Towards robust agroecological market-gardening systems: lessons from a system experiment in crop diversification

Farming systems are facing strong disturbances due to climate change, mounting pressure from pests and diseases, and economic and market crises. Increasing crop diversification promises to improve system robustness by reducing and spreading out crops’ exposure to hazards, mitigating their vulnerability if exposed, and thus preserving their performance. Vegetable crops face severe biotic and abiotic stresses. In southern France, most medium-sized market-gardening farms still rely on specialized and lettuce-centered winter cropping systems, compromising long-term field potential and robustness. Many other species are agronomically feasible, but farmers face numerous impediments to significantly diversifying their winter systems. Providing results from agronomic field trials of contrasted diversification options can help overcome these obstacles. Few system experiments target market-gardening cropping systems, and even fewer evaluate strategies of crop diversification combined with other agroecological levers. This article presents the system experiment DIVEGFOOD, implemented in the French Mediterranean region to assess three agroecological diversified cropping systems and a poorly diversified baseline. DIVEGFOOD provided an original assessment of connection between diversification levels and robustness of agroecological market-gardening systems. Diversified systems still tend to be exposed to biotic pressure and injuries to harvests, but less so than the baseline, and to be less exposed to non-optimal conditions. Their production was preserved or improved on average, although some trade-offs had to be accepted for agroeconomic outputs. As it involved complex agroecological systems, DIVEGFOOD illustrated how crop diversification design and assessment require time, trade-offs and a systemic approach. We discuss why this pluriannual system experiment is emblematic of agroecologists’ methodological challenge to design and test promising systems in consistent farming conditions, using relevant assessment and analysis methods. Systems design and outcomes are discussed beyond the single technical field level, highlighting the leeway that could be opened by better dialogue between production and supply chain stakeholders, to support the agroecological transition.