Intercropping and pollination mediate faba bean (Vicia faba ) yield and nodulation

Legume productivity depends on biotic interactions above and below ground, such as pollination and Rhizobia symbiosis. Yet, these interactions remain unexplored, particularly in the context of different cropping systems. This study investigated the interactive effects of intercropping and pollination on faba bean nodulation and yield in an organic system, where faba bean and pumpkin were alternated in 3 m-wide strips and compared to faba bean plants grown as a monocrop. Faba bean nodulation and yield were evaluated in open (insect-pollinated) and bagged (self-pollinated) plants. Results showed that faba bean yield and nodulation were enhanced at strip edges. Nodule mass increased by 45 %, the number of active nodules increased by 33 %, and seed weight per plant was 61 % higher compared to monocrops. Insect pollination treatment also increased nodule mass by 19 % and seed weight by 37 %. We found that pollination treatment influenced the relationship between active nodules and yield parameters with insect-pollinated plants being less dependent on active nodules for productivity. In addition, we found complex interactions between cropping system, pollination treatments and nodulation, whereby, in intercropping systems, both yield and nodulation benefit from pollination but not in monocropping systems. Our findings confirm that intercropping positively affects faba bean yield and nodulation, likely driven by nutrient competition and resource use complementarity between crops. Importantly, we provide the first evidence of pollination affecting faba bean- Rhizobia symbiosis, likely through shifts in plant resource allocation. These findings underscore the need to better understand interactions between above- and belowground symbioses for the transition towards sustainable agriculture. • Intercropping boosted faba bean nodulation (+45 %) and yield (+64 %). • Insect pollination increased faba bean nodule mass (+ 19 %) and seed mass (+34 %). • Pollination and intercropping interactively affect yield parameters via nodulation.