Co-designing innovative cropping systems using cover crops: Maintaining soil fertility in smallholder farming systems in Mayotte

Balandier Marie-Laure. 2017. Co-designing innovative cropping systems using cover crops: Maintaining soil fertility in smallholder farming systems in Mayotte. Wageningen : Wageningen University, 79 p. Master Thesis : Organic agriculture : Wageningen University

Encadrement : Huat, Joël ; Bianchi, Felix

Résumé : n Mayotte, 80% of the island population food needs are covered by the local food-crop productions (banana and cassava). However, a tremendous demographic pressure gradually led smallholder farmers to grow on shrinking land areas, and to abandon the traditional practice of fallow. Fallow was one of the key element for sustaining soil fertility and production levels. Previous research works suggested that using a cover crop would be a suitable alternative option to restore the soil fertility, but knowledge gaps remained to be filled. This research project outlined how to co-design innovative cropping systems using cover crops among Mahoran smallholders despite the knowledge scarcity and heterogeneity. A step-by-step co-design approach was implemented. First, data about perceptions of changes in production levels and soil fertility, soil fertility management practices, uses and limitations of cover crop were collected among 34 smallholder farmers during semi-directed interviews. Seventeen farmers were also asked about banana management and associated production levels. Later on, a rapid diagnosis enabled the identification of different banana management types. Then, a participatory workshop was organized to validate data, and reflect about possible solutions for improving soil fertility and banana production levels. Finally, solutions were assessed ex-ante using DEXi, a modelling tool for multi-criteria decision making. Three banana management were identified and validated by farmers and experts: extensive management with low planting density, low manure application and no irrigation (3.2 t banana/ha/year), semi-extensive management with medium planting density, medium manure application and no irrigation (15.4 t banana/ha/year), intensive management with high planting density, high manure application and irrigation (28.8 t banana/ha/year). Five nitrogen-fixing legumes were described by farmers as possible cover crops: Pueraria phaseoloides (tropical kudzu), Cajanus cajan (pigeon pea), Vigna radiata (mung bean), Vigna umbellata (rice bean) and Vigna unguiculata (cowpea). Beyond the ecosystem service of soil fertility restoration, these 5 cover crops were relevant from an ecological perspective since they provided other ecosystem services: soil erosion control, pest, disease and weed control, moisture retention, feed for cattle and/or food for humans. A knowledge gap did not allow the development of distinct scenarios for each cover crop species with DEXi. Overall, introduction of a cover crop at the banana management level might lower losses in extensive and semi-extensive scenarios (very high to high losses, moderate to low losses respectively), and it might maintain very low losses in intensive scenario. A sound data triangulation enabled the rapid production (in a few months) of a reliable data repository necessary for the success of further research projects. Dealing with a combination of farmer knowledge and scientist knowledge was possible with the use of DEXi. However, tracks were identified for further research works, e.g. the characterization of functional traits of the cover crop species under the local pedo-climatic conditions and the local agroecosystem management. By doing so, scenario could be refined. The scaling-up, from the crop management to the cropping system level, is the next step. It will be worthwhile reflecting upon the spatial and temporal arrangements of cover crops with banana plants. Furthermore, technical (and perhaps financial) support will be essential to encourage a great adoption of the innovative options among smallholders. To put it in a nutshell, method employed here and activities carried out in this step-by-step co-design process enabled the creation of scenarios of banana management using cover crops, being representative of the farmer diversity in Mayotte.

Auteurs et affiliations

• Balandier Marie-Laure, Wageningen University (NLD)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/592440/)

Métriques

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