Choosing the right associated crop species in soybean-based intercropping systems: Using a functional approach to understand crop growth dynamics

Abstract

Intercropping can contribute to increased crop production and stabilization while reducing biotic stress pressure such as that from weeds. In soybean-based intercropping systems, biomass production of the associated crop is a key performance trait for soybean grain production and weed control services. In some situations, spatial arrangement of crops changes the outcome of the intercropping system considered. Lastly, while trait-based approaches are promising for intercrops design, work remains to associate plant functional traits to crop performances. How are plants growth dynamics affected by the associated crop species and spatial arrangement in soybean-based intercrops? Can plant functional traits be related to the grow dynamics parameters? The growth dynamics of soybean, associated crop species and weeds were characterized in eight soybean-based intercropping systems differing in associated species (buckwheat, lentil, sorghum and sunflower) and spatial arrangement (alternate-row or within-row combinations). Leaf traits and plant height were measured for the four associated crops and were related to growth dynamics parameters. Biomass accumulation of the associated crop species was determinant in explaining that of weeds and soybean and thus intercrop performances. Fast and high biomass accumulation by the associated specie implied low weed biomass and to a lesser extent, low soybean biomass accumulation. For buckwheat-soybean and sorghum-soybean intercropping systems, spatial separation of crops in different rows increased soybean growth. Plant functional traits (particularly leaf area and maximum height) can provide valuable information on plant growth dynamics. Associated crop species growth dynamics are the main driver of both soybean and weeds biomass accumulation. To a lesser extent, spatial arrangement offers the opportunity to modulate the interspecific competition. Furthermore, some crop functional traits are related to growth dynamic parameters, offering new perspectives for understanding the performances and designing soybean-based intercrops. Our results underline that the use of easily measured functional traits can provide useful information for intercropping systems design, facilitating crop selection. Nonetheless, much work remains to understand functional traits combinations.