Increasing species richness and genetic diversity in agriculture: results of the Wheatamix project
Résumé
Homogenization and intensive use of inputs have provided major productivity gains in agriculture during the 20th century. However, new solutions are now needed to face the quest for greater agricultural sustainability. A better use of crop genetic diversity should be an essential leverage, as it could promote various ecosystem services, in a context of increasing environmental stochasticity caused by global change. Increasing within field diversity through the use of cultivar mixtures is a timely option, testified by with some significant “success stories” in the past, and recent bibliographic reviews. Yet, cultivar mixtures are poorly developed worldwide. In this context, the Wheatamix project studies the interest of mixing wheat genotypes to reinforce the sustainability, resilience, and multi-functionality of agriculture. Analyzing the interactions among genotypes and with the environment, Wheatamix develop new blending and breeding methods to obtain performing mixtures. Complementary experimental approaches are being deployed: i) a diversity experiment (88 large wheat plots with 1, 2, 4 or 8 varieties) to quantify the effects of wheat diversity on ecosystem services; ii) replicates of the same diversity experiment in 4 sites across France under low and high inputs, to test diversity effects under a wide range of soil and climate conditions; iii) a network of 30 farms, encompassing agro-climatic variability in the Paris basin, to compare the ecological and techno-economic performance of blends and monocultures. The first results characterize various ecosystem services provided by genetic diversity (yield stability; regulation of foliar diseases; insect pest and weed biocontrol; maintenance of soil fertility; biodiversity conservation), and raise important methodological and statistical issues, crucial when studying the causal link between bundles of functional traits and delivered groups of services. Finally, the Wheatamix project emphasizes the need of a pluri-disciplinary approach when addressing agroecological subjects, and illustrates the strong mutual benefices between agronomic and ecological sciences.
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