Co-design of agroecological diversified temperate fruit tree systems: feedback from three breakthrough experiments and experience sharing in the ALTO project
Co-conception de systèmes agroécologiques diversifiés de production de fruits tempérés : retours sur trois expérimentations innovantes et de partage d'expériences dans le projet ALTO
Résumé
An increase in biodiversity, either cultivated or associated to crops, is a way to foster ecosystem services, especially pest regulation. The ALTO project (2018-2023) developed within the Ecophyto national program to reduce pesticide use is a transdisciplinary project aiming at the design of diversified agroecosystems to produce fruit in pesticide-free or very low-input orchards. Three diversified orchards in three sites of Southern France were co-designed according to this objective considering agronomic, ecological, technico-economic and organizational dimensions. The first system investigated resource sharing in an agroforestry system. The second one was redesigned 'step by step' from stone fruit and olive orchards with agroecological infrastructures into a diversified production area. The last one was a young highly diversified circular orchard with a pest suppressive design. Three main questions were shared by one, two or all sites: (1) What is the effect of agroforestry on apple tree architecture and functioning? (2) Can diversity and spatial arrangement limit fruit damage by pests? (3) How does diversification impact work in the orchard? To share the approach with farmers, and because knowledge was missing, scattered or just being built, exchanges among researchers and stakeholders in the food sector were organized as thematic 'Cafés Agro' to share experiences and questions about orchard diversification.
Agroforestry negatively affected the vegetative/productive balance of apple trees with fewer flower clusters in the shade, while the total tree volume was similar to the control, leading to the consideration of other spatial and temporal assemblages that achieve the trade-off between the need to maintain production and to provide shade during heat waves to reduce thermal stress and sunburn on the fruit. The provision of functional biodiversity with habitats and food resources together with very soft crop protection practices resulted in a high abundance and diversity of natural enemies and high levels of predation. Yields in the highly diversified orchards were low to intermediate depending on species; frost was the main cause of irregular yield. Pest damage was high but not extreme considering the absence or the very low use of pesticides. The first technico-economic analyses highlight the importance to maximize fruit valorization, e.g. through direct sales. Such diversified systems also question the current evaluation methodologies that are calibrated to assess monocultures and production regardless of other services. In the diversified orchards, incorporated observation, i.e. implicitly carried out during other activities, was a key activity to survey and understand such complex systems, to adjust practices, make decisions, and build spatial and technical benchmarks. Finally, the format of the 'Cafés Agro', which brought together people from different professions and different food sectors, allowed participants to step back from their own practices and explore innovative practices in order to create a community of practice. Although this research is in progress and requires further developments, the first results of this transdisciplinary project provide feedback on innovative approaches for agroecological design in perennial crops.
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