Crop association with legumes: which advantages with minor cereals? (Deliverable 6.4)

Varietal mixture involves sowing different varieties of the same species in the same plot for their agronomic complementarity. Special attention must be paid to the complementarity of the growth cycles of different varieties. The processing stage can also cause problems for producers, as quality requirements imposed by millers and processors hinder the adoption of wheat variety mixtures. To design a mixture of several varieties, it is necessary to define the specific interactions between varieties as precisely as possible, as genetic diversity within a cultivated species does not always have positive effects on mixture performance. To design effective varietal mixtures, efforts should focus particularly on the ability of multiple genotypes to interact and associate. It is recommended to develop two complementary strategies to optimise variety mixtures by fostering the ecological mechanisms leading to a positive relationship between biodiversity and ecosystem functioning, and its stability over time. In the “trait-blind” approach, the design of high-performance mixtures is based on estimations of the mixing abilities of varieties. While this approach is operational because it does not require detailed trait knowledge, it relies on heavy experimental designs to evaluate mixing abilities. The "trait-based" approach is particularly efficient to design mixtures of varieties to provide particular baskets of services, but it requires building databases of traits for crop varieties and documenting the relations between traits and services.