Root growth and belowground interactions in spring wheat - faba bean intercrops

Abstract Background and Aims: Intercrops offer multiple advantages over sole crops. However, little is known about the mechanisms that govern the belowground interactions between mixed species. The aim of our study was to characterize root growth and interactions in spring wheat-faba bean intercrops for different sowing densities and spring wheat cultivars, evaluating the potential belowground interactions that governs resource capture. Material and Methods: A field experiment was conducted with one faba bean cultivar and two spring wheat cultivars sown at three sowing densities. Destructive root coring was conducted (0-100 cm) in the intercrops and sole crops at two development stages. The root samples were processed to assess the root mass, root length density, and root carbon and nitrogen concentrations. FTIR spectroscopy was used to discriminate the species’ root masses. Results: Root mass advantage of intercrops was observed for both cultivars and both development stages especially in the topsoil layers (0-20cm). A negative impact of intercropping on root mass was observed in the treatment with high total sowing density. Complementarity and cooperation were stronger than competition in the topsoil, but competition dominated root growth in the deeper soil layers. Lower sowing densities encouraged deep rooting of wheat (both cultivars) in intercropping. The early root dominance of one spring wheat cultivar impacted negatively faba bean root growth. Conclusion: Total root mass was affected more by sowing density and less by the spring wheat cultivar in this experiment. An improved understanding of root growth in intercrops can help to support yield advantages and the design of sustainable intercropping systems.