Conventional tillage systems are generally based on soil inversion using a mouldboard or disc plough, followed by various passes with a disc harrow to level the soil surface, control weeds and prepare a seedbed. This practice disturbs the soil and may cause surface compaction and a loss of soil structure leading to erosion and other types of degradation, thus becoming a great impediment to achieving sustainable agriculture and food security, the two most important priorities of FAO. 

In contrast, systems of conservation tillage limit, change or eliminate tillage operations and reduce soil damage, as they cause less or no soil disturbance, and leave a cover of crop residues to protect the soil from wind and water erosion. Conservation tillage therefore has an enormous potential for contributing to sustainable food production on a global scale at relatively low cost. 

FAO is supporting the reduction of conventional tillage practices, and is promoting conservation tillage and improved soil management to try and overcome the obstacles that impede the wide adoption of conservation tillage methods. FAO is also supporting the formulation of a code of conduct supporting the adoption of environmentally acceptable conservation tillage practices, approved by a consensus of governments. The adoption of a code of conduct could help to formulate regulations leading to legislation for soil conservation, standards and procedures for the inspection of tillage practices, training programmes for conservation tillage equipment operators, warning systems and restrictions on the use and sale of inadequate equipment that causes soil degradation problems. 

Introduction 

A number of resource poor countries suffer from serious problems of soil degradation, a decline in agricultural production and desertification as a consequence of inadequate soil use and management related to inadequate tillage practices. Conventional tillage practices which involve soil inversion with a mouldboard or disc plough, followed by various passes with a disc harrow to level the soil surface, prepare the seedbed and control weeds, are an impediment to sustainable agriculture, as they frequently cause soil compaction, affect soil physical properties, provoke biological degradation, and as a consequence, cause erosion, especially when tillage is carried out using heavy implements pulled by tractors driven at excessive speeds by inexpert personnel. 

Conventional tillage whether performed manually, by animal traction or with tractors, is the most time- and energy-consuming of all agricultural operations. Nevertheless, in developing countries conventional tillage equipment has the highest sales, with the numbers of sales steadily growing. Conventional tillage is considered the normal cultivation practice, whilst new „conservation" practices are the exception. 

Systems of conservation tillage are practices that reduce, change or eliminate tillage in ways that leave sufficient crop residues on the soil surface, giving adequate protection from wind and water erosion. Conservation tillage usually excludes operations of soil inversion using mouldboard and disc plough. Zero tillage is an extreme form of conservation tillage, which gives maximum control of erosion, as it does not disturb the soil apart from during the placement of fertilisers and seeds. 

Conservation tillage has enormous potential to contribute to sustainable, low-cost food production on a global scale due to its multiple benefits. These benefits include: a reduction in soil, nutrients and fertiliser losses by water erosion; better use of soil water resources, lower energy costs for soil preparation and less manual labour; and improvements in wildlife habitats, soil fertility and productivity. 

In most African and Latin American countries, conservation tillage techniques were first introduced to large-scale commercial farmers, and subsequently adjusted and disseminated to small-scale farmers who now use direct sowing with animal traction equipment. 

Socio-economic factors, such as shortage of adequate support services, insufficient market products and inputs due to restricted credit and information, often act as obstacles for the adoption of integrated soil management practices and the promotion of agricultural conservation concepts in resource poor countries. The aim of this document is to offer some initiatives, which may permit a greater adoption of conservation tillage systems, especially by small-scale farmers in Africa. 

Constraints to adoption by small-scale farmers 

Despite all the positive research results and efforts of extension service, tillage is often misunderstood and done out of tradition, without reflecting newer technical options. This is particularly critical in tropical climates if tillage concepts from moderate regions are applied. Tillage also is the most time- and energy-consuming operation in arable farming and often creates labour or farm power (animal draught or motor) bottlenecks. 

Hand tools (like hoes, forks, machetes, shovels and axes) are widely used in small-scale tropical farming areas. The hoe is used for tillage, harvesting or, with the axe, for bush clearing and in many parts of the tropics machetes are used for weeding. The most that can be prepared by hand per adult in any given season is about 0.5 ha. 

The use of animal draught power greatly reduces the human labour requirement for crop production by the small-scale farmer. For example, ox ploughing in Kenya can increase the productivity of human labour up to 4 times (Mburathi, 1984). The mouldboard plough seems to be the only implement generally used with animal draught power for all tilling operations (land preparation, ploughing, planting and weeding) in some of the tropical developing countries. Constraints to the use of the plough by farmers in semi-arid West Africa are the lack of time for this operation at the beginning of the cycle, given the shortness of the rainy season and the imperative need for early planting. Competition for time devoted to soil management, planting and weeding is particularly serious in the regions where rains start violently. 

In Kenya, for example, few small-scale farmers own tractors and most farmers rely heavily on the services of private contractors. Private contractors in very few tropical countries only offer mechanized equipment for direct planting. However, the services provided for land preparation are sometimes unsatisfactory and often offer only one type of implement, i.e. the disc plough or the disc harrow, whereas sometimes other implements like chisel ploughs or cultivators would be more appropriate. The farmer is therefore forced to accept several ploughing operations with a disc plough to achieve an adequate seedbed, while the use of the proper implements at the right time might give a better seedbed at a lower cost (Mburathi, 1984) and with less soil damage. This is a situation found in many other developing countries in the tropics. 

The transition from conventional to conservation-effective tillage practices requires more investment in management skills for some crops. If the machinery component has to be replaced or modified, adoption of conservation-effective tillage will be slower on small farms, in the tropics or elsewhere, where machinery is replaced less frequently. Usually equipment suitable for conservation tillage has a much higher purchase price than conventional equipment. That means that the capital investment for the transition to conservation farming is high. But, due to the higher work-capacity of the equipment, the actual operating costs are often lower than in conventional farming if farmers learn to share equipment and make the maximum use of it. 

A successful conservation-effective tillage programme, therefore, needs to be flexible enough to be adapted to a variety of economic, geographic, land-use and farmer-related variables by small-scale farmers in the tropics. 

STRATEGIES FOR FAVOURING THE ADOPTION OF CONSERVATION TILLAGE IN AGRICULTURE 

Research Needs 

During the last three decades intensive work has been carried out on tillage research, to better understand the physical, chemical and biological effects of different tillage alternatives on the soil and plant environment. 

Various aspects of conservation tillage including reduced, minimum and no-tillage systems have been covered, and the use of mulch and crop residue management as an essential component of a tillage system has been accorded special attention. However, much of this work has been carried out in temperate regions and under large-scale agricultural systems. Some of the areas requiring more research in tillage systems in the tropics include soils, climatic factors (especially rainfall characteristics), management of crop residues and equipment development, specifically for small-scale farmers. The parallel development of appropriate agricultural machinery and equipment would enable the farmer to effectively apply any recommended technological package suitable to the particular soils, crops to be cultivated and socio-economic conditions (Benites and Ofori, 1993). 

A concerted effort to understand and respond to the intertwine composed of (a) farmers, (b) crops and (c) soils from international as well as national research institutions will be essential in achieving the goal of increasing agricultural productivity while maintaining the soil resource on a sustainable basis. There is also a need to understand the local farmers' practices and direct additional research to improving these practices. 

It is well established that management of crop residue on the soil surface is a key element of any reduced tillage system. A major constraint of residue management under small farmer conditions in the tropics, however, still remains the quantity of residue available to be used as mulch. A no-tillage system cannot be adopted successfully without an adequate amount of residue mulch; the farmer is furthermore constrained by lack of economic resources to purchase herbicides. It is therefore important, particularly in the drier tropics where animal husbandry is practised, to study the effects of surface stubble management and tillage on the productivity of crop/livestock systems. Such studies may provide answers to the complex problem of the use of crop residues as feed, as well as in soil management practices for erosion control and water conservation. 

Development of Tillage Implements Suitable for Small Farm Holdings 

A number of centres and projects in the tropics have been engaged in the development of tillage implements suitable for small farm holdings, and these have made good progress in the past decades: for example, the development of single symmetrical, angled tines for tillage in semi-arid conditions by the Centre d'etudes et d'experimentation du machinisme agricole tropical (CEEMAT), the modification of the maresha for use with a single animal by the International Livestock Centre for Africa (ILCA), by combination with a multipurpose long-beamed tool-bar; various modifications of the ard in Egypt and India. Other implements such as seeders and ridge-tiers have also been developed (Starkey, 1989). However, the adoption of such equipment on a wide scale by small-scale farmers in various countries of the tropics remains limited. Implements for conservation farming were only successfully adopted by farmers where the private manufacturing sector, i.e. small workshops or manufacturers, took over the lead in further developing the equipment and offering it to the farmers. Possibilities have to be identified to include the private manufacturing sector in the technology development and transfer activities rather than leaving them to the research stations. 

Focus of Integral Management 

A system of production consists of various components, e.g. land preparation, tillage, crop rotation, sowing, application of pesticides including herbicides, fertilization, harvesting, storage of grain crops, management of crop residues, machinery, implements and equipment, systems of drainage and irrigation and soil conservation. If the introduction of a new management system requires changes in some components of the production system, it could signify changes in other components. For example, in systems of zero tillage, the greater part of the crop residues stays on the soil surface, which demands a well planned crop rotation to avoid the occurrence and proliferation of certain diseases and pests with a greater incidence in monocropping. 

A focus on integrated management, which permits conservation agriculture, would increase the efficiency of water use (rain and soil humidity) and the use of soil nutrients by plants through: 

• maintenance of a good soil cover;
• increase in water filtration in the soil profile (except obviously in soils susceptible to waterlogging, when drainage is the solution);
• the management of soil fertility by encouraging the recycling of nutrients; and
• better exploitation of the soil profile by plant roots.

On the basis of the experiences of various developing countries, it is notable that the sustainable adoption of direct planting systems is only possible if a production system is used which is based on crop rotations, an integrated management of the agronomic aspects, the organization and commercial development of farmers, and the availability of equipment adapted to the needs of small farmers. Organizations of field extension services can also play an important role. It is also necessary to involve regional local authorities. 

Amongst the mechanisms needed to implement integrated strategies of management to drive conservation agriculture are: 

• national and international agreements to elaborate integrated policies on conservation and the use of resources such as soil, water and plant nutrients, and above all to evaluate the limitations and potential of these resources in a wider context, in which in situ and ex situ factors are integrated;
• technical co-operation between farmer-farmer at the local level;
• restrengthening of institutional training through interdisciplinary consultations, training and appropriate reforms in institutional and social infrastructures;
• participation of all actors and pertinent institutions to plan and stimulate a better collaboration at all levels including the private and commercial sectors;
• co-ordination between national and local governments through consultative forums to facilitate the implementation of actions;
• monitoring to evaluate the effects of plans and policies, and changes that these produce, on the population and its natural resources.

Participatory Methodologies and Strategies 

Adoption of conservation agricultural systems is a slow process, which requires not only technical knowledge but also political goodwill, the availability of financial resources and services. For example, to promote the adoption of conservation tillage systems as a principal component of an integrated management strategy requires: 

• a better understanding of the perceptions and needs of farmers, and a better co-ordination with the priorities of government policies;
• global methodologies of planning and management which ensure better decision making at the level of farmers, community and catchment or microcatchment;
• a strategy of soil management and water conservation within production systems;
• improved technologies for soil, water and plant nutrients for different soil types and climatic zones which support conservation tillage;
• participatory methodologies for the identification, evaluation, selection and generation of technologies and their implementation;
• an institutional, political and social infrastructure to facilitate the transfer of knowledge, the implementation of activities, and access to necessary services including credit;
• operational strategies that include multidisciplinary teams, inter-institutional agreements and the integration of programmes;
• organizational strategies to improve economic gains and access to services;
• the creation of farmer training schools in sustainable and conservation agriculture;
• effective support to farmers' organizations and existing networks of technical co-operation;
• availability of the required inputs for conservation farming such as equipment, fertiliser and agro-chemicals.

Conservation tillage should be economically attractive to farmers by providing direct or indirect (incentives) improvements in income. 

In general, a better knowledge and understanding of the impact of conservation tillage on the sustainable use and conservation of soil, water and plant nutrients is required. A greater knowledge of environmental interactions of conservation tillage will facilitate these evaluations. 

Technology Transfer 

Country extension services need to pay more attention to those tillage practices developed by the farmers themselves, which have been proved effective in soil and water conservation. But with the increasing average age of farmers as a result of the migration of youth to the urban areas, tillage practices as well as tillage equipment will need to be adjusted to these labour constraints, although this can only be achieved within the financial resources of the farmer. Furthermore, it has been found that some of the improved implements introduced to farmers for effective tillage have not been widely adopted, and it is necessary to ascertain the reasons for this (Benites and Ofori, 1997). 

In the tropics, tillage research is limited and relatively few institutions undertake research and development. In many countries the links between research and extension services are weak or non-existent. Tillage systems developed in temperate regions have been introduced mainly through machinery agents or agricultural research station practices. There have been various degrees of short-term success on large-scale farms, but also failures in many instances where the soils were not adequately studied, resulting in degradation by erosion and compaction. 

Small-scale farming development needs to receive special attention if agricultural practices are to be changed and more sustainable techniques are to be adopted. The system or systems introduced must fit into the small-scale farmer's production pattern and cropping system and show the clear benefits available to the farmer at acceptable cost/benefit relations. Adequate knowledge of the soils, climate and cropping systems is indispensable for the development and choice of appropriate tillage systems. One of the promising approaches to such informal technological exchange is through networking. This could provide inspiration while the actual conservation tillage system will have to be developed site - specifically with the local farmers. 

Research and technology transfer networks are an effective way of using scientific resources, in addition to providing facilities for training technicians from participating countries. FAO supported the creation of the Latin American Conservation Farming Network (RELACO) in 1991 to facilitate an interchange of experiences among member countries. 

After this successful experience FAO now wishes to focus on Africa, to assist in reducing the damage caused by traditional tillage systems and other practices that impair agricultural sustainability, and to support modern agricultural systems that promote conservation tillage for the integrated management of soils, water and plant nutrients. 

Code of Conduct 

To reduce damage caused by conventional tillage and other practices that affect agricultural sustainability, greater emphasis should be placed on the benefits obtained from focusing on modern agriculture which promotes the integrated management of soil, plant nutrients and water, based on the use of conservation tillage. In addition, it is necessary to improve the technical and administrative aspects of soil conservation programmes to increase their cost effectiveness (Benites, 1997). 

Elaboration of a code of conduct, with support from governments, at a world-wide level, will encourage research, promotion and adoption of conservation tillage. This can contribute enormously to define and clarify the necessary actions and responsibilities of different governmental and non-governmental actors involved in development, production, distribution, sales, financial activities, technical support, maintenance, and the use of tillage equipment and inputs. 

To put the code of conduct into practice in order to promote the adoption of tillage practices acceptable from an environmental view point, it is recommended to prepare guidelines on how to overcome the numerous factors that impede the widespread adoption of conservation tillage and other conservationist management practices by small-scale farmers, together with recommendations of required actions and responsibilities on the part of governments, the private sector and farmers (Benites, 1997). 

The guidelines should also deal with problems of sale, distribution and supply of equipment and inputs, service structures for the repair and maintenance of equipment, financial mechanisms for small-scale producers, and the provision of information, technical advice and training. 

Also needed are guidelines on the selection of conservation agriculture practices and improved soil management. These practices would be based on success stories of long-term tillage and conservation practices on commercial crops, such as those which are being implemented in the southern states of Brazil, which were achieved through the development of a strong integration among government, industry and progressive farmers´ organizations. 

It is equally important to formulate rules leading to legislation on soil conservation which could include: 

• the inspection of tillage, soil management and conservation practices;
• procedures to organize training courses for operators of conservation tillage equipment;
• warning programmes and restrictions on the use and sale of inadequate agricultural equipment or of equipment causing soil degradation problems.

National Programmes of Conservation Tillage (NAPCOT) 

To put the code of conduct into practice, it is also recommended that a NAPCOT be prepared. National and private institutes for research, extension and the promotion of soil management and water conservation, plus farmer representatives, should review previous activities on the planning and development of national strategies concerned with the prevention and rehabilitation of degraded soils, research and technology transfer programmes on conservation tillage and other conservationist practices, and the identification of ways to improve the present situation by supporting, rather than competing with, other ongoing programmes (Benites, 1997). 

It is also suggested that NAPCOTs compile success stories about the long-term use of conservation tillage for commercial crops as in the case of the southern states of Brazil, where success was achieved through the strong integration among government, industry, conservation organizations and progressive farmers. These successful experiences could serve as examples for producing and publishing guidelines on conservation tillage and improved soil management. 

Conclusions and Recommendations 

Conservation-effective tillage can make a major contribution toward increased food production and intensification of agriculture in tropical countries via its effects on soil as a rooting-medium and store of water. However, the agronomic and economic performances of tillage are extremely location-specific. Therefore, to be successful a conservation-effective tillage programme needs to be flexible enough to be adapted to a variety of economic, geographic, land-use and variables related especially to small-scale farmers in the tropics. 

Research on conservation-effective tillage without an adequate interpretation of the soil and climate conditions where the research was conducted would severely limit the potential applicability. Local information on soil and climatic constraints should therefore be included in the diagnosis, design or improvement of conservation-effective tillage for the tropics and elsewhere. 

There are many ongoing investigations on conservation-effective tillage in various countries with similar financial resources available for research and development. Networking appears to be an appropriate operational model to meet the shortage of on-site trained personnel and the high operational costs and logistic problems of technology transfer. A concerted validation and extrapolation effort across the main agro-ecological zones of the tropics will not only encourage interaction among participating institutions but also identify refinements and modifications which should be pursued to improve existing tillage operations. While it is not anticipated that tillage expertise in national institutions will be fully implemented merely by participation in a network, it is fitting to consider supportive measures to ensure that experiences gained in the network are maintained and used in future national research endeavours. An important prerequisite for such an approach is therefore the development of country programmes with adequate funding which could be supported by external inputs. 

Greater effort must be directed to planning research programmes embracing problems of interaction among soil, climate and management of crop residues in the tropics, in particular the semi-arid areas. Concurrently the development of simple tools within the financial reach of small-scale farmers could contribute to the adoption of proven technologies. 

Elaboration of a code of conduct, with support from governments, at a world-wide level, will encourage research, promotion and adoption of conservation tillage. 

To put the code of conduct into practice it is recommended that a National Programmes of Conservation Tillage (NAPCOT) be prepared during a national forum. 

References 

^{Soil Resources Management and Conservation Service Theodor Friedrich, Agricultural Engineering Branch FAO}