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Évaluer la durabilité des systèmes de culture dans un contexte de transition rapide d’une agriculture familiale s’intégrant au marché : Cas de la monoculture mécanisée du maïs en Asie du Sud-Est


Author: Lairez, Juliette
Under the direction of: François Affholder and Damien Jourdain
Montpellier, SupAgro
Langue française English Language English and French text

Keywords : Functional Ecology and Agricultural Sciences, Southeast Asia, Modeling, Laos, Agronomic diagnosis, Multicriteria evaluation, Sustainability, Serious game.


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Assessing the sustainability of cropping systems is particularly challenging when subsistence oriented farms close to the poverty line are rapidly moving to intensive and market-integrated systems. The challenge for the assessment is twofold : to take into account both the short-term socio-economic objectives of farmers (moving out of poverty, food security, income) while at the same time providing indications on how to avoid rapid transitions to lead to conventionally intensified agriculture with irreversible social and environmental damage. This thesis contributes to advancement in the field of integrated and multicriteria assessment methods of cropping systems in transitioning farms. We combine several methodological tools in 3 steps : 1) Identification of locally relevant sustainability criteria by combining farmers’ perspectives with the results of an agronomic diagnosis. 2) Quantification of sustainability indicators of different cropping systems practiced by farmers and quantification of the potentials to improve sustainability according to the biophysical areas to which farmer have access. 3) Assessment of potentials to increase farm sustainability according to farm structure and farmer objectives. We apply the approach to a case study of maize monocropping in northern Laos where mechanized hybrid maize monocropping has replaced extensive slash-and-burn upland rice in less than 20 years. Step 1 shows that farmers have short-term socio-economic concerns (income, food security) but also medium- and long-term sustainability concerns (farm transmissibility, risks relative to herbicide use, fertility). The agronomic diagnosis indicates that crop establishment failure is the main driver leading to low yields and high herbicide use. Step 2 shows that an alternative system with successful crop establishment could double the sustainability performance on the following criteria : herbicide, land productivity, weed and water stress susceptibility and work productivity. However, the alternative reduces performance in terms of nitrogen use efficiency and erosion. Step 3 shows that increasing maize productivity will not lift the poorest farms out of poverty. Improving crop establishment has the potential to improve significantly the sustainability of the already wealthiest farms. The consequence would be a significant reduction of herbicide use and improvement of farm income.