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To promote greater sustainability in agriculture, development of agroecology is increasingly being invoked. What are the conditions for establishing agroecological production in tropical regions? Based upon case studies in several tropical areas, we provide here some answers to this question. We review the "pillars" (i.e. principles) and the "implementation levers" (i.e., tools) for the development of agroecology. We identify three main pillars: (1) the mobilization and management of ecological processes for the sustainable production and the resilience of agroecosystems; (2) the development of interactions between technical, social, environmental, and institutional components of agroecosystems for a holistic approach to agroecology; and (3) the scaling up of agroecology that takes place with a plurality of actions and pathways at different organization levels rather than an increase in resources and a replication of standardized technical processes. To implement these three pillars, we identify 11 main bio-technical, cognitive, socio-political, and organizational levers. Bio-technical levers include those for (1) mobilizing complementarity between crop species to optimize natural resources use, (2) mobilizing functional biodiversity at the plot scale to optimize natural regulation of pests and diseases, (3) managing biodiversity at landscape and territorial scales, (4) increasing the efficiency of biogeochemical cycles, and (5) renewing targets for genetic improvement. Cognitive, socio-political, and organizational levers include those for (6) political and institutional action at the national and global level, (7) action at the local level to support producers, (8) political and organizational action at the territorial level, (9) the marketing and the development of new agri-chains, (10) the development of new methods for evaluating production systems, and (11) the recognition of the values of gender and generation within families and other organisational levels. This paper provides an overall orientation for the agroecological transition in tropical agriculture and also considers the socio-political context that underlies this transition. [ABSTRACT FROM AUTHOR]

Traditional yam-based cropping systems (shifting cultivation, slash-and-burn, and short fallow) often result in deforestation and soil nutrient depletion. The objective of this study was to determine the impact of yam-based systems with herbaceous legumes on dry matter (DM) production (tubers, shoots), nutrients removed and recycled, and the soil fertility changes. We compared smallholders’ traditional systems (1-year fallow of Andropogon gayanus-yam rotation, maize-yam rotation) with yam-based systems integrated herbaceous legumes (Aeschynomene histrix/maize intercropping-yam rotation, Mucuna pruriens/maize intercropping-yam rotation). The experiment was conducted during the 2002 and 2004 cropping seasons with 32 farmers, eight in each site. For each of them, a randomized complete block design with four treatments and four replicates was carried out using a partial nested model with five factors: Year, Replicate, Farmer, Site, and Treatment. Analysis of variance (ANOVA) using the general linear model (GLM) procedure was applied to the dry matter (DM) production (tubers, shoots), nutrient contribution to the systems, and soil properties at depths 0–10 and 10–20 cm. DM removed and recycled, total N, P, and K recycled or removed, and soil chemical properties (SOM, N, P, K, and pH water) were significantly improved on yam-based systems with legumes in comparison with traditional systems. [ABSTRACT FROM AUTHOR]

Introduction. Mango-based orchards in Senegal occur in a large diversity of cropping systems, but few typologies of these systems exist and none are associated with their comprehensive and quantitative analysis. In this study we defined and characterized the typology of these systems based on a quantitative assessment of their planting design, management, vegetative state, hedgerow structure and infestation by a major pest of mango, the Bactrocera invadens fly. Materials and methods. Multivariate analysis and clustering methods were applied to data from 64 mango-based orchards and their surrounding hedgerows sampled in the Dakar and Thiès regions, in Senegal. Results and discussion. Four types of cropping systems were identified according to orchard design and management patterns: (1) ‘No-input mango diversified orchards’, (2) ‘Low-input mango orchards’, (3) ‘Medium-input citrus-predominant orchards’ and (4) ‘Medium-input large mango- or citrus-predominant orchards’. Orchard characteristics varied among these patterns. For instance, vegetation was dense and homogeneous in system 1, and the mortality rate of trees was high in system 2 but low in system 3. Orchards of systems 3 and 4 were mostly associated with hedgerows with, respectively, boundary-marking and defensive species. Lastly, the number of B. invadens flies was high in orchards of system 4, whereas it was low in those of system 2. Conclusion. The diversity of mango-based cropping systems in Senegal is now well described and quantified. This characterization is a preliminary step that is essential for further studies aiming to improve these systems. [ABSTRACT FROM AUTHOR]

Agricultural policymakers are addressing the sustainable development issue by designing new agricultural systems. Farmers are ultimately asked to make deep changes at field scale. Designing cropping systems has previously been done using prototyping methodologies. Prototyping methodologies use a five-step designing process at field scale and request multicriteria analysis of the resulting prototypes. However, sustainable dynamics implies considering changes at larger scales, farm and region, as well as creating feedback and facilitating participation of all the stakeholders involved in the process. Here we studied citrus production in Guadeloupe, French West Indies, where farmers must reduce pesticide loads despite unresolved weed control issues. We designed the DISCS method, which stands for 'participatory redesign and assess innovative cropping systems', to improve classical prototyping methods by implementing a multi-scale, multi-stakeholder, participatory approach. Compared to classical prototyping methods, the DISCS method differs by implementing three progress loops, at experimental field, farm, and regional scales. Three categories of professional stakeholders are involved: farmers, researchers, and agricultural advisers, who are collectively in charge of designing and testing cropping system prototypes. In addition, local public stakeholders including representatives of state institutions are consulted. Progress is assessed using scale-specific sets of indicators. The DISCS method was applied to develop low-pesticide citrus cropping systems. Five weed control prototypes were jointly designed by citrus farmers and researchers, and two multicriteria assessment tools were built for use at the experimental station and on the farms. Results show that involved farmers transferred the new techniques to their own farms on their own initiative, thus spontaneously becoming pilot farmers. The DISCS method is therefore the result of a co-design process between farmers and researchers. The DISCS method creates an ongoing dynamic relationship between agricultural and public stakeholders to build a solution that can continuously be adjusted to stakeholders' expectations. [ABSTRACT FROM AUTHOR]