Abstract
Global food security is increasingly threatened by climate change and population growth, necessitating agricultural strategies that enhance crop resilience and resource use efficiency under water-limited conditions. Intercropping, which mimics natural species diversity by growing two or more crop species together, can improve productivity and sustainability by promoting beneficial species interactions both above and below ground. This dissertation investigates the balance between competition and facilitation in cereal-pulse intercropping systems through a combination of controlled greenhouse experiments and multi-trials field studies.
The first chapter presents a greenhouse study where barley was intercropped with chickpea, lentil, and pea under contrasting water regimes. Results showed that barley was consistently the dominant competitor, while pulse responses were species-specific: pea was suppressed, whereas chickpea and lentil shifted toward neutral or facilitative interactions under drought, linked to adaptive root trait plasticity.
The subsequent field studies examined above- and belowground dynamics in barley-pea and wheat-pea systems during organic transition. Across years, both intercrops maintained high productivity, with land equivalent ratios (LERs) ranging from 1.02 to 1.34 for barley-pea and 1.09 to 1.32 for wheat-pea. Root biomass varied by depth, but not strongly by cropping system or water regime, suggesting that the species shared resource zones. The patterns also point to potential facilitation through nitrogen contribution from pea.
Together, these findings show that the stability of intercropping systems, particularly under drought, depends on the functional roles and compatibility of the species involved. Productive and resilient systems require a workable balance between competitive pressures and facilitative processes, the ecological “tug of war”, to optimize productivity and resource efficiency under environmental stress.