latosolo-Roxo-Böden in Nordparaná, Brasilien, in Feldversuchen zur Erosionskontrolle mit verschiedenen Bodenbearbeitungs-systemen und Rotationen. Göttinger Bodenkundliche Berichte, 83: 1-104.
Shaxson, T.F. 1993. Conservation effectiveness of farmers' actions: a criterion of good land husbandry. In: Topics in Applied Resource management in the Tropics. E. Baum, P. Wolff, M. Zobich. (Eds.) Vol. 3: `'Acceptance of Soil and Water Conservation: Strategies and Technologies" Witzenhausem (Germany): Deutsche Inst. Fur. Trop. Und Subtrop. Landwirt./DITSL. pp.103-128.
Shaxson, T.F. 1997. Soil Erosion and Land Husbandry. Land Husbandry, Volume 2(1):1-14.
Shaxson, T. F, Hudson, N.W., Sanders, D.W., Roose, E. Moldenhauer, W.C. 1989. Land Husbandry: A Framework for Soil and Water Conservation. Ankeny (USA): Soil & Water Conservation Society. 64p.
Shaxson, T.F., Tiffen, M., Wood, A. and Turton, C. 1999. Better Land Husbandry: Re-Thinking Approaches to Land Improvement and the Conservation of Water and Soil. Natural Resource Perspectives no. 19, June 1997. London: ODI. Overseas Development Institute Home Page.