The yield and phosphorus content of maize intercropped with faba bean are enhanced by belowground interspecies interactions at low phosphorus input and by aboveground interactions at high phosphorus input

Aims: Many studies used physical barriers to separate the roots of different species to dissect the contributions of above- and below-ground interspecies interactions to yield and phosphorus (P) uptake. However, the extent to which the presence of barriers itself alters these contributions remains unknown. Methods: The field study, conducted in 2010 and 2011, used root barriers in both sole cropped and intercropped maize at two P levels. We examined the contributions of interspecies interactions to yield, biomass and P content in all treatments. The field experiment followed a split plot design with two P levels (P0: 0 kg ha-1, and P35: 35 kg P ha-1), three cropping systems (sole maize, sole faba bean and maize/faba bean intercropping), and two types of root separation (solid barrier -SB- and no barrier -NB-). Results: The presence of a solid barrier negatively impacted the yield of sole maize, reducing it by 26% in 2010 and by 56% in 2011 compared with conditions without a barrier, indicating that the barrier itself adversely affected the growth of sole maize. Notwithstanding the barrier's influence, the belowground interspecies interactions were the primary contributors to the increased grain yield and P content observed in maize/faba bean intercropping under the P0 treatment. In contrast, aboveground interactions were more significant in enhancing the performance of the intercropping system at the P35 treatment. Conclusions: Phosphorus fertilization diminished the effects of belowground interspecies interactions while amplifying the impact of aboveground interspecies interaction on the advantages of intercropping, regarding grain yield and P uptake.