Conservation agriculture in West and Central Africa

Conservation agriculture (CA) is promoted as a resource conserving with high productivity agricultural technology consisting in the simultaneous application of (i) minimum or zero-tillage, (ii) permanent soil cover and (iii) crop diversification through crop rotation or intercropping. West and Central Africa (WCA) is part of areas where the potential benefits of CA are believed to be the highest and likely to enable farmers to meet the important challenge of sustainable intensification of production systems. However, the dissemination of CA in WCA is rather low so far, this tends to support the criticism and skepticisms on its applicability in smallholder farming in this sub-region. A review is carried out to appraise the current status of CA in WCA relative to trends and prospects. Research findings, conclusive and preliminary lessons of past and ongoing CA experiences in WCA were synthesized and analyzed to find out how far CA is really pertinent and accessible to WCA farmers. Results showed that CA is feasible in WCA. A conceptual typology including four types of CA systems is proposed to cover the existing socioeconomic and agroecological diversity in the sub-region. Cameroun and Ghana are the countries where CA has developed most. Research on CA in WCA started 40 years ago, but the scientific evidence on its effects are not yet comprehensive for application as a package in practical agriculture. Available evidence tend to confirm the expected positive effects of CA in combating soil degradation (improvement of soil properties, biodiversity, control of runoff and erosion) and its potential in the betterment of farmers livelihoods (increased of yield, productivity and margins) in the longer-term. CA is not a panacea and should be promoted with some site specific recommendations and preconditions. Shortcomings of CA are reported in some cases and they include risk of water logging in poorly drained soils, potential initial yield penalty particularly on unfertile and compacted soils, increase in labour requirements notably when the third principle of CA is implemented rather through crop association. There is apparently a gap between the vision of scientists focused on the impact of CA on soil properties and long-term sustainability of production systems and farmers' vision who are expecting from CA immediate solution to their urgent needs (food security, farm income and labour savings). Farmers are aware of the benefits of CA as a holistic innovation, but they adopt it rather through a stepwise process, progressing only by developing skills or received adequate support to overcome challenges emerging from an intensive implementation of the technology. These challenges are more organizational than technical (rules for the management of biomass at territory scale, availability and access to agricultural services) and somehow concern rather the whole agricultural sector rather than CA particularly. The biggest challenge appeared to be the lack of an enabling policy framework, given that decision makers seem not yet well aware of CA and tend to rely on the old model of green revolution to meet the urgent needs of food security. However, the increased awareness of stakeholders on issue of climatic change which is a reality in the sub-region would likely lead to more interest in CA and hence a more conducive policy for its promotion, if in the meanwhile its grey areas are clarified. These grey areas include mainly comprehensive performance and implementation modalities of different types of CA, long term biophysical and socioeconomic effects of CA, cost-benefits analysis of organizational innovations reforms required for the dissemination of CA, modalities to move from farm scale to landscape and national levels. (Résumé d'auteur