The idea is still too widespread that total knowledge and understanding of farmers’ practices, expectations and strategies should be sufficient before proposing guidelines for sustainable development tailored to meet their specific requirements. And this should be done by means of better structuring of rural communities, more rational management of traditional farming practices, improved supervision and training etc. This is often an illusion. In other words, considering only the farming system and the rural organization, without proposing true agrotechnical-technical innovations for the cropping system, is not enough to facilitate rural development.

Moreover, animal draught cultivation, involving ploughing (actually just rough scraping), is still too often considered as a compulsory step with unquestionable theoretical benefits ignoring the very serious soil damage caused by this practice in Africa (erosion, crusting of the ground surface, sealing of macro- and micropores, and subsoil compaction). For upland (rainfed) agriculture, draught animals should actually be pulling equipment other than ploughs, and weed control could also be dealt with in other ways.

We can no longer ask whether farmers in the tropics (especially in Africa), in the light of their traditions (socio-cultural, dietary, etc.), should or should not be involved in an agricultural revolution - they have no choice. This revolution, which must guarantee soil conservation, will be technical and agronomic, and should be supported by governments and well-targeted international aid. Southern farmers have to change their habits in order to survive and improve their current living conditions. This is already happening in Latin America and would be quite possible in Africa. However, farmers must be proposed efficient and attractive technologies, and the means to acquire them.

Many agricultural problems due to environmental constraints can be solved regionally, since the same constraints (specific to the tropics) are always present (with some variations in conditions and intensities): continuous loss of soil fertility through erosion, soil hardsetting, mineral leaching, acidification, climatic risks, weed invasion, etc. The conditions for solving and managing these constraints obviously have to be adjusted to the local socio-economic and political context. It would now be the right time to deal seriously with these basic constraints by all possible means. This should be done on an agronomic scale, by developing suitable cropping systems and adoptable technologies that are attractive to farmers, e.g. increasing crop yields and reducing labour intensive work (otherwise they will not be acceptable to farmers).

In a given area, the results of the preliminary appraisal should allow research scientists to work:

1. On solving major agrotechnological-technological problems and blockages in the region, which should be identified and classified at the outset and

2. On developing a wide range of alternative and innovative cropping systems whose advantages are assessed and compared by the farmers themselves in the field (real spatial and economic scales) following effective participative research that has been conducted with these farmers on their farms.

These innovations, which are developed for and in collaboration with farmers, will help guarantee a future for their children in agriculture. Without such promising and sustainable agricultural innovations, research interventions remain a caricature and geared towards organizing poverty.

The ultimate research goal cannot simply be to investigate agrarian diversity, which is obviously infinite and the results cannot be fully utilized. However, it is up to research to create this diversity through its proposals. Standard innovations will no longer be introduced on farms through extension activities (more or less discerning), instead they will be chosen by farmers on the basis of actual evidence in a range (showcase) of innovative cropping systems. Farmers decide according to their agrotechnical-technical and financial means, objectives and degree of intensification they aim. As these farmers are taking a risk in adopting unfamiliar technologies, they should be assisted, supervised and trained through research scientists and rational extension activities.

From this viewpoint, development-oriented research faces a much greater challenge, with the threat that any unsuccessful actions will be sanctioned very quickly. Agronomists again have a very basic role to play with much different objectives as compared to those in the 1960s and 1970s (and sometimes until the present), when they were mainly concerned with conducting research in closed experimental plots.

Participative research should therefore reverse its perspective and attract more farmers to real alternative agrotechnical-technical innovations created through research conducted with and for farmers, who in turn have full authority over their final choices.

This should be the main focus of field agronomy. No-till cropping practices could pave the way to an agricultural renewal, within the context of sustainability and the doubly-green revolution. Indeed, tropical agricultural research should be a key player in this rising revolution.

Overview: Real Problems facing Tropical Agriculture

To promote competitiveness and sustainability, tropical agricultural systems have to strive to maintain soil fertility, while becoming settled, intensified and diversified, despite substantial ecological and economic constraints.

These constraints are physical, agrotechnological-technological and economical:

Low or fragile soil fertility

mechanical erosion; mineral leaching, with acidification and aluminum toxicity; physical degradation loss of soil structure, compaction, surface crusting, hardsetting (blocking water infiltration and root penetration); rapid organic-matter mineralization.

High climatic risks, causing marked variations in production

Irregular rainfall distribution; heavy rainstorms; brief excessive water logging; high surface temperatures.

Agrotechnological-technological and crop protection problems

Weed invasion; diseases and pests, damping-off of seedlings; lack of equipment and inadequate tillage.

Problems of optimizing labour

Low productivity; labour intensive work; difficulty in setting up a projected cropping calendar.

Poor microeconomic conditions

No funds available; no input supplies; no economic channels; market dependency; no credit; discouraging land tenure problems.

• What can generalist agronomists do to begin solving these concrete problems?
• How can they deal systematically with all of these constraints under economically realistic conditions, even when it is assumed that point 5 (above) will long remain a complex problem?
• What can be done when there is no access to resources?

Short Background of Erosion Control Approaches and Techniques

For about 60 years, erosion control has been the focus of approaches that have varied according to the operator involved and changes in mentality. As an extreme simplification, one can say that we have moved from the external approaches of administration (rural engineering and water and forestry administrations, development agencies, etc.) to the participative approaches of NGOs. There has been a transition from the mechanical to the partially 'biological'.

• Mechanical techniques were favoured until the end of the 1960s for the protection of slopes and catchments. 'Soil protection and restoration' operations only took slopes into account. Discharge ditches and infiltration channels were dug. Contour benches, terraces and levees were constructed and planted with soil-fixing grasses. Slopes were rectified by earthwork. Rural engineers imported these techniques to Africa from the USA (USDA) via North Africa. The methods did not take local characteristics into account and were not negotiated with villagers, who were merely mobilised and sometimes paid as labour. These works and techniques were implemented at great expense with substantial investments but never appropriated, i.e. maintained and reproduced, by the village communities, who found that they brought more constraints for their traditional farming systems (they hindered cropping systems and made tasks too long, etc.) than advantages in the short term because these developments were not directly productive.

• From the end of the 1960s, under the influence of foresters, a second generation of approaches consisted of constructing less earthwork and introducing trees and plant cover (linear or in strips) in erosion control development operations. The first policy concerned reforestation and catchment development upstream of village areas and rice fields (in Madagascar) to be protected. Soil protection and restoration and reforestation and revegetation operations went together and were implemented by the rural engineering administration and the water and forestry department. As long as these developments were executed, monitored and maintained by the administration or under pressure from it. They were more or less sustainable. The were abandoned after the gradual withdrawal of the administration led to their being abandoned.

• Towards the end of the 1970s, there was a gradual change to agroforestry approaches, i.e. the introduction of ligneous species (useful ones if possible) in village territories and on farms. This trend was initially more forestry than agriculturally-oriented. It consisted of structuring and partitioning village land and its plot system using various spatial measures: hedgerow systems with live contour hedges at varying intervals, non-productive wooded or grassed strips, alley cropping, etc. 

• Today, the aim of agroforestry 'developments' is to integrate multiple purpose trees in the farming systems and therefore in the economies of farms. Trees must serve as protection but also be productive (forage, fruits, firewood, construction timber, etc.). There is now more talk of 'tree planting' than 're-forestation'. Local species are favoured and nurserymen are trained in villages. Participative research has become accepted (at least at the discussion level), meaning that proposed developments should no longer be standard and imposed but negotiated and decided in collaboration with village communities according to their agro-sylvo-pastoral wishes. Agroforestry thus represents a very significant advance in the protection of village rural lands and the integration of farming systems. However, this approach still generally concerns the borders of cultivated plots. Degradation and erosion are not treated at the source, i.e. in the cultivated fields. It is still more the field of foresters (who have created the 'agroforester' category) than that of agronomists who deal with cropped fields, cropping systems and farming systems. Thus, agroforestry theories designed and tested under experimental conditions often run into substantial difficulties when confronted with the real environment. The reasons are agronomic, agrotechnical-technical or microeconomic, with competition between trees and crops (for light, water, minerals and allelopathy), disturbance to traditional practices (tillage and livestock management), widespread immobilisation of areas previously used for food crops, maintenance requiring too much labour, no supplies of seed or planting material, etc. In addition, although participatory agroforestry research represents true progress, it does not yet provide full protection of crop fields from runoff and erosion. 

• A third pathway is taking shape which obviously does not exclude the agroforestry approach (which is more biological than agrobiological-biological) but completes it. This time, the method was developed by general agronomists (who were not very involved in the preceding initiatives) and covers cropping systems and the soils used for them. The approach is both agronomic and agrobiological-biological. Whereas agronomists had hitherto followed foresters rather than innovating in their own discipline with regards to erosion control, a trend has developed in the past 10 years in Latin America among farmers and agricultural systems theoreticians/practitioners who propose so-called „agro-biological tropical soil management methods". In soil conservation, the main anthropic cause of erosion is now addressed at the source, i.e. a level hitherto unexplored: the arable profile, plot, operational and cropping sequences of the cultivated environment, hence by means of the agronomic pathway. In addition, control of land degradation is no longer presented to farmers as an end in itself in a more or less long term perspective, with a set of specific exogenous techniques over and above their production objectives, poorly understood and hence little accepted. Control is now integrated in their agrarian practices as a whole and in their crop management sequences and the objectives are short to medium-term benefits: decreased expenses, larger net margins, labour savings, less arduous work, cushioning weather risks, etc. It is thus hoped that there will be a greater sense of responsibility and increased motivation.

An Outline on the Agrobiological Approach

The integrated agronomic concept that we cover in these innovation, dissemination and training aspects is an agrobiological-biological approach involving no tillage and direct seeding over permanent ground cover. The cropping system is the main topic of study, even though the whole farming system is involved.

Agrobiology consists of agronomically, technically and economically founded, practices and sets of techniques that have been tested and are reproducible. While reducing mechanical disturbance to soils and economizing chemical inputs, they are effective in protecting soil from erosion and improving its fertility, in improving the economic situation on the farm and in reducing task times and their arduousness.

It is important to note that the agrobiology approach is very different from organic agriculture which bans the use of chemicals.

These practices and techniques enhance sustainable agricultural production through free chemical, physical and energy processes of nature, whether they are derived from microflora, macro-and meso-fauna, plants (photosynthesis, production of biomass, root effects) or climate (light, rainfall, condensation, etc.).Through agrobiological management nature benefits of the farmer by maximal use and development its resources, while tapping favourable conditions and eliminating or reducing the undesired effects.

Direct seeding over permanent soil cover is a major agrobiological pathway for the management of cropping systems and aimed, among many other things, at completely halting erosion. The overall goal is to ensure that cropping systems that are developed and disseminated resemble tropical forest ecosystems, while keeping in mind that the latter function as a closed system with respect to mineral circulation. Organic matter, with rapid turnover (litter and roots), constantly renews soil fertility via biological recycling. The system is highly stable: water and mineral supplies and the microclimate are self-regulated. Nothing is lost. Biologically, the ecosystem functions perfectly, with permanent interactions with fauna and microflora, which continuously digest the biomass both above and below the soil surface.

One of the main thrusts of agriculture is therefore to tap the enormous photosynthetic and biological potential of the intertropical zone, with the aim of producing usable plant and animal biomass and managing it sustainably (economically and agronomically) within cropping systems. This biomass can be provided by the trash cover derived from the main crop, but can also result from other intercropped, sequentially cropped or relay cropped annual and perennial cover plants. This biomass can also be derived from the pruning of agroforestry hedges and external components such as bush straw. These beneficial effects of non-crop biomass should not be offset by further labour from farmers, especially as labour is economized elsewhere in such systems.

There are two basic underlying principles concerning these technologies:

• The first basic principle to be respected is that of limiting mechanical disturbance of the soil only to seeding, covering and protecting it fully throughout the year from erosive runoff, keeping temperature and moisture fluctuations to a minimum and thus reconstructing a stable ecosystem to favour biological activity and the conservation of organic matter in soil.
• The second principle taps nature’s resources (photosynthesis, macro and meso-fauna, microflora, release of immobilised and trapped minerals, etc.) through the beneficial effects of certain annual or perennial cover crops and the chosen crop sequences or combinations.

These principles might appear simple but the procedures for developing them and then the transfer, according to ecological features of the farming practices and agrarian systems concerned are complex. It should nevertheless be noted that direct seeding with zero tillage is practised in the ancestral manner in traditional smallholder farming based on shifting, slash and burn cultivation in the humid tropics. The agrobiological management procedures proposed for cropping systems are also based on direct seeding, but without any burning and with permanent soil cover (crop residues and biomass that can be cultivated cheaply). It is not a single technique but a set of techniques involving a combination of innovations that must be spatiotemporally coordinated on the farm. They comply with principles and practices that are now well known and well-mastered (cf. Latin America), but they must be adapted and re-adjusted according to local pedo-climatic and socioeconomic conditions. These techniques are often radically different from traditional practices and imperatively require full knowledge of traditional practices and active involvement of farmers. When these innovations are introduced, the entire farming system must be taken into account and the agrotechnical-technical and agro-economic feasibility of the alternatives proposed verified.

These principles are to be dealt with in terms of their agronomic, agro-technological, and agro-socioeconomic aspects, which are interconnected in different specific ways depending on local farming conditions.

Agronomically, water-soil-plant interactions

Agrobiological cropping practices should be efficient and assessed especially in terms of crop protection (phytopathology, entomology, weed science, and integrated control), mineral and water supplies, soil changes (scouring, organic matter content, biological activity, porosity, structure, mineral reserves, pH, etc.), and interactions between closely related plants (synergy, allelopathy, water and mineral competition, shading, etc.).

Agrotechnologically

The different improved and optimized agrobiological options involve agrotechnological solutions and choices, depending on the agronomic effects targeted, the extent of technical proficiency, as well as farmers’ economic status and labour potential. The equipment aspect should be investigated, along with the improvement potential, for situations involving manual, mechanized and motorized farming; this concerns land clearing, soil loosening, planting, maintenance and harvesting.

Agro-socioeconomically

Under the proposed conditions, agrobiological innovations are dependent on mesoeconomic and microeconomic conditions at regional, local and farm scales. In addition, to ensure that farmers will adopt these innovations, they should first (before improving the soil resource) represent a short-term source of economic and social benefit (improved living conditions and quality of life), e.g. reducing labour intensive work, diversifying production, improving the fodder assessment, increasing net margins, progressive capitalization and investment. Techniques like direct seeding can thus have an impact on overall farming system management.

Expected Effects of Direct Seeding over Permanent Vegetation Cover

The expected agronomic benefits are as follows:

Mineral balance

Fixation of atmospheric nitrogen (legumes), limiting mineral leaching by recycling complementary root systems and their biomass (a closed soil-crop system as in a forest ecosystem), 'unblocking' of immobilised elements such as phosphorus by sesquioxides (Fe, Al) and sometimes inactive organic matter, increased extraction and mobilisation of bases (K, Ca, Mg) and trace elements in the absorbing complex (through root exudates).

Physical improvement and aeration of the arable profile

By maintaining high macroporosity and the creation of a stable structure by means of deep growth of restructuring and recycling root systems that increase reserves of water and nutrients available for crops.

Micro-climate

By damping soil temperature variations, reducing evaporation and improving the water balance, hence reducing the effect of climatic risks

Favouring high biological activity

Macro-and meso-fauna, microflora, whose effects reinforce the preceding actions by maintenance of a buffered microclimate and stalling repeated soil disturbance;

Improved organic balance

In term of quality, quantity and depth through the preceding biological actions.

Weed management

Through the shade provided by cover plants and their allelopathic effects that effectively limit weed germination and emergence, strongly influence the choice of species, thus facilitating chemical control at low cost.

Reduction of crop pests and diseases

Contribution to integrated pest management.

These beneficial effects on the environment and its fertility are complemented by microeconomic advantages: reduced need for inputs, substantial labour savings, flexible cultural calendars and a clear improvement in farm resources. These advantages are essential factors for farmers' acceptation of agrobiological techniques.

These sets of techniques were first developed in sub-tropical regions, especially in the southern states of Brazil, and were then adapted specifically for tropical zones by CIRAD from 1983 onwards. The technical aspects have been well mastered since 1990 and extended very rapidly in tropical savanna and forest environments in central western Brazil (currently nearly 3 million hectares). Direct seeding is used on several million hectares in other Latin American countries (Argentina, Paraguay, Central American countries), both in small manual agriculture with animal traction and highly competitive mechanised agriculture. A true agricultural revolution is in progress.

Direct Seeding: CIRAD’s Expertise

CIRAD carries out development-oriented research projects in collaboration with its Southern partners with external funding, i.e. bilateral French and multilateral. Over the last 10 years, one of CIRAD’s agronomic priorities has been to develop cropping systems with direct seeding over permanent mulch or live vegetation cover, while tailoring them to different intertropical ecosystems.

The overall aim is to develop efficient, feasible, and reproducible innovative cropping systems. Technical, agronomic and economic factors are taken into account, as short-term microeconomic spin-offs (improvements in labour time and labouriousness, net margins, production regularity, etc.) represent an important incentive for farmers. These participative research projects are therefore implemented in the field, i.e. with, at and for farmers.

More targeted research projects are also carried out to understand processes involved in soil-plant systems (water and mineral dynamics, changes in soil properties, weed science, allelopathies, etc.) when the soil is no longer tilled and has a permanent mulch cover.

Technologies applied for direct seeding on permanent ground cover are clearly efficient for controlling soil erosion and enhancing fertility. A key imperative is to adapt these technologies to meet local needs and disseminate them to smallholders, thus enhancing the sustainability of tropical agriculture and paving the way to the second green revolution (doubly-green revolution). This strategy has already been proven effective in Brazil, first in the subtropical zone (southern Brazil) in collaboration with GTZ (Rolf Derpsch), and then in the intertropical zone (cerrados) with the support of CIRAD (Lucien Séguy and Serge Bouzinac)

Advantages expected from direct sowing over permanent vegetation cover
 
 

The features of 14 direct seeding projects currently under way or recently carried out in various environments by CIRAD and partners are presented below for the following regions:

Ivory Coast

• Direct Seeding on plant cover in two different ecological situations
• Direct Seeding of food crops on plant cover in forest regions

Gabon

Development and assessment of food cropping systems with manual direct seeding in the humid savanna region of Boumango

Cameroon

• Direct sowing and chemical weed control in cotton-growing regions

Madagascar :

• Sustainable, environment-friendly no-till cropping systems in the highlands
• Introduction of direct seeding to improve cropping systems in a semi-arid zone

Reunion Island

• Cover crops in humid zones
• Developing sustainable cropping systems with direct seeding over vegetation cover in the western highlands

South Vietnam

• Improvement of cropping systems in the songbe highlands

Western Mexico

• Direct seeding on mulch : new potential crop management sequences for rainfed maize production

Central America :

• Agrobiology and permanent plant-cover in Central America

South America

• The Procitropicos network, first steps and perspectives. development of a CD-ROM for training purposes about new technologies for sustainable soil management of tropical savannahs

Brazil

• Concepts and implementation of agrobiological soil management techniques adapted to acid soils in the humid tropics: the case of no-tillage in the cerrados
• No-till motorized industrial-Scale cotton cropping systems

Most of these projects were presented at an international workshop entitled Agrobiological Management of Soils and Cropping Systems that was held in Antsirabé (Madagascar) from 23 to 28 March 1998. Direct seeding and cover crops were the main topics covered in this meeting. The proceedings will be published in late 1998. CIRAD’s Brazilian partners were the guests of honour at this workshop, which was attended by 250 specialists. Networks on these themes have been initiated, particularly an Indian-Ocean/Southern Africa network.

Conclusions

So-called „traditional" farmers have not always relied solely on research for creating sustainable agrobiological cropping systems. For instance, in Central America (Guatemala, Nicaragua, Honduras, Costa Rica) farmers, on their own incentive, have developed no-till cropping systems with vegetation cover, such as Frijol-tapado (bean crops on green fallows) and maïze-Mucuna, which are being implemented on ten’s of thousands of hectares of land in these regions.

Experience, i.e. in Madagascar, has shown that farmers will take an interest in these techniques once they have visible proof of the short-term benefits (with roughly the same net margins), e.g. facilitation of labour, a reduction of labour time, and a more flexible cropping calendar. Over the medium- and long-term (time scales that are often difficult to propose when promoting innovation adoption because there are no immediate returns), farmers will notice supplementary beneficial effects targeted by research: buffering climatic hazards, potential for diversification, improvement of forage assessments, complete erosion control, and improved soil fertility. These production regularity and sustainability improvements are by-products that farmers will appreciate once they actually see the benefits.

The direct seeding strategy can be implemented in simple and in more complex ways (from simple dry mulching to establishing permanent vegetation cover). Some prerequisites have to be fulfilled and a certain degree of supervision is required to guarantee successful adoption and reproducibility of the systems in agricultural, technical and economic terms. These requirements can be more or less demanding, depending on the extent of technical proficiency targeted and on whether the farmers have sufficient means to enable them to reach these targets, as well as on the initial level of soil fertility.

In addition, to convince farmers that they should adopt the proposed innovations, research scientists and technicians have to be able to completely control and know how to reproduce these different alternatives on a farm scale. Obviously, this research also has to be credible a condition that is unfortunately not always fulfilled.

Direct seeding can be adapted to meet the requirements for a wide range of situations, from various viewpoints, i.e. socioeconomically (degree of capitalization, property status, etc.), level of technical proficiency, and physical conditions (soil type and fertility level, rainfall distribution, slope, etc.). Systems combining direct seeding - permanent ground cover - biological pumps, regardless of the conditions, should concern the cropping system and the farming system together. The green revolution involved crop improvement, whereas (beyond all the discussions) the famous and essential doubly-green revolution will focus on agrobiological aspects with direct seeding and all that this strategy encompasses. This is an incredible challenge to be addressed by tropical agriculture.

In the tropics, it is now clear that systems involving direct seeding over dry mulch or live plant cover should be a major agricultural research focus with the aim of developing sustainable farming systems. No-till farming is the only system that is suitably adapted to tropical soil and climate conditions. Moreover, it is the only system that enables cost-effective conversion of the incredible photosynthesis potential into assets for efficient sustainable manual and mechanized farming.

CIRAD, B.P. 5035, 34032 Montpellier Cédex, France.